[Stoves] stoves and credits again
Nikhil Desai
pienergy2008 at gmail.com
Sun Sep 24 01:35:34 CDT 2017
Crispin:
Would you or somebody else be kind enough to answer the following for me?
1. Is lab-tested energy efficiency of renewable biomass a significant consideration for buyers of a manufactured stove?
2. Is that true even when the test result is for fuels and pots that are unrepresentative of the users' customary use, and that too for just boiling water?
3. Is there any reason for prospective users to bother with ISO TC 285 pronouncements of stove ratings? How and when?
There needs to be a public airing of the discussion on this List that a) far, far too much is being assumed about fuels, operating practices, and cooks' preferences (rather, they are being ignored), and b) the ISO exercise is for the sole purpose of declaring that stoves for gaseous fuels (of whatever origin) and electricity are only ones meeting Tier 4 for hourly average emission rates of PM2.5.
When the definitions and theories of equations debated in this thread are explained to the proverbial "common woman" cooking in rural households of the developing world, I expect much mirth and amusement to follow.
ISO TC-285 has become a sideshow even before its work is completed. It is, after all, a project of the experts, for the experts, and by the experts. Experts who by and large know very little about the diversity in cooking, fuels, climates, in the world and even less about changes therein over the last 30 years or expected over the next 30 years.
Scientists who have reduced household cookstove, and human bodies, to mere oxidation machines should be held answerable to the 5-10 billion people they purport to use taxpayers' monies for.
I am afraid ISO TC 285 has become a millstone around the necks of those billions of people. A thorough independent audit of the US participants in that process must be initiated by US Congress to examine the objectives and the rationale of the exercise and the likely benefit of its Voluntary Performance Standards.
I don't for a moment believe that any public sector donor is desperate for the Tier ratings so billions of dollars can at last start flowing in subsidies.
Nikhil
> On Sep 23, 2017, at 6:42 PM, Crispin Pemberton-Pigott<crispinpigott at outlook.com> wrote:
>
> Dear Ron
>
> As you raise a number of new points that do not contain ad hominem attacks or imputations of motive I will resond to those.
>
> >>>[RWL5: What is the name and location of this “thorough investigation”?
>
> >>ISO TC-285 WG1 (Conceptual Review)
>
> >>As an ANSI nominated expert you should know that already. Your buddies participated in it.
>
> >[RWL1”: I guess I am slowing down - but it would’ve helped if Crispin had mentioned ISO, 285, or WG1.
>
> There is no need to mention everything to everyone. You have been beating this drum for years and it is not going to fly.
>
> For those who have come pate to this discussion, here is what Ron is trying to achieve:
>
> He wants to have it said that a stove which uses 2 kg of wood and a cooking efficiency of 25% and produces char with an energy equivalent of 1 kg of wood should be rated as cooking with an efficiency of 50%. That is how the WBT 2.0, 3.0, 3.1, 4.x and so on work.
>
> The mechanism for doubling the efficiency claim is that there is energy in the char that is left over after the cooking is completed. The WBT, and numerous other test protocols, claim to report the fuel consumption, and it is easy to support this assertion by looking at the wording on a report that has been made based on the WBT. This will help you to understand the level of deceit prevailing in Gold Standard and CDM calculations. Here is an example:
>
> <image002.jpg>
>
> That is a WBT report in standard format from the CREEC Lab in Uganda. The fuel consumption metric is Specific Fuel consumption per liter boiled, reported in g/litre.
>
> You might be induced by the mass and litre in the metric to think that it means that 102.8 g of fuel was consumed in order to bring a litre of water to a boil. You would be forgiven for thinking this because that is the obvious meaning of a claim to have boiled a volume of water and used a mass of fuel to do so.
>
> But in fact that is not a mass of fuel, that is the dry fuel mass equivalent of the energy theoretically released from the fuel fed into the stove, whether the remaining fuel has any use or not. “Raw” fuel that is the same as fuel places aside for the test is returned to the pile. The rest of the fuel is in fact used during the test. When the remaining fuel is largely char, that char is assigned an energy content per g (29,500 J) and deducted from the energy in the fuel fed. The remainder, the fuel energy theoretically, not actually, released, is converted into a wood fuel mass equivalent and that is reported above as the ‘fuel consumed’ after being divided by the number of litres remaining in the pot (itself a dubious step but we can discuss that separately).
>
> So it is not the mass of fuel needed to bring a litre of water to a boil. Ron would like the energy in the char to be ‘credited’ to the efficiency because while the fuel was indeed consumed, it was not combusted. When the amount of char produced is small, the influence on the efficiency number is altered only a little. When the amount is large, the influence is huge, double, in the example above.
>
> The question being asked is, “How much fuel is needed to bring a litre of water to a boil with this stove?” The number provided looks as it if answers that question correctly because it reports the ‘mass of fuel per litre boiled’, matching the question exactly. But it is the wrong answer. That is not he mass of fuel needed to bring a litre of water to a boil (based on a 5 litre pot-load).
