[Stoves] Purpose of testing and value given to char left.

[Crispin Pembert-Pigott]

Dear Frank

 

This is an important point you raise:

 

>>At the moment we are using a comparative test to pretend the result is
'certified', meaning 'absolute' but in reality, the lab and the procedure
and the number of replications, even the calibration protocols and lab
training would not really allow one to claim with precision that the result
was 'certified' correct. We have to do what we can with the equipment
available, in the time we have and in a spirit of fairness. 

 

>If the results from this process go into a list of stove and then used to
pick the one to be used - I think it not good enough, in fact meaningless,
with all the added variables. 

 

Well we have to be practical here: yes the number will have no meaning out
of context.

 

Let me rephrase that as I did during a comment presented to the ISO meeting
in Kenya:

 

A stove test result has no meaning without context. All test results require
context, there is no value in an abstract number - it is just a number.
Because all programmes intend to distribute stoves in a particular context,
that is the context in which the stove should be tested for the results to
be useful. Useful means relevant to the policy objectives of the project. 

 

What has been tried (without much success it is fair to point out) is to
produce a set of metrics for stoves that are 'universal' in the sense that
if the task and fuel were constant, one could compare the performance
universally. This is the stated intent of the IWA and other good and
well-intentioned works by the stove community. A universal translator, so to
speak, would be able to make comparisons across the board.

 

The problem with this is that such a comparison has to take place without
local context and local context is required to make a meaningful comparison.
In other words the universal test is a mirage. There is no such thing. As
soon as you change the fuel or the pot or the burn cycle or the operator's
technique, there is a different context and the test result has lost its
value. 

 

If you want to test a fish dryer, you should test it drying fish in a place
that it is intended to be used, using the fish and fuel available in that
place. How another device dries those same fish with that fuel cannot be
determined by using a 'universal fish' and a 'universal fuel'. Such things
do not exist, and you cannot make a technology choice based on it.

 

Supposed you wanted to buy a car to use as a taxi in Bangladesh. Which is
the 'best car' and 'best fuel'? First you have to see what the roads are
like in Bangladesh, which side of the road they drive on, whether or not it
is permitted to open the doors on the centre-lane side, and of course what
the fuel is like in that place. All these provide context. The taxi will
have to be maintained. Are parts available? 

 

While it may be possible to have some universal features of stoves judged,
it has proven impossible both theoretically and practically to choose a
stove on the basis of a de-contextualized assessment, and it will remain so.
If people boil 20 litres of water in 25 litre pots using palm fronds, then
that is the test that has to be applied when selecting technologies. How it
performs a '5 litre WBT' is literally irrelevant to that context.

 

 

>.We are just dealing with Fuel Consumption. Emissions and adaption is for a
later discussion - but very connected. 

 

OK, If you wish.

 

>>One of the very confusing things that has permeated the stove testing
community is the erroneous idea that the heat value in the fuel left over
has a great deal of significance. 

 

>Only important if you go through all the work of determining it and then
use it in the calculations. 

 

Well, you have to have an overview in mind when making calculations. You
don't just measure and divide things because they are there.  If the heat
content of the fuel remaining is not relevant, there is no need to measure
it. With an LPG stove, you just subtract the fuel remaining from the fuel
you had to begin with. End of short story. If a stove needs raw fuel and
produces char and ash, then you need that raw fuel next time. What is in the
char and ash is not relevant to the question of how much fuel new is being
consumed each time.

 

>.So should be mentioned with each stove and nice if we can come up with
best guess for the quality of the char and what it might be used for. Not
for fuel consumption discussions. 

 

There is a lot of value in looking into the char materials and applications.
I am personally excited by the possibility of using a pair of stoves to make
char and burn it later. The reason is that charcoal and wood are often used
for very different purposes in the kitchen. Having a dual fuel kitchen would
offer many advantages. A project could evaluate the stoves and fuels as a
pair of technologies - no problems. The calculations for each product on
their own would still of course have to be valid.

 

Thanks for you work on the 450C story. I am still interested in fully
understanding it.

Crispin

 

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