If you built a heliostat field with a concentration of say 10 and made the greenhouse an insulated building except for the window receiving the light from the heliostats you could reduce supplementary heating tremendously. The wall on the far side should be reflective. Window is of course at focal point of field and should be low iron glass. Even a building such as the passive solar rooms as in Rodale press book "Passive solar heating" with a tilt out reflector which is insulated on the back so when it is closed at night heat loss is more comparable to a regular house would save tremendous amounts of heat.
Look into PAR lamps for cloudy days. (Photosynthetically Available Radiation) " ________________________________ From: Darryl McMahon <[EMAIL PROTECTED]> To: sustainablelorgbiofuel@sustainablelists.org Sent: Wed, December 1, 2010 6:42:43 AM Subject: Re: [Biofuel] greenhouse farming This company supplies tomatoes to local stores year-round in Ottawa, Ontario, Canada. http://www.suntech.ca/ You might want to investigate how the do things. Looks like average temperatures are pretty comparable for SD and Ottawa over the course of the year (comparing http://www.weather.com/outlook/driving/interstate/wxclimatology/monthly/graph/57103 to http://www.weather.com/outlook/driving/interstate/wxclimatology/monthly/graph/57103). Darryl On 30/11/2010 11:43 PM, Dan Beukelman wrote: > Hello All, > > I have read your posts for several years, but have not ever posted - > lurking in the shadows I guess. > > > > I am wondering if anyone out there has any thoughts/experience with > production agriculture from a greenhouse/hothouse structure. I live in > South Dakota and have been thinking that with energy efficient glass and the > right setup that growing fresh vegetables likes tomatoes year around might > be possible (I say this with a wind chill today near 0 fahrenheit). I have > read that many of the US tomato supply is grown in Canada, which is colder > than us, our area is dominated by grain farming - but I think that local > foods stores would go nuts over a locally grown garden type tomato in the > Wintertime. The construction costs of a very efficient greenhouse should be > able to be covered by the profit from selling a well growing tomato crop, > but the profits go out the window if you have the heat much. All of the > greenhouses I know of around here use plastic coverings and that is only > useful for extending the growing season a little bit on both ends. I am > thinking of keeping growth all year or nearly all year. > > > > Any thoughts? > > Dan > -- Darryl McMahon The Emperor's New Hydrogen Economy (eBook and trade paper) http://www.econogics.com/TENHE/ _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/sustainablelorgbiofuel Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (70,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/ -------------- next part -------------- An HTML attachment was scrubbed... URL: /pipermail/attachments/20101201/47a101e8/attachment.html _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/sustainablelorgbiofuel Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (70,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
