[Stoves] Advocacy action: ask the GACC to stop promoting the WBT

[Ronal W. Larson]

List:    cc Crispin,  Tami,  Paul

	This is to pick out Crispin’s (only) paragraph below related to char and the “denominator equation” - with my emphasis added

	"One major reason for the failure to predict consumption correctly is of course the deduction of char energy from the denominator in the efficiency calculation.  So the source of the problem was easy enough to spot. What to do about it is now clear. We should all start using test protocols that report something close to the performance obtained in ‘normal conditions’, whatever that entails.  If ‘normal’ cannot be defined then we are on a hiding for nothing, as they say in South Africa. (taking a beating with no benefit).”

	[RWL:  I contend the bolded part makes zero sense. I don’t believe Crispin has ever given a reason (repeat “reason") for saying this deduction is a “major reason” for anything.  So I look forward to hearing from Crispin or anyone on details (type of stove especially) of the tests - and how much char was involved in any of the ratings or the analysis by the Gold Standard folk (who support the “ denominator equation”).  

	Note also that Crispin is saying he doesn’t have an alternative solution when he says “whatever that entails”.  Note also that Paul Anderson asked for the same detail earlier today.  But in the last paragraph below we learn that Crispin proposes to drop the WBT4.2.3 topic.  I take this as an admission he has been wrong.  If not, it is time to give us a real rationale - not just that one equation is wrong.

	I’ve watched (and a little participated in) this sort of testing at Aprovecho 3 or 4 times.   I say the reason that stove test results in the lab are always better than in the field is the extreme care that stove testers take with tending the fuel (rarely leaving the front of the stove).  In the real world, real cooks can’t afford that mode of operation - so naturally everything will be worse in the field.  To fix this, there could/should be an addition to WBT 4.2.3 with time limits for tending  to the stove.  I vaguely recall seeing this recommendation in print (and I think practiced in some country or countries) - anyone able to supply a reference?  I predict the WBT and field testing efficiencies and emission results will match better with that “time realistic mode of WBT testing.


	I don’t believe Crispin or anyone has yet given a citation that directly addresses this long term, logical subtraction in the denominator. So I strongly recommend these two reports by a person (Jim Jetter) who I think has given more attention to this than anyone:

	#1:   http://www.kirkrsmith.org/publications/2012/11/04/pollutant-emissions-and-energy-efficiency-under-controlled-conditions-for-household-biomass-cookstoves-and-implications-for-metrics-useful-in-setting-international-test-standards <http://www.kirkrsmith.org/publications/2012/11/04/pollutant-emissions-and-energy-efficiency-under-controlled-conditions-for-household-biomass-cookstoves-and-implications-for-metrics-useful-in-setting-international-test-standards>
	(separate non-fee downloads for the (8p) main and (102p) supplemental - first author Jim Jetter) 

Crispin has asserted that Professor Smith has doubts about the WBT - but Prof. Smith is 3rd author on this paper; it is hard to believe he doesn’t approve of this equation - which is key in handling char.    I was unable to find the actual “denominator equation” in this paper, but know that the values for OTE (= overall thermal efficiency) uses that equation, as shown in the next cite:


	#2.   http://cleancookstoves.org/events/55.html <http://cleancookstoves.org/events/55.html>     This is a 2013 EPA webinar (achieved by GACC) devoted to batch stoves - principally char-making.  The pertinent section on this equation begins at the 49.25 minute mark on slide 46.   I urge anyone thinking this topic of a “denominator equation” is important to listen to this.  It disproves Crispin.  Of course, the presenters and I could be dead wrong - but we need more than the repeated statement that we are simply wrong.

	I could not get this video in a full screen mode.  I have all the slides, but it is too large a file to transmit to this list.  The slide 46 says this:



and the oral material that goes with it is an abridged version of this:

Now let’s discuss efficiency calculations for char-producing stoves. As I mentioned before, there has been debate on this topic, and our goal at EPA is to report efficiency in a way that is fair and is clear to all stakeholders. I think it is easiest to explain the calculations using this hypothetical example. Let’s say we begin with a batch of fuel with 10 MJ of available energy. We find 2 MJ of energy remains in the unburned char at the end of the test, and 3 MJ went into the cooking process. 5 MJ of energy was “lost” to the surroundings. Let’s look at the first apple on the slide – the efficiency calculation specified in the WBT protocol gives full credit for the energy in the remaining char – the 2 MJ of char energy is subtracted from the 10 MJ of total energy – there is an assumption that the energy in the char represents unused energy that can be used later. In this example, thermal efficiency is 37.5%. Now let’s look at the second apple – efficiency can also be calculated with the char energy “excluded,” and this would apply only if the char is discarded or is used for some purpose other than for fuel (such as for biochar). Now let’s look at the orange on the slide – we can calculate the ratio of the energy in the remaining char to the total available fuel energy – in this case, it is 20%. You may want to maximize this number if an objective of your stove program is to produce char (whether it is for fuel, biochar, carbon credits, or other purposes). But if your stove program is in an area where people actually discard the char, then you may consider this number as a loss of potential energy from the fuel. On the other hand, if your fuel is some type of waste biomass (such as waste ricehulls)thelossmaynotmatteranyway. Let’slookatthetwoapplesontheslide again – we CAN compare thermal efficiencies with and without the char energy credit. However, we cannot add the numbers for the second apple and the orange – we cannot say the stove in this example is 50% efficient because the thermal efficiency is 30% and the char energy is 20%. While there is a common denominator (the 10 MJ of available energy), the numerators cannot be added, because they are different – they are useful energy versus potential energy. We are planning to report efficiencies both ways (the two apples) and to report the ratio of energy in char to fuel energy (the orange). We think this will provide complete information, and please let us know what you think.	


