Chanakya,<br><br>Jaime Marti has had success with digesters at 6000 meters in Bolivia with really cold temperatures. He uses a very nice design of adobe walls, southern aspects, and plastic greenhouse panels to heat the digester. Our temperatures are not as cold, but we often deal will near-freezing conditions, and we are using tunnel-type greenhouse structures that have been shown to maintain temperatures 15-20 degree above ambient temperature. We have considered thermal solar heating of water, with circulation mats installed under the digester. And we have tried this with biogas heated water. Our energy balance was not that great however... <br>
<br>I have experimented with hay water running through pipes inside the digester, and I will warn you that the pipes quickly become covered in the material and begin to become "insulated" and loose their effectiveness at transferring heat (has anyone else dealt with this?). On a larger scale, I have seen good option where sludge pumps pull materials from the bottom of a digester, run the material through an external heat exchanger, and then return it the system. These use waste heat from a biogas generator. <br>
<br>Best,<br><br>A <br><br><div class="gmail_quote">On Mon, Dec 6, 2010 at 6:56 AM, Hoysall Chanakya <span dir="ltr"><<a href="mailto:chanakya@astra.iisc.ernet.in">chanakya@astra.iisc.ernet.in</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">I am trying to get a few people to dream of solar assisted biogas plants<br>
for regions that may have temperatures nearer zero but are not under<br>
permafrost. Very long back I was involved with a prototype that used a<br>
solar water heated biogas plant roof (for Bangalore) and could raise the<br>
digester temperature from 16 to 28C. I am requesting list users if there<br>
is any past experience, current hope or promise for this idea of solar<br>
heated /assisted biogas plant to work in northern Europe and UK? or cite<br>
some examples that I could look up.<br>
Anaerobically!! Chanakya<br>
<br>
chanakya[ at ]<a href="http://astra.iisc.ernet.in" target="_blank">astra.iisc.ernet.in</a><br>
--<br>
Dr. Hoysall Chanakya<br>
Centre for Sustainable Technologies<br>
(Assoc. Faculty at Centre for Infrastructure, Sustainable Transport and<br>
Urban Planning (CiSTUP) and Centre for Contemporary Studies)<br>
Indian Institute of Science, Bangalore 560 012<br>
ph 91-80-2293 3046; fax-91 80 2360 0683<br>
<br>
<br>
--<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Alexander Eaton<br>Sistema Biobolsa<br>IRRI-Mexico<br>RedBioLAC<br><br>Mex cel: (55) 11522786<br>US cel: 970 275 4505<br><br><a href="mailto:alex@irrimexico.org" target="_blank">alex@irrimexico.org</a><br>
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