February 1996 Gasification Archive

For more information to help people develop better stoves for cooking with biomass fuels in developing regions, please see our web site: http://www.bioenergylists.org

From larcon at csn.net Thu Feb 8 01:42:56 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:47 2004
Subject: 1. draft purpose and scope
Message-ID: <Pine.3.89.9602072345.A26258-0100000@teal.csn.net>

Hi group:

Thanks to Tom Miles and Andrew Waegel we are now an operating
group, with Etienne and myself as co-moderators. Type "who stoves" in a
message to majordomo@crest.org to find out who else is aboard; the answer
should be back in a few minutes.

Tom and Andrew have asked that we make up an Introduction
containing a "Stoves" purpose and scope. Since everyone should have a
chance at this, here's a draft start:

The purpose of this "stoves" list is to promote the development
and introduction of improved biomass-burning stoves.

The scope is broad:
"promote" includes technical information exchange, discussion of
difficulties and means to overcome them, identification of pertinent
literature and expertise, etc.,
"development" includes such topics as research, development,
demonstration and commercial manufacturing techniques. International
competitions are specifically included,
"introduction" includes world-wide, using products fabricated in
factories, the traditional sector, or by users. Emphasis is expected on
developing countries,
"improved" refers to factors that will reduce biomass
consumption, improve the health of users, reduce pollution (both locally
and globally), and/or augment income (as through charcoal-making),
"biomass-burning" includes wood, charcoal, crop residues, and
animal manures. Emphasis is expected on wood collected by the users, but
might include production techniques,
"stoves" includes cookstoves, space-heating, water-heating, but
might also include small kilns, ovens, etc., with emphasis on the first
topic.

The scope excludes commercial promotion of any specific
corporation, but product identification and product factual information
is encouraged.

Comments needed from all. Note I put #1 on this message. Might it be
easier to find and identify messages with such a numbering system?

Ron

From E.Moerman at stud.tue.nl Thu Feb 8 11:49:56 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:47 2004
Subject: 1. draft purpose and scope. To: Ron 7 Feb.
Message-ID: <64290.s335192@popserver.tue.nl>

Welcome to all the members of the new STOVES LIST!

To proceed where Ron stopped his last message.

I think that numbering in the subjects heading will not help too much, since
crossing messages might results in several messages with the same number.
However it will probably improved the situation a bit. Perhaps the best
option is still to add to replies date and person like some of us did at the
bioenergy list (this subject header is an example).

But now more importantly a description of the list.

I assume you do not want to limit the description to the single line:

> The purpose of this "stoves" list is to promote the development
> and introduction of improved biomass-burning stoves.

If so I think the description is to brief and far too general. If you add
the explanations below to the line I think it looks a little scattered.

>
> The scope is broad:
> "promote" includes technical information exchange, discussion of
> difficulties and means to overcome them, identification of pertinent
> literature and expertise, etc.,
> "development" includes such topics as research, development,
> demonstration and commercial manufacturing techniques. International
> competitions are specifically included,
> "introduction" includes world-wide, using products fabricated in
> factories, the traditional sector, or by users. Emphasis is expected on
> developing countries,
> "improved" refers to factors that will reduce biomass
> consumption, improve the health of users, reduce pollution (both locally
> and globally), and/or augment income (as through charcoal-making),
> "biomass-burning" includes wood, charcoal, crop residues, and
> animal manures. Emphasis is expected on wood collected by the users, but
> might include production techniques,
> "stoves" includes cookstoves, space-heating, water-heating, but
> might also include small kilns, ovens, etc., with emphasis on the first
> topic.
>
> The scope excludes commercial promotion of any specific
> corporation, but product identification and product factual information
> is encouraged.
>

In general I agree with the trendm but I would like to see an integrated
story. Perhaps something like what you will see below.

-------------------
The purpose of the STOVES list is to enhance the information exchange about
small and medium scale biomass burning devices. The information we have in
mind is information about the user requirements on several biomass burning
devices, the efficiency and the emission levels of various pollutants. Also
information on the socio-economics and combustion research is welcome.
However it is expected that most of the information exchange will be about
research and experiments on biomass burning devices and the design and use
of these devices. Discussions will concentrate on the use of small-scale
combustion devices in developing countries. The devices that are subject of
discussion are for instance cookstoves, space heaters, water heaters, ovens
and kilns. Most discussions are expected to concentrate on wood, but other
fuels as charcoal, agricultural waste and dung will also be covered.

We hope that especially a lot of people from developing countries will join
the list.

----------------------
Please give your reactions on this proposed description.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN
The Netherlands

From larcon at csn.net Thu Feb 8 14:49:39 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:47 2004
Subject: Elderly Stove Research (fwd)
Message-ID: <Pine.3.89.9602081213.A26163-0100000@teal.csn.net>

I am taking the liberty of sending this on so that the full larger
stoves group receives it. I also add a few comments.

---------- Forwarded message ----------
Date: 08 Feb 96 06:38:22 EST
From: Thomas Reed <73002.1213@compuserve.com>
To: "Balwin, Sam" <baldwins@tcplink.nrel.gov>,
"S. C. Bhattacharya" <bhatta@ait.ac.th>,
"Duke, Tom" <tduke@igc.apc.org>, "Larson, Ron" <larcon@csn.org>,
"Miles, Tom" <tmiles@teleport.com>,
Etienne Moerman <E.Moerman@stud.tue.nl>,
Smith <smith%ewc.BITNET@vaxf.colorado.edu>,
"Verhaart, Piet" <Peter_Verhaart@msn.com>,
"Weigel, Andrew" <asw@crest.org>,
"West, Ron" <west@magellan.colorado.edu>
Subject: Elderly Stove Research

Hello Stove Researchers All:

(Or almost all). What a collection of talent! Many new people in the stove
dialogue. My computer was in the shop for a week and I got 62 E-mail hits -
about half on stoves. NEVER let your computer break down that long. Here are
a few comments on various observations I found.

Ken Bryden comments that we as a group are not ALL greybeards. True, but
someone else commented that semi-retired scientists can work in this field
because it doesn't take a lot of equipment and money - just persevereance, a
quality not always shown in our National Laboratories and funding agencies.
Those of us that are retired can direct their efforts more intelligently. (I'm
not retired - still a professor at Mines, but collecting all pensions, started 3
businesses, taking good care of 6 grandchildren etc.)

Personally, I have reached a position in life where I can do whatever I please
and I please to do gasifier-stove research. I can't think of anything that
could make such a contribution to the 5+ billion people on this planet as well
as the planet itself. I have a friend, Fred Hottenroth (Los Alimitos, CO) who
is exporting 100 stoves to Nepal. He is 93. His son, Fred III is in his
sixties. I hope they will be on line and in this forum soon. I hope some of
us can be that effective.

I detect a lot of dialogue at cross purposes. It is usually true that DOWNDRAFT
gasifiers (char on bottom, gases flowing down) produce a minimum of char. It is
equally true that INVERTED DOWNDRAFT gasifiers (char on top, gases flowing up)
produce a maximum of char. I know a few reasons for this, but would be
interested in any ideas any of you have. As Covey says," Strive to understand.
... so that you can be understood". We need to carefully define our terms in
this dialogue.

I just came across two beautiful pictures of the INVERTED DOWNDRAFT gasifier
that I took at NREL in 1985 after spending a week (with TOm Miles Jr.) in South
Africa. One picture shows a clean blue, premixed flame; The other shows
coffee boiling on the flame. (Too bad it's so hard to send photos in E-mail.)
Unfortunately that stove used forced convection. I have been trying to
accomplish the same with natural convection ever since.

In reading the material sent by Etienne, I noticed several times
a reference to a characteristic yellow flame for wood fires. The
natural draft stove that Tom and I have been working with certainly is
more blue than most, but always starts out more yellow than blue. Must it
be yellow?

At that time I considered the production of charcoal to be a drawback. Ron
Larson has convinced me that it is an advantage sometimes, and we are making
progress with that.

With the natural draft "inverted downdraft" stove under
discussion, I think it is almost always going to be advantage to harvest
charcoal. With a chimney, the flame is so small after the wood has turned
to charcoal that heat transfer to the cook pot is pretty poor. Because
charcoal is generally valued at 3-4 times wood prices per unit weight in
developing countries where both are heavily used, there is a financial
motivation to stop the conversion and start a new batch.

Other news: Dan Jantzen has moved to New Delhi to head up the WinRock office
there. He and they have a strong interest in GOOD stoves, but have been burnt
by many gasifier projects in the past.

I have Dan's new e-mail number and will add him to the list. I
think an important question is whether the "inverted updraft" is useful
for a gasifier - I think not, because it is batchmode. It seems that
the existing downdraft may be the preferred mode for gas for engines. Is
there agreement?

Can anyone tell me how to add address and phone numbers to E-mail (like a
letterhead) without typing it each time? (Of course I can copy it from previous
letters, but I hope there's an easier way. I notice some of you do - some
don't. E-mail can be confusing, because you have no sense of who you are
talking to and where they are. I presume this will all change when each of us
has a home page. I am working on one now for the Biomass Energy Foundation,
Inc.

Regards to all,
TOM REED
Thomas B. Reed E-mail: 73002@compuserve.com (soon to change)
1810 Smith Rd., Phone: 303-278 0558
Golden, CO 80401 Fax: 303-278 0560 (Phone +2)

From E.Moerman at stud.tue.nl Thu Feb 8 16:21:02 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:47 2004
Subject: Discussion subject
Message-ID: <80555.s335192@popserver.tue.nl>

To all-

To start the discussion on this new list, I think it is a good idea if
everybody that joined the list sends a few lines stating what his/her
involvement in stoves is and what subjects related to stoves are of
particular interest. I think this is the best way to keep the discussion
interesting to all participants.

To start with I will state my involvement in stoves.

I have been working with the Woodburning Stove Group (WSG) at the Eindhoven
University of Technology for the past 6 years. I have mainly been involved
in lab experiments and modeling on cookstoves (mainly the downdraft stove).
I am presently working on a combustion model to describe the influence of
moisture on the pyrolysis of wood. I also hope to include the combustion of
the formed char. This is the short term aim, in the long term I hope I will
be able to use this model to develop a model describing the combustion of
biomass in a fixed fuelbed. In turn that should be incorporated with a model
described in a Ph.D. thesis by Paul Bussmann. The final result should than
be incorporated in a PC computer program that will enable stove research
institutes in developing countries to design appropriate stoves in a matter
of hours or at most days. I am also together with Prasad trying to start up
three projects for the design of small-scale industrial woodburning devices
(again for developing countries). I would like to get a discussion along
these lines, with the addition of detailed user requirements. This last
point is probably difficult to get on this list.

This were more lines than I anticipated, but I hope more of you will make a
few of these statements and a lively debate on several topics will develop.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN
The Netherlands

From E.Moerman at stud.tue.nl Fri Feb 9 08:15:26 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:47 2004
Subject: Pyrolysis Modelling. To Thomas Reed 8th Feb.
Message-ID: <51416.s335192@popserver.tue.nl>

Tom

I think you are completely right in assuming a fast heating rate (high Biot
number). Indeed steam is formed and that is exactly were I get problems with
diverging solutions. I am still trying to address this problem, it is quite
complicated since I also have to take into account the maximum vapor
pressure which is strongly temperature dependant. I let you know as soon as
I get some meaningful results.

> In our "Survey of Biomass Gasification...." (NREL Contract, 1996, not the
> first SERI one in 1979) we will have a chapter on modelling. If you have
> any recent papers you recommend, I would appreciate receiving or learning
> about them.

There is a recent book I recommended to Ron. It extensively covers the
basics of fluid flow modelling. I am not sure whether you had this in mind.

Computational Fluid Dynamics - The basics with applications.
By John D. Anderson, Jr.
Published by McGraw-Hill International Editions, 1995.

As far as modelling pyrolysis is concerned my most recent useful article at
te moment is from 1993.
Analysis of convention and secondary reaction effects within porous solid
fuels undergoing pyrolysis. By Di Blasi. Published in: Combustion Science
and Technology, Vol. 90, pp.315-340.
QUITE INTERESTING. IT APPEARS TO EXPLAIN THE CONTRADICTORY RESULTS FOR THE
REACTION HEAT FOR THE PYROLYSIS PROCESS.

I have a few more, but they are not very interesting except on some details.
I will probably check a number of journals again in a few weeks time.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN
The Netherlands

From E.Moerman at stud.tue.nl Sat Feb 10 07:25:05 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:47 2004
Subject: Stove Publications
Message-ID: <48455.s335192@popserver.tue.nl>

I received several request for information on stove publications. I addition
of the list of books and reports still available from us I made the
following list. It is a list of journals and conference proceedings that
might be reasonably accessable for most of you. Of course the list is not
complete, but the other publications are usually difficult to obtain.

Etienne

-Woodburning Cookstoves (1985).
K. Krishna Prasad, E. Sangen and P. Visser.
In: Advances in heat transfer, Vol. 17, pp. 159-317
Academic Press Inc.

-On the testing of woodburning cookstoves (1985).
P. Bussmann, K. Krishna Prasad and W.F. Sulilatu.
In: Energy from biomass, proceedings of the International Conference on
biomass, Venice, Italy, March 25-29, 1985.
Elsevier Applied Science Publishers Ltd.

-Woodfired Heaters (1987).
K. Krishna Prasad.
In: Biomass Energy.
D.O. Hall and R. Overend (Eds.).
Published by John Wiley.

-Model predictions of temperatures and velocity profiles in turbulent
diffusion boyant flames (1987).
P. Bussmann and K. Krishna Prasad.
Proceedings of the 7th International Heat Transfer Conference, Munich.

-Parameter analysis of a simple woodburning cookstove (1986).
P. Bussmann and K. Krishna Prasad.
Proceedings of the 8th International Heat Transfer Conference. San
Fransisco. C.L. Tien, V.P. Carey and J.K. Ferrel (Eds.).

-A study on the performance of charcoal stoves (1987).
E. Sangen and P. Visser.
Paper presented at the Biomass for Energy and Industry 4th European
Conference of the Commission of the European Comminities at Orleans, France,
May, 1987. G. Grassi, B. Delmon, J.F. Molle and H. Zibetta (Eds.).
Elsevier Applied Science publishers Ltd.

-Clean burning biomass cookstoves (1989)
P. Verhaart and A.M. Hasan R. Khan.
Proceedings of the ISES World Congress, Kobe, sept. 4-8, 1989.

-Small scale clean biomass combustion devices (1989).
P. Verhaart, E. Schutte, K. Krishna Prasad and A.M. Hasan R. Khan.
Proceedings of the 5th European COnference on biomass for energy and
industry, Lisbon, Oct. 9-13, 1989.

-Applications of downdraft combustion to woodburning devices (1990).
A.M. Hasan R. Khan, E. Schutte, K. Krishna Prasad and P. Verhaart.
Paper presented at the 9th International heat transfer conference,
Jerusalem, August 19-24, 1990.

That's all. I hope it will be useful to at least some of you.
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN
The Netherlands

From tduke at igc.apc.org Sat Feb 10 21:29:34 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:47 2004
Subject: Stove Calculations & End users
Message-ID: <199602110232.SAA06984@igc3.igc.apc.org>

Hi all-

I am responding to Etienne's discussion on calculating, modeling wood
stoves in the computer and his concern with making contact with the
end users of these systems. I feel that my response makes sense in
context of his intorduction, so you will find my suggestions down a
ways in this copy.

> From: E.Moerman@stud.tue.nl
> Date: Thu, 8 Feb 1996 22:22:34 +0100 (MET)
> To: stoves@crest.org
> Subject: Discussion subject
> Reply-to: stoves@crest.org

> To all-
>
> To start the discussion on this new list, I think it is a good idea if
> everybody that joined the list sends a few lines stating what his/her
> involvement in stoves is and what subjects related to stoves are of
> particular interest. I think this is the best way to keep the discussion
> interesting to all participants.
>
>
> To start with I will state my involvement in stoves.
>
> I have been working with the Woodburning Stove Group (WSG) at the Eindhoven
> University of Technology for the past 6 years. I have mainly been involved
> in lab experiments and modeling on cookstoves (mainly the downdraft stove).
> I am presently working on a combustion model to describe the influence of
> moisture on the pyrolysis of wood. I also hope to include the combustion of
> the formed char. This is the short term aim, in the long term I hope I will
> be able to use this model to develop a model describing the combustion of
> biomass in a fixed fuelbed. In turn that should be incorporated with a model
> described in a Ph.D. thesis by Paul Bussmann. The final result should than
> be incorporated in a PC computer program that will enable stove research
> institutes in developing countries to design appropriate stoves in a matter
> of hours or at most days. I am also together with Prasad trying to start up
> three projects for the design of small-scale industrial woodburning devices

-----------------------------------------------------------------------
I sense and suspect that stove calculations are like weather
calculations where the butter fly effect exists. This is where very
small changes in the starting values causes very great changes in the
results. This is sometimes called chaos theroy or the theroy of
complexity. I am sure both exist in wood combustion. These are
non-liner systems and donot solve by liner formulas. However I have
good results solving some complex and chaotic systems using neural
networks and fuzzy logic. The results are not accurate to several
decimal places. However they are accurate to over 95 percent most of
the time. There is an indicator of the suspected accuracy of results.
Using neural networks and fuzzy logic probably will speed up the
process of modeling wood combustion, wood stoves tremendously.
----------------------------------------------------------------
> (again for developing countries). I would like to get a discussion along
> these lines, with the addition of detailed user requirements. This last
> point is probably difficult to get on this list.

-----------------------------------------------------------------------
Outreach International is an organization that I have some contact
with and friends in. They have people in the field on location making
friends with users of wood stoves, so I am working on getting you and
them together. Here is their e-mail address:
<JNXC37A@prodigy.com>.

>
> This were more lines than I anticipated, but I hope more of you will make a
> few of these statements and a lively debate on several topics will develop.
>
> Etienne
> **********************************************************************
> Etienne Moerman E-mail: E.Moerman@stud.tue.nl
> J. Buyslaan 71 Tel/Fax: +31-40-257 1491
> 5652 NJ EINDHOVEN
> The Netherlands
>
>
Thanks again Etienne, I will post a little note introducing myself
shortly, so you have some feel for where I am comming from and going
to.

Tom Duke

From verhaarp at cqu.edu.au Sun Feb 11 07:07:12 1996
From: verhaarp at cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:47 2004
Subject: Elderly Stove Research (fwd)
Message-ID: <9602111209.AA21080@janus.cqu.edu.au>

>From Piet Verhaart
Some loose items.

1. Have been incommunicado for a few days, (unprintable adjective) Windows
95 crashed, not for the first time so had to waste one of the few remaining
days of my life being patient in the face of glaring untruths on the screen
(not all hardware connected or switched on, cannot find file ....) and going
through setup after setup. Well there is still a lot to be set up but there
is one improvement over the last time before the crash. I can use
Trumpet/Winsock freely and go from there to Weudora. Before this I had to do
Telnet and make it disappear after winsock had connected me. Microsoft
Network does not connect in spite of having gone through the complete
troubleshooting rigmarole. Anyway, last night I was connected and a lot of
E-mail there was, all about stoves.

2. Reading through it, one comment. It is not always clear who is speaking
(writing), even after attempting to unravel the number of quotes within
quotes. Can we possibly in future insert the name of the author at the start
of a quote from that author?

3.Great news in a quote from either one of the Toms or from Ron. About Fred
Hottenroth, alive and kicking at 93. Great news about a great guy. Hope he
(both Freds actually) will be on the net soon. In the meantime please convey
my warmest regards to him.

4. Had a great day at the tip, came home with a 1.5 m length of rusted steel
pipe of 125 mm diameter and about 4 mm wall thickness. Managed to cut 4
sections of 300 mm with the cut off wheel and today squared the ends on my
Chinese lathe. First I had to make an internal brace to support the end in
order not to get it thrown at me as soon as the cutting tool bites. All went
well. Two sections will go into building a solid version of Ron's charcoal
making stove. The two remaining sections are going to form a stove with a
movable bottom with which the top of the fuelbed can be brought into contact
with the air drawn in (by natural draft) through the slit between top and
bottom pipe sections.

5. Someone asked about an automatic way to append one's address to E-mail.
In Eudora there is a simple way. Click on Window and on Signature. A blank
page will appear on which you can enter your data after which you save it by
clicking on File and Save. When you need it you click it. It will not appear
on your own copy, so to check it you will have to send yourself an E-mail.

6. Some thoughts re Etienne's description of the list. Introduction for new
members. Make clear that in the end efficiency of a cookstove is expressed in
(Mass of food cooked)/(mass of fuel used)
and that this involves not only a high heat transfer efficiency but also a
wide 'turndownability'.

7. Looking over the sheets and sheets of E-mail I am happy to realise that
we have come a long way since the days of the glorious statements about the
untried performance of ponderous mud castles by well meaning non engineers.

8. Is there a concensus on short Resumes of each member?

9. I like the name Elderly Stove Research. I have been thinking about a name
but haven't come any farther than 'Dinosaurs on Combuston Devices'

Obviously time to stop. Regards to all.

Piet Verhaart

==========================================================================
P.Verhaart
Phone: +61 79 331761 Fax: +61 79 332112
E-mail: verhaarp@cqu.edu.au
Snail Mail: 6 McDonald St, Gracemere Q 4702 Australia
Mobile 015 581 262

From E.Moerman at stud.tue.nl Sun Feb 11 07:57:04 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:47 2004
Subject: VITA stove participation
Message-ID: <50321.s335192@popserver.tue.nl>

Tom:

>From your description I gather that the stove you need is for a large
pancake. If so not many stoves can be used. Perhaps the Tandoor stove
(downdraft version) built and tested by IFRD in Bangladesh. The 'pancakes'
are here stuck to the wall. I think this is different from what people ar
using now, so I don't know if they will accept this. No tall and therefore
expensive chimney is required. Tests on it have been limited, but apparently
it has potential. A bit more tests and design effort are needed to
optimalize it, however it can be used. I don't know any other stove especially
designed for 'pancakes'. Perhaps they can use a 'heavy stove' like the
Lorena stove and just use a pan. However this option is probably far too
expensive for most.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN
The Netherlands

From bryden at cae.wisc.edu Sun Feb 11 13:45:37 1996
From: bryden at cae.wisc.edu (kenneth bryden)
Date: Tue Aug 31 21:34:47 2004
Subject: stoves
Message-ID: <199602111848.MAA99296@audumla.students.wisc.edu>

Stove group,

Yes, I am somewhat slow in responding to a variety of good comments and
observations. I try hard to limit myself to writing only one or two days a
week, so that I can spend more time on research.

In response to questions about my research from Piet and Etienne. My
research is motivated by the observation that although there are a number of
flame, pyrolysis, and char combustion models for wood (46 by my count
starting with the work of Bamford, et al.) few of these permit the
calculation of wood consumption rates from virgin wood to complete
consumption of the char and none that I am aware of provide a detailed
comparison of the results obtained against other experimental and
computational results. As a result when one uses a wood pyrolysis model,
char combustion and gasification model it is never quite clear what the
limitations are.

