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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=FR link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Philip,<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'>Thanks for sharing this experiment, this is edifying.<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'>It shows how the Dice Roll Test (DRT) is a very serious contender for the WBT. Both in term of practicality and statistical reliability.<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'>Best,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><br>Xavier<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 0cm 0cm 0cm'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>De :</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> Stoves [mailto:stoves-bounces@lists.bioenergylists.org] <b>De la part de</b> Philip Lloyd<br><b>Envoyé :</b> lundi 25 septembre 2017 11:30<br><b>À :</b> 'Discussion of biomass cooking stoves'<br><b>Objet :</b> Re: [Stoves] stoves and credits again<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I carried out a thought experiment.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>In case 1, a cookstove burning wood boiled 5 litres of water at an energy efficiency of 30%. The useful energy provided was 5*4.186*(100-15) = 1779kJ. This required 5*4.186*(100-15)/0.3 = 5930kJ. If the as-fired wood had a LHV of 15MJ/kg, it would have needed 5930/15000 = 0.395kg wood<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>In case 2, the same stove was operated to produce charcoal while also boiling 5litres of water. More wood would be needed, because not all the wood would be combusted – some would be left as char. If you fed 0.395kg wood to be turned into char at 29% efficiency, and the char had an LHV of 28MJ/kg, then the char would have an energy of 0.395*28000*0.29=3163kJ. The wood from which it was prepared had an energy content of 5930kJ, which was what was needed to boil the water in the absence of char production. So 5930-3163 = 2768kJ of additional energy* would be needed to boil the water if there was char production. At 15MJ/kg, this is 2768/15000 = 0.185kg extra wood, or an increase of 47% in the wood supply. The total energy supplied would then be 5930+2768 = 8698kJ. The energy efficiency of cooking would therefore fall to 1779/8698*100 = 20.5%, while the efficiency of char production would have been 3163/8698*100 = 36.4%. The system efficiency would have been 20.5+36.4 = 56.9%<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>If you used the WBT formula, the efficiency of boiling with char production would have been 1779/(8968-3163)*100 = 32.1%. Given the measurement errors inherent in the WBT method, this would have been statistically indistinguishable from the efficiency with no char production – i.e. it would have shown no benefit to char production. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Prof Philip Lloyd<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Energy Institute, CPUT<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>PO Box 1906<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Bellville 7535<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Tel 021 959 4323<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Cell 083 441 5247<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>PA Nadia 021 959 4330<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-ZA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>*This assumes that there is no endotherm in the pyrolysis of wood in the presence of air, and that all the pyrolysis products except the char burn to provide heat. There is evidence in the literature of no endotherm in the presence of air.<o:p></o:p></span></p></div><div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table style="border-top: 1px solid #D3D4DE;">
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