<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">List and Kevin:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>1. Thanks to Crispin for one earlier response. But the following is totally different, so I think it best to limit this to Kevin’s material.</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>2. I have communicated off-list some with Kevin - and don’t think any of the following is in conflict with his thinking.</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>3. I urge reading the three reports. I see some errors in them - but not in the main conclusion reached in each - that there was a BIG change in efficiency with this very simple low-cost modification. </div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>4. Kevin’s simple modificafion (see the simple sketch in his message) for a charcoal using stove follows naturally from his previous report on a similar big efficiency improvement with a simple layer of small stones under a 3-stone fire using wood. That was nice because it was essentially zero cost and possibly motivated by air management systems used in some (maybe now many or most) rocket stoves. This improvement to the 3-stone fire is apparently spreading rapidly.</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>5. That experience (unique to Kevin) is obviously his reason for asking whether something similar might work for charcoal using stoves. I have mixed feelings about this improvement - as I am so down on charcoal-using stoves. They have obvious advantages - but the making of the charcoal in the first place is horrible. Making charcoal in a cookstove seems much superior - IF the char is placed in soil. The cost of cooking should go down, much less harmful emissions, and a time saver. But that is a different story (with zero application to TLUD - as near as I can see).. Below - only picking up on Kevin’s query on a possibly pre-existing “<i class="">body of work on this</i>” (charcoal-using stoves with an added grate) .</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>6. I’ve googled around a bit on this and now feel pretty sure there is not; Kevin's idea seems quite new. And not surprising that it is new. Why would one need/want two perforated disks? The idea seems inherently un-necessary - maybe even illogical. But my brief search also tells me there is now a lot of useful information out there on charcoal-using stoves. Unfortunately almost all seemed to be behind a paywall. I’d like to hear if anyone know of any non-fee papers we could all comment on that touches on charcoal-using stove improvements. Anyone have a (free) computer program that might predict the improved efficiencies?</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>7. But even if there is no prior analysis on a second grate for a jiko-type stove, I think this list could still give some guidance on how now to optimize the further testing of Kevin’s ideas. This should be possible at near zero cost for any list member near users of charcoal-consuming stoves. Which of there following should NOT be done?</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>a. My first thought is that this second upper grate may allow significant air flow around the edges. The location of the modified air supply might be important, even though the overall flow resistance must be increased.</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>b. The added flow resistance may itself be important - so running tests with the same number but smaller (or larger) air holes might give better efficiency?</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>c. The air passing a second grate should be entering the charcoal at a higher temperature. Maybe a few thermocouples could tell a direction to go.</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>d. Must be less energy lost going downward. Maybe (not likely) one should have three grates?</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>f. The same amount of char means that the average distance to the cook-pot is reduced. What might the result be if that separation was maintained constant? </div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>g. Did the three (or more?) operators handle the stove operation differently - more attention to the main lower door aperture opening?</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>h. Maybe there was a curious optimum rock size separating the two disks? Or what about tests where only the rock size changed? (From 1 mm to several cm?)</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>i. As Crispin noted, some charcoal using stoves have been able to obtain very high efficiencies (> 50%). Could these already hit efficiency be improved with one more gram? (The cost of running a test might be $1?)</div><div class=""><br class=""></div><div class="">Anyway - thanks to Kevin for keeping us up to date on his very novel zero (or almost zero) cost ideas for saving trees.