[Stoves] Fuel Testing

[AJH]

On Sat, 7 Oct 2006 18:41:06 -0400, Crispin wrote:

>>>If your wood is 16% moisture WWB you deduct at a certain rate (Andrew
>>>proposes 2.7 MJ and if it is zero, you add.
>
>>No there's nothing to add, just subtract 2.7MJ/kg for water that is
>>present in the fuel.
>
>The crux of what I am proposing is that in order to have stove tests 
>calculated to represent reality instead of unreality, we should add to the 
>'fuel consumed' column if the moisture content is less than 12% and subtract 
>if it is more.

OK My mistake again, in butting in with my thoughts on how to
calculate the energy loss due to wood moisture content I missed the
point that you were thinking about a system of "handicaps" depending
on the quality of the fuel, in order to be more realistic in
comparison with "standards" set by laboratory tests.

>If wood is air-dried properly that is in accordance with standard household 
>management training.  I am suggesting that 12% moisture content would be 
>considered perfect in a normal rural household.

Yes there is some anecdotal evidence that 12% mc wwb is the optimum
but this probably needs refining.

>Enter, the Real World:
>I have some fuel consumption results from Lesotho (improved institutional 
>stoves) which do not approach the lab-calculated performance.  How shall I 
>deal with it?  Get wood samples, dry them, recalulate the consumption and 
>re-evaluate the peformance?  There are 128 samples to deal with.  Should I 
>rather recalculate the 'real performance' of the stove type for 12% WWB wood 
>and work with that as the expectation?  And if I do the latter, should I 
>choose 12% moisture as the expected water content?

Well again it is not my field but I think my conclusion to Paul was
that the energy wasted in boiling and discarding the free water in the
wood was insignificant at these low levels but the mass of water was a
significant part of the mass of fuel and this mass difference was
therefore significant in lowering the mass of dry biomass. Paul's
reply suggests he was moving to a volume measure, I think this is more
problematical because there will be more variation in the basic
densities of differing species. At the moment I cannot see a way
around having to weigh a sample of the fuel as used and then drying it
to deduce the moisture content if the contest is becoming that close.

AJH