Jim Franklin wrote:
> How does the ground temperature not eventually reach equilibrium with
> the shop? I can't see the transfer of heat in dirt being fast enough
> to absorb a summer's worth of 85+ temps.
It's not a straight heat exchanger. It's a heat pump, with compressor,
refrigerant, and all the same stuff as a regular air-source hat pump.
So it can move heat, even if it's going from warm to warmer. A regular
air conditioner or heat pump absorbs heat from the building, and dumps
it out into the hotter outdoor air (80 degF and up); In heating mode,
it flips around, and sucks heat from the outdoor air down to 20 degF and
lower, and brings it indoors. But it's fighting against the temperature
extremes of the outdoor air.
The ground source heat pump is really beautiful technology (tearing up
now, not unlike a T.S.C. shopping trip) and extremely efficient. Once
you're a couple feet underground, or below the frost line, the earth
stays a fairly constant 50 some degF. So it's very easy for common
refrigerants to dump or suck heat from it. Apparently with the moisture
content and what not, it's quite heat conductive does this very well.
Efficiency for heating can supposedly be over 600%, compared with
straight resistance electrical heating (which is assume is 100% by
definition.)
Google for "ground source heat pump" or "geothermal heat pump" Here are
a couple things I bookmarked:
http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12640
http://geoexchange.org/about/how.htm
-Wayne
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