Dear Frank
A lot of snipped but some relevant bits: >I think time spent in tending to the stoves is an important stove variable and >should fit there. Time and attention (attention demand) is an important metric for consumers. If we compare a fuel-fire-and-forget stove that runs by itself with one that needs attention every five minutes (for example a traditional 3-pot clay stove) there is a world of difference for the user. >Yes – the WBT as my understanding it from time back (I need to revisit) does >specify many of the variables. This is important. The WBT’s used to date specify much more than is necessary. The use of ‘normalisation’ means the variable is calculated to a normal, and does not have to be ‘fixed’. For example we do not have to fix the temperature of the day on which we test. Nor the temperature at which the water starts when put into the pot. These things are ‘normalised’ by calculations that account properly for the variations. Many of the elements of a test that are fixed can be handled correctly to allow for the use of, for example, more appropriate pots such as the ones in normal use in the community and ones for which a certain stove is designed. > I also think that the stove developer should be able to specify or veto the > fuel type (your 1 and 2). I don't know if that is always possible now. If you are trying to classify the performance of stoves using the same fuel this is wise. If you are testing the ability of stoves to burn a range of fuels, again it is helpful to use known fuel types and they properties. Some stoves handle wet wood much better than other so in a wet country, the comparison is important. Some stoves are operated in a manner that the fuel is dried by the stove before it is put into the fire. Some stoves can’t do that, some can. Comparisons cannot be arbitrary. Wisdom is needed to construct a valid assessment. The whole point of a testing toolbox is to have validated methods of dealing with such situations so that once an experiment (comparison) is designed, it provides validated results. You can’t just make up new metrics without check in they are valid. Many problems arise from this. >The stove developer should have no say as to how this test (WBT) is conducted >except for possible suggestions as to his findings to what makes it work best. Well, when designing a stove one may need very particular information that is not required to get a performance comparison with respect to cooking. If you are trying to improve the heat transfer efficiency, you need a method of determining it accurately because the different between two models may be slight, but consistent. A regular WBT is a blunt instrument and cannot tell if one stove is 5% better than another. A heat transfer efficiency test can, however. >…Anything to give a clue or info where a change can make the not-so-good stove >the same as the good stove and the good stove better. There are particular metrics which provide valuable information about performance. Designers need more information than policy managers. Regards Crispin
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