Crispin and all,
A part of the testing I would like to see changed is going from testing
the stove as 'we think it will be used' to 'a continuous run for hours'
to lower the percent errors when determining energy of remains fuel and
time a temperature reads simmer to boiling. These errors in their
measurements will be the same if we run the stove for an hour or for 20
hours but it will be a larger percentage of the one hour and a much
small percentage a 20 hour run. And the increase in fuel burned will
more represent an average of the fuel and changing conditions when
loading. We can then do a simmer test for 20 hours and keep the results
separate.
I realize 20 hours is too long and there is good reason to test the
stove as it will be used - but I think the errors we see is such a high
percentage of the final results until we get better methods that reduce
them we should increase the time.
Regards
Frank
Crispin Pemberton-Pigott wrote:
Dear Kobus
Thanks for the link to your un-popular report which should now get a read or
three....
http://www.bioenergylists.org/stovesdoc/Stanley/BriqGassstove.htm
Sorry for the major digression, but:
I want to comment on the reported efficiency of low power. I have serious
doubts that the need to reform the test reporting is being fully gripped
here.
It is great that you have a (meaningful) thermal efficiency based on the
heating and boiling of water but seriously folks, we have to stop reporting
the thermal efficiency of simmering calculated on that basis. It is simply
not true that the same stove has an efficiency of 3% on low power.
Think about it: you have a stove with a thermal efficiency of 35% on high
power and when going to low, the reported efficiency drops to 3%. That is
simply impossible save under very special circumstances. It is much more
likely that the efficiency is 50% or higher. 65% is not uncommon at low
power.
Because the METHOD of doing the calculation is the problem, not the stove or
the efficiency, we have to get to grips with this misrepresentation of lower
power because people take this 'low power efficiency' and average it with
the 'high power efficiency' to get some meaningless number that
misrepresents what is happening with the stove.
I would really appreciate Aprovecho getting engaged on this subject because
their long term support for the reporting of 'efficiency' on low power is a
long term source of this enduring confusion. Is this going to be carried
into the new WBT 4? Will we have to wait for WBT 5 to correct it?
Quite coincidentally Nat at Iowa State and I were talking about this earlier
today. We as stovers are not going to be taken seriously in the world of
thermal engineering if we can't get past these basic errors of science and
math. Missing water during simmering does not allow one to calculate the
thermal efficiency of a stove.
Determining the efficiency of low power operation includes calculating the
heat transferred to the pot, not the amount of water than happens to be
missing with its own arbitrary definitions.
Rok, that stove is not 3% efficient at low power. It is probably 10 times
that. Maybe 20 times.
Now, what can we doing about this? Stovers will converge on Washington to
assist/advise the DoE next week and we have to talk more sense than this if
we want to be taken seriously by those from the Energy field who have
nothing invested in the stove enthusiasts and its strange measures.
Stonewalling or hiding will not solve the problem.
We need better methods.
Regards
Crispin
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