>
> That arguments presented by Ron are based on the fact that there is energy in the remaining recoverable fuel. Well, there is also energy in the air heated by the stove that was not transferred to the pot, which could be used for heating a room. There is energy in the hot ash, something routinely monitored when tracking the systems in power stations. There are lots of places the heat or potential heat energy ends up. Some is in the char.
>
> So the argument came down to, why is the char energy to be treated differently from other energy paths? There was no clear answer why it should be. Char produced can be a metric: mass delivered. The energy in the char recovered can also be a metric: char energy. No one has any problem with that. They are standard measures.
>
> What is not standard is converting the energy in the recovered fuel into a mass of dry fuel equivalent and claiming that was the mass of fuel consumed, because that is a plain lie.
>
> However, that is not Ron’s ultimate goal. He wants to burn the char in the ground ‘to fight climate change’. In order to get this to happen, he wants to have the stoves rated as if the residual char contributes to increasing the reported fuel efficiency of the stove, as if the char is ‘fuel’ then turn around and bury it in the ground, rendering it useless as a fuel.
>
> By ‘playing’ the two goals, he wants to have stoves that make char ‘rated as very efficient’ and have them widely adopted on that basis, then sequester the carbon in the soil for several reasons.
>
> The objection to this is that the stoves cannot be rated as not requiring the total mount of fuel they actually need to cook. On the one hand, he wants the efficiency to be rated very highly based on the claim that “I have char to burn.”, and then turn around and speak to a different group and say, “I have char to bury.”
>
> As the fuel efficiency of char producing stoves is drastically lowered by the fact they are optimised to produce char, they do not rate well against stove that burn the fuel completely, often having a fuel consumption that is double that of wood fuel burning stoves with an equivalent level of technology in them.
>
> Ron, please correct any aspect of this description that is not in conformity with why you want to use the WBT fuel efficiency metric, and what you intend to do with the char, once produced.
>
> +++++++++++++
>
> >Some time back on this list, there was a discussion largely between the WG1 chair, Dr. Tami Bond, and myself on this topic.
>
> Dr Bond has not found any examples of a fuel efficiency metric in use that corresponds to the WBT calculation. She did locate a single reference to a division of energy in a dual-purpose process that tracked where the energy paths went, however it was not used to claim that the fuel consumption was reduced.
>
> No one was able to find a single example of a ‘char-deducted’ denominator in a fuel consumption calculation.
>
> >But now we have the unfortunate situation that two separate ISO groups are saying different things.
>
> I do not believe you are in a position to report what is happening in ISO groups or what those groups ‘are saying’.
>
> >I am told that (by far) the more important document is that from WG2.
>
> The WG2 document is guided by the contents of the WG1 document which contains the definitions and metrics as a self-consistent set and according to the work plan of the Technical Committee, the Definitions produced by WG1 are to be applied to all products of the TC. I refer you to the documentation because you have access to it.
>
> >I have been told that the WG1 report will make essentially no difference in the Tier ranking system - which is where the equation is of importance.
>
> You have been misinformed. There is no tier ranking system in the definitions, nor is one required. Performance tiers or benchmarks are not part of a test protocol. They are political decisions made by policy makers. Testing staff test stoves, and report their performance. What happens to the products after that is not a concern of the test method. One can easily change a performance target and leave the test protocol intact because such goals are quite separate.
>
> The ‘equation’ as you would have it, does not inform the policy goals of reporting fuel consumption, for example in the CDM and GS cases. Therefore it cannot find a use there. It would be very confusing to have a legitimate fuel consumption report and an illegitimate one that under-reported the mass of fuel required to replicate the task side by side in the same reporting template. What purpose could be served by having a true claim and a false one, side by side?
>
> >Keep tuned for that further dialog (which I believe Crispin admitted had validity as identified in my response RWL8, following Crispin’s stating:
> >>“If you wish to report the fraction of energy input that reached the pot and was not contained in the residual fuel, you could use the WBT formula” .
>
> >See the rest of my response RWL8 for why Crispin’s admission is so important.
>
> The fact that one can imagine a division and answer does not render that answer a meaningful metric. Suppose you wanted to know the fraction of energy reaching the pot that generated steam, and the fraction that heated water. The evaporation energy would be divided by the total energy reaching the pot. Suppose you wanted to know the ratio of the evaporation and heating energy? One can make such a calculation, but that does not make the result the energy efficiency or the fuel efficiency, it is just a number.
>
> I repeat: just because you can calculate a fraction does not mean it represents the fuel efficiency.
>
> >>If the energy in char is useful, then it is a product of the processing of the fuel fed, in which case it goes in the numerator: char energy over fuel energy.
