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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Frank<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>First, thanks for the offer to do fundamental research that will provide input to the development of better test methods. If you have the means to have them published, that will be best.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>My immediate suggestion is that you look at the heat content of typical charcoal residues from known wood and known stoves. For example a Rocket stove burning Douglas Fir as is common at Aprovecho. That is a particular stove type and the fuel is apparently constant. The question arises: what is the heat content of residue char and does it vary with the initial moisture level?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>We need to know the Carbon and Hydrogen content to determine the heat content without having to resort to a bomb calorimeter which is time consuming even if inexpensive. The heat potential can be calculated pretty well if you have the H2 and C content.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>From the gasifiers we know that the amount of char left varies greatly with moisture content. It is very likely that the heat content per g is also variable with the initial moisture content because ‘there is something else going on’. Rice hull char has a very low energy value, but what is it? Lots of post-grad work in there for the willing.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dr Penn Taylor (we can call him that now) outlined one method for determining the accuracy of two WBT’s. There were several steps or points that led to the total. Each point is an error that needs to be constrained. If a test method has fewer error points, the final result is more precise. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>WBT’s are not inaccurate because the measurements are not made precisely, but because the task given is complex and depends a great deal on the skill of the operator. One issue is the determination of heating efficiency of a stove. It could be the % of heat that goes from the fire to the pot (or the room if space heating) or it could be the % of heat that comes from the fire and is retained by the pot so some work is done (like heating the water). Those numbers are not the same. It could be the average efficiency including the ignition of the tinder and kindling all the way to the boiling point. That is a very different number because the stove body might absorb a lot of the heat initially. Also, the skill of the lighter of the fire (the cook) might be widely variable, introducing a systematic error. Similarly with emissions. If the skill of the cook is high, the fire will start cleanly in some stoves. In others it makes nearly no difference. Should dumb cooks be penalised? Or should we penalise the stove?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>One of the reasons to report the net heat transfer efficiency (the efficiency of the whole system) at different power levels is that not only is it a very useful metric for creating a performance curve of efficiency v.s. power, but it can be done quite precisely with simple equipment. You could easily make a determination within 3% in your lab right now. But you can’t light a stove within 3% each time on different days using a variety of fuels.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The heat transfer efficiency is largely an indication of the performance of the stove body with that pot(s) on it. It is a very valuable metric because if you make a change, you can see how the efficiency was affected. If that is determined under ‘constant conditions’, meaning a fire that is not currently changing in power level, the result can be really accurate, probably within 1% using a thermocouple that is accurate to 0.2%. You get the idea? So when reporting how a stove ‘performs’ one can generate accurate numbers of great value.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Determining the emissions from a stove during an ‘ignition phase’ (lighting to stable, full power) is a clearly defined section of a cooking event. Again it can be determined accurately by making sure the systematic errors are minimised and repeating the procedure a number of times, reducing experimental error (like fuel variation). Using this approach one can build up a characterisation of the stove that is precise and useful.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dr Nat Johnson (we can almost call him that) showed us a chart where he had the efficiency of a group of stoves plotted twice: once with the charcoal subtraction invoked and once by pretending the char remaining was tossed. The coefficient of variance (COV) with the (inaccurate) char heat content included was huge. When the char was ignored the COV dropped by 50%, the results were obviously more accurate (looking at the graph) and he wondered why we introduce such large errors into an otherwise pretty good test section. We may have to consider char, but how it is handled can be discussed to limit these large error bars.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The best way to start this process following the watershed IWAgreement is to ask first what the buyer (often a Donor) wants. They probably want to know if the stove they are selecting will perform as advertised. That is a starting point for selecting methods. If the method does not address the end goal, it has no value to anyone. If a designer wants to know what efficiency the user will experience, the test (or that section of it) has to provide the required information. You lead the rest of your life like that, why not stoves too??<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0mm 0mm 0mm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> stoves-bounces@lists.bioenergylists.org [mailto:stoves-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Frank Shields<br><b>Sent:</b> Friday, March 02, 2012 6:50 PM<br><b>To:</b> 'Discussion of biomass cooking stoves'<br><b>Subject:</b> Re: [Stoves] PCIA den Haag<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Crispin,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Perhaps lengthy but very well written and states the problems in rating stoves. All the work in the past (WBT etc.) were useful measures of a small part of the big picture. Starting with test methods that are simple and work on small units of the process are key. Then they need to work when used in the bigger lab scale of testing stoves. Then verified they represent what happen in the field.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>What would be useful is a list of the unit tests that need to be worked on. Then have labs suggest ideas for research and have money available for the research. Determining energy in ash-char mixes, carbon energy in particulates leaving the combustion box, and location of formation of these particles are a few I can think of. If we can develop simple methods that can be used by most labs that have been verified to work when correlated using costly lab equipment is a start.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>So much to do. Getting organized as to what needs to be done by posting a flow chart or tree. Then have a way to include all that want to contribute with suggestions of procedure etc. by e-mail directed to a sub-number of the tree. The ones making decisions can look at the list of all suggestions and move appropriately. But I am sure they have their own process. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thanks<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Frank<o:p></o:p></span></p></div></body></html>