[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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