Quote:
Originally Posted by skyking
That doesn't really address the problem, because of the insulative nature of that ground. Once you start extracting it starts cooling off rapidly. You need that high temperature differential so you can pull a lot of heat out of there with relatively little drilling and piping.
We bang into that insulative property problem with our ground source heat pumps. In the winter, the ground gets frozen around the coils from extracting heat.
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The DOE hydro-fracs their geothermal wells to blow the strata open, and keep it open with aggregate, amplifying its effective heat transfer surface area and working fluid permeability.
The rock is basaltic, like glass, and has a much higher heat transfer coefficient than sedimentary rock, where methane and liquid hydrocarbons would be found in the oil patch.