The emphasis on "engineering" models of wood combustion is because it seems
to me that a good set of workable engineering models of wood combustion for
use in design of wood fired boilers, stoves, etc. is essential if the
bioenergy field is going to be able to grow. I also have contacts among the
fire protection community and am interested (but don't have the time to
pursue) the issues behind wild (forest) fires.

In the March issue of Energy and Fuels my first journal article will appear
and will describe a model used to examine the behavior of the
whole-tree-energy combustor. The whole-tree-energy combustor/gasifier is a
deep packed bed in which whole trees 8 m in length are combusted in bed
which is approximately 4-5 m deep. I will send you a copy of the paper
Etienne. The same program written for the whole tree combustor has been
modified for smaller material, eg. stoves but no results have been
published, and I will probably wait until my current research is complete.

We (myself and my advisor) have also submitted a paper for Bannf on the
combustion of single large ~20 cm logs in a test rig under varying
conditions. Etienne, or others, let me know if you want a copy.

In addition to these two papers which represent work from a 1-2 years ago, I
am working on completing a boundary layer model of wood combustion which
accounts for all reaction zones and the coupling between them. My current
focus is on the construction of a large computational model of combustion of
a single particle of wood. The model is being built on a CRAY computer here
at UW which is used for combustion research. The hope is that a model which
includes all reaction zones and relevant phenomenon (in some cases in a
simplified manner and in others in detailed manner) will provide a basis for
the development of engineering models of wood combustion. Similar to the
development of engineering model of flames from more detailed computational
models.

It seems that the biggest problem with this modeling is trying to find high
quality wood combustion data which lends itself readily to the modeling
process. eg.. sufficient detail and a relatively simple geometry.

In answer to a couple of questions from Piet:
1) Yes it is very hard to keep from getting distracted because it seems that
there are many worthwhile and extremely interesting things happening in the
world of wood combustion. Thank you for being perceptive on this.
2) Professor Bird's email address is Bird@chewi.che.wisc.edu.

One final thought. Etienne, since a cook stove is a small scale wood fired
packed (fixed) bed I was wondering if you were familiar with the work of
Smoot, Brewster, Radulovic, etc. out of Salt Lake City Utah. Although they
work with coal and the translation is wood packed beds is not one for one,
they have written in several places a good summary of the current state of
coal packed bed combustion modeling. One reference would be Fundamental of
Coal Combustion, L. D. Smoot Ed., Elsevier, 1993, pp.630-676.

Ken Bryden
University of Wisconsin - Madison
126 Engineering Research Building
1500 Engineering Dr.
Madison, Wisconsin 53706

ph. 608-263-3231

From E.Moerman at stud.tue.nl Sun Feb 11 15:07:10 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:47 2004
Subject: Stove Calculations & End users. To Tom DUke 10 Feb.
Message-ID: <76120.s335192@popserver.tue.nl>

This is in reply to Tom Duke's comments:

I stated my involvement in stove modelling. Tom made this comment:
> -----------------------------------------------------------------------
> I sense and suspect that stove calculations are like weather
> calculations where the butter fly effect exists. This is where very
> small changes in the starting values causes very great changes in the
> results. This is sometimes called chaos theroy or the theroy of
> complexity. I am sure both exist in wood combustion. These are
> non-liner systems and donot solve by liner formulas. However I have
> good results solving some complex and chaotic systems using neural
> networks and fuzzy logic. The results are not accurate to several
> decimal places. However they are accurate to over 95 percent most of
> the time. There is an indicator of the suspected accuracy of results.
> Using neural networks and fuzzy logic probably will speed up the
> process of modeling wood combustion, wood stoves tremendously.
> ----------------------------------------------------------------
My reply:
The system of equations is indeed non-linear. However the situation is not
as bad as you described. The equations are linearised and then solved by an
iterative process. Usually the results are quite good and reproducable as
long as you make sure that a few conditions are met. The only problem I have
at the moment is including the evaporation of the moisture. However it looks
like this is not so much a numerical problem, but is due to an ill-posed
problem that is difficult to get rid off. I epxect that the same problem
would occur for neural network solutions or fuzy logic. I am familair with
chaos theory and I think that I can solve the problem by numerical
simulation. Still I have been thinking about the use of neural networks and
fuzzy logic. I am hardly familiar with these concepts and I would like to
hear more from you about this. (I am not quite sure if this list is a good
place to discuss these topics in detail, but you can send more info to my
personal address).

Further I stated what I would like to discuss on the list:
>> (again for developing countries). I would like to get a discussion along
>> these lines, with the addition of detailed user requirements. This last
>> point is probably difficult to get on this list.
>>
Tom's comment:
> -----------------------------------------------------------------------
> Outreach International is an organization that I have some contact
> with and friends in. They have people in the field on location making
> friends with users of wood stoves, so I am working on getting you and
> them together. Here is their e-mail address:
> <JNXC37A@prodigy.com>.
>
My reply:
I can only say that I hope that they will join us soon. Could you take care
of this?
>

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN
The Netherlands

From bhatta at ait.ac.th Sun Feb 11 23:33:42 1996
From: bhatta at ait.ac.th (S.C. Bhattacharya)
Date: Tue Aug 31 21:34:47 2004
Subject: stoves
In-Reply-To: <199602111848.MAA99296@audumla.students.wisc.edu>
Message-ID: <Pine.SOL.3.91.960212113137.20019B-100000@rccsun>

I would be interested to receive the copies of the two papers on packed
deep bed combustion/gasification you have mentioned in the email to stoves
group.

S.C. Bhattacharya

-------------------------------------------------------------------
S. C. Bhattacharya Voice : (66-2) 524 5403 (Off)
Professor 524 5913 (Res)
Asian Institute of Technology Fax : (66-2) 524 5439
GPO Box 2754, Bangkok 10501 516 2126
Thailand e-mail: bhatta@ait.ac.th
-------------------------------------------------------------------

From tduke at igc.apc.org Mon Feb 12 08:34:52 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:47 2004
Subject: Wood Stove Outreach (Liberia, Africa)
Message-ID: <199602121337.FAA23490@igc3.igc.apc.org>

Hi,

I showed Ron Larsons stove to a missionary from Liberia last night
and she has some advice and comments for us, so here they are.

A charcoal making wood stove will be very exciting to her friends
there especially the young people, because it will enable them to
make a little money by selling charcoal in the city.

They have trouble getting cans, and especially big cans (the 6 inch
diameter cans that Ron suggests. They have a better chance getting
smaller cans, so she is wondering if we can do something with them.
They have some buckets that have holes in them, so those buckets are
available for stoves.

She is concerned that the stove is not big enough. She feels it will
not be hot enough for long enough to get the job done, so she wonders
if we can make it bigger.

She talked about the cooking "pots" they are using and they seem to
be very large in diameter about 2 feet? and very heavy, so asked
about ways to hold up the pot so it doesn't crush the stove. I
suggested digging a hole in the ground to put the stove in and she
thought that would be a very good idea. Then we talked about the
stones they are already using to hold up the pot, so some combination
of stones and hole in the ground seemed like a good idea.

I am wondering about digging a hole in the ground for the wood
holding part of the stove. This would mean providing some way for
primary air to get to the bottom of the stack. So I am thinking of
cutting grooves around the side of the hole to let air down. There
would need to be a grate at the bottom, so I am thinking of stones or
other things they might be able to get to make a grate. The path for
the primary air could be a single tube, hole, groove, cut along side
the burning hole. Possibly with a cover on the groove to keep air
from leaking into the stack along the side.

She said she knows a group of young men who will get very excited
about the charcoal making wood stove and will stand around discussing
how to use the materials they have to make it work, if we can just
give them the basic idea, so she is asking for some drawings,
pictures and brief discription of the essentials. She wants to ship
these directions and drawings out in a container they are loading
right now, so she is asking for our help right away.

Thanks,

Tom Duke

From larcon at csn.net Mon Feb 12 11:54:29 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:47 2004
Subject: Response on Outreach
In-Reply-To: <199602121337.FAA23490@igc3.igc.apc.org>
Message-ID: <Pine.3.89.9602120906.A9010-0100000@teal.csn.net>

Comments below:

On Mon, 12 Feb 1996, Thomas Duke wrote:

> A charcoal making wood stove will be very exciting to her friends
> there especially the young people, because it will enable them to
> make a little money by selling charcoal in the city.

This worries me a good bit. This sounds like making charcoal
without using the waste heat. This will be more efficient in making
charcoal and will be better in a global warming sense, since the effluents
will just be CO2 and H2O, rather than CH4, CO and H2 and tars, etc.
However, young men cutting more trees for making charcoal sounds wrong. I
am hoping that charcoal making will be limited to women cooking meals (or
brickmaking, bakeries, etc.).

> They have trouble getting cans, and especially big cans (the 6 inch
> diameter cans that Ron suggests. They have a better chance getting
> smaller cans, so she is wondering if we can do something with them.
> They have some buckets that have holes in them, so those buckets are
> available for stoves.

In Ethiopia last year, I was depressed at the high price put on
the smallest cans, so I understand the better availability of small cans
(US$.50 for cans we throw away). I paid $2.00 (12 birr bargained down
from 14) for 20 liter (about 5 gallon) which is the size I think is
intended below. These are about 30 cm diameter and height and are about
the size of buckets which were about twice this price. They originally
were sold as food oil cans (from the US). The task may be to find the
right cooking task for the least expensive cans. But new metal was
almost the same price as old cans. I paid US$10 (60 birr) for a thicker
new metal sheet 1 m x 2 m. Local labor is often cheap enough to make
anything you need for a stove for a reasonable price if we think of the
stove as a money-making investment. Cans may be OK for cooking, but are
not necessary and are being promoted at first mainly as a cheap way to do
experiments.

> She is concerned that the stove is not big enough. She feels it will
> not be hot enough for long enough to get the job done, so she wonders
> if we can make it bigger.

If the job is making charcoal, it needs to be larger, but a 20
liter size lasted 2 hours - more than enough for almost all reasonable
cooking tasks. If local tradition requires simmering for four hours, it
may require two different batches.

> She talked about the cooking "pots" they are using and they seem to
> be very large in diameter about 2 feet? and very heavy, so asked
> about ways to hold up the pot so it doesn't crush the stove. I
> suggested digging a hole in the ground to put the stove in and she
> thought that would be a very good idea. Then we talked about the
> stones they are already using to hold up the pot, so some combination
> of stones and hole in the ground seemed like a good idea.
>
The twenty liter size was used with a 2 foot (60 cm) large griddle
(called a magogo), that had larger losses I believe than a similar pot.
It was fed by a conical feed from the 30 cm diameter can and worked well.
But the issue of support was not quite solved. I liked a tripod I tried,
but others thought it took up too much room. I also tried a metal 3-legged
"table", but I think this would be poor unless a perfect circle could be
obtained. I also bought bricks there and they worked fairly well.
Ethiopia has lots of stones, but I was told that many would break when
exposed to flames; I never got a chance to try it, since bricks were
available and easy to work with. I have been thinking about rebars
recently that are just pounded into the ground, but haven't tried them. I
am working now with concrete and pumice - a technology I saw being
developed for stoves in Addis Ababa. The point is that there are lots
of possible solutions - and it takes time to sort out the one that will be
best for particular cooking tasks in different countries.

> I am wondering about digging a hole in the ground for the wood
> holding part of the stove. This would mean providing some way for
> primary air to get to the bottom of the stack. So I am thinking of
> cutting grooves around the side of the hole to let air down. There
> would need to be a grate at the bottom, so I am thinking of stones or
> other things they might be able to get to make a grate. The path for
> the primary air could be a single tube, hole, groove, cut along side
> the burning hole. Possibly with a cover on the groove to keep air
> from leaking into the stack along the side.

This might work, but I have found it is critical to keep the
amount of primary air down. This sounds like too much air will leak
in. The beauty of a tin can is primarily that it is air tight. New or old
water buckets are probably OK and are probably a good analog
manufacturing technology - when locally made.

> She said she knows a group of young men who will get very excited
> about the charcoal making wood stove and will stand around discussing
> how to use the materials they have to make it work, if we can just
> give them the basic idea, so she is asking for some drawings,
> pictures and brief discription of the essentials. She wants to ship
> these directions and drawings out in a container they are loading
> right now, so she is asking for our help right away.
>
I doubt that the standard cook pot is as large as 2 foot
diameter, so I think we should be cautious of designing for that size,
although that could be one of several sizes. Also I'm worried about the
young men as the audience for making charcoal - unless they are, or could
be, in the stove-making business, for women. I may be wrong, but I don't
think we're ready to disseminate charcoal-making stoves yet anywhere, but
especially where we don't understand the culture at all. I strongly
support getting the idea to local developmental groups and hope that the
first descriptions of early January will describe the general
principles. But there are still problem areas - pot support and
extinguishment are the two most serious. I hope this group will discuss
these topics a bit longer before promoting the concept prematurely. The
idea of a world-wide competition is especially attractive in terms of
getting people to develop before disseminating.

Ron

From larcon at csn.net Mon Feb 12 11:57:45 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:47 2004
Subject: Majordomo results (fwd)
Message-ID: <Pine.3.89.9602120959.A9010-0100000@teal.csn.net>

I hope that we can send most messages to most of the still
relatively small group below. There are some addresses being used that
are not on the list shown below.

Ron

---------- Forwarded message ----------
Date: Mon, 12 Feb 1996 11:01:11 -0500
From:Majordomo@crest.org
To: larcon@csn.net
Subject: Majordomo results

>>>> who stoves
Members of list 'stoves':

From E.Moerman at stud.tue.nl Mon Feb 12 13:27:57 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:47 2004
Subject: stoves. To Kenneth Bryden
Message-ID: <70169.s335192@popserver.tue.nl>

I am interested to hear more about your models. I would therefore like to
receive the articles and any other publications that you have on your model.

I agree with you that most models have a very limited applicability, usually
only the pyrolysis, the char combustion or the flame spread are modeled.
Combinations of the two are very rare. As far as practical cases are
concerned I have never seen any inclusion of the effects of the moisture
content.

As far as wild forest fires are concerened I know that models exist and
experiments have been done. Usually these models concentrate on the flame
spread (upwind as well as downwind) as a function of tree density, etc.

Regarding the book you recommend I have to say that I have not yet come to
this point. At the moment I am modeling single pieces of wood (biomass) and
I am not yet ready to model the fuelbed. If I ever come to this point, I
will certainly checkout this book.

Thanks for the information. Please keep me informed.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN
The Netherlands

From tmiles at teleport.com Mon Feb 12 16:20:50 1996
From: tmiles at teleport.com (Tom Miles)
Date: Tue Aug 31 21:34:47 2004
Subject: Majordomo results (fwd)
Message-ID: <2.2.32.19960212212147.006f36a8@mail.teleport.com>

Ron et al,

Who's missing? I added Smith. I didn't find any others on previous copy
lists. Who did we miss?

Tom

At 10:00 AM 2/12/96 -0700, Ronal Larson wrote:
>
> I hope that we can send most messages to most of the still
>relatively small group below. There are some addresses being used that
>are not on the list shown below.
>
>Ron

E.Moerman@stud.tue.nl
verhaarp@cqu.edu.au
set@mt.luth.se
bryden@cae.wisc.edu
baldwins@tcplink.nrel.gov
tduke@igc.apc.org
73002.1213@compuserve.com
tmiles@teleport.com
prasad@tn7.phys.tue.nl
larcon@csn.net
krksmith@uclink4.berkeley.edu
westr@magellan.Colorado.EDU
vandema@earlham.edu
bhatta@ait.ac.th
asw@crest.org
andyo@inxpress.net
JATURNBU@EPRINET.EPRI.COM
smith@ewc.bitnet
----------------------------------------------------------------------------
-------
Tom Miles, Jr. Thomas R. Miles
tmiles@teleport.com, tmiles@ortel.org Consulting Design Engineer
http://www.teleport.com/~tmiles/ 5475 SW Arrowwood Lane
Tel (503) 591-1947 Fax (503) 292-2919 Portland, Oregon, USA 97225-1353

From tmiles at teleport.com Mon Feb 12 17:19:14 1996
From: tmiles at teleport.com (Tom Miles)
Date: Tue Aug 31 21:34:47 2004
Subject: Network procedures
Message-ID: <2.2.32.19960212222015.0071cf7c@mail.teleport.com>

Tom,

Thanks for the heads-up about my messages. I think I can solve that by
flipping the word wrap switch right on my mailer.

Some comments:

1. To reduce the number of server lines: address mail to stoves@crest.org
instead of to the long copy list. I just sent my own mail to my own CIS
address to see how it looks. When it gets there (in a few days :-)) I'll
tell you how it looks.

Letterhead. A signature file with the information you list is customary
on the internet. For most mailers it attaches automatically to the bottom of
each message. More than 4 lines is considered not "netiquette"

Internet Servers. Ron how do you like Colorado Supernet? It's an
alternative to CIS. The advante t CIS is that you can log in from almost
anywhere in the world.

>2) Tom Miles's latest communications didn't "word wrap" and would have
required a15 in wide paper to print out. Something busted.

Fixed, I think. We're testing.

>3) Do I need to store more permanently elsewhere? Should I concatenate
them into a more coherent whole (and get rid of the routing>garbage?) What
are you guys doing about this?
>
>Cheers TOM REED

Internet mailers like Eudora and Pegasus have filters that automatically
route messages into folders that you set up. So all the "stoves" messages go
into the "stoves" directory. Then you can go through and clean house once in
a while. It's the old filing problem. For CIS I use an offline reader
called Powwow. I haven't loaded the latest WinCim yet to see what it does.

Regards,

Tom Miles, Jr.
----------------------------------------------------------------------------
-------
Tom Miles, Jr. Thomas R. Miles
tmiles@teleport.com, tmiles@ortel.org Consulting Design Engineer
http://www.teleport.com/~tmiles/ 5475 SW Arrowwood Lane
Tel (503) 591-1947 Fax (503) 292-2919 Portland, Oregon, USA 97225-1353

From larcon at csn.net Tue Feb 13 00:20:36 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:47 2004
Subject: Network procedures
In-Reply-To: <2.2.32.19960212222015.0071cf7c@mail.teleport.com>
Message-ID: <Pine.3.89.9602122229.A20340-0100000@teal.csn.net>

On Mon, 12 Feb 1996, Tom Miles wrote:

> Internet Servers. Ron how do you like Colorado Supernet? It's an
> alternative to CIS. The advante t CIS is that you can log in from almost
> anywhere in the world.
>

I've been moderately happy, but during daylight hours, I'm
generally half speed. Also my costs are sneaking up. Can you supply a
little more data on CIS? I was frustrated in Africa by not having a
local line to call and still paying my monthly fee in Colorado.

Ron

From tduke at igc.apc.org Tue Feb 13 08:33:11 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:48 2004
Subject: Real World vs. World competition
Message-ID: <199602131335.FAA02158@igc3.igc.apc.org>

Hi,

Ships are safe in the harbor, but that is not what ships are made
for. Our stove design is to raise the quality of living for real
people in real cultures. So if we make a world competition we may
make as stove that is good at winning competion (like the America's
Cup yacht race) but no good for the dying people in liberia.

When we throw a life preserver to a man he does not ask many details
about it's boyancy, only will it hold him up. These men in Liberia
are dying and running out of wood, their families are starving, so I
donot feel they are concerned about details of the stoves combustion,
just can it save their lives.

In Apollo 13 Gene Kranz says something like: we have not lost a man
in space yet and we are not going to do it on my watch. I think it is
our resolve to lift humanity that holds this group together, so I am
infavor of directing our efforts toward desinging for the real needs
of real people as they exist now.

Sincerely,

Tom Duke

From tmiles at teleport.com Tue Feb 13 11:36:48 1996
From: tmiles at teleport.com (Tom Miles)
Date: Tue Aug 31 21:34:48 2004
Subject: Real World vs. World competition
Message-ID: <2.2.32.19960213163741.006bf85c@mail.teleport.com>

One of those real needs is the ability to use the only thing most people
have - sweat equity - to make charcoal that can be sold. If a stove design
can make saleable charcoal while recovering the 75% or so volatiles for
cooking meals then we have provided a means to satisfy an essential need,
generate income, and recover a scarce resource.

These requirements should be built into design categories for a stove
competition.

Tom

At 07:30 AM 2/13/96 +0000, Thomas Duke wrote:
I think it is
>our resolve to lift humanity that holds this group together, so I am
>infavor of directing our efforts toward desinging for the real needs
>of real people as they exist now.
>
>Sincerely,
>
>Tom Duke
>
>
----------------------------------------------------------------------------
-------
Tom Miles, Jr. Thomas R. Miles
tmiles@teleport.com, tmiles@ortel.org Consulting Design Engineer
http://www.teleport.com/~tmiles/ 5475 SW Arrowwood Lane
Tel (503) 591-1947 Fax (503) 292-2919 Portland, Oregon, USA 97225-1353

From larcon at csn.net Tue Feb 13 11:39:31 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: Real World vs. World competition
In-Reply-To: <199602131335.FAA02158@igc3.igc.apc.org>
Message-ID: <Pine.3.89.9602130901.A28310-0100000@teal.csn.net>

This is in response to Tom Duke's urging to move faster. I have no
objection to anyone trying a charcoal-making stove anywhere any time, but
I think we should recognize that all the world's improved stttve efforts
have not yet been really successful. This is a really rough task - and I
wouldn't put high odds of success on persons who don't have much idea of
what is going on inside a stove with as little testing as this one has had.
The people I have met overseas don't need a failure. My guess is that an
introducer who doesn't understand the principles has about a 10% chance
of success. Of course duplicating a successful shape and size has much
higher chance.

I also repeat that Tom's description sounded as the prospective users were
going to be young male charcoal-makers first or solely. I would like to
discourage that use of this stove - too large a part of the available
energy will be wasted. Tom: did I misinterpret your prospective users?
As bad as the situation is in Liberia for the young men, I'll bet the
situation is worse is for the women.

But Tom is correct that we shouldn't sit around and waste time either.

Any other thoughts on the desirability of speed vs. more knowledge and
answers first?

From asw at crest.org Tue Feb 13 21:00:59 1996
From: asw at crest.org (Andrew S. Waegel)
Date: Tue Aug 31 21:34:48 2004
Subject: test
Message-ID: <v01510112ad46827ade51@[198.68.224.49]>

this is a test of the stoves mailing list to ensure that all bells and
whistles are functioning normally. Please ignore this message.

-asw

...Andrew Waegel.asw@crest.org...Internet Services Manager...Center for
...Renewable Energy & Sustainable Technology...http://solstice.crest.org/

From tmiles at teleport.com Tue Feb 13 22:38:02 1996
From: tmiles at teleport.com (Tom Miles)
Date: Tue Aug 31 21:34:48 2004
Subject: Network procedures
Message-ID: <2.2.32.19960214033937.006c939c@mail.teleport.com>

Ron,
I don't know what people's aexperiences have been with CIS in Africa. I do
know they have access lines all over. Many of my friends in international
sales have CIS accounts for that reason.

