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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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Renewable Energy: Budget Airconditioning/Greenhouse Frost Protection

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    A thought occurred to me, I'm planning to use an old car radiator with 12v fan to provide frost protection to our greehouse, using water and gravity from a spring fed stream which never goes below 8 C for the heating. Now it struck me that I could also do this using a ground loop, extracting low level heat from the soil, and power it all from a 12v battery. If this worked then in the summer it would also be able to be used for cooling. I'm yet to try this, has any one else ?
    • CommentAuthortony
    • CommentTimeMay 9th 2007
     
    Hi, Keith The frost proofing may well work but you should be aware that your radiator will only be capable of giving out a small amount of heat so were it to be both windy and cold this may not be enough to do the job.

    As for air cooling the house -- no way will it be man enough for the job.

    You could think about using the spring water in conjunction with a heat pump to produce very efficient ( 350 > 400%) efficient heating.

    What is the flow rate and fall on your spring/stream?
    • CommentAuthorpyrogaz
    • CommentTimeMay 9th 2007
     
    To keep the greenhouse frost free on winter nights my father uses a system similar to that which you are describing, except the heat source is an insulated plastic barrel into which the grey water from the washing machine and bathrooms runs into during the day. He has an intercooler from a Mitsubishi Shogun submerged in the barrel and a fan from a large UPS (I think) circulating air from the greenhouse, through the intercooler and back into the greenhouse. It seems to work fine even though the water is rarely above 30c. The fan switches on by a socket timer and similarly a pump empties the barrel every morning.

    My personal preference for "green" greenhouse heating is to use a composting system similar to, but much smaller than, that used by Jean Pain

    http://journeytoforever.org/biofuel_library/methane_pain.html

    I had a system set up at my previous property and am working towards using to provide the majority of heat for the house I'm currently building.
  4.  
    Posted By: tonyAs for air cooling the house -- no way will it be man enough for the job.


    Do you actually know what heat transfer capacity a car radiator has? I suspect it is quite a bit larger than you'd imagine. I know the heat exchanger inside my GSHP is about the same size as my car radiator. His idea will work provided there is sufficient airflow - a 12V fan driven from a car battery probably won't cut it but such a system installed in a proper air handler would work. In fact, it's being done commercially here in Canada by a company called Nordic - they make heatpumps that also have a passive cooling mode whereby the ground loop fluid is circulated directly through the heat exchanger. Such as system provides enormous EER values since the power to run it is pretty low compared to running a full refrigeration circuit with compressor.

    http://www.nordicghp.com/mg/nordicJul-25-04/O_series/O%20Specification%20sheet.pdf
    • CommentAuthorkeithwhite
    • CommentTimeMay 13th 2007
     
    Hi

    Thanks for all your comments, looks like I will have to try it out and report back

    Cheers

    Keith

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