[Stoves] FW: ETHOS 2013: Where is the New Data on Stove Performance in the Field?
Paul Anderson
psanders at ilstu.edu
Sat Dec 8 00:03:52 CST 2012
Crispin and all,
With the exception of one point and one wording, I can agree with
Crispin's comments and I hope others also find these observations and
dialogues helpful.
One wording problem:
Paul wrote: >
Just please do not have testing that poisons the waterhole for those who
are working with TLUD and other micro-gasifier stoves.
Crispin replied:
Well, that is well put. The current WBT calculations do exactly that.
There are several 'fatal flaws' which means the final number(s)
misrepresent the true performance of the product. Some stoves are
accidentally 'optimised' to perform well on a given test but this does
not improve their actual performance when viewed through the lens of a
more rigorous test.
Comment: "The current WBT calculations do exactly that." refers to my
sentence that included the "not". So I think that Crispin is saying
that the current WBT actually DOES poison the waterhole.
One exception (or in need of clarification by Crispin). I leave below
the entirety of "Item 3" so that it is not out of context, but my point
is this:
With a good solid fuel and a sufficiently large TLUD (like the Quad
TLUD), you only need ONE fueling of the batch to complete BOTH the
boiling and simmering parts of a complete WBT. So if the unit is
loaded with fuel that would continue to pyrolyze AFTER the completion of
the test, that would mean that UNNECESSARY fuel is being charged as part
of the Fuel efficiency (fuel consumption). And that was clearly the
case in the 3 test runs of the Quad stove. Look at the total time of
operation of each batch of fuel.
Note the 3 different sizes of the pieces (shown in the photos) use in
the 3 runs. We were learning about fuels and extending the operating
time as well as about stove test results. (Should not mix 2
objectives, but time and money are rather limited when I am paying for
it all myself.) We learned that we can get more fuel into the fuel
chamber if the pieces are thicker, and that the total time will be
longer (because pyrolysis to the center of thick pieces is longer and
slower.)
And believe me, the cooks seem to be much more interested in the length
of the burning time than they are about any certified
correctly-conducted measurements for a WBT. I guess we Stover
designers are serving two masters: Those who check test results before
allocating any funding, and those who use the stoves to cook meals.
So, if the TLUD could complete the full WBT test with only 1.2 kg of
fuel on each of the 3 test runs, then the FUEL consumption would be 1.2
kg instead of the 1.6 kg average that Crispin calculated from the data
sheets.
So, let's make sure that FUEL efficiency is related to the task of the
WBT and not to the capacity of fuel in a batch fuel chamber. Let's have
test results that are clear about what is being stated.
(the referenced messages are below) Paul (In Kampala until 17 Dec)
On 12/7/2012 5:20 PM, Crispin Pemberton-Pigott wrote:
>
> Paul wrote:
>
> >3. This could imply that the stove was operated until the end of
> pyrolysis even if that was many minutes after the complete WBT was
> conducted.
>
> Crispin replied:
>
> I am not making that assumption t{h]ough it is one possibility. For
> example a stove may have a fire shut-off mechanism capable of
> extinguishing the flame within a short time. I do not want to
> anticipate what might be invented. Because the nature of a test to get
> a particular metric requires the fire to be stopped at the end, it is
> reasonable to make a plan to do so. There is a method called the
> Burn-Out Test which was specifically designed to test stoves with
> pellet-like fuel that cannot easily be shut down and which in any case
> contain all sorts of half-burned bits of fuel. Dr Taylor rated that
> method at about 15% error.
>
> PARTIAL SOLUTION that creates havoc is that the SAME stove could be
> operated identically with the amount of fuel carefully calculated to
> have pyroylsis end within a minute after the WBT was completed.
>
> Although this is possible, it is not necessary. The performance of any
> task like stir-frying, water heating or fish drying can be measured in
> a couple of ways. I won't bore you with them now. The penalty for an
> un-extinguishable or uncontrollable fire is real. They are, after all,
> dislikeable traits.
>
> >Fill a TLUD with 3 kg of fuel for one test run, and then do it with 1
> kg for the second test run.
>
> This needs to be considered. I don't see the obvious advantage through
> this explanation.
>
> >In other words, Crispin's correct statement (that the original
> loading of 1600 grams of wood) is NOT related to the amount of FUEL
> used up until the time of the completion of the WBT.
>
> Actually, it is.
>
> The test of the Quad 2 was conducted in 2 phases wherein the raw fuel
> was loaded twice (the amounts are indicated) and both burned well past
> the completion of the relevant section. The test as not completed in
> one go, in other words. The remaining fuel was discounted to obtain
> the fuel burned heat value (for getting the thermal efficiency, fire
> to water). The total raw fuel needed to conduct a complete WBT I
> calculated from the mass of raw fuel burned for each section and the
> char produced in that process. The average for the three tests was
> 1550 g of raw fuel with a moisture content of 15%. If the stove was
> loaded with 1600 g it would in in all likelihood complete the hot
> start and simmer sections in one go.
>
Paul S. Anderson, PhD aka "Dr TLUD"
Email: psanders at ilstu.edu Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
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