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Comment by blakesterz | Hacker News Reader

This seems to be all about Geothermal HEATING, which seems pretty tough in most places. I thought Geothermal Cooling is easier/cheaper in many areas? Heat from Geothermal seems really difficult because you have to drill so deep almost everywhere, but that's not the case for cooling, is it?

Iceland seems to have some decent heat there: https://en.wikipedia.org/wiki/Geothermal_power_in_Iceland

Five major geothermal power plants exist in Iceland, which produce approximately 26.2% (2010) of the nation's electricity.

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To heat a home with geothermal, you use a heat pump. It works better than an air source heat pump most places because the ground doesn't get as cold as the air does.

More widely deploying ground source heat pumps for home heating seems more promising than pursuing geothermal electricity generation. The problem with ground source heat pumps is that the lifecycle of the equivalent if 30-50 years, well outside the typical homeowner's planning or payback horizon.

For the same cost we could install multiple air-source heat pumps at nearly the same efficiency. That's a way better tradeoff.

I wish ground source heat pumps were more affordable, I asked my HVAC installer, he said I was looking at $30K+ including returning the yard to the state it was in before they trenched in the pipes. That's 3X the cost of the air source heat pump I ended up going with.

> I wish ground source heat pumps were more affordable

I don't think this will ever be the case. Water-to-water (ground source) and air-to-water (air source) heat pumps are effectively the same thing technically sans some tuning for temperatures, therefore the difference in cost of the heat pump itself is never going to be high.

The cost difference is in installation costs. Air-to-water heat pump installation is as simple as mounting the external unit and routing a few pipes back to interior unit while water-to-water installation is routing the distributed heat exchanger, which is significantly more labor intensive even if you do not account for landscaping (e.g. done as part of greenfield development which will have landscaping done anyway).

The house I grew up in had a geothermal system (installed when my parents built the house). I was a bit young to know the precise details, but I believe the idea was that the ground loop merely heated or cooled (depending on the season) to the ground's ambient temperature, around 60ºF. From there, it was further heated using traditional methods. I think that meant a heat pump, as you mention, but it might have been oil.

The energy savings in the winter (US-MA) was nice -- heating from 60 is a lot less energy than heating from 30 or below -- but the summer was the real reason I'll absolutely install geothermal in any house I build: basically free a/c. Not having to think about setting the thermostat for a relatively large house down to 72 (or even lower, if you want to freeze your tookus off) is so freeing.

Ground-source heating/cooling is quite different from geothermal heat or power. With ground-source, you just have a heat pump like an ordinary air conditioner, but using the ground as the heat sink instead of outside air. A couple of meters is deep enough. It's nothing like prospecting for the rare resource of accessible hot rock or natural steam, as in Iceland.

Same heat transfer dynamics apply to cooling as well. Earth is a really good insulator, that's why it has a steady temperature in the first place. If you dump too much heat in it, it will warm up. That's seen as an advantage when you can harvest the same heat in the colder months using geothermal heat pumps.

Some buildings that have access to the ocean or a lake can use that for heat rejection because those take the heat away.

None of these applications require going too deep in the ground. This article is all about going deep.

Iceland has access to very hot water in shallow ground. They are unique that way.

Keep in mind Iceland's population is under 400k. That's less than the city proper of Minneapolis, for example.

That said, Iceland does in effect export a ton of power by importing bauxite and turning it into aluminum.

Indeed, in 2011, 71% [1] of the electricity production of Iceland was used by the aluminum industry!

[1] https://en.wikipedia.org/wiki/Electricity_sector_in_Iceland#...

True, although I think that's hydropower? At least that's what I remember from when I studied there ~15 years ago.

The systems used for cooling work just as well for heating. Really heating is probably the reason most of them are installed, and then, hey, why not also use it during the summer.

Your comment is entirely unrelated to the article, which is about using the very hot rock several kilometers underground to drive turbines to generate electricity.

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