Odds and Ends
6 2, 6:06am
Geothermal relies on a temperature differential to work. You can't just throw a machine in lava and expect it to convert heat into electricity. Instead, you half to throw one half the machine in lava, and the other half in ice.
Or just fresh air, or any other medium cooler than the lava.
(Theoretically, you could use lava as a coolant for something that was REALLY hot. I think I recall reading of some reactor using a liquid metal as a coolant.)
All heat engines work this way.
Any geothermal plant, regardless of where or how it works, is going to produce waste heat. You enjoy some really nice steam heating options because you've been smart about not wasting the waste heat.
At least until someone breaks that law of thermodynamics that says you can't just turn heat back into usable energy.
Further, how much heat can you retain pumping that water to the surface? How much energy are you using just circulating that water through a multi-kilometer vertical pipe?
And, yes. I know you don't need to dig down until you hit magma. I'm using molten rock as an example of something really hot.
You can't throw one of those Peltier junction cell phone charger camp furnaces in a fire and expect it to produce heat, either, even if you could keep it from melting. It only works when one side, (the inside,) is cooler than the other side, (the outside,) and works by tapping that differential for electricity while the differential equalizes, (while the outside gets hot.)