<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Andrew: cc List</div><div class=""><br class=""></div><div class=""> <span class="Apple-tab-span" style="white-space:pre"> </span>See more below.</div><div class=""><br class=""></div><div class=""><br class=""></div><div><blockquote type="cite" class=""><div class="">On May 7, 2017, at 5:28 AM, Andrew Heggie <<a href="mailto:aj.heggie@gmail.com" class="">aj.heggie@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Ronal you seem to be responding to original post from elsewhere? I<br class="">don’t see a copy on stoves.<br class=""></div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span> </div><div><span class="Apple-tab-span" style="white-space:pre"> </span><b class=""> </b>Apologies (to the full list - maybe also Dave). You are right. I just assumed that the two messages I was responding to were from the list. At the end I re-append the two photos that I thought everyone would have seen. (Not sure if they will be stripped or not because of size limits.)</div><blockquote type="cite" class=""><div class=""><div class=""><br class="">David also has an article on the stoves website<br class=""><br class=""><a href="http://stoves.bioenergylists.org/content/elsa-stove" class="">http://stoves.bioenergylists.org/content/elsa-stove</a><br class=""></div></div></blockquote><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span>Different Dave.<br class=""><blockquote type="cite" class=""><div class=""><div class=""><br class="">I've looked at some of the videos and there seems to be different<br class="">iterations of the stove dating from 2014.<br class=""></div></div></blockquote><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span>Yup. Dave Lello has done a good job of documenting via videos. This message was also on a new stove.<br class=""><blockquote type="cite" class=""><div class=""><div class=""><br class="">Just two comments at this stage:<br class=""><br class="">On 7 May 2017 at 02:28, Ronal W. Larson <<a href="mailto:rongretlarson@comcast.net" class="">rongretlarson@comcast.net</a>> wrote:<br class=""><br class=""><blockquote type="cite" class="">It's weight is about 1kg and at about 15 MJ for air dried wood should<br class="">produce about 4kw of heating power. (Of which we use 70 % in the gasifier).<br class=""><br class="">[RWL2: I see numbers above 15 MJ/kg for wood (and you use 18 MJ/kg for<br class="">pellets).<br class=""></blockquote><br class="">I believe softwood pellets can exceed 20MJ/kg because of their higher<br class="">lignin content.<br class=""></div></div></blockquote><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span>I don’t recall ever seeing such a high number - but I like that since it better justifies the number 18 MJ/kg, which is so nice to work with (being exactly 5 kWh/kg)</div><div><br class=""></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>In googling I found some references that could be helpful:</div><div><br class=""></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>a. FAO <a href="http://www.fao.org/3/a-i4441e.pdf" class="">http://www.fao.org/3/a-i4441e.pdf</a> uses kWh/kg. That value close to 4 (not 5) with moisture content of 20%. Lots on densities.</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>b. <a href="http://www.forestbioenergy.net/training-materials/fact-sheets/module-5-fact-sheets/fact-sheet-5-8-energy-basics/" class="">http://www.forestbioenergy.net/training-materials/fact-sheets/module-5-fact-sheets/fact-sheet-5-8-energy-basics/</a> Found a value of 22.5 MJ/kg for 0 moisture resinous woods! And below 10 for 50% moisture.</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>c. <a href="http://www.biomasstradecentre2.eu/available-literature/#CmsC34E1" class="">http://www.biomasstradecentre2.eu/available-literature/#CmsC34E1</a> (and then choose the handbook) This seemed the most thorough. From the EU.</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>d. Wiki <a href="https://en.wikipedia.org/wiki/Energy_content_of_biofuel" class="">https://en.wikipedia.org/wiki/Energy_content_of_biofuel</a> was interesting because of the many leads toothed wiki sites</div><div><br class=""></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>My conclusions: I will try to switch to kWh units rather than MJ. I will try to do computations with both 4 and 5 kWh/kg. Might also stat thinking also about kWh in volume rather than weight units.</div><div><br class=""><blockquote type="cite" class=""><div class=""><div class=""><br class=""><br class=""><blockquote type="cite" class=""><br class="">[RWL5: Dave is here saying he is recommending a larger diameter for the<br class="">less dense wood stick fuel.<br class=""></blockquote><br class="">This makes logical sense in that the power varies with the amount of<br class="">offgas being produced, as pellets are denser for a given amount of<br class="">primary air the same offgas will be produced from the smaller area<br class="">with the denser fuel. One of the reasons a pellet stove burns well is<br class="">that the combustion takes place in a more compact volume.