Tom

At 10:23 PM 2/12/96 -0700, you wrote:
Can you supply a
>little more data on CIS? I was frustrated in Africa by not having a
>local line to call and still paying my monthly fee in Colorado.
>
>Ron
>
>
Tom Miles, Jr.
tmiles@teleport.com

From prasad at tn7.phys.tue.nl Wed Feb 14 04:01:15 1996
From: prasad at tn7.phys.tue.nl (prasad)
Date: Tue Aug 31 21:34:48 2004
Subject: Real World vs. World competition
In-Reply-To: <Pine.3.89.9602130901.A28310-0100000@teal.csn.net>
Message-ID: <9602140856.AA17170@tn7.phys.tue.nl>

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From tduke at igc.apc.org Wed Feb 14 23:04:04 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:48 2004
Subject: Real World vs. World competition
Message-ID: <199602150406.UAA25205@igc3.igc.apc.org>

Hi Ron and all,

I think Ron is raising some foundational issues, so I am responding
briefly below.

>
> This is in response to Tom Duke's urging to move faster. I have no
> objection to anyone trying a charcoal-making stove anywhere any time, but
> I think we should recognize that all the world's improved stttve efforts
> have not yet been really successful. This is a really rough task - and I
> wouldn't put high odds of success on persons who don't have much idea of
> what is going on inside a stove with as little testing as this one has had.
> The people I have met overseas don't need a failure. My guess is that an
> introducer who doesn't understand the principles has about a 10% chance
> of success. Of course duplicating a successful shape and size has much
> higher chance.

It is easy for us to get caught in the trap of exploring without
applying, so I want to elaborate on my intent. If Edison kept
developing his light-bulb untill it was just right before using what
he already knew for the benefit of man, then its comming would be
delayed a while, perhaps a long time, so I feel it is important that
we apply what we already know as we continue to develop. I feel that
it is in the process of struggling to apply our knowledge that our
thinking develops. I think we should do both (try to apply what we
know and develop more).
>
> I also repeat that Tom's description sounded as the prospective users were
> going to be young male charcoal-makers first or solely. I would like to
> discourage that use of this stove - too large a part of the available
> energy will be wasted. Tom: did I misinterpret your prospective users?
> As bad as the situation is in Liberia for the young men, I'll bet the
> situation is worse is for the women.

Sorry this raised a discussion about men and women, about cooking and
not cooking. I only repeated what my missionary friend told me in a
brief visit as she was looking at Ron's stove and getting very
excited about the potential it has in helping her Liberian friends.
>
> But Tom is correct that we shouldn't sit around and waste time either.
>
> Any other thoughts on the desirability of speed vs. more knowledge and
> answers first?
>
>
Onward and upward,

Tom Duke

From tmiles at teleport.com Thu Feb 15 00:16:57 1996
From: tmiles at teleport.com (Tom Miles)
Date: Tue Aug 31 21:34:48 2004
Subject: Real World vs. World competition
Message-ID: <2.2.32.19960215051833.006cf814@mail.teleport.com>

Why not set up a tiered strategy by categorizing the types and uses of cook
stoves developed to date? I think we'll find a spectrum that encompasses
different levels of efficiency and types of use.

My suggestion for a charcoal making stove stems from two or three sources.
First, charcoal has its uses and I don't think we'll ever move people away
from some form of charcoal. Second, charcoal has commercial value, even in
small quantities. Therefore it represents a cash income, however small, to
those who make it. Third, while testing the ZMart stove models mentioned
earlier, that allowed separate control of primary and secondary air, we
found that you could do useful work - boiling water, etc - with the volatile
portion of the fuel and be left with a very useable charcoal fraction. If
that charcoal is set aside each use it can accumulate.

The social context of stove manufacture, distribution or use is obviously
important. It too must be classified in some manner. There are probably some
"markets" where improved cookstoves are more acceptable than others. I don't
say sold because I do not see cookstoves as a cottage industry. I see them
more as a strategy to satisfy needs with scare resources and help to
conserve resources.

TOM MILES
Tom Miles, Jr.
tmiles@teleport.com

From bhatta at ait.ac.th Thu Feb 15 05:54:55 1996
From: bhatta at ait.ac.th (S.C. Bhattacharya)
Date: Tue Aug 31 21:34:48 2004
Subject: Cookstove round table: Time to sail (leave harbor)
Message-ID: <Pine.SOL.3.91.960215170918.9987B-100000@rccsun>

Nice to see the stove discussions warming up. One can observe a general
agreement in the group that it is desirable to move fast(er?). Going by
the decalred purpose of the stoves list (i.e. "promote development and
diffussion of improved biomass-burning stoves" - email of Ronal Larson
dated 7 Feb.) here are some random suggestions/thoughts:

1. The first step of an action program of the stoves group (SG) could be
to spend a few days (even weeks?) to shortlist a small number of promising
stove designs, e.g. charcoal-producing and downdraft stoves.

The second step could be deliberations among the SG members regarding
possible improvement in design features, materials of construction etc.

The third step could be for some of us to come forward to actually
to fabricate a stove according to agreed suggestions and test its
performance in one or (preferably) more institutions.

Further feedback from the SG can be used for improving the design.

Finally a phase of diffussion could start.

I am ready to explore funds fot the third and a few succeeding steps by
proposing a stove project for donor funding with the SG members
recognized/regarded as collaboratoring international experts.

2. I agree with Prof. Prasad's remark that charcoal making stoves are
(sort of) non-starter as household stoves. I have seen such a stove at IIT
Delhi and find the design to be inherently too cumbersome and bulky for
domestic use. However pros and cons of charcoal making stoves can be
considered in more details if we agree with the action program suggested above.

3. I agree with Prof. Prasad's remark that charcoal making stoves
could be interesting for small-scale industries. However, please note
that commercial/established techniques of carbonization with waste heat
recovery are already available. These can be regarded as very large
charcoal making stoves.

Perhaps we could consider charcoal making stoves for an intermediate scale,
e.g. restaurants, which are large but not very large compared to a cookstove.

S.C. Bhattacharya

From verhaarp at cqu.edu.au Thu Feb 15 09:10:41 1996
From: verhaarp at cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:48 2004
Subject: C.V. P.V.
Message-ID: <9602151413.AA15228@janus.cqu.edu.au>

Dear Stovers, all,

Let me follow the examples of Etienne Moerman and Tom Reed and give
you a (short) CV.

Piet Verhaart, born in The Hague in 1929. Travelled on a steamship
to the then Netherlands East Indies in 1931, both parents medical
professionals. Grew up in Batavia until October 1945, the last 3 years as a
Guest of Dai Nippon which brought the Greater Asian Co-Prosperity Sphere to
us. October 1945 to Melbourne to recover. I stayed to finish High School and
travelled to Holland in 1948.
Graduated from Delft University of Technology with the equivalent of M.M.E
in 1964. First job in a small company designing and building Freeze Drying
equipment.
Next job with Philips in Eindhoven, mechanical design of tuning elements.
Third job with the Eindhoven University of Technology, Faculty of Mechanical
Engineering, section for Fluid Machinery. Joined a group dispensing
technical advice by correspondence to individual development workers in 3rd
World countries. This led to a trip to Indonesia in 1971 to form ideas about
a cooperation project between EUT and the Bandung Institute of Technology on
small scale Hydro Electric Generating Plant in Rural Areas. In 1974 moved to
Bandung as Project Manager and guest lecturer and stayed for 4.5 years,
lecturing, coaching final year Engineering students and designing and
building Micro Hydro Turbines. Met my present wife, Irma Pasaribu in Bandung.
In 1978 back to Eindhoven with the idea that we had to do something about
wood burning cookstoves. Soon a student proved willing to do his final
assignment on woodstoves. Piet Visser is his name, he studied the open fire,
probably a first. At the same time Cor Nieuwvelt and Prasad, both working at
the Faculty of Technical Physics, had received requests to look into ways of
improving the performance of wood burning cookstoves and soon after the
Eindhoven Woodburning Stove Group was born.
I have worked part time in this group, with great pleasure, until my
retirement in 1990.
On retiring Irma and I swapped cold, overpopulated Holland (365 persons per
sq km) for warm, sparsely populated (2 persons per sq km) Australia, where,
we feel, one can breathe freely.
The last two years I have helped out at the Central Queensland University in
Rockhampton for a few hours a week, tutoring in Dynamics and correcting
Thermo lab reports. As compensation I can make use of the computer and thus
do E-mail.

(Co) authored several articles on downdraft stoves and edited (with Prasad)
Wood Heat for Cooking.

Father of none, husband to one. Sports pistol and rifle shooting, a cautious
game of tennis, member of the Field Naturalists, a group of people
interested in plants and animals.
I have been interested in snakes from a very early age and have come to the
right place, have had fascinating encounters.
Lots of time is spent in the shed where I have my workshop. I have almost
finished two experimental stoves, one to test an idea of mine, the second a
charcoal producing stove according to Ronal. Apart from that I spend a lot
of time on improving the quality of life on our property. I have been
talking of building a solar still to produce water of reasonable quality
for watering plants. Our bore water has about 2g/litre dissolved solids in
it. Anybody with ideas?
At times when I should be doing other things I like to read, also like to
listen to classical music and that about sums me up.

Regards to all,

Piet Verhaart
==========================================================================
P.Verhaart
Phone: +61 79 331761 Fax: +61 79 332112
E-mail: verhaarp@cqu.edu.au
Snail Mail: 6 McDonald St, Gracemere Q 4702 Australia
Mobile 015 581 262

From prasad at tn7.phys.tue.nl Thu Feb 15 09:30:31 1996
From: prasad at tn7.phys.tue.nl (prasad)
Date: Tue Aug 31 21:34:48 2004
Subject: Time to sail
In-Reply-To: <Pine.SOL.3.91.960215170918.9987B-100000@rccsun>
Message-ID: <9602151425.AA19327@tn7.phys.tue.nl>

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From E.Moerman at stud.tue.nl Thu Feb 15 13:10:42 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:48 2004
Subject: Let's take action
Message-ID: <69130.s335192@popserver.tue.nl>

I agree with the comments made by Thomas Duke, Prasad, Tom Miles on 'Real
World vs World Competition' over the last few days. By the way, what is the
state of affairs on the stove competition.

I especially agree with Thomas Duke that we should not keep talking, but do
something. However I also agree with (I think it was) Ron Larson that we
cannot promote stoves that are not tested. Prasad and Piet will have the
details of the example of the 'Family Cooker'. As far as I know this stove
was promoted for a number of years as efficient and clean. However tests at
Eindhoven showed that it was less efficient than a well tended open fire
(admittedly in the lab). Furthermore it was hardly no cleaner than any
other stove and in addition there was a risk of explosion under certain
circumstances.

I suggest that we try to find out as many user demands as we can for a
specific case. We than select the three stoves that look most useful in that
situation and try an improve it until it meats most of the user demands.
This is more effective than everybody working on his/her own stove. In
addition to this I think we should have a general discussion about the
direction into which we want to move. Do we really want to promote the use
of charcoal? Like Prasad I am not in favor of this, in fact I think we
should look at ways to shift the small-scale industries that are now using
charcoal towards wood, since this has a higher overall efficieny.

As far as the user demands are concerned I will put a list of it on
the stoves-list. I hope I will be able to do this in the next few days,
otherwise you'll have to wait until the end of next week. The list was
described by Krishna Prasad, Piet Verhaart and Paul Bussmann.

As stoves worthwile of more attention I propose Ron Larson's charcoal
producing stoves which has some interesting possibilities (not the charcoal
production in my view) and the shielded fire which is cheap to produce and
very efficient.

In answer to Tom Miles. Piet Verhaart already made a categorization of
cooking tasks. From the top of my hat:
boiling, frying, deep-frying, parboiling, steaming, grilling, keeping the
food warm, smoking, baking.
Did Ileave out anything?

I hope this little piece of writing will spark off some more discussion, but
most of all some action.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From E.Moerman at stud.tue.nl Thu Feb 15 13:29:47 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:48 2004
Subject: Cookstove round table: Time to sail (leave harbor)
Message-ID: <70275.s335192@popserver.tue.nl>

After sending my message I found aout that Bhattacharya had virtaully the
same ideas, so my mail was a bit superfluous. I am sorry about that.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From larcon at csn.net Thu Feb 15 16:17:26 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: Response to Prasad on charcoal-making stoves
In-Reply-To: <9602140856.AA17170@tn7.phys.tue.nl>
Message-ID: <Pine.3.89.9602151402.A10300-0100000@teal.csn.net>

Stoves Group - This is in response to the Prasad message of 14 Feb.

1. Prasad said: ".. the charcoal making stove .. must be a
non-starter. ... it is vital for us to separate primary and secondary air."
I hope this separation has been made clear previously - as well
as that control is possible and even mandatory for the primary air.

2. Prasad: "There is no cookstove in the developing world that has
sold even a 1000 in number with such a stove."
I would love to know who has sold any - for purposes of speeding
up (or maybe terminating) the development process. The nearest I've seen
is one attributed to Professor Grover - but this had no primary air
control. Professor Tom Reed developed one similar with forced draft (no
chimney) and, I believe, a focus on gas production rather than
charcoal-making and cookstoves.

3. Prasad: "At Eindhoven we have worked on such stoves, but not with
the purpose of producing charcoal but for the purpose of reducing the
minimum power level of a stove. For a description, see:
"Woodburning Cookstoves" by K.Krishna Prasad, E.Sangen and P.Visser, in
Advances in Heat Transfer, vol.17, pp 159 - 317, Academic Press, 1985."
Having obtained this yesterday, I can now strongly recommend this
article as an excellent survey. There are numerous references close to
the topic, but as Prasad notes - there is nothing there on making
charcoal. On p212 of this article, the authors state, relative to air
control: "So the controlling action can only influence the flow through
the stove in a very limited way, because the main governing resistance is
confined to the annulus."
Unfortunately, I think that one cannot extrapolate from these
authors' experiences - because Eindhoven always had to have enough air
to burn up the charcoal - which was at the bottom of the "updraft" batch,
not the top. Had this article addressed downdraft stoves, I would be
more concerned about the supposed inability to use air flow to control
power levels. I strongly agree with Prasad on the importance of air
control for power control purposes. It is my belief that we can achieve
about a turn-down ratio of about 5. It may even be larger if the
smallest material is placed on the top of the stack.

4. Prasad: "Apart from this there is the question of selling charcoal
which presumably is sold in cities. Collection, storing, and marketing
this charcoal is a mind-boggling organizational problem. Please let us
have a sense of proportion before advocating such ideas."
On p 181 of the above article, the authors state (after
cleanliness and power control advantages) for charcoal: "The third point
in favor of charcoal is that there exists a well-developed marketing
system for the fuel as well as the appliance."
My experience in Kenya, Sudan and Ethiopia (but not Zimbabwe)
strongly supports this observation. In these counties, charcoal is
available for sale everywhere - from less than a kilo up to 50 kilo
bags. It is my sense that this may be the single largest industry in
Sudan; bags are for sale along every rural highway as well. Rural or
urban charcoal-making stoves can save about 2 out of 3 trees already
being cut as the 70% loss of energy in present-day charcoal making is
removed. The cost of charcoal might go down as competition increases -
helping charcoal users substantially. The concept of a charcoal-making
stove may not go over everywhere, but my Sudanese and Ethiopian friends
have expressed no doubt that it has a potential place in their countries.

5. Prasad: "...silver lining ...small scale industrial .. brick
making...professionalism ..marketing...useful to look into such
applications."
I agree that such industrial applications as brickmaking is an
important possibility and perhaps should even be the first test.
However, I think this stove has such sufficient potential for all (not
just a few) of the other reasons (higher efficiency, cleaner, easier to
use) for introducing improved stoves, that one cannot ignore the rural
(and maybe the urban) charcoal-making cookstove opportunity as well.
Despite these other advantages, I believe it is primarily the possibility
of charcoal sale that will drive sales. It is my impression that
something new is needed to reinvigorate the stove development effort.

6. Prasad: "I have written ...need postal addresses.
I very much look forward to hearing more on your (anyone's) past
research in this charcoal-making cookstove area . It is my perception
that although the "inverted downdraft" (Tom Reed's preferred
nomenclature) stove is substantially similar to downdraft gasifiers, it
is the production and selling of charcoal that makes the stove design
both easier and more salable. That design activity is not yet complete.

Ron Larson
21547 Mountsfield Drive
Golden. CO 80401

From larcon at csn.net Thu Feb 15 16:33:12 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: Response to Bhattacharya
In-Reply-To: <Pine.SOL.3.91.960215170918.9987B-100000@rccsun>
Message-ID: <Pine.3.89.9602151426.A10300-0100000@teal.csn.net>

I like very much the proposal from Professor Bhattacharya. Just
a few additional small comments.

On Thu, 15 Feb 1996, S.C. Bhattacharya wrote:

> I am ready to explore funds fot the third and a few succeeding steps by
> proposing a stove project for donor funding with the SG members
> recognized/regarded as collaboratoring international experts.

This has been a substantial stumbling block. Good luck

>
> 2. I agree with Prof. Prasad's remark that charcoal making stoves are
> (sort of) non-starter as household stoves. I have seen such a stove at IIT
> Delhi and find the design to be inherently too cumbersome and bulky for
> domestic use. However pros and cons of charcoal making stoves can be
> considered in more details if we agree with the action program suggested above.
>
I believe this was the "Grover pyrolyzer". I saw one in Harare
and another felt to be an improvement. Neither contained a primary air
control and they seemed to be designed to pyrolyze small material - not
to make charcoal. What is your ( or anyone's) recollection on this point?

> 3. I agree with Prof. Prasad's remark that charcoal making stoves
> could be interesting for small-scale industries. However, please note
> that commercial/established techniques of carbonization with waste heat
> recovery are already available. These can be regarded as very large
> charcoal making stoves.
>
I hope you will give a little more data on this. Are these
downdraft gasifiers?

> Perhaps we could consider charcoal making stoves for an intermediate scale,
> e.g. restaurants, which are large but not very large compared to a cookstove.
>
I agree that this could be interesting - but stoves for
residences also may be easier. As the stove gets bigger, getting the
secondary air to the interior becomes more difficult (not impossible).

Thanks for your contribution.

Ron

From larcon at csn.net Thu Feb 15 16:42:53 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: Response to Prasad of 15 Feb.
In-Reply-To: <9602151425.AA19327@tn7.phys.tue.nl>
Message-ID: <Pine.3.89.9602151457.A10300-0100000@teal.csn.net>

On Thu, 15 Feb 1996, prasad wrote:

> Hi, Stove Folks

> are doing the work on their own. While this is as things should be, I get a
> feeling that they can use all the help they can get.

I agree wholeheartedly. I see this as the most serious problem
facing the most poor - and that the world is doing way too little.

>
> The reason I state this arises out of a recent article in "Scientific
> American" (July 1995) by Kammen. The article is deafeningly silent about the

I today placed Dr. kammen on the list, so perhaps he will be able
to repond on this point when he returns from a present trip.

>
> More on the competition bit tomorrow.
>
Great. I saw a nice list of desired stove characteristics in an
article by Piet Verhaart. Piet? I want to see on that list that the
stove should be an income generator.

> Here are a couple of additional addresses who are likely to be interested in
> this group.

The Visser address seemed OK, but not that for Dr. Ellegard.
Could you or someone check that one?

I see many other good names (most associated with Eindhoven) who
are not yet signed up. Any more I can add?

Ron

From verhaarp at cqu.edu.au Fri Feb 16 01:35:57 1996
From: verhaarp at cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:48 2004
Subject: Time to sail
Message-ID: <9602160638.AA22867@janus.cqu.edu.au>

>From Piet Verhaart

Hi, Stove Folks
Some loose comment on today's E-mail harvest
To Prasad Re Kenya Stoves:
Hear, hear!. Glad we didn't urge you to have your tongue beaten into
a ploughshare upon retirement!
Yes, I remember reading the article (only partly probably) and thinking
something like, "yeah, one of them".

About categorical statements on primary and secondary air from Eindhoven. To
my knowledge we never investigated the role of primary air in a setup like
Ron's. The closest we ever came to it was when we force fed air up through a
grate and a thick fuelbed. The fuelbed was lighted on top and I remember
noting the good appearance of the combustion. In a few days I will be able
to find out for myself how Ron's stove performs.

I agree that the criterion for disseminatable stoves is the ease of use
first and the economical use of wood second. If it makes charcoal as well
that is fine but that aspect should not be considered very seriously if it
is more difficult to handle than other stoves.

As for our Eindhoven downdraft stove, the difficulty is making use of the
heat generated. One way would be to have a hot steel or cast iron plate on
top of the combustion space downstream from the grate, like an electric hot
plate, on which a flat bottomed pan is placed. I know these things are not
universally available, certainly not to the very poor. But what can the
very poor afford, nothing per definition and I don't believe in everybody
D.I.Y - ing (just ask Prasad). The thing to hope for is a filtering down
effect from those who can afford good stoves.

Ron had trouble locating Mr.Anders Ellegard. If the man is in Sweden, then
the address should have a two letter indication of the country at the end,
possibly se.

That is all for now, I am going do do another stint at the charcoal
generating stove now that the worst heat of the day is gone, the time being
16.35. To think that for Ron c.s. the day has just begun.

See youse later!

From prasad at tn7.phys.tue.nl Fri Feb 16 04:01:20 1996
From: prasad at tn7.phys.tue.nl (prasad)
Date: Tue Aug 31 21:34:48 2004
Subject: Time to sail
In-Reply-To: <9602160638.AA22867@janus.cqu.edu.au>
Message-ID: <9602160856.AA20406@tn7.phys.tue.nl>

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From tduke at igc.apc.org Fri Feb 16 15:49:05 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:48 2004
Subject: Whole world vs. Third World Applications
Message-ID: <199602161725.JAA25989@igc3.igc.apc.org>

Hi all,

One question we are often asked when introducing new technology to
Third World countries is this: "If this technology is so good why
aren't you using it yourself." So I am beginning to think how this
stove technology applies to my near-by neighbors. Many of our
neighbor fram families are suffering because the price of grain has
been so low for so long. More are suffering because we have had to
change some of our tillage practices to save soil, causing a
signigicant loss in yeild. Jane T. of NREL suggests that we should
grow switch-grass and trees to truly save soil. So I am wondering if
we can apply any already known stove technology to converting
switch-grass and trees into a valuable product, perhaps electricity.

Even a 1kW generator can supply all of our electrical needs and save
us $1,000.00 U. S. per year. 20kw will doubble our income. I have
steam power data from people with this address:
The Steam Outlet
P. O. Box 1426
Thonotassassa, FL 33592
They say this: "A wood fired, fire tube boiler will burn about 2
pounds of seasoned hardwood per hour per HP, i.e. one 5 HP boiler
will use approximately 10 pounds of wood per hour to keep it going
once everything is hot. So I am wondering if we can do better then
this?

Also I would prefere to use Stirling engines instead of steam, so to
avoid the problems with steam boilers. Again I am working with Dr. L.
C. Anderson of Iowa State University concerning growing sweet sorghum
on some of our non-errodiable land, which is expected to yeild 50
tons per acre, so I am wondering if this can be used as fuel. I also
have some solar ovens and think I can use solar heat to provide some
of the heat some of the time directly from the sun, so I am saving
some of the biomass. There are times that the primary and secondary
air can be solar heated. One solar cooker design I have can provide
air at 600 degrees F.

