Re: Stove efficiency

["Paul S. Anderson" <psanders@ilstu.edu>]

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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