Don't need to use cooling to make it work, I live in a fairly large house without cooling and a bore down into the mountain below is good enough even though we have -15 to -25C for weeks during winter. It's in a small town so not an isolated location. Most people around here have air-to-water or air-to-air, because it's good enough and cheaper to install.
And it's not a hollow, it's a plastic ~1 decimeter pipe with ethanol going through stone some distance down from the surface. Not sure how long this collector is, but 70-200 meters is common depending on how large the house is and conditions in the ground.
Ethanol is an interesting choice... lower specific heat when compared with water. Is that to discourage things like tree roots from making a home in your well?
It's stable, cheap, carries heat OK enough, so it gets pumped through the pipe in the ground to collect heat and bring it back up to the heat pump.
If there's a leak it's bad since it's quite toxic to organic life. If you collect in soil rather than drilling into rock tree roots might push around the collector pipe a bit over the years but I've never heard about that being a problem.
And it's not a hollow, it's a plastic ~1 decimeter pipe with ethanol going through stone some distance down from the surface. Not sure how long this collector is, but 70-200 meters is common depending on how large the house is and conditions in the ground.