>
> >[RWL3”: That has never been in dispute.
>
> If so then we are in agreement. Char energy expressed as a faction of fuel energy fed is the correct way to report char energy, if one wanted to know what fraction that was.
>
> >>No publication shows that the WBT thermal efficiency calculation is valid.
>
> [RWL6”: Wrong. The main one I am defending from WG2 uses the formula, because it is so obviously reporting on physical reality. The denominator (1-e2) is real - it is the energy available to achieve the desired e1. There are probably at least a hundred cites using this equation.
>
> One would do. 100 uses of an erroneous equation does not validate it. The great majority of people using the WBT honestly believe that the fuel consumption metric “Specific fuel consumption” (SFC) refers to the mass of fuel needed to bring a litre of water to a boil using that stove. As explained in detail above, it does not, and all those people are being fooled. Those who are aware that it does not represent the mass of fuel needed to boil a litre of water with that stove, but who continue to pretend that it does, are guilty of something. Those who are aware and who protest against the cheating, are in my good books.
>
> >>Using something is not an argument for validity. Copying an error does not correct it.
>
> >[RWL7”: You are totally avoiding the issue of tiers.
>
> I believe I have addressed the issue of tiers above. Char production has nothing to do with the fuel consumption metric and tiers of performance. As I explained to those new to the conversation, you want to over-rate stoves that produce char to ‘make them look good’ then burn that char in the ground as a soil amendment and carbon sequestration.
>
> How does that reduce the amount of fuel needed to operate the stove? It doesn’t. So we report what fuel is needed.
>
> >To be able to compare all stoves fairly, the amount of char MUST be taken into account.
>
> No, to compare all stoves unfairly you take amount of the energy in the char. You want to burn your candle at both ends.
>
> >>The WBT contains numerous conceptual errors, and using it does not constitute an argument in favor of any of them.
>
> >[RWL8” I know of no conceptual errors, much less “numerous”. Please cite some.
>
> Please read Zhang, Y 2014, often referred to on this list and cited by Riva et al in his 2016 and 2017 papers.
>
> KEY DIFFERENCES OF PERFORMANCE TEST PROTOCOLS FOR HOUSEHOLD BIOMASS COOKSTOVES,
> Yixiang Zhang, Crispin Pemberton-Pigott, Zongxi Zhang, Hongyan Ding,
> Yuguang Zhou, Renjie Dong
>
> DOI:10.1109/DUE.2014.6827753
> http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6827753
>
> Yixiang has published other papers detailing other errors. Riva list several more related to the statistical methods used. Here is a recent one:
>
> “Systematic and conceptual errors in standards and protocols for thermal performance of biomass stoves” (Renewable & Sustainable Energy Reviews, 2016). Zongxi Zhang, Yixiang Zhang, Yuguang Zhou, Riaz Ahmad, Crispin Pemberton-Pigott, Harold Annegarn, Renjie Dong.
> https://doi.org/10.1016/j.rser.2016.10.037
>
>
> >[RWL10”: I don’t know whether this is an important issue - but it would be simple to calculate both ways. If all tests are done the same way, it doesn’t seem likely to influence anything important about tiers.
>
> This fundamental misunderstanding about how performance ratings compare and how they are influenced by simple errors in the test method is something you should study.
>
> >It rarely reports the actual performance, even on those metrics which are valid. (None of the low power metrics are valid.)
>
> >[RWL11”: Where should people go to see your argument on this topic? Are we talking 3rd decimal point in these metrics?
>
> It would be helpful , if you want to make so many comments on these topics, if you were to keep abreast of the published literature on the subject. Please start with all the Zhang and Riva papers starting from 2013. Errors in the Indian National Standards IS13152 and the Chinese national standard for heating and cookstove stoves are also described and corrections proposed.
>
> When it comes to the WBT I don’t think anyone is listening. Penn Taylor pointed out the “ash mass error” many years ago (I recall it was 2009) and proposed a simple and easy-to-implement correction to it, a mere formula change. It has not been implemented even in the most recent WBT 4.2.3.
>
> In the WBT 3.1 there are about 120 mathematical and conceptual errors and error propagations. There are a similar number in the WBT 4.0. There were about 140 in the PEMS Hood spreadsheet v7.0 which approximates to WBT 4.1.2. There are about 75 in the current PEMS/LEMS Hood spreadsheet v4.2.4 (is it still called that?). There are at least as many in the WBT 4.2.3 spreadsheet. I didn’t count them all.
>
> In terms of impact, by far the worst is the reported SFC per litre boiled. People using that number to buy fuel savings are being robbed. The SFC numbers for low power are meaningless because the mass of fuel burned to maintain a simmer has nothing to do with the mass of water in the pot, and never will. We commemorate this year the 30th anniversary of the introduction of that error into the WBT by Sam Baldwin.
>
> Regards
> Crispin
>
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