So I am wondering if the work and discussions we are having about
Third World countries can apply to my friends and neighbors here in
Iowa U. S. A.? Can we learn something from trying to design systems
for people like in Liberia that cannot even aford to buy used tin
cans that applys here in Iowa?

Thanks again,

From E.Moerman at stud.tue.nl Fri Feb 16 17:17:09 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:48 2004
Subject: Forced draft,....
Message-ID: <83917.s335192@popserver.tue.nl>

Tom Reed-

I would like to make a remark about downdraft stoves. You seem to have the
impression that downdraft stoves require forced draft. While this might be
true for downdraft gasifiers it is not the case for downdraft stoves.
Sufficient draft is obtained for chimneys as small as 0.6m while 1m chimneys
provide more than enough draft. These lenghts are smaller than those of
other chimney stoves and small enough to be
practical. The temperatures that we reached with the downdraft stove were
between 1300-1500 K, so the downdraft principle might be very useful as a
forge for melting metals.

About batteries for draft. What are we thinking of. People in South Africa
cannot afford batteries. That is why a hand powered radio was developed and
is a great succes. Why than would they want to spent money for batteries for
their stove. Keep in mind that commercially successful stoves cost only a
few US$. We should not be blind to the specific needs, opportunities and
limitations that are imposed by prevailing conditions. This applies to
developing as well as to developed countries. People that can afford
batteries to provide the draft for a woodstove will switch to kerosene or
LPG. You see this happening all over the world.

Mind you all this doesn't mean that we have to stop working on woodstoves or
for research purposes not use high tech materials. However we should always
keep in mind who we are trying to help.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From E.Moerman at stud.tue.nl Fri Feb 16 17:17:25 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:48 2004
Subject: Whole world vs. Third World Applications
Message-ID: <83937.s335192@popserver.tue.nl>

Thomas,

Of course we can design and produce generators burning wood for
developed countries. However there is a profit here and as a result work on
this has been done and I know of 2 commercially available woodburners. As
far as I remember the price was someting like 1500-2000 US$. I don't know if
I will be able to dig up details.

Regarding solar enery for heating the air supply. This sounds interesting,
however if this is an economic option I don't know. I will certainly look
into this.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From larcon at csn.net Fri Feb 16 23:29:30 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: A first list of desired stove specs
Message-ID: <Pine.3.89.9602162101.A3403-0100000@teal.csn.net>

Greetings to the stoves group

Yesterday, I left an obscure (because I had forgotten where I had
seen it) reference to a Verhaart list of seven stove specifications,
intended to move forward the Bhattacharya plan of attack from a few days
ago. Probably even Piet didn't know what I meant - so here is the
Verhaart list (from "Wood Heat for Cooking", ed. Prasad and Verhaart,
Indian Academy of Sciences, 1983, p43). The square brackets are changes
I would make:

1. At least half of the heat liberated by the wood on combustion
should get transferred to the pan [or two-thirds of energy when charcoal
or other useful by-products are produced].
2. The heat output rate can be varied from full power (100%) to
about 15% of full power.
3. The change from full power to minimum power and vice versa
must be achieved within 30 [5?] seconds.
4. No dangerous, noxious or poisonous gases may be given off
[during normal operation].
5. Pans must remain clean on the outside.
6. No other (auxiliary) energy sources such as electricity may be used.
7. Easy to light, full power is liberated within 2 minutes after
a cold start.

Here are 8 more possible specs that come from contemplating
Piet's excellent Figure 1 from the above paper (entitled "Considerations
that may influence stove design":

[8. Able to perform at least two (e.g. simmering and frying)
cooking tasks.]
[9. Must pose no burn or fire safety hazard.]
[10. Easy to operate, taking less time to cook than existing
alternatives, and requiring fuel additions or air control no more
frequently than every __ minutes.]
[11. Should have an economic payback in fuel savings and/or
salable by-products not exceeding __ months, when compared to the
available alternatives.]
[12. Should have an expected lifetime of at least __ years.]
[13. Should be able to accept a pot diameter range of at least
+/- ___ % from the optimum.]
[14. Should have design power variation capability such that a
water quantity up to __ liters can be brought to a boil in less than __
minutes.]
[15. Allow portability and alternative cooking postures when so
desired by the user.]

I think the charcoal-making stove can do most of the above, with
perhaps the most serious problems for item #5 (pot cleanliness). I have
changed item #1 because I think we should encourage by-product designs,
item # 3 because 30 seconds seems too long for convenient use, and item #
4 because every known stove already is hazardous when used improperly. I
add 8 specs as possibly worth consideration. I have left six blanks to
encourage general discussion.

Any other changes or additions to this list of specs?

The article by Prasad, Sangen, and Visser (Advances in Heat
Transfer, 17, p 159 ff, 1985) covers many of these same issues. I liked
these sentences from the Concluding Remarks (p308), as an introduction to
the next design phase:

"Stove research as described in this work is really in its
initial stages. While the information can result in improved designs, it
falls short of providing a set of design charts that could be used to
develop stoves with a minimum amount of additional experimentation. One
of the priority areas of work is the generation of a set of performance
curves for a wide range of design and operating conditions -things that
we take for granted for equipment such as centrifugal pumps, internal
combustion engines, electric motors, etc. This is engineering work in the
classic style requiring diligent effort."

My guess is that Prasad would say that these thoughts are still
correct 11 years later. I'm sure everyone will agree for charcoal-making
stoves, as apparently there are none in regular use. Does anyone
disagree for any other type woodburning cookstove?

Regards

Ron

From verhaarp at cqu.edu.au Sat Feb 17 02:18:59 1996
From: verhaarp at cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:48 2004
Subject: First trial charcoal making stove
Message-ID: <9602170721.AA06558@janus.cqu.edu.au>

Dear Tom,
Last night I finished my charcoal making stove. It consists of two
sections of equal length, 300 mm, of old steel pipe with an inside diameter
of 115 mm. The bottom section is closed off with a 3/4" pipe and elbow
connected to a small valve to feed compressed air. The top section is
connected to the lower section with 3 lugs and 10 mm bolts so that I can
create a slit from 0 to 30 mm wide at the top of the bottom section.
This morning I took it out and filled the bottom section with pieces of dry
wood, probably silky oak or paperbark (from a tree trunk that landed on our
property during the 1991 floods) roughly 30 * 50 mm, right to the top. It is
quite a dense and hard kind of wood.
Lighting it was easy (with a propane burner, an indispensible piece of
equipment). Well, we produced quite a lot of smoke. The stove burned for 55
minutes. After about 30 minutes I turned the air up until there was a nice
mass of flames in the upper section. No smoke but a slight smell
(aldehydes?). I kept up the high air flow until the flames lost most of
their colour. I turned off the air then and the stove emitted thin smoke
with a tarry smell so I concluded that the charring process had been completed.
Clearly I will need a flowmeter for the air and do a lot more fiddling
around and use scales etc.
I have taken photographs in the hope of one day soon having a colour scanner
and being able to attach pictures. With my server I can attach, I received a
.WAV file from Eindhoven the other day which I could play. Lots of bytes.
There will be more experiments but first I have to cool down in my
airconditioned study for a while. We are, I believe, having rather similar
outdoor temperatures, the only difference being the sign ( in C).
Now here is hoping the University computer will be back to normal, earlier
this morning it kept disconnecting me while admitting to an error.
See you later.

From larcon at csn.net Sat Feb 17 11:27:17 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: New Recruit Elderly Woodstove Research
In-Reply-To: <9602170721.AA06132@janus.cqu.edu.au>
Message-ID: <Pine.3.89.9602170952.A2682-0100000@teal.csn.net>

Piet: I hope you don't mind my sending this response to the full group,
since it starts the desired discussion.

On Sat, 17 Feb 1996, Peter Verhaart wrote:

> Dear Ron,
> This is to let you know I thought of another woodstover who might
> possibly join our club. He is Dr. John Todd at the University of Tasmania in
> Hobart. He has been involved in space heating woodstoves (are used a lot in
> Tas) and has been instrumental in setting up emission regulations.
>
I have sent his name in. This will sort of introduce John to the
group. Thanks.

> Re. the list of desired stove characteristics: Generating income seems
> rather a distant gaol to achieve. I think it would be great if newly
> developed woodstoves decrease hardship for the user e.g. less wood to gather
> for the daily cooking tasks, less attention required to keep it going, less
> smoke, more comfortable position etc.
>
Maybe I'm wrong, but I think that income geneation is the most
important item on the list. I believe that husbands will buy stoves for
income generation when they won't for all the other reasons. The
charcoal - making is important as a way of discouraging the present means
of making charcoal - which should be outlawed because of the
global-warming gases produced - all much worse than CO2.

> We are getting together a great group of talent, I am sure something good
> will come out of it.
>
> Best regards,
>
> Piet Verhaart

I agree on both of your last two points.

Ron

From larcon at csn.net Tue Feb 20 20:08:04 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: Questions on Verhaart's First trial charcoal making stove
In-Reply-To: <9602170721.AA06558@janus.cqu.edu.au>
Message-ID: <Pine.3.89.9602201745.A12469-0100000@teal.csn.net>

Questions below:

On Sat, 17 Feb 1996, Peter Verhaart wrote:

> Dear Tom,
> Last night I finished my charcoal making stove. It consists of two
> sections of equal length, 300 mm, of old steel pipe with an inside diameter
> of 115 mm. The bottom section is closed off with a 3/4" pipe and elbow
> connected to a small valve to feed compressed air. The top section is
> connected to the lower section with 3 lugs and 10 mm bolts so that I can
> create a slit from 0 to 30 mm wide at the top of the bottom section.
> This morning I took it out and filled the bottom section with pieces of dry
> wood, probably silky oak or paperbark (from a tree trunk that landed on our
> property during the 1991 floods) roughly 30 * 50 mm, right to the top. It is
> quite a dense and hard kind of wood.

I believe that at this diameter, the upper pipe could be
appreciably shorter - especially if you have forced draft. I hope you'll
try a shorter piece here at some point. I am concerned about your wood
shape also. Is the length 50 cm? I have found that the resistance is
too high for a natural draft when chips are used. Let me urge you to
also try long branches of diameter 20-30 mm.

> Lighting it was easy (with a propane burner, an indispensible piece of
> equipment). Well, we produced quite a lot of smoke. The stove burned for 55

I hope you'll try small scrap material for starting soon.
Lighting is very easy with the upper cylinder draft. But I'm worried
about the smoke. What was the gap spacing? How long did the smoke last?
I never get smoke for very long.

> minutes. After about 30 minutes I turned the air up until there was a nice
> mass of flames in the upper section. No smoke but a slight smell

Where did the flame seem to attach? Any sense of the difference
in power levels for the second case (which I gather was acceptable)?
I only have smelled something when I burned a (buffalo gourd) rootfuel.

> (aldehydes?). I kept up the high air flow until the flames lost most of
> their colour. I turned off the air then and the stove emitted thin smoke
> with a tarry smell so I concluded that the charring process had been completed.
> Clearly I will need a flowmeter for the air and do a lot more fiddling
> around and use scales etc.

Would you say that the charcoal looked good? Any weight
measurement yet? Can you turn off the compressed air and still allow
primary air in?

> I have taken photographs in the hope of one day soon having a colour scanner
> and being able to attach pictures. With my server I can attach, I received a
> .WAV file from Eindhoven the other day which I could play. Lots of bytes.
> There will be more experiments but first I have to cool down in my
> airconditioned study for a while. We are, I believe, having rather similar
> outdoor temperatures, the only difference being the sign ( in C).
> Now here is hoping the University computer will be back to normal, earlier
> this morning it kept disconnecting me while admitting to an error.
> See you later.
>
> Piet Verhaart

I am quite uncertain on whether an air compressor can be of help
in the testing. It seems that the pressure difference will be quite
different inside the stove and that the secondary air will be fouled up as
the natural draft amount will be influenced adversely. Or do you have two
separate air supplies? (which Tom Reed is using).

I have seen no modeling results that print out the pressure
throughout any stove; can anyone provide a reference with such? I'm not
sure whether the pressure in the pyrolysis zone is more or less negative
than that in the upper combustion zone.

Lastly, are you now encouraged or discouraged to believe that a
charcoal-making stove might be accepted by rural users?

Regards,

Ron

From JATURNBU at EPRINET.EPRI.COM Tue Feb 20 23:08:39 1996
From: JATURNBU at EPRINET.EPRI.COM (Turnbull, Jane@G&S M)
Date: Tue Aug 31 21:34:48 2004
Subject: Questions on Verhaart's First trial charcoal making stov
Message-ID: <MSM.JATURNBU.824609200096051FMSM@EPRI.COM>

I really don't know much about stoves - except to appreciate those that work,
though I'm learning. In any case, I think that the international interaction
and sharing of experience that I've been privileged to view reflects the best
that our WWW offers and is intended to offer. I'm really hoping that this
results in a product. Granted it would not be one that might be marketed over
the WWW, but it would demonstrate that international sharing of concerns and
ideas has a whole lot of merit.

Guess I am reacting - or perhaps over-reacting - to Pat Buchanan's lead in the
New Hampshire (US) primary. We have so much to gain from working
collaboratively. But there remain elements of isolationism (Neandrathalism)
still to contend with.

I am hoping to meet Ron next week at the village power meeting in D.C. because
that is a topic on which I can converse more readily.
Jane
_______________________________________________________________________________
From: SMTP.STOVES on Tue, Feb 20, 1996 5:28 PM
Subject: Questions on Verhaart's First trial charcoal making stove
To: ÿÿSTOVESÿ(SMTP.STOVES); Turnbull, Jane@G&S Mail Center #2230

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Date: Tue, 20 Feb 1996 18:10:55 -0700 (MST)
From: Ronal Larson <larcon@csn.net>
Subject: Questions on Verhaart's First trial charcoal making stove
To: stoves@crest.org
In-Reply-To: <9602170721.AA06558@janus.cqu.edu.au>
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Questions below:

On Sat, 17 Feb 1996, Peter Verhaart wrote:

> Lighting it was easy (with a propane burner, an indispensible piece of
> equipment). Well, we produced quite a lot of smoke. The stove burned for 55

> minutes. After about 30 minutes I turned the air up until there was a nice
> mass of flames in the upper section. No smoke but a slight smell

> (aldehydes?). I kept up the high air flow until the flames lost most of
> their colour. I turned off the air then and the stove emitted thin smoke
> with a tarry smell so I concluded that the charring process had been
completed.
> Clearly I will need a flowmeter for the air and do a lot more fiddling
> around and use scales etc.

Would you say that the charcoal looked good? Any weight
measurement yet? Can you turn off the compressed air and still allow
primary air in?

Lastly, are you now encouraged or discouraged to believe that a
charcoal-making stove might be accepted by rural users?

Regards,

Ron

From prasad at tn7.phys.tue.nl Wed Feb 21 10:19:37 1996
From: prasad at tn7.phys.tue.nl (prasad)
Date: Tue Aug 31 21:34:48 2004
Subject: Questions on Verhaart's First trial charcoal making stove
In-Reply-To: <Pine.3.89.9602201745.A12469-0100000@teal.csn.net>
Message-ID: <9602211514.AA26586@tn7.phys.tue.nl>

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From larcon at csn.net Wed Feb 21 11:32:41 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: Reply to Jane Turnbull on Buchanan
In-Reply-To: <MSM.JATURNBU.824609200096051FMSM@EPRI.COM>
Message-ID: <Pine.3.89.9602210942.A24700-0100000@teal.csn.net>

Comments below

On 20 Feb 1996, Turnbull, Jane@G&S M wrote:

> Guess I am reacting - or perhaps over-reacting - to Pat Buchanan's lead in the
> New Hampshire (US) primary. We have so much to gain from working
> collaboratively. But there remain elements of isolationism (Neandrathalism)
> still to contend with.

To those outside the US, who wonder about how Buchanan can win a
primary, I think that Jane and I would agree that it is
incomprehensible. Fortunately, it seems that his win in New Hampshire is
possible only because his supporters are more fervent; they are not more
numerous.
He has a comic line that really bugs me when he mentions Earth
Day in one sentence and then laughs about worshipping "dirt". I spend a
fair amount of time with a local Earth Day group - so if he somehow gets
more support, I'll have to drop off this group in order to work for his
defeat full time.

> I am hoping to meet Ron next week at the village power meeting in D.C. because
> that is a topic on which I can converse more readily.
> Jane

Jane is modest - she runs a major biomass program for the
Electric Power Research Institute (EPRI). But I look forward to meeting
Jane (for the first time) at that meeting - along with Sam Baldwin and
Dan Kammen. Anyone else going to be there? (Feb28-29, $50)

That reminds me that the World Renewable Energy Conference (WREC)
is held in Denver this June. I can offer free lodging for anyone
thinking about that meeting.

I am working on a response for Prasad's message today.

Ron

From E.Moerman at stud.tue.nl Wed Feb 21 15:29:12 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:48 2004
Subject: Modelling of pressure in a stove
Message-ID: <77456.s335192@popserver.tue.nl>

Ron-

In Paul Bussmann's thesis pressure modelling is described. Also pressure
measurements are described. A few years back
I rewrote the original program Paul made to incorporate the pressure in the
way he described in the thesis.

Furthermore I think a compressor can be helpful in experimenting as long as
it is done with the utmost care. THis however is quite difficult when no
pressure or gas analyzers and balances are used.

By the way Ron or Tom I think mentioned to be in the possesion of a balance
with a range of 50kg and an accuracy of 0.1g costing at a few thousand $. Is
this correct. The best accuracy I found until now was 1g in that range.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From larcon at csn.net Wed Feb 21 23:46:17 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:48 2004
Subject: Comments on Prasad paper
In-Reply-To: <9602211514.AA26586@tn7.phys.tue.nl>
Message-ID: <Pine.3.89.9602212112.A21286-0100000@teal.csn.net>

Prasad:

Your last question in your e-mail of 20 Feb. was on which
publications I had received. In fact, I have spent the last day reading
what might have been the intent of your question - possibly your most
recent (?) article, entitled "Off-Design Performance of Woodburning
Cookstoves" (Journal of Energy, Heat and Mass Transfer, Vol. 15, pp.
21-44, 1993). Thank you for sending that. I will get the others all
together, and summarize them soon. You can see I am reading them, since
I have quoted a few recently, and I have enjoyed them all. You and your
Eindhoven group have done a lot of excellent work on a very difficult topic.

Your "Off-Design" article makes it clear why you (and others
from Eindhoven) have been so skeptical on claims for a charcoal-making
stove, so I feel I must try to explain the differences I see between the
charcoal-making stove and those you have analyzed. Your skepticism,
which I hope to reverse, is nicely summarized in your last paragraph
(p43):
"To conclude, it is FUTILE (emphasis added) to believe that there
exists a high performance stove - by which I mean that efficiencies hover
around 50%, combustion qualities are high, maximum to minimum power
ratios are around 4 or higher - that is catholic in it taste for fuel."

Although I have been claiming most of the above are possible, let
me emphasize that we agree on your last point. Specifically, I think
most charcoal-making stoves will be poor in burning charcoal, dung, small
scraps and chips, or very large pieces. However, it seems to be
relatively indifferent to the density of the wood, or the volatile
content, with "branches" in the diameter range 2-4 cm range.

The major difference I see in the results of your analysis result
from the meaning of the word "primary". In your work, this is the air
needed to burn up (consume) the charcoal phase of the fire. I have been
using the term "primary" in a different sense - to mean the smaller
amount of air required only to make the charcoal. To be able to
communicate on this difference, I propose using "fundamental" for the
charcoal-making meaning - until this group suggests a better solution to
this vocabulary problem.

The other differences have been mentioned earlier: 1) top
lighting of 2) a single, large (no fuel-loading door) fuel charge with 3)
constant location of the volatiles combustion. These (with the
controllable "fundamental" air) are claimed to allow the desired high
efficiency, high combustion quality, and high turn-down ratio. The proof
is having done this experimentally in several dozen different designs
(after having failed in the first ten or so). However, the experimental
evidence is still very skimpy - especially on combustion quality.

Now, to a few comments, compliments, and questions:
1. This is the only paper I have seen that addresses this issue
of off-design performance - varying fuels and varying power levels. I
recommend it to everyone.
2. Your Fig. 2 shows flame height as a function of the mass
percentage of volatiles. Is this curve only for D=18 cm? What happens
if the flow is laminar (which I almost always see), rather than
turbulent? Can I get a copy of your 1982 paper with Bussman, on which
this is based?
3. You say (p 24): "The amount of air drawn by a naturally
aspirated stove is one of the most difficult quantities to measure."
"... only measurement... Dunn". The Dunn reference (pp. 107-118) of your
"Wood Heating for Cooking") shows they were using a thermistor anemometer
to measure velocity (for a charcoal using stove). Is this still the best
approach? I wonder about using chemical analysis of the effluents to
deduce air flow. I am told that modern cars measure O2 content and cheap
fire detection systems monitor CO. Are there possibly any other cheap
simple devices out there that we could use to measure air quantity and
quality?
4. Your table 1 shows that the fixed carbon for Eucalyptus
camaldulensis is 11%. I believe this species is used to make charcoal,
which would seem unlikely with this low yield. What is the reference for
this value?
5. On p31, you begin stove control with a quote (p32-33) from
Emmons and Atteya, from the same "Wood Heat for Cooking". I interpret
this quote to support the idea of air control with charcoal making stoves
when they say: " ... only practical control is the air supply...
preventing the rapid burning of charcoal ... reduces the energy feedback
to the fuel, thus reducing its pyrolysis ... control of the heat release
in the flames was accomplished by supplying insufficient air to burn all
the fuel." Are you moving yet toward agreement that the making of
charcoal may be a key to both technical and economic improved stove success?
6. On pages 33-34, you introduced and then rejected the air
control alone option because "...there are no simple methods available to
estimate the consequences of changing just the air flow without altering
the charge". I wonder if the constancy of fuel charge in a
charcoal-maker would allow one "to estimate the consequences." I
believe one can change the initial charge size in a charcoal-maker
without redesigning the stove, but haven't done any testing of that type.
7. In para. 2 of p 41, you answer the question: "..why not
introduce the control mechanism at the inlet." by saying "It can be
easily demonstrated by using Eq. (16) that this is a non-starter for the
quantities of air flow and pressure drops required. It simply demands
the closing of the fuel loading port." Since the charcoal-makers will be
top-loaded, would you agree that "fundamental" air inlet control becomes
more practical? Should the difference between fundamental and primary
air help or hurt?
8. Lastly, I was intrigued by the large change you calculated in
lambda, the excess air factor, in your several tables as a function of
power level. I have only had a single chance to explore this
experimentally, but believe that the charcoal-maker has a much smaller
change (O2 variation from 8 to 12%) with a power level change that I
believe was greater than 3:1. Can you suggest any means of further
reducing the lambda variation?
9. Your set of equations goes a long way toward allowing me to
better model the charcoal maker. What I now need is a means of predicting
the pressure drop above and below the moving pyrolysis front. I believe
that there may be a helpful effect going on here - as the pyrolysis front
moves down, the buoyancy effect increases and the "vacuum" (negative
pressure) is increased - perhaps approximately as the increase in
resistance - as the volatiles must pass through a longer distance.
10. Again, thanks very much for sending this excellent article.

