[Stoves] PCIA den Haag

Sat Mar 3 20:44:10 CST 2012

Dear Frank

>>We need to know the Carbon and Hydrogen content to determine the heat
content without having to resort to a bomb calorimeter which is time
consuming even if inexpensive. The heat potential can be calculated pretty
well if you have the H2 and C content.

[*]How much char-ash left may depend on fuel type, moisture and stove
performance or when the cooking (or task) was complete. But I would think
the test method for determining energy left would not be concerned with
these. Only make-up of the char-ash mix. Some chars and ash have a lot of
carbonates. I'm sure the carbon comes from the biomass but not sure how that
calculates in the energy left. A calorimeter I think would show none with
CaCO3 but was energy used to create it?  And we (our lab) would need a grant
to move into research not directly related to projects we hope to make a
profit on. And there are so many.  

The only question is how much energy remains in the fuel that could be
released by burning it. It can be done by analysis, but is most easily
determined with a bomb calorimeter. I hope we can constrain the error by
learning what some typical values are for fuels and stove, but make no
mistake, the stove has a strong influence on the nature of the char
remaining. It is not just about the fuel type. What looks like char might be
mostly ash and so on.

>>Dr Penn Taylor (we can call him that now) outlined one method for
determining the accuracy of two WBT's. There were several steps or points
that led to the total. Each point is an error that needs to be constrained.
If a test method has fewer error points, the final result is more precise. 

[*]Looking for a  limiting factor and correcting it then on to the next is
the way to approach it as he is doing. 

The test methods need to be examined one step at a time to see what the
errors are. First eliminate all errors that are unnecessary. Second
determine what question is being asked and don't provide unneeded answers
that create additional errors.

[*].This is the same issue as with many of these complex problems. Like
determining if biochar improves crop production by adding to one field and
not to the next. One will always be different than the other but relating it
to biochar when there are so many other variables. They need to look at what
biochar will, or will not,  do and stop there.  Then the field trial can be
designed around one or two of these improvements biochar makes and it might
show better crop production or $ saving of water or fertilizer. . 

You can do multivariate testing if you already know the effect of the
fertiliser and water and mulch etc. Randomised trials are designed to
uncover previously unknown combinations of effects. Biochar seems to fall
into that category.

>>One of the reasons to report the net heat transfer efficiency (the
efficiency of the whole system) at different power levels is that not only
is it a very useful metric for creating a performance curve of efficiency
v.s. power, but it can be done quite precisely with simple equipment. You
could easily make a determination within 3% in your lab right now. But you
can't light a stove within 3% each time on different days using a variety of
fuels..

[*]It seems that the ignition stage is the problem in the lab and in the
field regarding producing particles. Therefore it seems we should be
designing a 'fuel starter' made of distillate from the fuel in another
operation (or something like that) that when lite will burn fast, clean and
pre-heat the stove before the biomass is applied.  Like a Richard Stanley
briquette made of special material. Perhaps that simple first step could do
more to reduce health issues than making improved stoves. 

I agree that we should pay attention the ignition sequence. Some stoves are
very easy to light and there is little skill involved. Others not so.
Charcoal stoves usually make a lot of smoke when being ignited but as Peter
Coughlin has shown in Maputo, the ignition time can be reduce from 20 to 2
minutes using a sheet metal cone of appropriate dimension. That make a big
reduction if PM2.5 emissions and is very convenient for the cook.

>>.If a designer wants to know what efficiency the user will experience, the
test (or that section of it) has to provide the required information. You
lead the rest of your life like that, why not stoves too??

[*]The buyer will know nothing about stoves and have no idea what to ask for
- except the obvious you have states. They will not know what the results
mean. Only what we tell them with a rating system or picture diagram of
compared stoves. At least that is my experience working with regulators and
end users. We need to tell them what they want. : )

The stated purpose for the testing of stoves at the IWA meeting was for
'informing policy makers'. Policy makers are not your average Joe Public.
They are making key decisions about technology selection and training,
distribution and marketing support. They cannot be ignorant of the subject.
Let's assume they 'have a clue' and then look at the tests. Do the tests
accurately reflect future performance for stoves in that tier? They are lab
tests. Do we have a history of lab tests predicting field performance? No.
Well, perhaps the reason they have not been all that predictive is because
the test methods themselves are not accurate, or measure the wrong things,
or because the measured things are reported in the wrong fashion.

It does not really matter what the reasons are, but it does matter that
whatever we do from now on is legitimate. There is no point saying to a
policy advisor, sorry your stove programme failed, but I followed the
protocol correctly so it is not my fault. If the protocol can't give a
determination that is helpful, it needs to be updated or replaced. Stoves
are not 'special' in this regard.

You would not accept a cellphone which can't make calls is OK 'because it
was lab tested and passed all the tests required'. What is surprising is
that so many people think it is not possible to conduct a lab test that
predicts field performance. Murphy's Law says that, "Two units that perform
identically in the lab will perform differently in the field." Well.OK, but
at least they are performing in the field.

Regards

Crispin

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