[Haplo]

Similar systems are actually being build, but with a bigger scale (like big office buildings). There is no freezing involved, just heating the office space with warm water in the winter (cooling the water to ~10°C) and cooling it in the summer (heating the water to about 40°C).

[mnahkies]

During the rebuild of Christchurch, NZ they used this technique for a number of buildings, basically pumping out water with one well, then re-injecting it with another as I understand.

Essentially exploits the ground water remaining a constant temperature year around, warmer than the surface in winter and colder in summer