Ron

From bryden at cae.wisc.edu Thu Feb 22 07:12:12 1996
From: bryden at cae.wisc.edu (kenneth bryden)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Jane Turnbull on Buchanan
Message-ID: <199602221215.GAA83019@audumla.students.wisc.edu>

> But I look forward to meeting
>Jane (for the first time) at that meeting - along with Sam Baldwin and
>Dan Kammen. Anyone else going to be there? (Feb28-29, $50)
>
> That reminds me that the World Renewable Energy Conference (WREC)
>is held in Denver this June. I can offer free lodging for anyone
>thinking about that meeting.
>
Ron,

I was unaware of the February or June meetings. Any suggestions as to how I
can keep closer track of these meetings (find out about them) and can you
provide a description of the June meeting?

Thanks

Ken Bryden
Dept. of Mechanical Engineering
University of Wisconsin - Madison

From E.Moerman at stud.tue.nl Thu Feb 22 08:14:34 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:49 2004
Subject: Fw: Tiny Pressure drops
Message-ID: <51363.s335192@popserver.tue.nl>

Small pressure drops can be measured by a digital pressure cell. Accuracy
0.1 Pa. However this reading is unstable in stoves. Also the meter was
expensive some time ago over 9,000$.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From E.Moerman at stud.tue.nl Thu Feb 22 08:14:52 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:49 2004
Subject: Comments on Prasad paper. To Ron Larson 21 Feb.
Message-ID: <51381.s335192@popserver.tue.nl>

Ron:

Again a brief explanation to get up to date with email. I will add names
before all quotes and other text.

Ron-
> I have quoted a few recently, and I have enjoyed them all. You and your
> Eindhoven group have done a lot of excellent work on a very difficult topic.

Etienne-
Thanks

Ron-
> Your "Off-Design" article makes it clear why you (and others
> from Eindhoven) have been so skeptical on claims for a charcoal-making
> stove, so I feel I must try to explain the differences I see between the

Etienne-
I am sceptical about charcoal-making because it introduces additional energy
loss processes. If you take the same measures for improving as you would for
improving a charcoal stove I think the woodstove would always win. Apart
from this I like the (possible) controllability of your stove and limited
need for attention during the cooking process. I think these two points are
important to users. I don't think much of the income-genrating part for
several reasons.

Prasad-
> "To conclude, it is FUTILE (emphasis added) to believe that there
> exists a high performance stove - by which I mean that efficiencies hover
> around 50%, combustion qualities are high, maximum to minimum power
> ratios are around 4 or higher - that is catholic in it taste for fuel."

Etienne-
I am convinced that such a stove can be designed and built. However it would
be too costly and require too much technology during the production to be
commercially succesful.

Ron-
> The major difference I see in the results of your analysis result
> from the meaning of the word "primary". In your work, this is the air
> needed to burn up (consume) the charcoal phase of the fire. I have been
> using the term "primary" in a different sense - to mean the smaller
> amount of air required only to make the charcoal. To be able to
> communicate on this difference, I propose using "fundamental" for the
> charcoal-making meaning - until this group suggests a better solution to
> this vocabulary problem.

Etienne-
I have been using the word in both meanings, but in case of your stove as
meaning 'fundamental'.

Ron-
> (after having failed in the first ten or so). However, the experimental
> evidence is still very skimpy - especially on combustion quality.

Etienne-
If I remember correctly I did forget to answer on your CO data that you sent
around some time ago. 0.1% CO at 10% CO2? Good values, still no match for
the downdraft stove but a lot cleaner than other stoves.

Ron-
> 2. Your Fig. 2 shows flame height as a function of the mass
> percentage of volatiles. Is this curve only for D=18 cm? What happens
> if the flow is laminar (which I almost always see), rather than
> turbulent? Can I get a copy of your 1982 paper with Bussman, on which
> this is based?

Etienne-
I can't remember anymore. I hope to take up this model again in a few months
time. I will keep you informed about the results.

Ron-
> 3. You (Prasad) say (p 24): "The amount of air drawn by a naturally
> aspirated stove is one of the most difficult quantities to measure."
> "... only measurement... Dunn". The Dunn reference (pp. 107-118) of your
> "Wood Heating for Cooking") shows they were using a thermistor anemometer
> to measure velocity (for a charcoal using stove). Is this still the best
> approach? I wonder about using chemical analysis of the effluents to
> deduce air flow. I am told that modern cars measure O2 content and cheap
> fire detection systems monitor CO. Are there possibly any other cheap
> simple devices out there that we could use to measure air quantity and
> quality?

Etienne-
In Woodcombustion STudies II you will find a method described to derive the
airflow. It is the same as you just described. The problem is that it is
highly inaccurate. It requires knowledge of the exact composition of the
fuel at all times, Since at the start mostly volatile combustion occurs and
at the end mainly char combustion. That is why I am working on a reasonably
accurate combuston model. If you also want to determine the absolute airflwo
you have to determine the mass loss rate too. For the stoves we have been
using this is difficult due to the given accuracy/range ratio of the balance
and the small burning rates.

Ron-
> 9. Your set of equations goes a long way toward allowing me to
> better model the charcoal maker. What I now need is a means of predicting
> the pressure drop above and below the moving pyrolysis front. I believe
> that there may be a helpful effect going on here - as the pyrolysis front
> moves down, the buoyancy effect increases and the "vacuum" (negative
> pressure) is increased - perhaps approximately as the increase in
> resistance - as the volatiles must pass through a longer distance.

Etienne-
Again I did some measurements on this. For wood the pressure difference is
rougly linear with fuelbed thickness (for a non-burning fuelbed), while for
charcoal the pressure difference was exponential (for a burning fuelbed).

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From larcon at csn.net Thu Feb 22 10:07:44 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Response to Moerman .
In-Reply-To: <51381.s335192@popserver.tue.nl>
Message-ID: <Pine.3.89.9602220704.A19928-0100000@teal.csn.net>

Thanks for the quick response. Comments below (deleting as much as I can)

On Thu, 22 Feb 1996 E.Moerman@stud.tue.nl wrote:

> Etienne-
> I am sceptical about charcoal-making because it introduces additional energy
> loss processes. If you take the same measures for improving as you would for
> improving a charcoal stove I think the woodstove would always win. Apart
> from this I like the (possible) controllability of your stove and limited
> need for attention during the cooking process. I think these two points are
> important to users. I don't think much of the income-genrating part for
> several reasons.

Please add more on the energy loss processes you are thinking
of. I am motivated mostly by the horrible losses in present day
charcoal-making (pits in the ground that probably average 75% losses (of
energy)). I think the energy losses are comparable, if not worse for the
standard stove. Major losses avoided with the charcoal-maker come from
eliminating the fuel-loading port, having a (low) power level appropriate
for the task, complete combustion at all times, and operating much of the
stove at a low temperature.

I see income generation as important both to help the women and
to help sell this (or any) stove. Mainly, income generation is needed to
get rid of the present horrible approach to making charcoal. In many
countries, charcoal making is a very important source of income for
poor rural farmers whenever they can break away from their farming
duties. I want them to use this time for getting the wood for their
wives to use all year - probably a pipe dream, but justified by the
wife providing some income generation and the fact the men don't have to
do the charcoal making (which is a nasty dangerous business also).

> Etienne-
> I am convinced that such a stove can be designed and built. However it would
> be too costly and require too much technology during the production to be
> commercially succesful.

The first model I described a month ago used only two scrap cans -
costing nothing here and only a few bucks in Ethiopia. I find the design
to be fairly tolerant of dimensions and believe that village metal workers
and potters can make them. (I feel confident on this since I have made
quite a few from sheet metal and clay with only crude tools). The only
critical dimension (0.1 mm) is in being able to shut the "fundamental" air
supply and I am doing that with a round conical ceramic plug in a round
hole - negligible cost.

> Etienne-
> If I remember correctly I did forget to answer on your CO data that you sent
> around some time ago. 0.1% CO at 10% CO2? Good values, still no match for
> the downdraft stove but a lot cleaner than other stoves.

The measuring equipment had a lower limit of 0.1%, so I don't
know how low it got. I guess that the CO results will be similar because
the gases flow through non-burning charcoal in both cases.

> Etienne-
> In Woodcombustion STudies II you will find a method described to derive the
> airflow. It is the same as you just described. The problem is that it is
> highly inaccurate. It requires knowledge of the exact composition of the
> fuel at all times, Since at the start mostly volatile combustion occurs and
> at the end mainly char combustion. That is why I am working on a reasonably

This (char combustion) is not true for the charcoal-maker - with
only volatile combustion throughout. Perhaps the Woodcombustion Studies
II method will help. If you can send it or the method component, it might
be helpful for optimizing the charcoal-maker.

> accurate combuston model. If you also want to determine the absolute airflwo
> you have to determine the mass loss rate too. For the stoves we have been
> using this is difficult due to the given accuracy/range ratio of the balance
> and the small burning rates.
>
I agree on the importance of modeling of the type you are doing.

I liked very much your scale for monitoring weight during
operation and I am going to try to build one. Because of the relative
time invariance of the volatile combustion in a charcoal-maker, I would
guess that a less accurate scale would be acceptable.

>
> Etienne-
> Again I did some measurements on this. For wood the pressure difference is
> rougly linear with fuelbed thickness (for a non-burning fuelbed), while for
> charcoal the pressure difference was exponential (for a burning fuelbed).
>
But with a charcoal maker, the fuelbed isn't "burning" - but
rather partly (75%) volatizing. My point was to emphasize that the flame
seems to stay constant for tens of minutes and that I'm uncertain as to
the exact reaon as the pyrolysis front moves over tens of centimeters
(also not yet really studied in detail).

Thanks again. I hope I'm changing your mind. I think I have to
prove I can do this with a piece of pottery - which should get the cost
down well below $5.00 in Ethiopia for smaller units.

Ron

From E.Moerman at stud.tue.nl Thu Feb 22 11:00:35 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:49 2004
Subject: Response to Moerman .
Message-ID: <61338.s335192@popserver.tue.nl>

Ron:

Judging by the very quick responses today we might as well be on the phone.

Ron-
> Please add more on the energy loss processes you are thinking
> of. I am motivated mostly by the horrible losses in present day
> charcoal-making (pits in the ground that probably average 75% losses (of
> energy)). I think the energy losses are comparable, if not worse for the
> standard stove. Major losses avoided with the charcoal-maker come from
> eliminating the fuel-loading port, having a (low) power level appropriate
> for the task, complete combustion at all times, and operating much of the
> stove at a low temperature.

Etienne-
I will do so when I have some more time for it. But I am thinking about
additional heatlosses because of the large distance between pan and flames.
Additional heat loss due to the longer path the formed volatiles have to
travel. More details will follow.

Ron-
> I see income generation as important both to help the women and
> to help sell this (or any) stove. Mainly, income generation is needed to
> get rid of the present horrible approach to making charcoal. In many
> countries, charcoal making is a very important source of income for
> poor rural farmers whenever they can break away from their farming
> duties. I want them to use this time for getting the wood for their
> wives to use all year - probably a pipe dream, but justified by the
> wife providing some income generation and the fact the men don't have to
> do the charcoal making (which is a nasty dangerous business also).

Etienne- I am not so optimistic.

>> Etienne-
>> I am convinced that such a stove can be designed and built. However it
>> would be too costly and require too much technology during the
>> production to be commercially succesful.
>>
Ron-
> The first model I described a month ago used only two scrap cans -
> costing nothing here and only a few bucks in Ethiopia. I find the design
> to be fairly tolerant of dimensions and believe that village metal workers
> and potters can make them. (I feel confident on this since I have made
> quite a few from sheet metal and clay with only crude tools). The only
> critical dimension (0.1 mm) is in being able to shut the "fundamental" air
> supply and I am doing that with a round conical ceramic plug in a round
> hole - negligible cost.

Etienne- I was talking about a clean burning stove with a turn-down ratio of
at least for and an efficiency of at least 50%. As far as I remember you
quoted an efficiency of 30 or 35%.

>> Etienne-
>> If I remember correctly I did forget to answer on your CO data that you
>> sent around some time ago. 0.1% CO at 10% CO2? Good values, still no
>> match for the downdraft stove but a lot cleaner than other stoves.
>>
Ron-
> The measuring equipment had a lower limit of 0.1%, so I don't
> know how low it got. I guess that the CO results will be similar because
> the gases flow through non-burning charcoal in both cases.
>
Etienne- In the downdraft stove we used the charcoal is burning vigorously,
but I am curious to see the results with higher accuracy.

Ron-
> This (char combustion) is not true for the charcoal-maker - with
> only volatile combustion throughout. Perhaps the Woodcombustion Studies
> II method will help. If you can send it or the method component, it might
> be helpful for optimizing the charcoal-maker.

Etienne- I thought you already had Woodcombustion Studies II. If not I will
sent you a copy. I agree that the method is better suited for the
charcoal-maker than for most other stoves.

Ron-
> I liked very much your scale for monitoring weight during
> operation and I am going to try to build one. Because of the relative
> time invariance of the volatile combustion in a charcoal-maker, I would
> guess that a less accurate scale would be acceptable.
>
Etienne- I don't think you should go for less accurate than 1g. The changes
in your burning rate cannot be measured to even a single digit (especially
for your stove). I have had some experience with kerosene stoves where we
had the same problem.

Ron-
> But with a charcoal maker, the fuelbed isn't "burning" - but
> rather partly (75%) volatizing. My point was to emphasize that the flame
> seems to stay constant for tens of minutes and that I'm uncertain as to
> the exact reaon as the pyrolysis front moves over tens of centimeters
> (also not yet really studied in detail).

Etienne- Is your flame constant relative to the position of the pyrolysis
front or relative to your secondary air-supply?

Ron-
> Thanks again. I hope I'm changing your mind. I think I have to
> prove I can do this with a piece of pottery - which should get the cost
> down well below $5.00 in Ethiopia for smaller units.
>
Etienne-
So far you don't have to change my mind on the cost of this stove. Although
I think you indeed should aim for a price well below $5. I need convincing
on the overall efficiency compared to woodstoves (not charcoal kilns) and on
the need to promote charcoal use. On both these points I will believe it
when I see it. I still hope to test your stove in a few months time, but I
would be interested in the experiences of others. Piet?
By the way I forgot to mention that by efficiency I mean fuel use (kg) per
kg food. I think this is a week point in your stove. Again if I have more
time I will look into this.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From prasad at tn7.phys.tue.nl Fri Feb 23 07:26:07 1996
From: prasad at tn7.phys.tue.nl (prasad)
Date: Tue Aug 31 21:34:49 2004
Subject: Response to Moerman .
In-Reply-To: <Pine.3.89.9602220704.A19928-0100000@teal.csn.net>
Message-ID: <9602231220.AA29350@tn7.phys.tue.nl>

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From verhaarp at janus.cqu.edu.au Fri Feb 23 08:13:55 1996
From: verhaarp at janus.cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Jane Turnbull on Buchanan
Message-ID: <9602231316.AA24817@janus.cqu.edu.au>

Ron typed
>> That reminds me that the World Renewable Energy Conference (WREC)
>>is held in Denver this June. I can offer free lodging for anyone

>>Ron,

Comment from Piet Verhaart

Hm, tell me more about this June Conference. Does the lodging offer include
a (one) wife?
==========================================================================
P.Verhaart
Phone: +61 79 331761 Fax: +61 79 332112
E-mail: verhaarp@cqu.edu.au
Snail Mail: 6 McDonald St, Gracemere Q 4702 Australia
Mobile 015 581 262

From verhaarp at janus.cqu.edu.au Fri Feb 23 08:14:21 1996
From: verhaarp at janus.cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:49 2004
Subject: Comments on Prasad paper. To Ron Larson 21 Feb.
Message-ID: <9602231317.AA24618@janus.cqu.edu.au>

>Ron-
>> The major difference I see in the results of your analysis result
>> from the meaning of the word "primary". In your work, this is the air
>> needed to burn up (consume) the charcoal phase of the fire. I have been
>> using the term "primary" in a different sense - to mean the smaller
>> amount of air required only to make the charcoal. To be able to
>> communicate on this difference, I propose using "fundamental" for the
>> charcoal-making meaning - until this group suggests a better solution to
>> this vocabulary problem.

Piet
So you use "Primary air" to burn volatiles and "Secundary air" to burn
volatiles.
Are you convinced only volatiles are burned in the wood containing section?
At the same time the combustion products leaving the wood containing section
have sufficient combustion value to be able to burn in a stable manner in
the upper section?
The modelling does not appear completely satisfactory.

On 17 and 18 February 1996 I conducted (wild) experiments on my charcoal
making stove just finished. The first experiment is described in an earlier
E-mail.
960218
16.34 Lit the stove with air feed pipe (3/4") open. For a while flames (in
the upper section) alternated with smoke.
16.55 Only smoke. After a boost with the dustblower there were some flames,
again alternating with smoke which after some time caught fire from the
underlying fuel.
17.05 Continuous smoke. Fitted the air supply and turned it up until upper
section was filled with flames. Kept varying the air supply to maintain
flames. Sometimes air had to be turned down, at other times up, to restart
flames.
17.25 Diminishing smoke production. Air supply cut off and lower section
closed off from the top. (yesterdays yield of charcoal was disappointing,
Several hours after closing the air supply the lower section was still hot,
e.g. charcoal was burning in air that sneaked in from the top.)
For next experiments I have to find a way to measure the air flow rate and
use scales and a stopwatch.

A two acre plot is barely large enough to test one experimental stove.

The day after, the lower section was found to contain incompletely charred
pieces of wood next to charcoal.

>Ron-
>> What I now need is a means of predicting the pressure drop above and
below the moving pyrolysis front. I believe
>> that there may be a helpful effect going on here - as the pyrolysis front
moves down, the buoyancy effect increases and the >>"vacuum" (negative >>
pressure) is increased - perhaps approximately as the increase in >>
resistance - as the volatiles must >>pass through a longer distance.

Piet
Yes, if you can assume the combustion front moves downward in a horizontal
plane, you might conclude the negative pressure (draft) increases linearly
with the distance from the top of the combustion front. Flow will be
determined by the resistances encountered by hot gas (high viscosity).
Resistance to the hot gases will increase roughly linearly with the distance
travelled.

>Etienne-
>Again I did some measurements on this. For wood the pressure difference is
>rougly linear with fuelbed thickness (for a non-burning fuelbed), while for
> charcoal the pressure difference was exponential (for a burning fuelbed).

Like Etienne said.

Piet resumes
A recent E-mail improvement I am not sure I had a hand in is smaller
characters (about 10, I suppose). I have found no way in Eudora to change
the size, so it must have come from outside.
A further improvement in compactness could be achieved it the powers that be
could find a way to use the full width of the more or less standard papers
we are using.

Have a nice day,

From set at mt.luth.se Fri Feb 23 11:23:17 1996
From: set at mt.luth.se (Sven-Erik Tiberg)
Date: Tue Aug 31 21:34:49 2004
Subject: Introduction and sketch of a new stove
Message-ID: <v02130502ad538be0b6cd@[130.240.1.145]>

Hi all.

May I first introduce myselve to this list.

I'm a research enginner with speciallity mechatronic, ergonomics, and
electronic/computer. I'm also maintaing our web-info at the div. of mech.
enginnering, and by this Dr. Brage Norin asked me to ask about market for
his stoves and ideas about a "rural" model. A tread about this was started
before x-mas and it has been very interesting and informative to follow the
discussions.

On the subject chaircoal making stove, there where a lot of chaircole
produced in our forrests for our steel mills. But this "stoves" was a hudge
pile of wood covered with turf, and it was probably the same basic model as
in UK and belgium. If anyone are interested please send me a mail.

About the higheffective downsstream stove that has been tested at goverment
teststation in boraas in sweden, are the results delayed 2 weeks due to
calibration of equipment after the test. And will be presented ASAP on our
homepage.

We have made a skeetch of a new upstream stove, based on the discussion on
this list, that are included on our web-page.
http://www.luth.se/depts/mt/ene/articles/ETC_pan/

I'm forwarding mail from this discussion to Dr. Norin.

--- Your cincearly ---

***********************************************
* Sven-Erik Tiberg
*
* Div. of Energy Enginnering
*
* Dep. of Mechanical Enginnering
*
* Lulea Univ. of Technology S 98787 SWEDEN
*
* email set@mt.luth.se Loc. 65.57N 22.22E
* PGP Public key; on request.
*
* phone +46 920 91218 55190 and 55542 ( home)
*
* fax +46 920 91047, 920 55190 ( fax home ).
*
* http://www.luth.se/depts/mt/ene/staff/set/

***********************************************

From larcon at csn.net Fri Feb 23 11:37:56 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Piet and Ken on conferences and lodgings
In-Reply-To: <9602231316.AA24817@janus.cqu.edu.au>
Message-ID: <Pine.3.89.9602230919.A3813-0100000@teal.csn.net>

> Comment from Piet Verhaart
>
> Hm, tell me more about this June Conference. Does the lodging offer include
> a (one) wife?

Response:
The offer can include more than one wife also if that will be of
help. The conference is from Saturday, 15 June through Friday, 21 June
- price about $350 I think (for the conference, not the lodgings). I am
told this is on the WWW at NREL.gov (under events). The deadline for
abstract submission is well past. I believe that I saw this conference
first listed in Solar Todoy (ASES) magazine, or the ISES equivalent.

Ken Bryden also asked about the Washington meeting and I will try to send
him something separately on that. I believe the word "bioenergy" or
"stoves" probably will not come up at that meeting The sponsoring group
at NREL has what used to be a closed list, but I am sure that anyone on
"stoves" can get on - Let me know if I should try to assist. The topics
of interest there are largely wind and PV village electric power systems -
maybe 1-100kW? I presume that it is still possible to show up at the
Dupont Plaza Hotel at 8:00 AM and pay $25 per day for either Feb. 28 or 29.

Piet: We have had a lot of returned or slow mail notices, and we haven't
heard from you for awhile. Might you not have received some mail? (which
we can resend). Colorado is the summer vacation capital of the US. Tell
any of your wives that we would welcome them also. We have two spare
bedrooms, so (if Piet only brings one wife) there is still room for
someone else.

Regards

Ron

From larcon at csn.net Fri Feb 23 12:28:43 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Verhaart
In-Reply-To: <9602231317.AA24618@janus.cqu.edu.au>
Message-ID: <Pine.3.89.9602230930.A3813-0100000@teal.csn.net>

(Condensing and cutting out as much as I can)

On Fri, 23 Feb 1996, Peter Verhaart wrote:

> >Ron-
> >> The major difference I see in the results of your analysis result
> >> from the meaning of the word "primary". In your work, this is the air
> >> needed to burn up (consume) the charcoal phase of the fire. I have been
> >> using the term "primary" in a different sense - to mean the smaller
> >> amount of air required only to make the charcoal. To be able to
> >> communicate on this difference, I propose using "fundamental" for the
> >> charcoal-making meaning - until this group suggests a better solution to
> >> this vocabulary problem.
>
> Piet
> So you use "Primary air" to burn volatiles and "Secundary air" to burn
> volatiles.

