<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin-top:0mm;
margin-right:0mm;
margin-bottom:10.0pt;
margin-left:0mm;
line-height:115%;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoPlainText, li.MsoPlainText, div.MsoPlainText
{mso-style-priority:99;
mso-style-link:"Plain Text Char";
margin:0mm;
margin-bottom:.0001pt;
line-height:115%;
font-size:10.5pt;
font-family:Consolas;}
p.MsoNoSpacing, li.MsoNoSpacing, div.MsoNoSpacing
{mso-style-priority:1;
margin-top:5.0pt;
margin-right:0mm;
margin-bottom:5.0pt;
margin-left:0mm;
mso-add-space:auto;
line-height:115%;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
p.MsoNoSpacingCxSpFirst, li.MsoNoSpacingCxSpFirst, div.MsoNoSpacingCxSpFirst
{mso-style-priority:1;
mso-style-type:export-only;
margin-top:5.0pt;
margin-right:0mm;
margin-bottom:0mm;
margin-left:0mm;
margin-bottom:.0001pt;
mso-add-space:auto;
line-height:115%;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
p.MsoNoSpacingCxSpMiddle, li.MsoNoSpacingCxSpMiddle, div.MsoNoSpacingCxSpMiddle
{mso-style-priority:1;
mso-style-type:export-only;
margin:0mm;
margin-bottom:.0001pt;
mso-add-space:auto;
line-height:115%;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
p.MsoNoSpacingCxSpLast, li.MsoNoSpacingCxSpLast, div.MsoNoSpacingCxSpLast
{mso-style-priority:1;
mso-style-type:export-only;
margin-top:0mm;
margin-right:0mm;
margin-bottom:5.0pt;
margin-left:0mm;
mso-add-space:auto;
line-height:115%;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
span.PlainTextChar
{mso-style-name:"Plain Text Char";
mso-style-priority:99;
mso-style-link:"Plain Text";
font-family:Consolas;}
span.EmailStyle20
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle21
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>Dear Xavier<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Gee, it would be easy to add a skirt to that rim-stove. It already has a lip to hold it in position! You should check that the vertical ‘chimney effect’ does not drive a lot of extra air through the stove, cooling the gases. If you painted the outside silver it would keep the radiation of heat down from the rim.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>You could put clay /sand into the base leaving only enough room to get air in and distributed around the burner. This is a great place for a combustion analyser. Put on a skirt and measure the excess air coming through and close the hole until it is about 25%. Probably reduce fuel consumption considerably and increase the heating speed. It is really hard to guess what the EA is by looking at a gas flame.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Crispin<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 0mm 0mm 0mm'><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt;line-height:normal'><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US 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>Xavier Brandao<br><b>Sent:</b> 29 July 2011 15:00<br><b>To:</b> stoves@lists.bioenergylists.org<br><b>Subject:</b> [Stoves] Improve gas burners efficiency?<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>Dear stovers,<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt;text-align:justify'><span lang=EN-US>When promoting the institutional rocket stoves in public administrations kitchens, restaurants, hotels in South Benin, mostly in the cities of Cotonou and Porto-Novo, I am told more than once that wood is not used anymore, because of the smoke, the cost, or the hassle. Many moved to gas burners, which is of course great. We produce and sell wood stoves, but we always encourage people to use gas cookers, because they are cleaner, more ecological and economical. We only produce wood stoves for people who would have use wood for cooking anyway (for certain dishes, certain quantities, or in certain big institutions).<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt;text-align:justify'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>Many people liked the sturdy design of the stoves and asked if they could have the same for gas stoves. I always reply that is was designed for wood only, and promise we’ll think about a model for gas burners.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>My question is: how much can a gas burner be improved in terms of energy efficiency? Is it worth spending metal in making a skirt around the burner and the pot? I was thinking also of a surface under the burner, perhaps just like the institutional stoves, made of a mix of clay, to radiate heat upwards. It would give a traditional look to a modern cooking device.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>My quick calculations showed it could cost in the very very worst case up to 30 000 CFA francs all included (about 45 euros) for a skirt for one burner. People seem to be ready to pay that, if it means savings. A lady who runs a restaurant paid a welder 60 000 CFA for two skirts, which amusingly enough is in line with my calculations. They are not made yet, I’m curious to see how they look.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>Here is a picture of the burners:<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><a href="http://imageshack.us/photo/my-images/803/rimg1222.jpg/">http://imageshack.us/photo/my-images/803/rimg1222.jpg/</a> <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>Another burner, inserted in a truck rim:<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><a href="http://imageshack.us/photo/my-images/834/rimg1229.jpg/">http://imageshack.us/photo/my-images/834/rimg1229.jpg/</a> <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>Here is a picture of a small burner, with a small skirt which only protects the flame from wind, not the pot:<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><a href="http://imageshack.us/photo/my-images/38/rimg1228.jpg/">http://imageshack.us/photo/my-images/38/rimg1228.jpg/</a><o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>I’ve searched a bit on Bioenergylist, and in <i>Micro Gasification Cooking with gas from biomass</i>, I could only find the Vesto stove as a gas stove with a skirt.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>This post brings another question, which I will detail in another issue.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>Thanks in advance,<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0mm;margin-bottom:.0001pt'><span lang=EN-US>Xavier<o:p></o:p></span></p></div></body></html>