Re: Stove efficiency

["Kevin Chisholm" <kchisholm@ca.inter.net>]

Dear Dr. Karve

Subject: Re: Stove efficiency


> 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.

You have hit upon an extremely important point here, one that is usually
overlooked because of its simplicity and obviousness.

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.

Consider a stove or furnace designed to run efficiently on kerosene. It
won't run efficiently on furnace oil, natural gas, or Bunker C. Yet these
fuels that won't work in a kerosene stove don't have any moisture, and they
are fluid also.

It is thus very difficult to imagine how a stove that was designed to run on
"stick fuel" could run efficiently on leaves, solid and irregular roots, and
lump fuels all with very different moisture contents and burning properties.

Among all the fuels used in rural India, charcoal burns the
> cleanest.

Is that perhaps because charcoal is reasonably consistent in size, moisture
and burning characteristics, and that perhaps that the stoves in which the
charcoal is burned are of a design which is appropriate to burning charcoal?

 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.

Yes indeed. Anyone can "set fire to biomass." It takes a clever design
indeed to optomise the relevant variables and get the most out of 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).

This is indeed an excellent design. What you have done is found a way to
work with the selected fuel, and the have come up with a design which is
appropriate for the circumstances at hand. That is the way stove design
should be done.

There is no such thing as a "universal stove". There are many excellent
stoves, all appropriate for particular fuel and utilization circumstances.

Kindest regards,

Kevin Chisholm

> 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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>


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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
>
List-Post: <mailto:stoves@crest.org>
List-Help: <mailto:stoves-help@crest.org>
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List-Subscribe: <mailto:stoves-subscribe@crest.org>
>
Sponsor the Stoves List: http://www.crest.org/discuss3.html
-
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