[russellbeattie]

I've had an idea that is probably impractical and/or impossible, but seems like it would be neat: Every house should have a super deep hole drilled in their back yard, and a small self-contained Stirling engine [1] generator lowered into it, with wires up to the house. Free electricity on a micro scale, 24/7. I'm sure the idea has been explored by people with a much better grasp of physics and engineering than myself. But we've done crazier things as humans - like covering half of the ground in asphalt and stringing wires point to point around the globe, so it doesn't seem unreasonable to me.

1. https://en.m.wikipedia.org/wiki/Stirling_engine

[m4rtink]

For any heat engine - including a stirling engine - you need a heat difference between the hot and cold side, ideally as big as possible. If you put the stirling engine at the bottom of the hot hole, the whole machine will be hot, there will be no difference in temperature and it will not run.

This also discounts stuff like the need for maintenance, that is hard to achieve at the bottom of a hot & likely very humid if not water filled borehole.

For that reason, most geothermal systems pump water down & then back up again (possibly using multiple wells) & have the heat engines at the surface, where they can be easily serviced & a good heat differential can be achieved, via air or water cooling.

This in the end, is generally an industrial operation though, not really something suitable for every single house. Still helps with maintenance, as you can provide energy for many houses & don't hat to maintain the geothermal power production equipment for each house separately.