Comment by WarOnPrivacy
18 hours ago
I worked on geothermal control systems a decade or so back. There are some less obvious applications for geothermal that reduce electric use (as opposed to generating electricity).
The systems I worked on were for cooling larger structures like commercial greenhouses, gov installations and mansions. 64° degree water would be pumped up from 400' down, run thru a series of chillers (for a/c) and then returned underground - about 20° or 25° warmer.
I always thought this method could be used to provide a/c for neighborhoods, operated as a neighborhood utility. I've not seen it done tho. I've seen neighborhood owned water supplies and sewer systems; it tells me the ownership part seems feasible.
In the nordics it is common to have ground source heat pumps (brine in closed circuit pipe or bore hole) that are run backwards in summer to cool the house while actually assisting in storing heat back in the ground to extract in the winter. It’s a bit like regenerative breaking on electric cars.
No it's not. It exists but it's certainly not common for individual dwelling to use ground source heat pumps, at least in Norway. It is more common in Sweden[1] but still far less common than air source and over 90% of heat pump installations in Norway are air source[2].
The only ground source installations I can think of in Norway serve large office buildings and similar. The largest heat pump installation I know of in Norway is actually a third kind: water source[3]. It takes heat from the Drammen river to provide heat for a district heating system and for keeping the town centre clear of ice in the winter as well as supplying the new hospital with heat.
I imagine that the rest of the Nordic region is similar.
See:
[1] http://publications.jrc.ec.europa.eu/repository/bitstream/JR...
[2] https://www.sciencedirect.com/science/article/pii/S221313882...
[3] https://energiteknikk.net/2023/11/drammen-fjernvarme-storst-...
If by Nordics you mean Norway, Sweden and Finland, then the most correct way to say would be that ground source heat pumps for redidential heating are (very) common in Sweden and Finland, especially in newer and larger buildings. Norway is somewhat different in energy and climate perspective than its eastern neighbours.
The biggest reason to not install ground source heat pump is high installation cost. This means that it makes more sense for larger residential buildings. Also If you have district heating available then this might be more economical in the long run.
In Finland around 50% of new single-family homes use ground source heat pumps. So it's definitely popular here.
3 schools in my neighborhood (barneskole, ungdomsskole & videregående) all use ground source heat pumps.
There was a new in 1988 house in Champaign, Illinois, USA that used the same system, and i mention that because it was a normal modern house, and it's the only one i've heard of with that system.
It seems so smart.
There's a pretty significant upfront cost in getting them drilled, and many homes need the vertical drilling if they don't have sufficient yard space for a horizontal system. It gets harder if you have your own septic drain field too, as that will complete for yard space.
The cost difference is pretty massive- 3-10x for a vertical system. If you live in a city or a suburb with tiny lots, that's your only option though.
Nat gas and central AC are way cheaper.
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It's expensive. A relative has one in the northern Great Lakes, they wouldn't have installed it if their house had access to natural gas.
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Shallow geothermal works fine for heating. And you can use the ground as a heat sink. But if you want to generate power, you need to get down to where temperatures can boil water. That's deeper than most oil wells. Fervo Energy claims to have found 270C at 3350 meters well depth. That's progress.
> if you want to generate power, you need to get down to where temperatures can boil water. That's deeper than most oil wells.
That’s going to be very dependant on location.
Here in NZ there are regions where water is boiling at surface level.
According to the below, 18% of our power is produced with it.
https://www.eeca.govt.nz/insights/energy-in-new-zealand/rene...
"New Zealand has an abundant supply of geothermal energy because we are located on the boundary between two tectonic plates. ... Total geothermal electricity capacity in New Zealand stands at over 900 MW, making us the fifth largest generator of geothermal in the world. It has been estimated that there is sufficient geothermal resource for another 1,000 MW of electricity generation."
That's not all that much. That total would be about equal to the 75th largest nuclear plant in the world.
Good sites where high temperatures are near the surface are rare. California has a few, but no promising locations for more.
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You brought the conversation in a circle, since the point of this new technology is the geology you speak of is rare.
There are also places in the US with boiling water at the surface. I live near one of those places so always curious about geothermal. There's a spot near my house in a creek bed where snow always melts even in deep winter so apparently I have some potential heat source. Our well water is cold though.
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> But if you want to generate power, you need to get down to where temperatures can boil water.
Why is that the case? Can't you go down to where it's like 70-80 deg C and close the gap using heat pumps? Yes, you need to put some energy in, but I would expect that the whole process would still be energy-positive at some temperature that's lower than 100C?
I think this looks interesting, but still very early stage. The “150 GW revolution” sounds more like theoretical potential, not something we will see soon in real deployment.
Main problems: drilling is still expensive, managing induced seismic activity is not trivial, permitting can take long time, and you also need transmission infrastructure. Also not yet proven that companies like Fervo can scale this in reliable and low-cost way.