The next slide shows the spread sheet - which I can send interested persons - but I need (and will try to obtain) the underlying equations.  The end of the webinar has a Q&A showing why we are seeing a growth in char-making stoves.  That growth will drop precipitously if Crispin wins this argument.

	I look forward to hearing why the explanation of this webinar, by the persons who probably have put the most time and effort into this topic, should not be the final word.  I repeat the word “why”;  it is not enough to refer to some vague higher authority.

	I am again amazed that Crispin below finds it so difficult to give any citations throughout this response- just names.  I pick on only the next-to-last paragraph below - but I thank Paul Anderson for asking Crispin to give specific sites for the slew of supposedly more valid protocols in the final sentence.  If any of them give a rationale for opposing the “denominator” I will be amazed, but look forward to seeing it.

Ron


> On Jan 22, 2017, at 2:36 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> 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, Yet al 2014 which challenged the validity of all three IWA low power metrics on the basis that the numbers reported, emissions per litre simmered (etc) did not rely directly on the performance of the stove. The reason is that the number of litres simmered has no influence on the emissions from the fire needed to keep the hot pot hot. Jiddu already commented on this list that it was, in effect, taking a valid number (emissions) and dividing it by a random number (litres in the pot).
>  
> The origin of this metric was, I think, the IWA but it was incorporated into the WBT. Please correct me if the WBT came with it first. What matters is that the experimental proof, done to a high precision by Yixiang Zhang et al, proved definitively what was ‘understood’ for a long time (i.e. Rani et al 1992) but experimental proof beyond all doubt was lacking. The experiment was reproduced by Jim Jetter with the same result: the amount of water in the pot (which is of course variable when boiling or simmering) has no effect on the heat required to keep it hot. This is true whether there is a lid used, or not.  Prof Annegarn has produced a theoretical analysis from first principles showing why this is true. 
>  
> Therefore all three IWA low power metrics carry no clear performance information, and in fact introduce a variability in the reported result that is not present in the raw data – something quite unusual, if you check around. The increase in the variability is the result of a conceptual error, not something from the experiment such as operator inconsistency or a breeze etc.
>  
> Tami: I will provide this comment as my response to your earlier post about testing the tests and also Ranyee’s earlier post about waiting for some process of review. I think the reviews completed to date (and two more are arriving soon) are sufficient to say that the best thing we can do at the moment is to stop using the WBT and compare the results of other tests, particularly those that have been reviewed, to see what should replace it.
>  
> No one is bound in any way by the IWA. There is no ISO Standard and when there is it too will be reviewed to see how the test and metrics etc stand up to scrutiny. I was shown a comparison chart for stoves that was produced based on a different approach to the testing (note the WBT) and the relative performance of all products shits significantly, which is to say, they are re-classified onto different tiers.
>  
> A conversation with the Gold Standard technical staff gave me an insight into how they accommodate the difference between the field performance and the WBT ratings. It was illuminating, but disconcerting, because they had taken the position that the WBT ratings were ‘correct’ reports of the comparative fuel consumption and that all departures from that were ‘suppressed demand’ not consistent errors in the rating. In no case did a stove perform above the WBT rating for fuel consumption in the ‘standard comparison mode’, meaning standard working conditions and standard fuel. That is the same as saying, the stove comparison chart produced by Berkeley.
>  
> One major reason for the failure to predict consumption correctly is of course the deduction of char energy from the denominator in the efficiency calculation.  So the source of the problem was easy enough to spot. What to do about it is now clear. We should all start using test protocols that report something close to the performance obtained in ‘normal conditions’, whatever that entails.  If ‘normal’ cannot be defined then we are on a hiding for nothing, as they say in South Africa. (taking a beating with no benefit)
>  
> 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
>  
>  
> Dear Frank,
> > What makes a test method good or bad is only how the results are
> > interpreted and used. 
> The results WILL be interpreted and used. There's no way around that. I
> test something because I want results. I want results because it allows
> me to take a decision, on which depends time, money, and people.
> Humanitarian agencies, development agencies, companies and NGOs have
> been testing stoves and disseminating them for decades. This is not
> gonna change in the future.
> If the results are irrelevant, it doesn't matter how they are
> interpreted, and used. The results are useless. By pure chance, the
> results may be correct and you may have developed a stove that is
> improved. It's like playing Russian roulette.
>  
> What makes a test method bad is if the validity of its results is highly
> uncertain. It is the case for the WBT.
>  
> Best regards,
>  
> Xavier
>  
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