</div><div class=""><br class=""></div><div class="">Ron</div><div class=""><br class=""></div><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Oct 10, 2019, at 11:37 AM, K McLean <<a href="mailto:info@sun24.solar" class="">info@sun24.solar</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="gmail_default" style="font-size:small"><div dir="ltr" class=""><div class="gmail_default">Listmates,</div><div class="gmail_default"><br class=""></div><div class="gmail_default">Has anyone tried this?</div><div class="gmail_default"><br class=""></div><div class="gmail_default"><div class="gmail_default">We seem to have significantly increased the efficiency of charcoal jikos by putting a bed of rocks on the jiko's grate and putting second metal grate on the rock bed. The charcoal goes on the second metal grate. 2-3 cm rocks work. It works in all metal jikos and clay jikos that we've tested. </div><div class="gmail_default"><br class=""></div><div class="gmail_default">Our testing is early and unscientific, but consistent. 25-50% less fuel used. Here are three reports. The Sierra Leone report has good photos at the bottom.</div><div class="gmail_default"><span id="m_4206997578200011798gmail-m_-5379600863218226737gmail-m_-1297279476715938052gmail-m_1825955397064429865gmail-docs-internal-guid-10e1cdb9-7fff-27f8-efcc-c921a0e5cc06" class=""><div style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;" class=""><a href="https://drive.google.com/file/d/12MvBKjxq6PCGCcCHAjSYSeVXXvl7jWjD/view?usp=sharing" style="text-decoration-line:none" target="_blank" class=""><span style="font-size:10pt;font-family:Arial;background-color:transparent;font-variant-numeric:normal;font-variant-east-asian:normal;text-decoration-line:underline;vertical-align:baseline;white-space:pre-wrap" class="">Sierra Leone</span></a></div><div style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;" class=""><a href="https://drive.google.com/open?id=1zQIY49E1vrfjYl7t5V_shvw70d67QirGWUrbW51tDxo" style="text-decoration-line:none" target="_blank" class=""><span style="font-size:10pt;font-family:Arial;background-color:transparent;font-variant-numeric:normal;font-variant-east-asian:normal;text-decoration-line:underline;vertical-align:baseline;white-space:pre-wrap" class="">Uganda</span></a></div><div style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;" class=""><span style="text-decoration-line:underline;font-size:10pt;font-family:Arial;background-color:transparent;font-variant-numeric:normal;font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap" class=""><a href="https://drive.google.com/open?id=1MPwHCwKEVqJvuybKB5Yj39nr8fbcopBP" style="text-decoration-line:none" target="_blank" class="">Kenya (very few rocks)</a></span></div><div style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;" class="">(The report authors are untrained and not native English speakers. Especially the Kenya report contains many errors. Please focus on the consistent final conclusion that a rock bed and second metal grate significantly reduce firewood usage.)</div></span><br class=""></div><div class="gmail_default">This may be a very low cost, very easy way to greatly improved the efficiency of charcoal jikos. I'd like to hear if there is already a body of work on this. Here is my rough drawing:</div><div class="gmail_default"><br class=""></div><div class="gmail_default"><div class=""><div class=""><span id="cid:ii_k1kzflrt1"><20191010_133359.jpg></span><br class=""></div></div></div></div></div></div><div class=""><div dir="ltr" data-smartmail="gmail_signature" class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class=""><br class=""></div><div class="">Thank you,<br class=""></div><div class="">Kevin</div><div dir="ltr" class=""><i class=""><br class=""></i></div><div dir="ltr" class=""><i class="">Kevin McLean, President</i></div><div dir="ltr" class=""><div class=""><i class="">Sun24</i></div><div class=""><i class=""><a href="https://sun24.solar/" target="_blank" class="">https://sun24.solar</a> <a href="https://docs.google.com/document/d/1ZryS7gQ1q3zKLZPM2KcXdtIHbOYQp4PbloPqMvrlZ5Y/edit?usp=sharing" target="_blank" class="">Sun24 Cookstoves Overview</a><br class=""></i></div><div class=""><i class="">Tampa, Florida, USA</i></div><div class=""><i class=""><span title="Call with Google Voice" class=""><span title="Call with Google Voice" class=""><span title="Call with Google Voice" class="">+1 (813) 505-3340</span></span></span></i></div><div class=""><br class=""></div><div class=""> <img src="https://docs.google.com/uc?export=download&id=13teZQbnv_6ek6JkEy-4n0yyUVTrl3M2W&revid=0B8zNcWsuiuj3N2RuVFFYL3EvdElxR1lDcm9QQVlaL0F4VnVFPQ" width="200" height="200" class=""> <img src="https://docs.google.com/uc?export=download&id=11k6wcaMcCbykOoLu-Qo4n6Kbdhplk_er&revid=0B8zNcWsuiuj3ejdsRjRXQWU2OW4rVUpwMUx0Q0U0eXgxcStBPQ" width="200" height="200" class=""></div><div class=""><br class=""><i class=""><span title="Call with Google Voice" class=""><span title="Call with Google Voice" class=""><span title="Call with Google Voice" class=""><br class=""><br class=""></span></span></span></i></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
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