Dear David W > Interesting comments Crispin. Did no one listen to you in the Hague?
The Hague meeting was interesting and all the more interesting on that no comment has been raised here about what took place there. There were two general problems for everyone to handle. The first was that there really was an expectation that the WBT 4.1.2 was going to be rubber-stamped as the test to be used for placing stoves in a set of tiers. As anyone who has used it knows, there is nearly no relationship between the results of a set of such tests and performance in the field. This has been said by all sorts of people: Dean Still, Penn Taylor, Nate Johnson, Rob Baylis, you truly and so on. It is widely stated that in order to get any idea what the fuel consumption and emissions will be one should conduct some sort of field test. So think about this: the test proposed, and assumed to become the 'international standard test' to place stoves on performance tiers was the very test that pretty much all agree cannot do that particular task. This was addressed in the following manner: two main thrusts were taken by delegates. First, it was necessary to add wording that did not limit the tests to be applied to the problem of differentiating between stoves. An important 'removal' was the word and concept of 'simmering' which has no scientific definition, is not defined in the document, and which is not a standard metric in common use. Some stoves never simmer. That is just one example. A second approach was to entrench the necessity to have a stove testing protocol rated for precision in order to be able to state that the rating of the stove is 'real'. There is no point in having a test method that places a stove in three tiers simultaneously. As people may or may not know, the regular Water Boiling Tests have not been reviewed formally by an independent lab as suitable for the purpose for which they are being employed. Penn Taylor reviewed the UCB WBT in at least two or three papers and said it has systematic errors of about 50% in total. To put a number on it, if you test repeatedly using the UCB WBT and average the results, you can get a thermal efficiency number of 30%, plus or minus 15%. That is about the best you can get. That means it can place a stove on a tier that is 45% from one to another. As you can imagine, that is not going to fly very far. As we do not know what the final text will look like (still with the editorial committee) we have to wait. I submitted 18 suggestions for text edits to remove some of the internal contradictions, in keeping with the decisions of the group, but they 'don't work that way'. The text as edited is the final text, basically. Of the 18, 13 were rejected, some accepted partially and one or two accepted. It is not going to be internally consistent. I do not know where that will leave the community as a whole. One way forward is to find accurate ways to measure individual attributes of the stoves. This can be done at fairly low cost but it will not be a 'water boiling test' which contains so many steps each of which has large inherent errors (systematic one). It will be interesting of course to hear from others and what they think will have to be done to place stoves on tiers. Regards Crispin _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/
