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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><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><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>></span></b><span style='font-family:"Arial","sans-serif"'>I think we all recognize that you were designing a stove with an intent to consume char - not produce it, although the latter was possible in part with appropriate timing of extinguishment. </span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>There are a couple of answers here. The original patent is not fully reflected in the current model, mostly because no one has expressed interested in manufacturing this product. I no longer personally manufacture stoves, only prototypes. The ‘whole design’ includes the ability to close off the primary air completely should that be interesting to the user. It will also operate in a combined mode of partial burning of the char, or making it, or burning whole fuel. This approach is never discussed here – everyone refers to char making stoves or ‘the other kind’. There is no reason (as demonstrated) not to have all methods employed in a single device. <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 main reason for adopting the approach was to make a stove that could be fuelled and then operated with a controllable flame (power level) using a wide variety of fuels. If you re all at the time (2003) everything was a stick burning Rocket Stove or a fan-assisted gasifier. Or a Jiko, I guess.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Arial","sans-serif"'>Your objective seems to have been well met - especially with the reduced amount of secondary air in the latest mods..</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 change was introduced in 2008 or 2009, can’t remember. It did reduce the total airflow and increased heat transfer but not so anyone would notice. It remains about 35% burning wood and >60% burning small amounts of charcoal (meaning at low power). Because it has not been properly tested in a good lab we don’t really know what the PM emissions are. When it was tested in Germany in 2004 it only got the repot ‘very low’. Even then, the test was done with a most inappropriate pot and the fuel affects things, plus the operator was inexperienced so I am hoping that will be corrected in the coming months.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Arial","sans-serif"'>Would you agree that if one is striving for char production, that the amount of primary air flow can/should be much reduced over the present design? </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 current layout can make charcoal from wood or wood pellets (and switchgrass pellets). The primary just needs to be turned off. If I were designing it for char production I would make a grate that can be dropped with a lever to dump it out. It is not convenient to tip a hot stove over, even one with a handle. <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'>As you know my view is that if someone wants charcoal they are far better off to build something that does it controllably to give a predictable result – something biochar experiments show as necessary. It should be a self-heating retort so there are no smoke emissions and the least possible amount of fuel is burned in order to process the resource. It is already done in several countries. There is very little waste heat if it is done properly so there is no question of cooking on such a device. The cooking-while-making-char is done at the expense of burning some of the char. There is nothing magical about it.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Arial","sans-serif"'>The only remaining design feature I can't see in the cutaway or your comments is how you are controlling secondary air flow with the right hand slide control. A similar (unshown) angular rotation slide?<br><br></span><span style='font-size:11.0pt;font-family:"Calibri","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 secondary air is drawn into the stove by the updraft in the centre. The quantity of air is in principle, self-regulating. This is different from the ‘enter-at-the-bottom’ stoves where secondary air has to be controlled manually. My idea was to make the suppy automatic based on the draft in the central space.<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'>When the fire is turned down and the whole thing is hot, the amount of secondary air flowing in drops. I manufactured a small number with a secondary air controller and a second lever but the marketing people (at New Dawn Energy Systems) demanded it be removed because it was too difficult to teach people in a couple of minutes how to operate the stove. Oh well. I even made a tool for bending it into its complex shape. What was a big surprise is that one of those few stoves made it to the Philippines and was given to YDD in Central Java where I found it, unused, in 2012. The second controller makes it possible to have 100% control over what happens without perfecting the design (it is not optimised yet). If the design principles were studied and applied with some modelling effort, I believe the full value of the invention can be realised.<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'>One the major benefits of the design is that the flame is kept away from the combustion chamber walls which greatly extends the working life, plus the fact the wall is cooled from behind which extends its working life (something invented by a Brit in 1948). In fact we have never sold a replacement combustion chamber. Perhaps there are 100 reasons for that, but I think it is because they don’t burn out. Consider how brief is the life of metal combustion chambers that are either insulated behind (a big no-no) or have the flame running against the wall most of the time.<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'>Regard<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>