No - relative to the charcoal-making stove, I am going to avoid
the term "primary" altogether (now). The air coming in the bottom is to
be called "fundamental" - and is to be used as much as possible to make
charcoal. Of course, some of the made-charcoal will be consumed, but my
visual observations suggest that little is (I rarely see any ash).

> Are you convinced only volatiles are burned in the wood containing section?

No, I think there is very little volatile combustion in this
region. Below the pyrolysis zone there is nothing happening; above, there
is not enough oxygen left to combust much of the volatiles. Above the
wood (and charcoal) region, the volatiles are burned with the resulting
flame producing buoyancy and negative pressure drawing in the secondary
air (same meaning of "secondary", I believe).

> At the same time the combustion products leaving the wood containing section
> have sufficient combustion value to be able to burn in a stable manner in
> the upper section?

The word "combustion" should probably be replaced by "pyrolysis".
The desired products (CO, CH4, and H2) are mixed with some CO2, but still
has plenty of capability to now "combust" above the secondary air inlet.

> The modelling does not appear completely satisfactory.
>
This sentence is not clear. Eindhoven seems to have done little
if any modeling on charcoal making. I have not offered any. There is
some literature out there of course on pyrolysis and charcoal making (if
you take pyrolysis to mean heating in the absence of oxygen).

> On 17 and 18 February 1996 I conducted (wild) experiments on my charcoal
> making stove just finished. The first experiment is described in an earlier
> E-mail.
> 960218
> 16.34 Lit the stove with air feed pipe (3/4") open. For a while flames (in
> the upper section) alternated with smoke.

My fear in this experiment comes from your use of compressed
air, which I have not attempted, but have observed in some tests with Tom
Reed. I just don't know what is happening - especially at the secondary
air inlet. I urge trying an experiment with natural draft. In Tom's
experiments, there were clearly some interactions between the two
supplies depending on the flow settings - as some of the secondary air
was sometimes probably being drawn down to the pyrolysis zone, for
instance - not what is wanted.

> 16.55 Only smoke. After a boost with the dustblower there were some flames,
> again alternating with smoke which after some time caught fire from the
> underlying fuel.
> 17.05 Continuous smoke. Fitted the air supply and turned it up until upper
> section was filled with flames. Kept varying the air supply to maintain
> flames. Sometimes air had to be turned down, at other times up, to restart
> flames.

I believe that you had too much primary (as opposed to
"fundamental") air. When the system is working well, there is such a
draft that the "fundamental" air holes are difficult to close up (but
when you do, then the secondary combustion will also cease and smoke
occurs). When this occurs, I usually can open the "fundamental" ports,
and throw in a match and get immediate re-ignition. Sometimes I can
avoid the match and just blow in from the top. As I have become more
skilled in operation (especially in preventing the effects of a small
breeze), the secondary combustion flame now rarely goes out.

> 17.25 Diminishing smoke production. Air supply cut off and lower section
> closed off from the top. (yesterdays yield of charcoal was disappointing,
> Several hours after closing the air supply the lower section was still hot,
> e.g. charcoal was burning in air that sneaked in from the top.)

This is the biggest problem I find with this approach (probably
existent for all charcoal makers). The main solution I am using is to
dump the glowing charcoal into a closed container - but this requires
some skill and I still bear some scars while learning how to do it. The
yield I see is always very near 25% by weight.

> For next experiments I have to find a way to measure the air flow rate and
> use scales and a stopwatch.
>
> A two acre plot is barely large enough to test one experimental stove.
>
> The day after, the lower section was found to contain incompletely charred
> pieces of wood next to charcoal.
>
I see this sometimes when the wood is not packed well. I still
don't udnerstand the shape of your wood pieces. I believe that a hot
column can form, turning the "fundamental" air into "primary" air. But I
don't usually see this.

> Piet
> Yes, if you can assume the combustion front moves downward in a horizontal

Again I want to avoid the term "combustion" front here and below.

> plane, you might conclude the negative pressure (draft) increases linearly
> with the distance from the top of the combustion front. Flow will be
> determined by the resistances encountered by hot gas (high viscosity).
> Resistance to the hot gases will increase roughly linearly with the distance
> travelled.
>
> >Etienne-
> >Again I did some measurements on this. For wood the pressure difference is
> >rougly linear with fuelbed thickness (for a non-burning fuelbed), while for
> > charcoal the pressure difference was exponential (for a burning fuelbed).
>
> Like Etienne said.

But we are looking at a third situation - these are not the only two
choices; the downward-moving "pyrolysis" zone leaves behind a volume of
charcoal that is not much changed from that of the original wood.

I believe that your upper pipe may be too tall also.

Regards

Ron

From E.Moerman at stud.tue.nl Fri Feb 23 16:14:46 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Verhaart. Ronal Larson 23 Feb.
Message-ID: <80163.s335192@popserver.tue.nl>

I have a small question to Ron and any others testing Ron's stove (or Tom's
stove). What
happens if the 'fundamental' is completely shut down? Can sufficient
secondary air be supplied to keep the stove burning well? I am really
curious to know what will happen. From the descriptions I gather that it
should make little difference to omit the 'fundamental' air and it might
improve the charcoal yield a bit.

Ron's comment on pressure losses-
> But we are looking at a third situation - these are not the only two
> choices; the downward-moving "pyrolysis" zone leaves behind a volume of
> charcoal that is not much changed from that of the original wood.

Etienne-
I noticed that the charcoal will regularly form smaller particles and fall
in on itself. In addition the gases are heated in the pyrolysis zone
resulting in a higher viscosity, higher average velocity and consequently a
higher flow resistance. I think I estimated the difference between buring
wood and burning char to be about a factor 3.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From larcon at csn.net Fri Feb 23 18:41:56 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Response to E. Moerman.
In-Reply-To: <80163.s335192@popserver.tue.nl>
Message-ID: <Pine.3.89.9602231645.A26641-0100000@teal.csn.net>

Comments and answers below:

On Fri, 23 Feb 1996 E.Moerman@stud.tue.nl wrote:

> I have a small question to Ron and any others testing Ron's stove (or Tom's
> stove). What
> happens if the 'fundamental' is completely shut down? Can sufficient

One should avoid a complete shutdown of the "fundamental air, of
course - but if it occurs, then not enough volatiles are produced and the
upper flame goes out and lots of smoke appears.

> secondary air be supplied to keep the stove burning well? I am really

The secondary air supply presumably allows some air to travel
downward, but the flame has always gone out for me (within seconds) under
this circumstance.

> curious to know what will happen. From the descriptions I gather that it
> should make little difference to omit the 'fundamental' air and it might
> improve the charcoal yield a bit.
>
My experience is that it won't work at all without the
"fundamental" air supply, but I'd like to hear if anyone can make it do
so. I doubt that anyone can make it work without two air sources.
>
> Ron's comment on pressure losses-
> > But we are looking at a third situation - these are not the only two
> > choices; the downward-moving "pyrolysis" zone leaves behind a volume of
> > charcoal that is not much changed from that of the original wood.
>
> Etienne-
> I noticed that the charcoal will regularly form smaller particles and fall

This I don't see - the charcoal produced is a slightly smaller
replica of the initial wood - of course much less dense (about 1/4 the
density).

> in on itself. In addition the gases are heated in the pyrolysis zone
> resulting in a higher viscosity, higher average velocity and consequently a
> higher flow resistance. I think I estimated the difference between buring
> wood and burning char to be about a factor 3.

Etienne - I don't understand this point. What has changed by
this factor of 3? Is it the flow resistance? If so, this is a most
interesting observation, and might explain my concern. How was this
determined?

Regards, Ron

From E.Moerman at stud.tue.nl Sat Feb 24 10:05:49 1996
From: E.Moerman at stud.tue.nl (E.Moerman@stud.tue.nl)
Date: Tue Aug 31 21:34:49 2004
Subject: Response to Ron Larson.
Message-ID: <58067.s335192@popserver.tue.nl>

Ron-
> One should avoid a complete shutdown of the "fundamental air, of
> course - but if it occurs, then not enough volatiles are produced and the
> upper flame goes out and lots of smoke appears.

Etienne- I think this is an interesting observation. If recent pyrolysis
models are correct this would mean that the temperature is too low for
sustained exothermic reactions and that the heat required for the pyrolysis
is given off by a partial combustion of char. This would reduce the upper
limit of the char yield a bit.
Ron-
> My experience is that it won't work at all without the
> "fundamental" air supply, but I'd like to hear if anyone can make it do
> so. I doubt that anyone can make it work without two air sources.

Etienne- What if you reduce the height of the chimney (stove body). This
should reduce the heat losses due to the airflow. This in turn would result
in a higher temperature which would favor exothermic pyrolysis reactions.

>> Etienne-
>> I noticed that the charcoal will regularly form smaller particles and
>> fall

Ron-
> This I don't see - the charcoal produced is a slightly smaller
> replica of the initial wood - of course much less dense (about 1/4 the
> density).

Etienne- These small size reductions is sufficient for the particles to fall
down regularly to form a slightly denser packing.

Etienne-
>> in on itself. In addition the gases are heated in the pyrolysis zone
>> resulting in a higher viscosity, higher average velocity and
>> consequently a higher flow resistance. I think I estimated the
>> difference between buring wood and burning char to be about a factor 3.
>>
>
> Ron - I don't understand this point. What has changed by
> this factor of 3? Is it the flow resistance? If so, this is a most
> interesting observation, and might explain my concern. How was this
> determined?
>
Etienne- I think I determined the airflow. Obviuosly when the airflow
changes by a factor 3 without other changes than the resistance will also
change by a factor 3. Next week I will explain how I determined this. By
the way I only determined the difference between wood and char for a cold
(non-burning) fuelbed. For a burning fuelbed only the case of char could
provide a sufficiently accurate reading.

During the phase where most of the fuel was burning I represented the
airflow by a*exp(-b*M) or by c/(d+M). Here M is the mass of the fuelbed and
a,b,c,d are constants (different for different fuels and situations).

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From tduke at igc.apc.org Sun Feb 25 00:48:38 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:49 2004
Subject: Wood Match Anaology
Message-ID: <199602250551.VAA26593@igc3.igc.apc.org>

Hi Friends,

I am back in here on the discussion of charcoal making. I am doing
it. The stove works great! We can make them without any metal or
other purchased materials. So I have come to help explain how it
works.

When you light a wood match and hold it up it burns much like a
candle. Which I will explain later. It usually leaves the black
chared remains of the match standing for some time before it breaks
off further down. Sometimes it does not break off. This is what we
have in this stove. It is just like a stand of individual match
sticks. The flame burns and the char remains.

In more detail the flame burns poorly with restricted air and some of
the gassed ignite above the secondary air inlet. This is just like
when you blow a candle out and relight the little whisp of smoke that
rises. The flame usually jumbs right back down to where it was on the
candle wick. In the stove the flame holds just above the secondary
air inlet.

Actually you have two flames. A very poor one down where the candle
flame normally would be. And a good mostly blue one above the top of
the fuel where the secondary air comes in. It is as though you are
partly putting out the candle flame letting a little smoke rise above
the top of the chared wick and burning the smoke there.

What you get is a much lower temperature in the fuel bed. And a nice
mostly blue flame above the fuel. The lower temperature in the fuel
bed means it does not burn the can and you can use thin cheap metal
to contain the fuel bed. If you choose to use metal.

When I look at a candle burning I see the black part of the wick
above where the flame starts. Also when I burn a wood match holding
it vertical I see the black char standing above the beginning of the
flame. In this charcoal making stove I see exactly the same thing.

When a candle burns heat melts and evaporates wax drawn up the wick.
The gas jets shooting outward then upward burn (release energy). I
see the same thing in this stove. I see the more volitile part of the
wood being evaporated and shooting out of the wood and burning.
Leaving the less volitile charcoal standing. Just like the wick of a
candle and the wood match stick. The lowered temperature in the fuel
bed seems to favor the leaving of charcoal. Which I think it should
because carbon needs higher temperature to react.

I think we see the same thing in the burning of a candle. The hottest
part of the flame is at the flame tip. As we go down the temperature
decreases. This is where we find the black chared remains of the
wick. As the candle is consumed the flame progresses down the wick.
However the tip of the wick seldom gets longer. It burns off as it
gets into the hotter part of the flame.

I think what we have in this stove is exactly what we have in a
candle flame. So I don't think there is any mystery in it's opertion,
in it's function.

I have and am using the stove in several different configurations and
it works! It makes charcoal. It is easy to save the charcoal. This is
not a difficult stove to operate. So I want to assure you all that
it works! That in time you can all make it work very well. It costs
nothing to build. Even if you cannot afford to buy used cans as they
have to do in some places in Africa.

Please let me know if you have any problems in getting your stoves to
work or in understanding how it works. It realy is a very simple
stove. It is just new to us to think of it this way. It is new to us
to expect to get charcoal. So I am sure that as these expectations
sink into our thinking it will all become clear.

As a friend and a brother,

From verhaarp at janus.cqu.edu.au Sun Feb 25 05:42:01 1996
From: verhaarp at janus.cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Piet and Ken on conferences and lodgings
Message-ID: <9602251044.AA06470@janus.cqu.edu.au>

Dear Ron,

Thank you very much for the accomodation offer, the idea was to
bring all present wives (one) and combine it with trips to other places and
persons e.g. my cousin in Arizona and if possible the Fred Hottenroths in L.A.
However, the admission fee of the congress is lethal. Are you taking part? >

I don't think I missed out on any mail, I am not feeling as if there is any
hyatus.

Today I did another experiment with the charcoal making stove. This time I
had made an insert for the top part consisting of a steel pipe of 80 mm
inside diameter (also found at the tip together with the 127 mm pipe). The
bottom end has a flange snugly fitting inside the top section and it
protrudes 25 mm from the top to take three pan supports (you see I am an
optimist). Again we produced a lot of smoke. (the 2-acre remark should
contain "to test one stove at a time") and occasional flames reaching the
top of the insert. Unfortunately I trusted modern Japanee electronics in the
form of a Pearlcorder into which I spoke all the observations. Now, behind
the keyboard the tape appears filled with white or grey noise with my tinny
voice in the background like flood victims weak cries for help,
unintelligible. Next time I will use a tested piece of equipment, 25 years
older than the junk that let me down today.

That is all for now, the line is still open and I will send this off.

Thank you, best regards. It would be nice if our group could meet some time
this year.

Piet>

From verhaarp at janus.cqu.edu.au Sun Feb 25 06:07:45 1996
From: verhaarp at janus.cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:49 2004
Subject: Mail not received by Piet
Message-ID: <9602251110.AA07214@janus.cqu.edu.au>

Piet talking.
Ron asked me if there was any mail I have not received. Apparently some was
returned.

Now I have checked my files and this is what I find.
7/2 2; 8/2 3; 9/2 1; 10/2 2; 11/2 5; 12/2 9; 13/2 4; 14/2 2; 15/2 7;
16/2 4; 17/2 6; 21/2 4; 22/2 5; 23/2 10; 24/2 2
25/2 1

So there is a gap between 17/2 and 21/2 but maybe by unwritten consent
everybody kept quiet those days

Hope this is of help in sorting things out.

Cheers,

Piet

From tduke at igc.apc.org Sun Feb 25 09:37:55 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:49 2004
Subject: Stove Smoke?
Message-ID: <199602251440.GAA04715@igc3.igc.apc.org>

Peter V. Wrote Sun Feb 25:

> Today I did another experiment with the charcoal making stove. This time I
> had made an insert for the top part consisting of a steel pipe of 80 mm
> inside diameter (also found at the tip together with the 127 mm pipe). The
> bottom end has a flange snugly fitting inside the top section and it
> protrudes 25 mm from the top to take three pan supports (you see I am an
> optimist). Again we produced a lot of smoke. (the 2-acre remark should
> contain "to test one stove at a time") and occasional flames reaching the
> top of the insert.

Piet, I make excellent charcoal and no smoke! So tell me more what is
happening. Something is wrong. This is an easy stove to operate, so I
think as it becomes clear what is expected the problems will go away.
I put a little discussion explaining the observable functioning of
the stove on the stoves list titled Wood Match Anaology.

There is more to the process. A little organic cheistry involved. The
concentration of various gasses at various times influnces which
reactions are favored. If this comes up in the discussion I will
address it also, so we can get a better feel for what can be
expected.

My main point is this: The Stove Works! It is not expensive or
difficult. People can make good charcoal and cook their meal at the
same time! So let me know if you have problems. It is not that
difficult.

> Thank you, best regards. It would be nice if our group could meet some time
> this year.

How about the Midwest Renewable Energy Association Fair At Amherst
Wisconsin. Around the summer Solstis.

More then happy to help anyone get their stove going good,

Tom Duke

--------------------------------------------------------------------
Tom Duke
4363 Hunt Road
Burlington, Iowa 52601-8917 U. S. A.
The Renewable Energy Research Center and Farm
--------------------------------------------------------------------

From larcon at csn.net Sun Feb 25 14:08:55 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Response to E.Moerman
In-Reply-To: <58067.s335192@popserver.tue.nl>
Message-ID: <Pine.3.89.9602251154.A12092-0100000@teal.csn.net>

To all: This response from Etienne allows me to backtrack a bit and raise
a subject that I've alluded to a bit, but not really discussed - the
Grover pyrolyzing stove. This stove has the zero air input of the next
paragraph - and I wasn't thinking about it when I said "avoid a complete
shutdown of the "fundamental" air - which is what Grover (and Choto in
Zimbabwe) did. They both used a "donut" geometry and the donut (filled
with scrap ag wastes, etc, - but it could be wood) has no "fundamental"
air. The gases driven off are combusted in the center of the donut and
the thermal feedback outward radially keeps the process going. Similarly,
with some larger designs I have worked on, it seems better to put the
central-most wood inside a smaller inverted can, which also receives no
"fundamental" air. So, I should have been less categorical about shutting
off the "fundamental" air. I was referring only to the simplest design I
originally described.

On Sat, 24 Feb 1996 E.Moerman@stud.tue.nl wrote:

> Ron-
> > One should avoid a complete shutdown of the "fundamental air, of
> > course - but if it occurs, then not enough volatiles are produced and the
> > upper flame goes out and lots of smoke appears.
>
> Etienne- I think this is an interesting observation. If recent pyrolysis
> models are correct this would mean that the temperature is too low for
> sustained exothermic reactions and that the heat required for the pyrolysis
> is given off by a partial combustion of char. This would reduce the upper
> limit of the char yield a bit.

I agree with all of this - adding that the Grover stove uses heat
release from combustion of the volatiles.

> Etienne- What if you reduce the height of the chimney (stove body). This
> should reduce the heat losses due to the airflow. This in turn would result
> in a higher temperature which would favor exothermic pyrolysis reactions.
>
My experience is that reduced chimney height hurts as it reduces
the buoyancy required to draw in the secondary air. A height somewhat
larger than or equal to the diameter seems to balance off the need for
draught and height for full combustion against the need for minimum
height to reduce radial heat losses Of course, insulation surrounding
the combustion zone has to balance its cost with the savings.
Intuitively, I believe the insulation of a thin sheet of metal is
probably usually justified.

> Etienne- These small size reductions is sufficient for the particles to fall
> down regularly to form a slightly denser packing.

I strongly urge that the height of the wood pieces equals the full
height of the region below the secondary air inlets. Then the reduction
of piece size during pyrolysis seems to lead to less densing packing. At
the end, you can generally see all the way to the bottom in at least a
place or two.

> Etienne- I think I determined the airflow. Obviuosly when the airflow
> changes by a factor 3 without other changes than the resistance will also
> change by a factor 3. Next week I will explain how I determined this. By
> the way I only determined the difference between wood and char for a cold
> (non-burning) fuelbed. For a burning fuelbed only the case of char could
> provide a sufficiently accurate reading.
>
> During the phase where most of the fuel was burning I represented the
> airflow by a*exp(-b*M) or by c/(d+M). Here M is the mass of the fuelbed and
> a,b,c,d are constants (different for different fuels and situations).

I look forward to the further detail.

Regards,

Ron

From larcon at csn.net Sun Feb 25 14:20:21 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Piet
In-Reply-To: <9602251044.AA06470@janus.cqu.edu.au>
Message-ID: <Pine.3.89.9602251258.A12092-0100000@teal.csn.net>

On Sun, 25 Feb 1996, Peter Verhaart wrote:

> Dear Ron,
>
> Thank you very much for the accomodation offer, the idea was to
> bring all present wives (one) and combine it with trips to other places and
> persons e.g. my cousin in Arizona and if possible the Fred Hottenroths in L.A.
> However, the admission fee of the congress is lethal. Are you taking part? >

Yes - and I agree on the price. I'm hoping for a price break for
retirees, and haven't yet asked. I probably wouldn't go except that I
expect there will be a lot of people going I would not normally meet at
this price.

"tip" is a word we replace by "dump".

> bottom end has a flange snugly fitting inside the top section and it
> protrudes 25 mm from the top to take three pan supports (you see I am an

I haven't quite visualized how the heat gets out, but I'm glad to
hear of the optimism.

> optimist). Again we produced a lot of smoke. (the 2-acre remark should

I hope the suggestions from Tom Duke and myself will soon make
the smoke disappear.

> Thank you, best regards. It would be nice if our group could meet some time
> this year.

I agree. The e-mail is fantastic, but face-to-face is better.

Ron

From larcon at csn.net Sun Feb 25 14:37:44 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Mail not received by Piet
In-Reply-To: <9602251110.AA07214@janus.cqu.edu.au>
Message-ID: <Pine.3.89.9602251228.A12092-0100000@teal.csn.net>

I am just learning (Etienne is much better) this moderator role.
We two receive messages when Crest is unable to deliver and we received a
few for Piet in that category. I still don't know what they mean but
will try to learn from Crest. I am afraid that I scrapped most (and some
to others - especially Bhattacharya), in the belief that crest kept
trying and we were usually hearing from Piet and others. I won't ignore
again, without checking. See below.

On Sun, 25 Feb 1996, Peter Verhaart wrote:

> Piet talking.
> Ron asked me if there was any mail I have not received. Apparently some was
> returned.
>
> Now I have checked my files and this is what I find.
> 7/2 2; 8/2 3; 9/2 1; 10/2 2; 11/2 5; 12/2 9; 13/2 4; 14/2 2; 15/2 7;
> 16/2 4; 17/2 6; 21/2 4; 22/2 5; 23/2 10; 24/2 2
> 25/2 1
>
> So there is a gap between 17/2 and 21/2 but maybe by unwritten consent
> everybody kept quiet those days

I found 2 on the 20th and will send them and try to look at the full
list you have provided. I concur on the number for the 17th and 21st.
Anyone else think they need something?