Nope. To efficiently tap geothermal energy, you need to boil something but not necessarily water. Isopentane, for example, boils at 28º at standard pressure, so they pressurize the secondary loop to raise the boiling point close to whatever the primary loop temperature is.
The idea that geothermal only works well at steam temperatures is outdated 20th-century thinking.
But the energy in boiling isopentane would be less right?
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I think you're describing what is known as "district energy" systems.
Framingham, MA has a geothermal system using ground source heat pumps like what you are describing
https://www.smartcitiesdive.com/news/first-networked-geother...
Whisper Valley in Austin Texas is one example of a neighborhood geothermal installation: https://www.canarymedia.com/articles/geothermal/texas-whispe...
Maybe not quite exactly what you envision.
> Maybe not quite exactly what you envision.
I'm too zonked to pick out the method from the article - but I'll offer that geo methods can be region specific. What I described fits the SE US, with our 13 month summers and abundant underground water.
District heating and chilled water is uneconomical for single-family homes. It does work well in medium to high density areas.
I don't know how economical that is, but just as an anecdote - the town I'm from in Poland has district heating to all single family homes, town of about 20k people. And coincidentally, I now live in the UK and a new estate near me has district heating to all the houses they are building, not apartment blocks. So it must make some sense to someone, or they wouldn't be outfitting 100+ houses this way.
It’s uneconomical in an already built out area or a non central planned economy, and also the US is special case since we have dirt cheap natural gas that is used for heating.
Digging up streets to run distribution lines, running service drops to every existing house, installing a heat exchanger and valves in every house is astronomically expensive given the amount of energy used by a single residence.
If you’re building out a new neighborhood on a greenspace plot, installing the district heating/cooling piping is much cheaper since you’re already laying electric, water, sewer, and mane gas lines.
At least in parts of Eastern Europe (especially the former GDR) district heating systems were introduced as a response to the oil crises of the 70s, resulting price shocks and the transport of coal to households being very labor and resource incentive [1].
[1] https://www.ndr.de/geschichte/schauplaetze/Windkraft-und-Erd...
"I don't know how economical that is"
Sure you do. Think about it. Its just drilling a hole and making electricity from the heat. We have been able to do this for a very long time. So if people aren't really doing it much, its not economical. If it was now becoming economical, the article would describe some new way of doing it that makes it economical. The article doesn't, so you "know" it isn't.
PS This has been tried many time, it only works in very specific situations, usually places where building a full PP doesn't make sense or where you are making a lot of electricity for some other purpose (mining usually).
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Isn't that similar to how neighborhood heat pumps work?
https://www.araner.com/blog/district-heating-in-sweden-effic...
Heat pumps require a specific temperate differential to work. So they work in zones with are a bit hotter or colder than you would like and so require moderate amounts of heating or cooling. They don't work in temperate zones nor in very hot or cold places. So Santa Fe or Minneapolis for example they work but Mexico City or San Francisco they don't. If you are in a place where they work and that isn't too dense or has earthquakes, go for it. If not, don't. There are businesses that will help you understand when they do and don't make sense. Those businesses don't sell heat pumps though (the businesses that sell things will almost always tell you it works, even when it doesn't, for example PV in the UK doesn't work).
I’ve never heard a claim that heat pumps won’t work well in a climate like San Francisco and, from looking at the annual temperature patterns, it seems like both air source and ground source heat pumps should work extremely well as they do in the “shoulder seasons” here in New England.
> pv in the UK doesn't work
tell that to 6% of UK electric production https://www.bbc.com/news/articles/cz947djd3d3o (up from 5% in 2024
Heat pumps have gotten a lot better, you need a pretty extreme climate for them to start to struggle, even the air-source ones.
(And PV works well enough in the UK for it to be a no-brainer to put on residentials roofs, which is on the whole the most expensive way to deploy it. Though this is in large part due to the way that it competes with retail prices and not wholesale prices)
Wait Minneapolis is definitely very cold for about half the year.
One of the problems with the data center boom is its use of fresh water. How does geo-thermal plants use water and how much?
The water at these temperature / depths has a lot of dissolved salts and minerals so it's not (human / ag) usable. Modern designs are closed loop systems where production wells bringing the hot water to the surface go through a heat exchanger to a different working fluid to drive the turbine and then is re-injected back into the reservoir. There is consumptive water use for fracking the reservoirs in these types of enhanced geothermal systems, but beyond that it's more water redistribution in the area around the well systems where re-injection and production lead to different pressurization from pumping / natural ground water replenishment rates.
I dont know why this keeps coming up? It is a closed loop system. The water aren't used at all.
It's a closed loop on the geo side sure.
How do you cool the steam off enough to condense so it can go and be boiler feed water again?
Lots of power plants use cooling towers for this which are typically evaporative. Some are dry, sure, but most are wet.
Many data centers use evaporative cooling.
> One of the problems with the data center boom is its use of fresh water. How does geo-thermal plants use water and how much?
Baring leaks, ground source heat pump geo will consume no water at all. Water is pumped from one layer of the aquifer and is returned to a slightly higher layer.