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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 Ron<o:p></o:p></span></p><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Arial","sans-serif";color:black'><br> 2. Re the use of 18 vs 15 - I agree. I have just gotten used to working with nice easy divisible numbers so folks could easily follow the math. I apologize; I should have put in a warning to that effect. Any idea how the energy value of char should be similarly devalued by humidity? </span><span style='font-family:"Arial","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The char coming out of a stove will have no moisture init. If it is kept around (under shelter) it will still pick up 3-5% over a period of weeks. If it a really humid place like Maputo it can reach 10% but that is not so common. The devaluation is then (for 5% WWB) is about 1.5%. You can probably use 29 MJ/kg if you are assuming a pyrolyser and not be too far wrong. IF it is char recovered from a fire, anything goes. Perhaps Jim Jetter is the best to talk about that because he tested so many samples recently. There is not much published on the subject. A piece of fireplace charcoal might be mostly ash or contain some wood in the centre. Hard to know.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It is reasonable to assume that the volatiles content of charcoal is 15% if it is intended for sale as fuel (i.e. from a forest) because if it is a lot lower it is hard to light. Old char can be added to an existing fire but has unpredictable heat content.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Arial","sans-serif";color:#1F497D'>></span><span style='font-family:"Arial","sans-serif";color:black'>I have been amazed at how uniform power levels can be once one has set a desired power level; that converts to saved time.(and therefore another income aspect of a cost comparison.</span><span style='font-family:"Arial","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The problem I have seen is virtually no control over the power level at all. It is a big minus for cooking and a plus for home industry.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Arial","sans-serif";color:#1F497D'>></span><span style='font-family:"Arial","sans-serif";color:black'>I give a talk at ETHOS on the handling of char in stove efficiency computations - that will take issue with some of your thoughts below. Let's revisit this after you have heard my view on this topic. <br><br></span><span style='font-family:"Arial","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Great. It needs to be discussed. Also please see the talk/paper by Prof Harold Annegarn and yours truly where metrics are discussed because it is directly related: different players want different metrics out of a test and ‘efficiency’ has different meanings to different stakeholders representing different (and all valid) aspects of stove performance.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div></div></body></html>