[Stoves] Celebrate! First-ever international standard for laboratory testing of cookstoves published.

Wed Jun 27 23:07:05 CDT 2018

Dear Ronal and All

Just on comment:

>>“I hope this standard is the last nail in the WBT coffin.”
>             [RWL:  I hope you are willing to change your mind on "coffin", per the above.  What I do hope will soon be dead is the Chinese stove standard which says to treat intentionally-produced char the same as unburned fuel or ash.  I think the same for the South African standard.   I can think of no reasonable rationale for such a position.

I think you may be misunderstanding something about how calculations are made in the ISO test method. One of the most important metrics for stove performance is assessing the amount of fuel fed into the stove in order to accomplish a task such as baking 1000 cookies or boiling 200 ears of corn.

The metric is “Fuel Fed” (please see the list of definitions).

The mass of fuel fed was carefully written to capture the quantity of fuel needed to accomplish some cooking task. Whether the stove produces char or not is a secondary point. IT is easy to report the amount of char produced, and there are metrics for doing so. It is the amount of char produced per kg or per dry kg of fuel fed.

Importantly, the cheating that has been taking place using the WBT is not brought to an end. If I look for the amount of fuel fed into the stove per replication of some task, be it the standard one or a relevant one, I will find the amount of fuel needed to do so. If there is a secondary product such as condensate, char, heat that can be used for a secondary purpose such as space heating, or electricity, these are all recorded in an appropriate manner.

The cheat that was with us for so long, claiming as the WBT1.x, 2.x, 3.x and 4.x that a stove did not consume fuel because it emerged from the cooking session in the form of char, is gone, thankfully. Please refer again to the definitions.

That ‘char deducted’ formula that you refer to is an energy calculation that relates to the fraction of energy in the fuel fed that was released (theoretically) during cooking. It no longer refers to the mass of fuel fed, as it once did.

This is a major advance in testing methods. Only the stove testing groups used the erroneous ‘char-deducted’ formula. When searching the literature for some example elsewhere in industry, not a single one could be found because the claim was fundamentally misrepresentative. That has now been cleared up.

The remaining mentions of the WBT are for PR purposes only. Not a single voice supporting the use of a “WBT-like” test was raised in the ISO process. In fact it was put to a vote in exactly that form, in those words: “WBT-like”. No one wanted it. Now, it is only for the organisations who supported the WBT for so long to be given enough space for them to quietly drop it while pretending that it was a valid method all along. To do otherwise would be to admit they were cheating donors. We do not have to extract that pound of flesh.

The ISO Standard is not anyone’s standard – it only has meaning when a country adopts it, or adapts it. Any country contemplating adopting this document as a national standard will have to consider how it will be implemented, and whether all of it or some of it will apply. When it comes to things like fuel efficiency, which is important in some regions, it is likely the national standards body will apply its collective mind to what portions of this massive document they will use. As anyone reading it will quickly see, it is unnecessarily complex, and requires numerous pieces of equipment that are very expensive if one is to have a reasonable level of confidence in the result. Because a national standard provides a warranty of performance, it is pointless to have as a test method something that doesn’t provide it.

People seeking lower cost and more accurate alternatives may consider adapting Indian IS–13152, China’s NB/T 43008 – 2012, or the CSI test method which has been used internationally in some form since 2009.

The WBT 4.2.3 contained, when it does, some 75 systematic errors as well as its much-discussed conceptual errors. We do not know yet how many are contained in the ISO-19867-1 because it has not been reviewed conceptually or systematically. Because the test method is novel, (untested) problems with its implementation will have to be resolved at the national adoption level, if it turns out to be acceptable ahead of other options.

The problems created by the WBT remain, however, as witnessed by the recent release of the second edition of the Micro-gasifier Handbook which makes barley any mention of testing and includes multiple references to ‘performance’ based on the obviously erroneous fuel consumption claims of the WBT.

For anyone who is new to this topic I recommend reading the CREEC Lab test of the Quad II stove (featured in that Handbook) which shows that the fuel fed per replication of the test is 1.3 kg (as received) and claims a dry wood fuel consumption of 636 g. I will read it again, but I think the handbook does not address this issue squarely and it must in the next edition. Char production is a secondary benefit and can negatively affect the fuel consumption rate. Advocates should not shy away from discussing it. A good example of how to handle secondary benefits is heating stoves, which are assessed on the basis of the cooking provided, the heat provided, and the combination. Where char is an additional secondary benefit, it should also be listed in the form of carbon mass, if it is for sequestering, energy, if it is for fuel, or total surface per gram if it is for “activated” uses.

Regards
Crispin

ISO TC-285 WG1, WG2, WG3, WG4.
P-member SABS TC-1043
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