Ron

From larcon at csn.net Sun Feb 25 20:02:21 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Reply to Verhaart
In-Reply-To: <960225214301_73002.1213_FHM62-5@CompuServe.COM>
Message-ID: <Pine.3.89.9602251715.A9076-0100000@teal.csn.net>

Comments below

Ron

On 25 Feb 1996, Thomas Reed wrote:

> RON & PIET:
>
> Objection! We are talking about a GASIFIER WOOD STOVE. You new stove people
> need to read the gasification literature rather than making up a whole new
> vocabulary of your own. "Primary air" has been used for decades to mean the air
> that causes pyrolysis (whether to char plus volatiles or mainly producer gas or
> everything in between).
>
Is there a way to distinguish these two extremes? In the present
juncture of three disciplines: cookstoves (rarely having separate air
supplies), charcoal making (throwing away the volatiles normally) and
(producer) gasifiers (rarely wanting any charcoal), I hope that we can
find some different terms - since the amounts of "primary" air are
considerably different. Some modifying adjective would be helpful; I
hold no brief for "fundamental", but clarity is needed when we mean very
different things by the same word.

> On the other hand, I have "invented a number of words over the past two decades
> of working in gasification that seem to be sticking - like "flaming pyrolysis"
> for pyrolysis in the presence of air to burn the volatiles and supply heat. So
> I wouldn't discourage you from inventing new words - if none are available.
>
> As James Kilpatrick said in his syndicated column this AM (Rocky Mountain News)
> "a writer ought to think twice before needlessly resorting to our-of-town words.
>
> *****
> I was off-net for three days and received 42 messages. On to the next!
>
> Love you all TOM REED
>
>

From larcon at csn.net Mon Feb 26 02:33:45 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:49 2004
Subject: Response to Prasad's of 23 Feb
Message-ID: <Pine.3.89.9602260029.A3623-0100000@teal.csn.net>

To Prasad (and alll others in the Stoves group):

This is a response to your message of 23 Feb. (with heavy editing).

1. You said "A drawing showing the different components etc. would be
useful. "
I can only recommend loooking at the "drawing" I sent out in mid
January. I have the same problem with you as e-mail computer graphics.
Perhaps you or others could ask for clarification on this as necessary -
its the best I can do right now.

2. You said: " The task is to cook food. In order to go further we
need four more pieces of information." which, with your answers were
(with comments in parentheses) [and/or square brackets]:
a. "What kind of food?" Your answer - "Rice"
b. "How much of food?" Your answer - ".. 3kg of cooked rice per meal
for the family."
c. "What type of fuel?" Your answer : first- "the energy required for
the task is 9000 kJ/meal" and " .. our family requires 0.6 kg of
wood/meal." (If this were a standard type of stove.)
d.1 "The stove.." being one in which "you are going to load all the
fuel at one go and recover the charcoal at the end of cooking." Then
using a fixed carbon content to be 20% , you said "..you will need 0.7 kg
of fuel" and "you will recover 100g of charcoal per meal."
[I don't believe you should simply add the 0.1 kg to the supply
of wood. You need about 0.4 kg of wood to get 0.1 kg of charcoal.
Because I find that the measured weight of charcoal is 25% of the initial
weight and therefore contains about half the original energy, I need
about 1.2 kg of wood and will recover 0.3 kg of charcoal. The 0.9 kg of
volatiles has an energy content of about 9 MJ, as desired. All this is
consistent with 30 MJ/kg for charcoal - which is probably a bit high.]
d2) You found "the volume of wood would be 1.16 litres" - which
you later double to "occupy a volume of 2.32 litres"
[And with 1.2 kg of wood to start, I would find 2 liters before
doubling, but I think another factor of 1.5 is plenty since I jam it in
tightly, thereby going to a required approximate 3 liters.]
d3) You assumed ".. a combustion chamber diameter of
20 cm ... fuelbed thickness .. just under 8 cm ... the combustion
space to be 10 cm. That gives a total stove height to be 18 cm. Not
unreasonable."
[Option A: Because I think I can do this cooking job with the
present 15 cm diameter cans, I might keep the can height at the present
value of 17 cm, and will need to obtain an efficiency higher than your
assumption. I of course propose another 17 cm of combustion space,
obtaining a total height of 34 cm - clearly not stable, but presumably
that is fixable by good artisans.]
[Option B. If we used a 20 cm diameter can and further modify
your values, then the height would be 8 cm * (1.2/.7) * (1.5/2) = 10.3 cm.
My experience says your additional 10 cm height won't give enough draft -
so my first experiment would probably be for at least 15 cm - giving a
total of about 28 cm, after adding space for the grate and the secondary
air slit. ]
[The choice between Option A or Option B should be based on the
size of the cook pot and the time needed for cooking. I think your
proposed first rice cooking test favors Option B, but we need both
laboratory and field research to determine this.]

3. You then switched to Tom Duke, noting "he is working with a 24 inch
thick wood pile (that is 60cm). "
[Tom is working in an unheated barn and has primarily been
studying space heating - not cooking, so this is not a fair comparison.}
[A better question is whether twice the original wood amount
producing a saleable product with half the original energy content in a
stove that is about twice as large is a societal step forward (buttressed
by being easier to use, cleaner, and displacing a highly polluting
present method of producing charcoal)]

4. My only disagreement with your thought that " a wood heating device
is best combined with a relatively large device like brick kiln etc." is
that I think we can do both.

5. Concerning the need you point out to "..persuade the users to cut
their wood into small sizes.....we have never been able to persuade this
group of people to persuade their clientele to do this" -- I am in
complete agreement.
Controlling wood diameter and length is a major disadvantage;
however, making longer lengths (Option A) is presumably better than
Option B or requiring even smaller pieces. I controlled length for
about fifteen tests in Ethiopia (and many dooozens of tests in Colorado
using smaller wood), using wood purchased in the market. It was of
course painful. But for wood branches in the range already of 2 to 3 cm,
I can now get the required length with a single "eye-balled" hatchet blow
and often only by stomping on it. This size is being, and should be,
collected by women anyway; larger pieces have better uses. Using
required lengths may discourage the present practice (by men) of digging
up still-living trees for their roots.
If the stove is twice as efficient as their present stove
(because of being closed, mainly), then the women collect no more wood
and they can still sell energy (charcoal) equivalent to their own use,
while inhaling little if any smoke and rarely tending the fire. Or maybe
they just displace the purchase of charcoal they are already making.

6. Your suggestion that we "get a few women to join this club" is
excellent, and I look forward to being able to ask them to join. We
apparently do not have the correct address yet for Karekezi.

Prasad: Thank you for taking such a full and thorough look at
one specific charcoal-making design. I hope my comments will cause
further computation and dialog by you and others. I will of course make
your suggested rice-cooking test, but can't until next week. In fact I
may be silent for that full period - wow!

Regards

Ron

From aellegaard at nn.apc.org Mon Feb 26 04:00:11 1996
From: aellegaard at nn.apc.org (aellegaard@nn.apc.org)
Date: Tue Aug 31 21:34:49 2004
Subject: Questions. fundamental and technical
Message-ID: <199602261003.KAA02017@nn.apc.org>

Dear Stove Group,
My name is Anders Ellegard, and I was introduced to this list by
Prasad about a week ago. I have been working mainly on air
pollution from stoves and health effects of this pollution, but
also a little on design of coal (not charcoal) stoves in Maputo,
Mozambique. Otherwise most of my experience is from Zambia.

I have two questions for anyone of you who feels up to answering,
one is more fundamental and the other is technical.

Fundamental on charcoal stove:
While this contraption seems an interesting piece from the point
of engineering (and certainly discussion) I have some problems
understanding what it should be for.

In those Sub-Saharan African countries from which I have an
experience (Mozambique, Zambia, Tanzania) and probably Kenya,
charcoal in the rural areas is not a fuel but a SOURCE OF INCOME.
In the rural area people are using wood for cooking. They are
making charcoal for sale, especially in the dry season. When the
rains fail, charcoal production is one of few sources of income.

These people are not talking one or two kg of charcoal, but 2-3
orders of magnitude more, 0.5- several tonnes. If they would
like to use some of the charcoal in their own stoves, they can
clearly do so, but do it only rarely.

The urban households, on the other hand, are using charcoal
because it is the most convenient of the biomass based fuels:
easy to ignite, little smoke, good heat, high calorific value per
unit mass. And usually it is exchanged in a virtually FREE
MARKET (with its problems, of course) which makes it available
at most times and at an affordable cost, much to the difference
of "modern" alternatives such as LPG, kerosene and electricity
which may be cheap as fuels but require infrastructure and
investment costs both from society and the user. These
households do not use wood, and have no access to wood in their
surroundings, so they can not use the charcoal making stove,
either.

So, who is going to use it?

By the way, I saw a similar stove in an old pamphlet published
by TERI (around 1985), but it was using coal and producing cokes
in the "charring" compartment. It appears similar to what you
are referring to as the "Grover stove".

Technical:
In my design studies I was monitoring the combustion rate by
placing the whole stove on a balance. Span 50kg, precision 1g.
This happened in a large room with several doors and other types
of equipment, so the air pressure was not completely steady, and
this may have some caused fluctuations in the readings as we went
along. However, in EACH experiment (we did about 12), we noticed
initially an INCREASE in weight of the whole system, maybe for
the first 5 minutes.

You people who obviously do this every day, have you noticed
anything similar and kept it secret, or do you have any good
explanation for this? At the time we speculated that the
increase might be due to condensation in the chimney due to
release of SO2 which strongly affects the condensation point.
However we never pursued this and I still have no explanation.

Th reason for wanting more exact burn rates was in order to be
able to more accurately determine the emissions. A small
percentage of pollution during a high burn rate might be a lot
of pollution. However, there were no large differences from
using the averages (fuel before-fuel after).

From prasad at tn7.phys.tue.nl Mon Feb 26 09:32:38 1996
From: prasad at tn7.phys.tue.nl (prasad)
Date: Tue Aug 31 21:34:49 2004
Subject: Questions. fundamental and technical
In-Reply-To: <199602261003.KAA02017@nn.apc.org>
Message-ID: <9602261427.AA02718@tn7.phys.tue.nl>

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From tduke at igc.apc.org Mon Feb 26 09:45:05 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:49 2004
Subject: 3 successful stoves
Message-ID: <199602261447.GAA16253@igc3.igc.apc.org>

To the team,

A comment was made about the space heating stove I am using and if
this experience applies to some of the other questions. Actually I am
now running three succesful stoves. So I will describe them briefly.

(1) Space heating stove 24 inch tall fuel bed.
(2) Space heating stove 6 inch tall fuel bed.
(3) Cooking stove 6 inch tall fuel bed.

All of these are 6 inch dia.

Plan two more tests for today.
(1) Hole in the ground stove.
(2) 3 inch dia stove.

The hole in the ground stove to prove we can make them at no cost for
materials. The 3 inch dia stove for simmering. The question of
efficiently simmering a pot after we get it up to temperature is
addressed by this test.

The question has been raised about what do we do when commercial
producers make 0.5 ton or more charcoal per batch. Energy is of
value. I am planning tests of lagre batches. For generating
electricity. For distilling out chemical products. For making liquid
fuels. So any suggestions for what we can make with the energy
released from large batches is helpful. I want to test these.

Keep up the good work! We are progressing swiftly.

From E.Moerman at stud.tue.nl Mon Feb 26 11:06:38 1996
From: E.Moerman at stud.tue.nl (E.Moerman)
Date: Tue Aug 31 21:34:49 2004
Subject: Messages not received?
Message-ID: <61701.s335192@popserver.tue.nl>

I think I will also speak for Ron if I say that we will check the error
messages better. I suggest the following. If you did not receive any mail
from the stoves list for a given day check with Ron and me. This week you
best check with me, saturday Ron will take over again (we take turns of a
week each). If Ron and I receive a strange error message we will send you a
brief message to check if you received the mail concerned. If you did not
receive it Ron or I will send you either a copy of the original message or
the relevant volume of the stoves-digest list.

I hope we can keep everybody 'connected' in this way.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From E.Moerman at stud.tue.nl Mon Feb 26 11:07:00 1996
From: E.Moerman at stud.tue.nl (E.Moerman)
Date: Tue Aug 31 21:34:49 2004
Subject: Ron 25 Feb
Message-ID: <61718.s335192@popserver.tue.nl>

Tom Reed-
>> Objection! We are talking about a GASIFIER WOOD STOVE. You new stove
>> people need to read the gasification literature rather than making up a
>> whole new vocabulary of your own. "Primary air" has been used for
>> decades to mean the air that causes pyrolysis (whether to char plus
>> volatiles or mainly producer gas or everything in between).
>>
>>
Ron- Is there a way to distinguish these two extremes? In the present
> juncture of three disciplines: cookstoves (rarely having separate air
> supplies), charcoal making (throwing away the volatiles normally) and
> (producer) gasifiers (rarely wanting any charcoal), I hope that we can
> find some different terms - since the amounts of "primary" air are
> considerably different. Some modifying adjective would be helpful; I
> hold no brief for "fundamental", but clarity is needed when we mean very
> different things by the same word.
>
Etienne- Sorry Ron I have to agree with Tom on this. I was never confused by
the use of the term primary air. Furthermore both in stoves and gasifier
literature the term primary air is commonly used, while I have also seen it
in connection with charcoal production.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From E.Moerman at stud.tue.nl Mon Feb 26 11:07:39 1996
From: E.Moerman at stud.tue.nl (E.Moerman)
Date: Tue Aug 31 21:34:49 2004
Subject: Stoves development
Message-ID: <61756.s335192@popserver.tue.nl>

To start the discusion again I would like to put forward the following
questions:

Do we want to promote charcoal stove use? Why (not)?
Do we want to promote wood stove use? Why (not)?
Do we want to promote kerosene stove use? Why (not)?
Do we want to promote gas stove use? Why (not)?
What are the target groups of a stove that we want to develop?
What are the demands of these target groups and whatare they willing to put
up with?

I think these questions should be answered before developing a stove. I
suppose that any marketeer can tell you that you will have to know what
(potential) costumers want.

I understand that Ron will do a cooking test with his stove. I will try to
do a cooking test next week with a shielded fire. I suggest that we should
meet the following demands for a fair comparison.
-Use 2 kg of rice.
-Use 4 kg of water.
-Put water in a pan. For optimal performace water + rice should reach to
about 2/3 of the pan height.
-Bring the water to the boil within 20 min.
-Add the rice.
-If you can split a grain of rice with a nail of your thumb without
difficulty it is done.

Data to be collected for a fair comparison:
-Amount of water at start (kg)
-Amount of rice (kg)
-Temperature of the water at the start (K or Celcius)
-total amount of Wood species used
-Moisture content of the wood (ratio on a dry mass basis)
-total amount of char left

I am looking forward to the results.

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From E.Moerman at stud.tue.nl Mon Feb 26 11:07:54 1996
From: E.Moerman at stud.tue.nl (E.Moerman)
Date: Tue Aug 31 21:34:50 2004
Subject: Questions. fundamental and technical
Message-ID: <61727.s335192@popserver.tue.nl>

Dear Anders,

In the name of Ron and the rest of the group I welcome you to the
discussion.

As far as your doubts about the need for the inverted downdraft stove
(charcoal making stove) are concerned, you described something I wrote about
a month back although you wrote it down in a more illuminating way. I also
think that the stove should be considered as replacing other stoves and NOT
as replacing charcoal production methods. After all it is meant for cooking.

About your technical question.
> Technical:
> In my design studies I was monitoring the combustion rate by
> placing the whole stove on a balance. Span 50kg, precision 1g.
> This happened in a large room with several doors and other types
> of equipment, so the air pressure was not completely steady, and
> this may have some caused fluctuations in the readings as we went
> along. However, in EACH experiment (we did about 12), we noticed
> initially an INCREASE in weight of the whole system, maybe for
> the first 5 minutes.
>
> You people who obviously do this every day, have you noticed
> anything similar and kept it secret, or do you have any good
> explanation for this? At the time we speculated that the
> increase might be due to condensation in the chimney due to
> release of SO2 which strongly affects the condensation point.
> However we never pursued this and I still have no explanation.
>
> Th reason for wanting more exact burn rates was in order to be
> able to more accurately determine the emissions. A small
> percentage of pollution during a high burn rate might be a lot
> of pollution. However, there were no large differences from
> using the averages (fuel before-fuel after).
>
Etienne-
I would say that it cannot be SO2 since the condensing water comes from the
wood itself. I have observed something similar, however never this serious.
I have observed it during calibrations and measurements on kerosene stoves.
In our case it was cause by an incorrectly placed balance platform. I will
describe what happened in our case.

Below the loose platform there is another platform. This platform is
fastened by a few screws. This platform has 4 legs (pins) which are placed
in 4 shafts. Below these shafts you have the weighing elements, so the 4
legs rest directly on the weighing elements. If the platform is not placed
correctly the legs will make contact with the walls of the shafts, which
introduced friction. If you now place a weight on the balance the friction
will keep the legs from making their full movement and as a result the scale
shows a weight that is too low. If you leave the balance like this the legs
will slowly move downward, thus increasing the reading of the weight. This
effect can be quite serious and you can correct it by loosening the platform
and replacing it correctly. After fastening the platform you have to check
again since it is difficult to get rid of all the friction. Most of the time
you will have a small amount of friction left. Keep trying until things are
ok again. Replace top platform and also important place the balance in a
horizontal position. Our balance contains a small eye for this. If the
balance is not completely level stresses can occur which can cause the legs
to make contact with the shaft walls again. Probably your manual describes
how to reposition the 2nd platform.

Good Luck!

Etienne
**********************************************************************
Etienne Moerman E-mail: E.Moerman@stud.tue.nl
J. Buyslaan 71 Tel/Fax: +31-40-257 1491
5652 NJ EINDHOVEN The Netherlands

From tduke at igc.apc.org Mon Feb 26 15:14:27 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Hole in the Ground Stove
Message-ID: <199602262017.MAA29323@igc3.igc.apc.org>

To the stove team,

No metal or other purchased materials necessary to make a good
charcoal producing stove. I just constructed a successful stove by
diging a 6 inch dia hole in the ground. Digging a second hole near-by
for air. Tunneling between holes in two places. At the bottom for
primary air. At the mid point for secondary air. Put chicken wire in
bottom for grate. However I think other things will work for a grate.

From tduke at igc.apc.org Mon Feb 26 15:14:37 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Annular Heat Transfere
Message-ID: <199602262017.MAA29367@igc3.igc.apc.org>

Stoves Team,

Achieved annular heat transfere configuration with hole in the ground
stove. Making chimney hole a little larger in diameter then can and
suspending can in the chimney. Boils water quickly.

From tduke at igc.apc.org Mon Feb 26 15:14:30 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: One Can Stove
Message-ID: <199602262017.MAA29337@igc3.igc.apc.org>

Stove Team,

I have just constructed a charcoal producing stove with one can. By
digging a hole for the fuel holding part of the stove. And digging an
air passage to the bottom of the stove. Then placing a can over the
hole. Sitting it on some small diameter rods to provide a gap for
secondary air.

From tduke at igc.apc.org Mon Feb 26 15:14:22 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Great Hotdog Cooker
Message-ID: <199602262016.MAA29303@igc3.igc.apc.org>

To the team,

Just made a great hotdog cooker. Constructed a 4 inch dia charcoal
making stove with a 5 inch deep fuel bed. The intent is to see if we
can make a stove that will provide the correct heat for simmer. After
bringing to boil. Looks good! Also makes a great hotdog cooker. Runs
for about 45 minutes. Can cook 3 or 4 hotdogs at a time.

From tduke at igc.apc.org Mon Feb 26 15:14:52 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Liquid Piston Stirling Engine
Message-ID: <199602262017.MAA29396@igc3.igc.apc.org>

To the Stove Team,

I am considering generating electricity during charcoal production.
Especially in relation to the 0.5 ton or more commercial operations.
Considering building a liquid piston stirling engine for this
purpose.

In this regard some think that we should just go for gasogen gas and
skip the charcoal. Then use the gas to run internal combustion
engines. I think we should do both, to some degree.

From larcon at csn.net Mon Feb 26 19:03:39 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:50 2004
Subject: Hole in the Ground Stove
In-Reply-To: <199602262017.MAA29323@igc3.igc.apc.org>
Message-ID: <Pine.3.89.9602261734.A1551-0100000@teal.csn.net>

Tom: Congratulations! This sounds very creative. I think you
have solved two very big issues - cost and stability.

I have not yet heard you talk about the quantity of charcoal.
Have you tried any measurements to show the efficiency of making charcoal?

How do you recover the charcoal? Can you shut off all air and
snuff the process?

Can you estimate turn-down ratio? How do you control the primary
and secondary air (wooden plugs?)

Ron

On Mon, 26 Feb 1996, Thomas Duke wrote:

> To the stove team,
>
> No metal or other purchased materials necessary to make a good
> charcoal producing stove. I just constructed a successful stove by
> diging a 6 inch dia hole in the ground. Digging a second hole near-by
> for air. Tunneling between holes in two places. At the bottom for
> primary air. At the mid point for secondary air. Put chicken wire in
> bottom for grate. However I think other things will work for a grate.
>
> Tom Duke
> --------------------------------------------------------------------
> Tom Duke
> 4363 Hunt Road
> Burlington, Iowa 52601-8917 U. S. A.
> The Renewable Energy Research Center and Farm
> --------------------------------------------------------------------
>

From larcon at csn.net Mon Feb 26 20:12:18 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:50 2004
Subject: Response to Ellegard's of 26 Feb.
In-Reply-To: <199602261003.KAA02017@nn.apc.org>
Message-ID: <Pine.3.89.9602261735.A1551-0100000@teal.csn.net>

Comments below with some editing out.

On Mon, 26 Feb 1996 aellegaard@nn.apc.org wrote:

> Dear Stove Group,
> My name is Anders Ellegard, and I was introduced to this list by
> Prasad about a week ago. I have been working mainly on air
> pollution from stoves and health effects of this pollution, but
> also a little on design of coal (not charcoal) stoves in Maputo,
> Mozambique. Otherwise most of my experience is from Zambia.

Have you done any work on pollution from charcoal making? Kirk
Smith has and hope he will chime in on this point of how bad
charcoal making is - with release of all the volatiles that we can be
using productively. In rural areas, the charcoal-making efficiency is
perhaps close to half of the 25% I believe we can achieve.

>
> I have two questions for anyone of you who feels up to answering,
> one is more fundamental and the other is technical.
>
> Fundamental on charcoal stove:
> While this contraption seems an interesting piece from the point
> of engineering (and certainly discussion) I have some problems
> understanding what it should be for.
>
> In those Sub-Saharan African countries from which I have an
> experience (Mozambique, Zambia, Tanzania) and probably Kenya,
> charcoal in the rural areas is not a fuel but a SOURCE OF INCOME.
> In the rural area people are using wood for cooking. They are
> making charcoal for sale, especially in the dry season. When the
> rains fail, charcoal production is one of few sources of income.
>
I see the same families being involved in rural areas, and for the
same reason - income generation ( but more for less work). During the
appropriate season, the wood is gathered in the same way, but the charcoal
would be made differently. For instance the wood could be "given"to women
for cooking (all year) in exchange for the resultant charcoal(twice as
much as from the traditional pits). Or the wood could be "sold", with the
understanding that the charcoal would be purchased back at a fair price -
at much less effort for the person already involved in the charcoal trade.
I am hoping that this is a win-win situation.

> These people are not talking one or two kg of charcoal, but 2-3
> orders of magnitude more, 0.5- several tonnes. If they would
> like to use some of the charcoal in their own stoves, they can
> clearly do so, but do it only rarely.
>
My guess is they don't use charcoal because they would rather
have the money. But that is exactly why I think one could sell such
stoves. (although I am very excited about Tom Duke's demonstration of a
zero-cost stove. That should make dissemination much more rapid.)

