Re: Stove efficiency

["A.D. Karve" <adkarve@pn2.vsnl.net.in>]

The user is concerned both about clean burning as well as fuel saving. Clean
burning is a function of the stove design, as well as of the nature of the
fuel. In the Indian rural situation, people use a variety of fuels including
underground rhizomes of sugarcane, coconut hulls, corn shanks, cattle dung
cakes, cotton stalks, midribs of coconut leaves, etc. Some of this material
burns with a tall flame while some doesn't.  Also their moisture content
varies. Among all the fuels used in rural India, charcoal burns the
cleanest. The rate of heat transfer is certainly dependant on the stove
design and also on the size, shape, material and position of the pot from
the fuel. City housewives have started using stainless steel pots with
copper or aluminium bottom, but in villages people still use pots, made of
brass, aluminium or mild steel.  The shapes and sizes of the pots vary to a
great extent.  We have designed a cooker and stove system,in which the
cooker has a double wall, with a quarter inch gap between the cooking vessel
and its outer jacket. The flue gases pass through the gap, so that the
cooker is heated from all sides. The cooker generates steam which cooks four
substances in four pots simultaneously.  With our configuration of the stove
and cooker, and using charcoal briquettes having a calorific value of about
5200 kcal/kg, we get an efficiency of almost 60%.  The charcoal burns
cleanly, and because of the extremely high efficiency of the cooking device,
we require just 100 g briquettes to cook rice, vegetables, beans and meat
for a family of 5. The individually handcrafted prototypes of the
stove-and-cooker assembly cost us about Rs. 550 each, but the mass produced
system would cost about Rs. 350 (US$ 1= Indian Rs.47).
Dr. A.D.Karve, President,
Appropriate Rural Technology Institute
Pune, India.

-----Original Message-----
From: Paul S. Anderson <psanders@ilstu.edu>
To: Stoves <stoves@crest.org>
Cc: Bob and Karla Weldon <bobkarlaweldon@cs.com>; Ed Francis
<cfranc@ilstu.edu>; Tsamba--Alberto Julio <ajtsamba@zebra.uem.mz>; Lily
Coyle <astrozen2000@hotmail.com>; David Kennell - ISU <drkenne@ilstu.edu>
Date: Monday, May 06, 2002 9:37 PM
Subject: Re: Stove efficiency


>Stovers,   Please allow the novice to argue about words, because the words
>are exactly where the confusion lies.  Please read on:
>
>>John wrote:
>>
>> >It is my conclusion that the above statement is irrelevant.
>> >We need minimum air pollution, so keep on finding better
>> >ways to capture the heat from good combustion.
>
>>At 12:36 AM 5/5/02 +0200, Crispin wrote:
>
>>I agree with this approach.  It is easier to collect heat if it is there
in
>>the first place.
>
>While APPEARING to disagree with my earlier questioning about "stove
>efficiency", BOTH John and Crispin have provided support for my position.
>
>We must not use the word "efficiency" to refer to two very different
>aspects of stove functions.   ONE is "how well the fuel is
>consumed",    The SECOND is "how well is the available heat captured".
>
>If you re-read the opening two statements (from John and Crispin, and there
>was another one also),  BOTH are mixing the two uses of the concept of
>"efficiency"
>
>John wrote:  "finding better ways to capture the heat from good
combustion."
>
>Crispin wrote:  "easier to collect heat if it is there in the first place."
>
>"from good combustion" and "there in the first place" refer to getting the
>fuel converted into heat energy.  A very worthy cause.  and let that be
>known as "combustion efficiency"
>
>"Collect and capture" deal with "getting the heat to do something
>useful".  That is another worthy cause.   and let it be known as
>"heat-capture efficiency".
>
>They are VERY different, and we should NOT use the expression "stove
>efficiency" because BOTH efficiencies (combustion AND heat-capture) are
>playing roles simultaneously and often in ways that cannot be separated.
>
>Therefore, FOR ISSUES ABOUT POLLUTION FROM STOVES (that is, the fuels and
>combustion chamber aspects of stoves), combustion efficiency is extremely
>important.
>
>And FOR ISSUES OF COOKING AND SPACE HEATING (that is, the physical stove
>structure and the cooking aspects of stoves), heat-capture efficiency is
>what is important.
>
>example:  98% combustion efficiency that is only 50% captured yields 49% ,
>while a 80% combustion efficiency that is 80% captured yields 64%
>
>Our work on stoves must be concerned with BOTH aspects of
>efficiency.   Both aspects are linked together (and overall we do evaluate
>them together in a "replicable" stove that many people can acquire and
use).
>
>But we need to find ways to measure EACH ASPECT SEPARATELY, that is, to
>hold one of the two constant during the tests of the other one.  Said
>differently, the shape and material of the cooking pot impact "heat-capture
>efficiency" while primary air and moisture level impact "combustion
>efficiency."
>
>Please note that we are NOT in disagreement on the importance of
>efficiency, but that we need to be careful to distinguish between the two
>in both discussions and measurements.
>
>Paul
>
>
>
>
>
>
>
>
>Paul S. Anderson, Ph.D.,  Fulbright Prof. to Mozambique 8/99 - 7/00
>Rotary University Teacher Grantee to Mozambique >10 mo of 2001-2003
>Dept of Geography - Geology (Box 4400), Illinois State University
>Normal, IL  61790-4400   Voice:  309-438-7360;  FAX:  309-438-5310
>E-mail: psanders@ilstu.edu - Internet items: www.ilstu.edu/~psanders
>
>
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>>
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m
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>


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Stoves List Archives and Website:
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http://crest.org/discussiongroups/resources/stoves/
>
Stoves List Moderators:
Ron Larson, ronallarson@qwest.net
Elsen L. Karstad, elk@wananchi.com www.chardust.com
>
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Other Biomass Stoves Events and Information:
http://www.bioenergy2002.org
http://www.crest.org/articles/static/1/1010424940_7.html Bioenergy
http://www.crest.org/articles/static/1/1011975339_7.html Gasification
http://www.crest.org/articles/static/1/1011975672_7.html Carbon
>
For information about CHAMBERS STOVES
>http://www.repp.org/discussiongroups/resources/stoves/Chambers/Chambers.htm