Re: Geothermal. There was a cover story a month ago in Popular Science (or somesuch) on the potential for geothermal power in the US. There are a few locations where it makes sense and is becoming commercially viable. It's nice because it's available 24/7, so makes for a good source fr baseline demand. There are, however, large portions of the US where no hot spots are close enough to the surface.
OTOH, using the steady-state temps of the earth underneath homes/businesses, etc as a source for earth-coupled heatpumps is an idea that is very practical in most of the US. It's especially attractive if you live in a cold climate and don't have access to natural gas for heating.
In the more distant future when costs come down for direct conversion of heat energy to electricity (via reverse Peltier solid-state devices, etc) I imagine it might even be possible to generate energy from the difference in temp between underground earth temps everywhere and the surface temperature. That will be a long way off, as this low-grade heat difference (30-50 deg F) is just not practical to exploit with present technology (and might never be).
OTOH, using the steady-state temps of the earth underneath homes/businesses, etc as a source for earth-coupled heatpumps is an idea that is very practical in most of the US. It's especially attractive if you live in a cold climate and don't have access to natural gas for heating.
In the more distant future when costs come down for direct conversion of heat energy to electricity (via reverse Peltier solid-state devices, etc) I imagine it might even be possible to generate energy from the difference in temp between underground earth temps everywhere and the surface temperature. That will be a long way off, as this low-grade heat difference (30-50 deg F) is just not practical to exploit with present technology (and might never be).