> The urban households, on the other hand, are using charcoal
> because it is the most convenient of the biomass based fuels:
> easy to ignite, little smoke, good heat, high calorific value per
> unit mass. And usually it is exchanged in a virtually FREE
> MARKET (with its problems, of course) which makes it available
> at most times and at an affordable cost,

My experience is that the cost is outrageous in their terms, but
I agree that it is deemed a desirable fuel. I think it possible that a
wood-burning, charcoal-making stove may be used even in cities if it is
clean and convenient and lower cost. The suppply of wood will certainly
appear if there is a demand. My experience is that wood costs about 1/3
by weight what charcoal costs and I think this may drive the market
toward wood burning for some in cities.

> much to the difference
> of "modern" alternatives such as LPG, kerosene and electricity
> which may be cheap as fuels but require infrastructure and
> investment costs both from society and the user. These
> households do not use wood, and have no access to wood in their
> surroundings, so they can not use the charcoal making stove,
> either.
>
I believe if they have access to charcoal, they can also have
access to wood. The problem is that the existing wood stoves don't offer
enough for their cost.

> So, who is going to use it?
>
See the above - but I am not claiming this will take over
everywhere - only where there is now a substantial use and sale of charcoal.

> By the way, I saw a similar stove in an old pamphlet published
> by TERI (around 1985), but it was using coal and producing cokes
> in the "charring" compartment. It appears similar to what you
> are referring to as the "Grover stove".

Do you think this provided any air control? I believe this stove
would be very much more attractive if it was controllable. Also, it
seemed very expensive (because it got so hot). Might anyone have a
price?

Anders, It was good to hear from you for the first time. We need
to hear a lot more on pollution and especially on how to measure it
cheaply.

Ron

From larcon at csn.net Mon Feb 26 20:16:03 1996
From: larcon at csn.net (Ronal Larson)
Date: Tue Aug 31 21:34:50 2004
Subject: Response to Prasad's 26 Feb.
In-Reply-To: <9602261427.AA02718@tn7.phys.tue.nl>
Message-ID: <Pine.3.89.9602261757.A1551-0100000@teal.csn.net>

Comments below:

On Mon, 26 Feb 1996, prasad wrote:

> Dear Stove folks
> Here is one more guy who shares my pessimism about charcoal making stoves.

See my previous response to Ellegard. I confess I still don't
understand the pessimism.

>
> With the corrections made to my calculations by Ron, we at most produce 200g
> of charcoal for the meal I described in my previous message. After recovery
> this will mean under 3kg per week.
>
Prasad, please reread my comments, especially under item d1. To
do the cooking task using your values, will require 1.2 kg of wood,
rather than 0.6 kg, but will give 0.3 kg of charcoal, not 0.2 kg. If we
don't agree on these numbers, we need some more dialog on this point. I
get 4.2 kg / week with your numbers - 50% more than your numbers, so this
is a significant point of disagreement.

> Since rural folk do not use the charcoal, it should be sold in the nearest

In Ethiopia, I found rural folk using lots of charcoal - for
making coffee especially. And the present manufacture is very inefficient.

> city. That means, one needs to transport it to the place. That will make
> sense if about 200 families join together they will have about 600kg to
> transport per week. This will require some organizing.

I get .84 tonnes to transport per week for this scenario - I
think it is enough and that the organization will occur - when funds are
involved. Because charcoal stores well, this transport can occur when
transport costs are least. My experience is that there is more flow of
goods out to the rural areas than inward, so transport should not be a
major problem.

> from the countries concerned to talk to us. Maybe Bhattacharya can throw
> some light on this discussion with his experience in Thailand. Haven't heard
> from him for some time!

My personal contact with refugees from charcoal-using countries
(Ethiopia and Sudan) has been very positive. I hope others will make
such contacts also. Prasad, thank you for this suggestion; we definitely
need more repesentation from wood- and charcoal-using societies..

Ron

From krksmith at uclink4.berkeley.edu Mon Feb 26 21:04:45 1996
From: krksmith at uclink4.berkeley.edu (Kirk R. Smith)
Date: Tue Aug 31 21:34:50 2004
Subject: Ron's request re stove and kiln emissions
Message-ID: <199602270207.SAA10554@uclink4.berkeley.edu>

We have just finished extensive measurements of emissions (about 65
different gases plus particulates) from the 30 most common stove/fuel
combinations in China and are just finishing up such measurements for a set
of 30 in India. These include a wide range of traditional and modern fuels.
(Our colleagues in India have also done some work on producer gas devices.)

We are also just starting such measurements of five types of charcoal kilns
(mud beehive, brick beehive, earth mound, single oil drum, rice husk mound)
in Thailand. We have just finished measurements of Michael Antal's
high-efficiency high-pressure kiln in Hawaii.

All these measurements are done, of course, with complete mass, carbon, and
energy accounting of fuel inputs and outputs such as ash and charcoal.

Soon (a few months) we should have a quite useful database to share. It is
being paid for by the EPA greenhouse gas people, but has health and other
implications as well.

Best/K

Kirk R. Smith
Professor of Environmental Health Sciences
(Associate Director of International Programs,
Center for Occupational and Environmental Health)
Warren 7360
University of California
Berkeley, CA 94720

phone: 510-643-0793; fax: 510-642-5815
email: krksmith@uclink4.berkeley.edu

From aellegaard at nn.apc.org Tue Feb 27 04:32:21 1996
From: aellegaard at nn.apc.org (aellegaard@nn.apc.org)
Date: Tue Aug 31 21:34:50 2004
Subject: Comments on charcoal
Message-ID: <199602271036.KAA01004@nn.apc.org>

Dear Stove friends,

I am impressed by your enthusiasm and readiness to respond. This
is how I hoped several of my email groups would work.

Response to Etienne:
On the weight increase -the increase did not start until the
fire was ignited, so it seemed to have something to do with the
combustion. It may, of course, be some technical reason to it
but this I cannot check, since it is many years ago. I was
just curious to know if this was a common occurrence.

Response Tom Duke, re. electricity production:
There have been some experiences with electricity production
using gasifiers in Tanzania. The problem is usually that the
gasifiers are not easy to keep inrepair using the rural tech-
nology available, and the combustion engines used are often
esoteric (uncommon in the local market) making spares supply
difficult.

To Ron
re. rural charcoal production efficiency.
I dont know where you get your figures on rural charcoal
production. Results from Zambia indicate that the output from
earth-mound kilns is 20-25% charcoal/wood by weight on a dry
wood basis (ref. E.N. Chidumayo, University of Zambia, Lusaka).
Remember stoves people initially believed they had an easy win
by assuming too low efficiencies for traditional fires (See eg.
Jas Gill, "Improved Stoves in Developing Countries -A Criti-
que", Energy Policy, 135-144, April 1987). We shouldnt make
the same mistake again.

re. pollution from charcoal production.
I have not made any emission assessments, but I have measured
the exposure of charcoal producers to particulates and carbon
monoxide (in Zambia). Much higher, of course, than those of
the women using the stuff in the city, but apparently not very
high compared to occupational standards in industrialized
countries. There is a report of this from the Stockholm
Environment Institute, (seihq@nn.apc.org). I am the author.

Re. making charcoal for profit
We agree on the point of making money for as little work as
possible. This is where I doubt that it would be less work to
chop all this wood into small pieces to feed the stove. One of
the reasons to make charcoal is actually that much of the wood
is too hard to chop. The whole stem of such trees is put at
the base of the kiln and the branches are stacked around it.

Rural people collect dry branches and twigs for their fire.
They do not use any stove. There is no cash outlay to save for
a stove or fuel costing anything. Trees are usually not cut
for rural fuel consumption.

Re. charcoal storage:
At least in Zambia, urban consumers avoid buying charcoal in
small pieces, it should preferably be in the size of 0.5 to 1
litre to attract consumer interest. We have just completed a
project on charcoal storage in Lusaka, and almost half of the
charcoal (though completely useful for fuel) had to be dis-
carded because it had been crushed into small pieces during
handling. Nobody would buy it.

Charcoal does not store well.

Re. charcoal cost.
In running terms the charcoal price has increased by figures
around 10,000 - 100,000 percents in the past thirty years,
depending where you look. In real terms it has been stable,
though there are seasonal variations. In Zambia a bag of
charcoal (40 kg) costs around 3 USD. This was also the price
in 1978. An average urban family uses slightly more than two
bags per month. Charcoal cost is not outrageous.

Re wood use in urban areas.
True, wood would be available in the cities, given there is a
market. Actually there is a for wood, used for funerals, which
is an increasing market due to the effects of the Virus.

But using wood for cooking? It seems far less convenient than
using charcoal. And regarding the pollution, results from an
exposure survey of women in Maputo indicate that wood use is
associated with increased health problems, while charcoal use
is not.

So what is the emission spectrum of the charcoal making stove.
And what are the chances of guaranteeing first rate operation
by all the users? I say, keep charcoal production in the rural
areas. Also realize from above that the rural people do not
need to be deprived of their income.

Re. the TERI stove.
I tried to find the paper which was essentially a list of
stoves that had been tried in India, but failed. Prasad should
have it, no doubt.

To Kirk Smith:
Good to hear you are still around! Looking forward to seeing
your data.

Regards to all
Anders

From tduke at igc.apc.org Tue Feb 27 11:28:02 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Thanks Team
Message-ID: <199602271630.IAA25204@igc3.igc.apc.org>

To the stoves Team,

When we stand on the shoulders of giants then we can see the way to
go! You truly are giants in penetrating insight into your various
fields. Your understanding of the needs. Your knowledge of what
materials are available. Your depth of character in sharing your
talents for the welfare of humanity.

My warmest thanks for getting to work together with you in this
achievement for humanity.

Tom Duke
--------------------------------------------------------------------
Tom Duke
4363 Hunt Road
Burlington, Iowa 52601-8917 U. S. A.
The Renewable Energy Research Center and Farm
--------------------------------------------------------------------
>From Ron Larson Feb 26
>Tom: Congratulations! This sounds very creative. I think you
>have solved two very big issues - cost and stability.

>From Hole in the Ground Stove reply.

From tduke at igc.apc.org Wed Feb 28 11:49:28 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Hole in the Ground Stove
Message-ID: <199602281648.IAA03971@igc3.igc.apc.org>

To Tom Reed and all:

I am using oak wood. I cut it to 5 inch long. Split it to 1 inch
triangles (all sides 1 inch) + - 3/8 inch.

I pulled the hot charcoal out with metal tongs. Put it in a can and
covered it to snuff it out.

As soon as I get a chance I will snuff it in the ground. Probably
will plug the two air holes and plug the air gap around the bottom
of the pot with mud.

I get good charcoal. However a little charcoal was consumed on the
side where the air comes in at the bottom. I plan to trench some
groves in the bottom for air distribution, to see if this will enable
even charcoal production.

I think more then one hole for air can be dug if more even
distribution of air becomes a serious issue. The simplicity of one
air hole feels about right, so we could try digging two or more
tunnels for primary air. Two or more tunnels from the bottom of the
air hole to entry points in the bottom of the fire hole.

The amount of charcoal seems to be about 25%. Which is about what is
expected if I am reading everyone else correctly. There is little
shrinkage of the original size and shape of the wood bits. There is
very little ash.

Turn-down ratio seems to be about 1/2 or a little more. My first
crude attempts. I think with some practice this will improve.

I am passing on what we learn to some missionaries in africa. So I
hope to hear, in time, how it works in the field. I want to hear if
they have problems, because I feel we need to apply our knowledge to
it's on-going development.

I see potential design changes that will fit it for wet climates or
places where there are periods of heavy rain. This may including
building a mound of mud under a shelter and digging a hole in the
mound for the stove. Digging primary and secondary air holes in the
sides.

I suspect we can put the wood in a chicken-wire basket. This way we
can remove the finished charcoal as a unit (in the basket). This may
work in places where they have access to and can afford chicken wire.
If this is of interest I will test it soon. I think I will test it
soon any way.

Any other issues you would like me to test, please let me know. So I
can try them out.

in friendly spirit,

Tom Duke
> --------------------------------------------------------------------
> Tom Duke
> 4363 Hunt Road
> Burlington, Iowa 52601-8917 U. S. A.
> The Renewable Energy Research Center and Farm
> --------------------------------------------------------------------

From verhaarp at janus.cqu.edu.au Thu Feb 29 00:22:37 1996
From: verhaarp at janus.cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:50 2004
Subject: Annular Heat Transfere
Message-ID: <9602290525.AA14908@janus.cqu.edu.au>

>Stoves Team,
>
>Achieved annular heat transfere configuration with hole in the ground
>stove. Making chimney hole a little larger in diameter then can and
>suspending can in the chimney. Boils water quickly.
>
>Tom Duke
>--------------------------------------------------------------------
>Tom Duke
>4363 Hunt Road
>Burlington, Iowa 52601-8917 U. S. A.
>The Renewable Energy Research Center and Farm
>--------------------------------------------------------------------
>
Piet Verhaart

Dear Tom,
From the above description I can't get any idea about the
configuration of your hole in the ground stove. Further, did you do any
measurements? How much wood to boil how much water, how long to heat x kg of
water from y C to 100 C.

This was my immediate reaction to your message. From your other messages I
found out some data on your stove, not the depth.
These experiments are very useful but only if they are well documented so
that others, reading about it can duplicate your experiments. I do
appreciate your continuous commitment to our cause.

Piet

From verhaarp at janus.cqu.edu.au Thu Feb 29 00:23:25 1996
From: verhaarp at janus.cqu.edu.au (Peter Verhaart)
Date: Tue Aug 31 21:34:50 2004
Subject: Iets Anders
Message-ID: <9602290526.AA15622@janus.cqu.edu.au>

Piet
First of all, welcome on the scene, Anders. You made a lot of sense.
On the weight increase of your stove on ignition. Was it your scales that
could carry up to 50 kg while maintaining an accuracy of .1 g? If so, the
initial weight increase might be very small and due to condensation of water
vapour. How did you light the stove, with gas? Was it a heavy stove? In
Eindhoven we never had any measurable condensation because our stoves were
mostly very light and/or had very little solid parts downstream of the fire
for condensation to settle on.

Very well put, "...had an easy win assuming too low efficiencies for
traditional fires." So far as I know even today nobody has made efficiency
measurements in the field of the traditional stoves AS USED BY THE
TRADITIONAL USERS.

What do you mean by "Charcoal does not store well" ?

I can see two reasons for not having a market for firewood in cities.
1. There are no halfway decent stoves that burn wood and are as easy to tend
and maintain as charcoal stoves.
2. It takes more effort to reduce hunks of wood to useable size than charcoal.

I am sure if there were a stove with the specifications we dream of, the
market mechanism would provide firewood in any desired size.

Cheers,

Piet Verhaart

From prasad at tn7.phys.tue.nl Thu Feb 29 08:54:36 1996
From: prasad at tn7.phys.tue.nl (prasad)
Date: Tue Aug 31 21:34:50 2004
Subject: I am still alive
Message-ID: <9602291349.AA07660@tn7.phys.tue.nl>

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From E.Moerman at stud.tue.nl Thu Feb 29 11:14:06 1996
From: E.Moerman at stud.tue.nl (E.Moerman)
Date: Tue Aug 31 21:34:50 2004
Subject: Comments on charcoal
Message-ID: <62179.s335192@popserver.tue.nl>

Anders
> Response to Etienne:
> On the weight increase -the increase did not start until the
> fire was ignited, so it seemed to have something to do with the
> combustion. It may, of course, be some technical reason to it
> but this I cannot check, since it is many years ago. I was
> just curious to know if this was a common occurrence.

A change in weight (eg. due to combustion) can cause the pegs to move a bit
and reduce the friction (I did observe this) and thus increase the weight
reading. Too bad you are not able to check this. I don't think it was a
combustion effect, since I have never obtained such an unexplainable
reading and I have never heard of others who have.

I would also like to say that I am glad that we now have somebody on the
list with knowledge of the fuelmarket.

> re. pollution from charcoal production.
> I have not made any emission assessments, but I have measured
> the exposure of charcoal producers to particulates and carbon
> monoxide (in Zambia). Much higher, of course, than those of
> the women using the stuff in the city, but apparently not very
> high compared to occupational standards in industrialized
> countries. There is a report of this from the Stockholm
> Environment Institute, (seihq@nn.apc.org). I am the author.

According to Ron's measurement this stove is reasonably clean. You might
have heard from the downdraft stove which is very clean. It can meet the CO
emission standards (old ones, I don't know about the new emission standards)
for gas appliances.

> Re. making charcoal for profit
> We agree on the point of making money for as little work as
> possible. This is where I doubt that it would be less work to
> chop all this wood into small pieces to feed the stove. One of
> the reasons to make charcoal is actually that much of the wood
> is too hard to chop. The whole stem of such trees is put at
> the base of the kiln and the branches are stacked around it.

I did not realize that charcoal was made because part of the wood is too
hard to chop.

> But using wood for cooking? It seems far less convenient than
> using charcoal. And regarding the pollution, results from an
> exposure survey of women in Maputo indicate that wood use is
> associated with increased health problems, while charcoal use
> is not.

See my comment above.

Since pollutant emissions for stoves presently in use are harmful I think it
is more obvious to work on the improvement of woodstoves than on a
substitution by charcoal. Especially if you can expect charcoal production
in pits on a large scale, this you cannot avoid.

Etienne
---------------------------------------------
Etienne Moerman
Joh. Buyslaan 71 tel. +31-40-2571491
5652 NJ EINDHOVEN The Netherlands

From tduke at igc.apc.org Thu Feb 29 14:44:52 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Annular Heat Transfere
Message-ID: <199602291947.LAA06275@igc3.igc.apc.org>

Dear Piet,

Thanks for the message. It helps me see how I can help. My comments
are below amid your message. So let me know what you think.

> Date: Thu, 29 Feb 1996 15:25:28 +1000
> To: stoves@crest.org
> From: verhaarp@janus.cqu.edu.au (Peter Verhaart)
> Subject: Re: Annular Heat Transfere
> Reply-to: stoves@crest.org

> >Stoves Team,
> >
> >Achieved annular heat transfere configuration with hole in the ground
> >stove. Making chimney hole a little larger in diameter then can and
> >suspending can in the chimney. Boils water quickly.
> >
> >Tom Duke
> >--------------------------------------------------------------------
> >Tom Duke
> >4363 Hunt Road
> >Burlington, Iowa 52601-8917 U. S. A.
> >The Renewable Energy Research Center and Farm
> >--------------------------------------------------------------------
> >
> Piet Verhaart
>
> Dear Tom,
> From the above description I can't get any idea about the
> configuration of your hole in the ground stove. Further, did you do any
> measurements? How much wood to boil how much water, how long to heat x kg of
> water from y C to 100 C.
>
> This was my immediate reaction to your message. From your other messages I
> found out some data on your stove, not the depth.

Dear Piet,
The stove is 14 and 1/8 inches deep. I used about 1 kg of wood.

> These experiments are very useful but only if they are well documented so
> that others, reading about it can duplicate your experiments. I do
> appreciate your continuous commitment to our cause.
>
> Piet

The primary air passage is about 2.35 sq inches. The secondary air
passage is about the same (2.35 sq inches).

I plan to get some rough measurements of time, kg water, kg wood
today. I need to pull together some measuring tools so will have more
accurate data as time goes on.

I also plan to try an 8 and 1/2 inch diameter chimney with a 6 inch
diameter can suspended inside it. This should leave about 28 and 1/4
sq. inches of area for gas flow in the chimney. The same as the
original 6 inch diameter chimney.

More then happy to supply all details to help anyone duplicate them.
First of all I am looking forward to the results others are getting,
so I can tell how well I am doing. Secondly I am hoping others will
suggest and try improvements. So I can try them also.

I also have questions about the second run vs. a first run. This is
because of thermal-mass. Heat storage in the ground. I have very
little experience with heat conduction or insulating qualities of
soil. So I am wondering if lining the fire hole with something cheap
will make a significant difference.

Damp soil vs. dry soil is also a question for me. I am wondering if
it is important. In the field it may not be a valid issue. so I would
like to make measurments under various conditions. Some of these will
not take very long and give us a more rounded picture.

Right now our ground is frozen (7 degrees F.) so I suspect this will
have some bearing on kg of wood and time necessary to boil a measured
amount of water. I plan to run as many tests as I can today. So we
have some data. Perhaps enough to plot a curve (as the ground warms
up).

So we have a 6 inch diameter hole in the ground 14 and 1/8 inches
deep. With a primary air hole about 1 and 3/4 inches dia. (oval) and
a secondary air hole the same dia. about 7 inches up from the bottom.
There is a little chicken wire in the bottom for a grate. There is
another hole 7 and 1/2 inches away for air. The primary and secondary
air holes connect the air hole to the stove. The air hole is also 14
and 1/8 inches deep. It is six inches wide and has one sloping wall.
The sloping wall goes away from the stove, and the top opening is 15
inches. This is so I could reach in and drill the primary and
secondary air holes into the stove.

To test the annular heat transfere I plan to widen the upper 7 inches
of the hole to 8.5 inches dia and suspend a 6 inch diameter can inside
it. For accurate tests for field conditions some different
configurations to fit the cooking "pots" they are using will be
necessary. so I feel this 8 inch dia test will give us some idea, a
measurment that can be used as a guide to understanding how it works
with other cooking pots.

I briefly tested the annular heat transfere by widening the upper
three inches of the chimney to about 7 inches. The results were
exciting, so that is why I am extending and widening the heat transfere
area in the chimney. I boiled about 500 g of water in that first
test. However the stove had been operating for some time so I have no
data except that it took much less then 1 kg of wood.

Going out to make some measurments :)

Tom Duke

From tduke at igc.apc.org Thu Feb 29 15:40:34 1996
From: tduke at igc.apc.org (Thomas Duke)
Date: Tue Aug 31 21:34:50 2004
Subject: Annular Heat Transfere (2)
Message-ID: <199602292043.MAA16657@igc3.igc.apc.org>

> >
> Piet Verhaart
>
> Dear Tom,
> From the above description I can't get any idea about the
> configuration of your hole in the ground stove. Further, did you do any
> measurements? How much wood to boil how much water, how long to heat x kg of
> water from y C to 100 C.
> Piet

Dear Piet,
This is the second message today. The first contains a more complete
discription of the hole in the ground stove. These are the results of
todays tests.

I just boiled 2 liters of water in 16 minutes from 57 degrees F.
With no lid on the can. Expect 1 kg of wood to last about one hour.
Two tests (1) in frozen ground (2) in wet ground. Should get better
results in dry warm ground with lid on.

These results seem reasonable to me. How do they seem to you?

Wood standing vertically. Top light. With 2 inch long 1/4 inch thick
slivers of wood to start fire. About a cup and 1/2 of slivers.

Getting some smoke. However it is windy here today. May need more
space between bottom of can and top of fire?

Thanks,

BioEnergy Lists: Improved Biomass Cooking Stoves

February 1996 Biomass Cooking Stoves Archive