[Stoves] How other tests calculate with remaining charcoal ... was Re: Advocacy action: ask the GACC to stop promoting the WBT

[Crispin Pemberton-Pigott]

Dear Paul

There are two things to check. First, what is the question that is being answered? Second, does the metric provide the answer to that question.

‎Of course it is obvious that the question has to be valid in the first place and the method of determining the answer has to follow basic principles.

Something that is surely not well understood by the 'results-using public' is that all measurements have an uncertainty. All calculations involving measurements pass that uncertainty on. The result given in response to any question therefore has an uncertainty. When that uncertainty is larger than the supposed benefit there is doubt that the stove meets the standard of 'better'. When the uncertainty is much larger than the gain or loss, benefit claims are worthless. That is the point of Fabio's paper.

‎There is a study of indoor air quality in Ulaanbaatar gers (yurts) by a Korean team. They concluded that homes with improved stoves have 'significantly worse air quality' than homes with traditional stoves. 260 v.s. 210 microgrammes per cubic metre 24 hr average (in winter).

Gasp! Horror! Solid fuel improved stoves make the problem 'worse'!‎ Alert! Alert!

Let's look at the statistics. The uncertainty on the '201' number is ±187. On the 260 it is ±201.  The claimed difference is 50. The uncertainty is >3.5 times larger than the 'difference'. The claim for 'significance' is meaningless.

Next, what was the outdoor air quality during these measurements? All combustion and excess air has to enter the home from outside. ‎It was >300, higher than 260 the whole time. Oops.

They only proved that there is statistically no detectable difference between indoor and outdoor air quality whatever the stove type.

Cancel the alert.

So it is not enough to provide a test 'answer' it has to be accompanied by a range of uncertainty, or factored into it as I am suggesting for a 'warrantied rating'. ‎The uncertainty can be limited by very accurate instruments and a well-designed protocol and zero conceptual errors.

Regards
Crispin



To Crispin and all,

Crispin wrote about other tests of stoves (not the WBT water boiling test):

We should concentrate on evaluating others. There are several. EPTP, MWBT, CSI, BST, HTP, IS 15132 and so on and on. Let’s get on with it.



That is quite a list, including the "and so on and on."

I would greatly appreciate some knowledgeable comments about how THOSE OTHER TESTS handle the issue of charcoal that is left in the stoves.   Is there some agreement between those many tests?

And be sure that the discussion relates to the stoves that INTENTIONALLY DO LEAVE CHARCOAL BEHIND.

Some useful numbers (in general) relating to char-making stoves (specifically TLUDs), and based on dry weight of fuel and charcoal:

100% of fuel (wood) includes 100% of the carbon in the fuel

Charcoal (weight) yield is about 20% of the dry weight of the fuel.

Char (energy) contains about 30% of the ENERGY that was in the fuel (char is more energy-dense (by weight, not volume).

Char (carbon atoms)contains about 50% of the carbon atoms of the original fuel.

The big cause of those different percentages is that wood is a carbohydrate, which includes some oxygen and hydrogen atoms which influence the possible energy (release and burn the hydrogen) and influence the weight (Oxygen has weight but no energy value).

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>
Skype:   paultlud    Phone: +1-309-452-7072
Website:  www.drtlud.com<http://www.drtlud.com>

On 1/22/2017 3:36 PM, Crispin Pemberton-Pigott wrote:

Dear Frank



I can add to the uncertainty, which I think has been pretty well covered in the journal articles, the issue of the validity of the reporting metrics themselves. This was addressed squarely in Zhang, Y et al 2014 which challenged the validity of all three IWA low power metrics

 .... snip.....

So I am dropping my call for a review of the WBT 4.2.3. Looking through the available literature, it has been done by several groups and all a new one will show is more details and defects.  We should concentrate on evaluating others. There are several. EPTP, MWBT, CSI, BST, HTP, IS 15132 and so on and on. Let’s get on with it.



Regards

Crispin





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