[Stoves] Re: WBT disagrements


I highly agree with what Crispin and Xavier are intending to do.   Their method of compaisons (the spreadsheets) needs to be very clearly explained so that others can see what are the differences and then clearly see what are the concequences.   Will this be “operational” in time to have some results to be discussed at ETHOS?

I suspect that INTERPRETATION of the results might still be different.  For example, how charcoal (a byproduct, if any) is acknowledged (or omitted) needs to be clearly stated.

At ETHOS this month I will present some quantitative (financial) results about charcoal  from some TLUD stoves in India.  The results are quite favorable and will give one perspective on the value of produced charcoal, and that can be compared with the value of the wood fuel that did not get burned to do the residential cooking.

And then there is the case of when pellet fuel is made from either agro-refuse (like corn/maize cobs)  or from non-wood energy crops (grown to be fuel), IN CONTRAST TO WOOD FUEL that impacts forests that are either sustainable or forest-depleting.  


On 1/10/2018 10:56 AM, tmiles@trmiles.com wrote:


Thanks to Crispin and Xavier for working up a spreadsheet comparing results from the three methods. Hopefully that will show the strengths and weaknesses of each of them. Repeatability within a reasonable range is clearly important.




From: Stoves [mailto:stoves-bounces@lists.bioenergylists.org] On Behalf Of Kirk H.
Sent: Wednesday, January 10, 2018 8:46 AM
To: Discussion of biomass cooking stoves <stoves@lists.bioenergylists.org&gt;
Subject: Re: [Stoves] WBT disagrements




No, there was no discussion on this topic.


Kirk H.


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From: Ronal W. Larson
Sent: Tuesday, January 9, 2018 5:19 PM
To: Discussion of biomass
Subject: Re: [Stoves] WBT disagrements


Kirk: cc list


              Thanks for hanging in there.


              I wonder if,  in your off-list dialogs with Crispin and Xavier, you could determine how they would go about utilizing your own work in charcoal-making stoves – in the Tier ranking system.   


              The WBT methodology coming out of the ISO-285 activities (in WG2 and many other methodologies) supports what I have termed the “denominator equation”  e3=e1/(1-e2). e3 (to be used in the Tier rankings)  can also be written as e3=e1/(e1+i) = 1/(1+i/e1).  This, since e1+ e2 + i = 1 (where i is the inefficiency).   Note no negative sign in the denominator, when written this way.


              It seems they want to treat all char as a waste material (become part of the inefficiency term i);   e2 should apparently always be zero in their thinking.  Did you learn anything on this point?





On Jan 9, 2018, at 1:12 PM, Kirk H. <gkharris316@comcast.net> wrote:




I think your question was appropriate and the answers were hopefully helpful.


No, you don’t deserve credit for being helpful.  I asked my question and instead of answering it you projected your agenda into me and proceeded to answer your own projections, not my question.  Without an answer from you I had to make a guess.  You didn’t like my guess and became angry and in that anger actually gave me a partial answer.  You proceeded to push your agenda using me as a pawn, but not fully answering my question.  I had to fight tooth and nail with you and Xavier to get tid-bits of information.  Finally I had enough tid-bits of information to assemble a coherent answer.  The credit is mine for fighting for an answer.


Kirk H.


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From: Crispin Pemberton-Pigott
Sent: Tuesday, January 9, 2018 2:13 AM
To: Kirk H.; Discussion of biomass cooking stoves
Subject: Re: [Stoves] WBT disagrements


Dear Kirk


I think your question was appropriate and the answers were hopefully helpful. There are many lab based systems of ‎measurement and sometimes only a few measurements are necessary to make great progress in improving an existing product. 


Something that can be separated ‎is this: Aprovecho is not ‘the WBT’. What they do and how they do it is not dependent on using the WBT which is merely a fixed test sequence with a set of measurements and calculations. 


Philip’s comment about the WBT telling you whether or not the stove is improved is most pertinent. If the test didn’t tell you how it performed the first time, getting a different wrong answer later may, or may not, be helpful. This is the crux of the problem. 


Tuning a stove requires making refined measurements, not generalizations. A series of small, say, 3% improvements can result in a 12-15% improvement in fuel consumption or power change time, or turn down ratio. If the test cannot reliably tell you the change ‎for better or worse is 1% vs 4%, the results are guiding you by chance. 


A very carefully done experiment must, not should, deliver reproducible results‎. Prof Lloyd has I think been the most specific on this point, much more than most commenters. As an experimentalist not familiar with small stoves, he was expecting that stove performance tests would deliver the same sort of replicability as other physics experiments. The WBT doesn’t do that because of the conceptual errors embedded in what it measures, when, and how it calculates the outputs. 


On the face of it, why should the calculations make a result variable? Dean once posted here that if there is a mistake that is applied to every test, then it is not important. 


The difficulty is that the mistakes manifest errors unequally in different stove types, additional to the variability created by conceptual errors. Prof Lloyd was forced to abandon the WBT in favour of a method without those errors in order to continue his work.  


Thank you for participating offlist in the discussions. ‎Xavier are I are discussing the preparation of a spreadsheet with a number of tabs, one each for different versions of the WBT and CCT. Putting in the lab info from a test will create copies of the test on each tab with the different calculations so the outputs can be compared. I think we will be able to find 12 versions of the calculations, maybe 15.


We can also prepare one tab without the errors. This will be the formulas to be applied that are developed from first principles as per the HTP/CSI where the requested metric is calculated from only the necessary measurements made to achieve it. 


Given the limitation of the test sequence itself,, high, high, low power, it would give ‘an answer’ that could be used to compare the performance of two slightly different versions of a stove, or different fuels, pots, ambient temperature and so on. 


In South Africa, any kerosene stove tested in Johannesburg or similar altitude must also have an emissions test conducted at a coastal location. Similarly in reverse. The performance on such a pair of tests must be highly reproducible. 


Such a comparison sheet can be very helpful for convincing the casual user that only the corrected version should be relied upon. Failing that, we must retire, as there are always going to be those who will not make the effort to understand the technicalities of the field in which they choose to dabble. 


After that comes the issue of contextuality. If the WBT with ‘standard wood’‎ is used to develop a stove that will be used to simmer soup burning dung, there is no hope. It would be like perfecting a gasoline engine for 89 octane fuel then operating it with diesel oil. 


All stoves are used in some context so the assessment will be most relevant, even for internal metrics for sub-systems, if the test conditions are relevant to the expected pattern of use. The WBT is advertised as a ‘cooking simulation’. That’s OK. Pick and report. 








I recently asked a question about whether the disagreement with the WBT included the sensors, filters and computer graphing as well as the water boiling portion of the overall test.  I have received several responses from Crispin and Xavier (some off list).  From all that was said by them I have assembled an answer:  The sensors, filters and computer read-outs are part of the WBT, but not part of the disagreement with the WBT.  So this disagreement is with a portion of the WBT test, not all of it.  Also, I believe that Crispin has a second disagreement that questions whether some sensors and setups are able to provide accurate read-outs.  I believe that this is a legitimate concern for scientific study, however I also believe in different standards for different purposes.  Perfection is not always needed.


This is an acceptable answer for me.  It is not pro or con to the WBT or any protocol.  My question was intentionally neutral.  I just wanted to know the extent of the disagreement.  


My position on the WBT remains neutral.  I use it because it is available for me in a lab, whereas the other protocols are not.  The WBT does very well for what I need.  It tells me if a change in the stove is helpful or not.  Whether or not it is perfect science is not important for my interests.  


I believe that Aprovecho (ARC) plays an important part for wood stove development and education and I remain a supporter.  


Kirk H.



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