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<div style="width:100%; font-size:initial; font-family:Calibri,'Slate Pro',sans-serif,sans-serif; color:rgb(31,73,125); text-align:initial; background-color:rgb(255,255,255)">
Dear Kirk</div>
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<span style="font-size:initial; text-align:initial; line-height:initial">I think your question was appropriate and the answers were hopefully helpful. There are many lab based systems of ýmeasurement and sometimes only a few measurements are necessary to make
great progress in improving an existing product. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Something that can be separated ýis this: Aprovecho is not 'the WBT'. What they do and how they do it is not dependent on using the WBT which is merely a fixed test sequence with a set
of measurements and calculations. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Philip's comment about the WBT telling you whether or not the stove is improved is most pertinent. If the test didn't tell you how it performed the first time, getting a different wrong
answer later may, or may not, be helpful. This is the crux of the problem. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Tuning a stove requires making refined measurements, not generalizations. A series of small, say, 3% improvements can result in a 12-15% improvement in fuel consumption or power change
time, or turn down ratio. If the test cannot reliably tell you the change ýfor better or worse is 1% vs 4%, the results are guiding you by chance. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">A very carefully done experiment must, not should, deliver reproducible resultsý. Prof Lloyd has I think been the most specific on this point, much more than most commenters. As an experimentalist
not familiar with small stoves, he was expecting that stove performance tests would deliver the same sort of replicability as other physics experiments. The WBT doesn't do that because of the conceptual errors embedded in what it measures, when, and how it
calculates the outputs. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">On the face of it, why should the calculations make a result variable? Dean once posted here that if there is a mistake that is applied to every test, then it is not important. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">The difficulty is that the mistakes manifest errors unequally in different stove types, additional to the variability created by conceptual errors. Prof Lloyd was forced to abandon the
WBT in favour of a method without those errors in order to continue his work. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Thank you for participating offlist in the discussions. ýXavier are I are discussing the preparation of a spreadsheet with a number of tabs, one each for different versions of the WBT
and CCT. Putting in the lab info from a test will create copies of the test on each tab with the different calculations so the outputs can be compared. I think we will be able to find 12 versions of the calculations, maybe 15.</span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">We can also prepare one tab without the errors. This will be the formulas to be applied that are developed from first principles as per the HTP/CSI where the requested metric is calculated
from only the necessary measurements made to achieve it. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Given the limitation of the test sequence itself,, high, high, low power, it would give 'an answer' that could be used to compare the performance of two slightly different versions of
a stove, or different fuels, pots, ambient temperature and so on. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">In South Africa, any kerosene stove tested in Johannesburg or similar altitude must also have an emissions test conducted at a coastal location. Similarly in reverse. The performance on
such a pair of tests must be highly reproducible. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Such a comparison sheet can be very helpful for convincing the casual user that only the corrected version should be relied upon. Failing that, we must retire, as there are always going
to be those who will not make the effort to understand the technicalities of the field in which they choose to dabble.
</span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">After that comes the issue of contextuality. If the WBT with 'standard wood'ý is used to develop a stove that will be used to simmer soup burning dung, there is no hope. It would be like
perfecting a gasoline engine for 89 octane fuel then operating it with diesel oil. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">All stoves are used in some context so the assessment will be most relevant, even for internal metrics for sub-systems, if the test conditions are relevant to the expected pattern of use.
The WBT is advertised as a 'cooking simulation'. That's OK. Pick and report. </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Regards </span></div>
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<span style="font-size:initial; text-align:initial; line-height:initial">Crispin </span></div>
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<p class="MsoNormal">All,</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">I recently asked a question about whether the disagreement with the WBT included the sensors, filters and computer graphing as well as the water boiling portion of the overall test. I have received several responses from Crispin and Xavier
(some off list). From all that was said by them I have assembled an answer: The sensors, filters and computer read-outs are part of the WBT, but not part of the disagreement with the WBT. So this disagreement is with a portion of the WBT test, not all of
it. Also, I believe that Crispin has a second disagreement that questions whether some sensors and setups are able to provide accurate read-outs. I believe that this is a legitimate concern for scientific study, however I also believe in different standards
for different purposes. Perfection is not always needed.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">This is an acceptable answer for me. It is not pro or con to the WBT or any protocol. My question was intentionally neutral. I just wanted to know the extent of the disagreement.
</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">My position on the WBT remains neutral. I use it because it is available for me in a lab, whereas the other protocols are not. The WBT does very well for what I need. It tells me if a change in the stove is helpful or not. Whether or
not it is perfect science is not important for my interests. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">I believe that Aprovecho (ARC) plays an important part for wood stove development and education and I remain a supporter.
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<p class="MsoNormal">Kirk H.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
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