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Geothermal's path to relevance: cheap drilling

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Re: Geothermal's path to relevance: cheap drilling

#51

Post by kragen »

Retric wrote: post #7
phreeza wrote: post #2

I am always a bit bearish on geothermal, because the energy flow through the earths crust is just so damn low. Per surface area, it is about 3 orders of magnitude less than solar irradiation, which means that the circumstances in which it really makes sense to exploit geothermal are those where you can effectively harvest flows from a much larger area, most likely due to convection of water or magma. My understanding…

It’s often less about the heat flow than simply the amount of heat contained in that volume of rock. For your example: A 1/2 acre home is 2023 m2, 1kg of rock is ~2000j/degrees Celsius, 1 cubic meter of rock is ~2500 kg, down 1k = ~2000 j * 2500 * 2023 * 1000 / 60 / 60 / 1000 ~= 2,800,000 kWh per degC. If you’re talking 1kw of heat on average from that rock you only drop 1 degree after 300 years. Of course 1km is a f…

This is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. You can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.

Re: Geothermal's path to relevance: cheap drilling

#52

Post by kragen »

shireboy wrote: post #41

Anecdotally, I looked into this when building our house, and can confirm - the bulk of costs was drilling, and it was expensive. When I did the math at the time, the cost of ground source heat pump over air source heat pump was several times more. Energy bills would be much less, but the payoff was around 20 years, assuming the unit lasted that long.

This is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. You can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.

Re: Geothermal's path to relevance: cheap drilling

#53

Post by shireboy »

kragen wrote: post #52
shireboy wrote: post #41

Anecdotally, I looked into this when building our house, and can confirm - the bulk of costs was drilling, and it was expensive. When I did the math at the time, the cost of ground source heat pump over air source heat pump was several times more. Energy bills would be much less, but the payoff was around 20 years, assuming the unit lasted that long.

This is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. You can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.

Both require drilling that is a major factor in their cost and inhibit adoption was my point. Ground source heat pumps are called “geothermal” systems even though they don’t generate electricity.

Re: Geothermal's path to relevance: cheap drilling

#54

Post by BooneJS »

shagie wrote: post #48
infogulch wrote: post #37

Earlier quoted context omitted.

Wow that's amazing! Basically a community-sized thermal battery. I find the design curious; they use insulation around the outside, but still bored 144 holes on the inside, I guess the bottom is just left alone as solid rock. They heat it with solar energy, and pull out heat during the winter. I wonder how well this would work to provide both AC/cooling during the summer and heating during the winter in climates that…

> I wonder how well this would work to provide both AC/cooling during the summer and heating during the winter in climates that experience both, like the midwest US. If there is a difference in the temperature, then the heat can be moved around. However, that doesn't mean you can run the entirety of the heating for the house in the winter off of the heat battery. https://dnr.wisconsin.gov/topic/Wells/Geothermal.html…

We put geothermal in a house we built outside of Madison, WI. 4 wells dug, 150 ft each, for hearing and cooling. We set our home to 70F 24/7/365 and left it alone. We usually get a week to 10 days of never going above 0 F, and on some of those days the unit ran 20 hours a day to keep up.

Re: Geothermal's path to relevance: cheap drilling

#55

Post by fulafel »

kragen wrote: post #49
Factorium wrote: post #11

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneat…

No, this is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. The difference is not just a matter of sexiness; you can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.

Maybe a factory, many of them use heat in the range that heat pumps are suited for.

Re: Geothermal's path to relevance: cheap drilling

#58

Post by goldenshale »

Factorium wrote: post #11

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneat…

Not really. A ground-source heat pump uses the thermally stable ground below a house to heat in the winter and cool in the summer, while a geothermal power plant pumps cool water down a well and then gets hot steam out another connected well to drive turbines.

Re: Geothermal's path to relevance: cheap drilling

#59

Post by fulafel »

goldenshale wrote: post #58
Factorium wrote: post #11

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneat…

Not really. A ground-source heat pump uses the thermally stable ground below a house to heat in the winter and cool in the summer, while a geothermal power plant pumps cool water down a well and then gets hot steam out another connected well to drive turbines.

Geothermal can be used for just heat too, eg district heating. eg https://www.euroheat.org/knowledge-hub/district-energy-icela...

Re: Geothermal's path to relevance: cheap drilling

#60

Post by kragen »

shireboy wrote: post #53
kragen wrote: post #52

Earlier quoted context omitted.

This is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. You can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.

Both require drilling that is a major factor in their cost and inhibit adoption was my point. Ground source heat pumps are called “geothermal” systems even though they don’t generate electricity.

You can build ground-source heat pumps by laying pipe in trenches in your yard, which is almost, but not quite, completely unlike drilling through kilometers of rock. It's true that they're sometimes called "geothermal", but they're still totally irrelevant to this article.
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