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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>Crispin,<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>In concept you are describing what larry Dobson built in the 1970s and called the Grendle. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Alternative Sources of Energy Magazine, 1980, The Grendle Report <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'> The Mother Earth News Guide to Home Energy, 1980, An Amazingly Efficient Sawdust Stove<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>It was a "hanging grate" furnace with an afterburning chamber for wet bulk fuels like sawdust and hog fuel that would burn efficiently. Heat transfer to the house was through hot gas in roman-style hypocaust ducting. http://en.wikipedia.org/wiki/Hypocaust<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Grendle was followed by Helen and Gertrude. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Since then Larry has built a dozen different designs, some of which can be seen at: <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>http://www.stiltman.com/html/energy_from_waste.htm<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>It seems to me that for stick wood your hybrid cross-draft design would be a useful heat generator for a bench heating system. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Tom<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span 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>Crispin Pemberton-Pigott<br><b>Sent:</b> Thursday, June 23, 2011 9:47 AM<br><b>To:</b> 'Discussion of biomass cooking stoves'<br><b>Subject:</b> Re: [Stoves] Anticipating future markets for stoves and fuels<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>Dear Tom<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>Thanks for the industry update.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>The device I am thinking of is called the Rocket Mass Heater. Just found the email. I did not see much ‘rocket’ about the design but it may be that the name is an older use of it. Not sure. He says Larry was working on it, or something that inspired it. The guy is Daniel Roggema. He has been working on stoves for about 35 years, by my reckoning. I do not know much about him though we have corresponded a number of times. There is an Apro’ publication from 2006 called Rocket Mass Heaters that describes at least one version of it.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>The interesting part of the design is the use of an insulated chimney riser and a heat exchanging drop, with no chimney exhaust. I have not seen this before, but it is hard to know when it was first used. There are many strange things in the old libraries. Made from tincanium the thing looks dangerous, but the principle makes sense: you use the heat rising in the insulated part to push (under a low pressure) gases horizontally under sleeping benches. The benches are made from pounded (crackable/shrinkable) clay so having a positive pressure in them sounds really dangerous. But again, the principle is sound. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>According to my analysis, it should be possible to make a condensing furnace in this manner without a fan, meaning we should be able to get >92% efficiency as a heater. This holds open the possibility that in Nepal, switching from an open fire to a stove would actually increase the system efficiency, even though nearly all the heat from the open fire is deposited into the room. It might be too expensive or heavy but should work. In Mongolia it would be affordable.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>Combined with a good combustor, the up-down system in a tight stove should decrease the total heat requirement by reducing the excess air ratio in the stove (and air exchanges in the room), ergo, less fuel required.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>It is on the agenda for this year’s work.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='color:#1F497D'>Crispin<o:p></o:p></span></p></div></body></html>