<br class=""></div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span><b class="">RWL: There is also the issue of using fans/blowers. Dave has two speeds plus a rotating micro-controller</b></div><br class=""><blockquote type="cite" class=""><div class=""><div class=""><br class="">Crispin made a comment in the "List of woods for TLUDs?" thread<br class="">regarding denser fuels needing to be more finely comminuted in order<br class="">that more surface area is initially presented to the descending<br class="">pyrolysis front.<br class=""></div></div></blockquote><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span><b class="">[RWL: I’ll give this more thought, but we also know that the power level is directly related to the air (oxygen) flow. Again the fans can overcome a lot of size considerations.</b><br class=""><blockquote type="cite" class=""><div class=""><div class=""><br class="">Actually this bears a bit more thought in itself. The less dense fuels<br class="">are so because there is more air between the fibres and air is an<br class="">insulator. So that the surface of a "light" wood like willow or<br class="">poplar will reach pyrolysis temperature faster than a dense wood like<br class="">beech, which conducts heat into it's interior and this heat loss means<br class="">the surface stays cooler for longer. Way back Tom Reed introduced us<br class="">to the concept of Biot number which is a measure of the ratio between<br class="">heat received at the surface to the heat conducted to the interior of<br class="">a particle.<br class=""></div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span><b class="">[RWL: The air and thermal flows in wood is decidedly different in branches and chips (not pellets) with and cross grain. Heat can travel longitudinally inside the branch than across, so one sees conical changes of color if one stops the pyrolysis process.</b></div><div><br class=""></div><blockquote type="cite" class=""><div class=""><div class=""><br class="">So for a given air flow and with woods of the same moisture content<br class="">and size does the pyrolysis front migrate migrate downward faster?<br class=""></div></div></blockquote><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span><b class="">[RWL: I haven’t got the question. Faster than what? I guess maybe the question is beech vs willow? I think there are list members who have the equipment to test this. </b></div><div><b class=""><br class=""></b><blockquote type="cite" class=""><div class=""><div class="">Because more heat should initially be available to radiate and conduct<br class="">downward.<br class=""></div></div></blockquote><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span><b class="">[RWL: One important point may be that most/much of the heating in advance of the falling pyrolysis front is via radiation. This has to be a function of packing for branches stacked vertically for instance vs horizontally.</b><br class=""><blockquote type="cite" class=""><div class=""><div class=""><br class="">Does the net effect mean the pyrolysis zone is deeper with one or<br class="">other densities? At end of burn the result is much the same as all<br class="">particles are charred.<br class=""></div></div></blockquote><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span><b class="">RWL: We had a dialog on this list (or was in the biochar list) about watching the pyrolysis from move downward using a pyrex window. The surprise then was periodic views of downward-flowing gases. But I think a visual test on pyrolysis zone thickness might be possible. I’d wager there is a big difference in the height of the region from which visible radiation is being radiated for different packing densities. As you say we are fortunate that this does not seem to be a critical parameter. They all work.</b></div><div><b class=""><br class=""></b></div><div><b class="">Ron (being sent without a final check. Apologies for typos)<br class=""></b><blockquote type="cite" class=""><div class=""><div class=""><br class="">Andrew<br class=""><br class="">_______________________________________________ <br class="">Stoves mailing list<br class=""><br class=""></div></div></blockquote><br class=""></div><div>Two photos that Dave sent to Paul and I:</div><div><img apple-inline="yes" id="B871B27F-DBE8-4125-A498-B2067D6403FD" height="240" width="320" apple-width="yes" apple-height="yes" src="cid:1BE26F8A-5549-46DE-8E78-A0AB2063208E" class=""><br class=""><img apple-inline="yes" id="806AA49F-75E8-4B4D-8151-597719BBF81D" height="240" width="320" apple-width="yes" apple-height="yes" src="cid:0F3F619B-891E-43A4-BE9E-DAD16D118BF2" class=""></div><br class=""></body></html>