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Comment by adverbly | Hacker News Reader

Amazing.

Geothermal has actually become my favorite energy "pie in the sky" source.

If drilling was 10x cheaper, we'd all be using geothermal for everything.

If we could just figure out how to drill a bit better, the world would be a fundamentally different place from the perspective of transportation, housing, and energy.

Why pay to boil water when it's hundreds of degrees right under our feet? Here is a crazy fact: if you go down 15 feel and measure the temperature in the middle of winter even in the frigid cold of Alaska, it will be about 45 F or 8C.

It has amazing consistency, works during night, can give you heat via a ground source heat pump. It has basically zero environmental impact.

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I am quite optimistic about some of the high energy non-mechanical drilling methods being developed. Conventional drilling necessitates the use of water/mud to constantly flush out of the pulverized rock. Some of the newer methods vaporize the rock and then exhaust it out as a gas. This allows drilling to depths where the mud would typically boil off.

https://www.quaise.energy/news/major-demo-keeps-quaise-energ...

Reminds me of Subselene, the plan for to send a nuclear-powered thermal-bore on the moon.

https://www.osti.gov/biblio/5262838-subselene-nuclear-powere... https://news.ycombinator.com/item?id=28561236

Mud isn't just to flush out cuttings. It's also to support the borehole. At large depths, you can't keep an open borehole and the "high energy" methods can't work because the borehole will collapse in on itself as it's created. Rocks are quite weak in tension. Drilling mud is dense and offsets the stresses trying to close to borehole as you get deeper.

I thought the big limitation was how much heat could be drawn from around the borehole? i.e. The earth isn't that conductive to move much heat from the surrounding material after operating for awhile.

I believe Fervo Energy is doing a scheme with two boreholes, one for sending down water, the other for bringing it back up. The two wells will be connected by a fracture zone.

There's another company, XGS Energy, that's working on a single well system of the kind you're describing. Their trick is a highly thermally conductive material that can be injected into fractures around the borehole to increase its thermal conductivity. Since the rock near the borehole contributes much of the thermal resistance, this will not have to be injected too far to have a significant effect.

https://jpt.spe.org/hot-rock-slurry-developer-of-emerging-ge...

https://www.businesswire.com/news/home/20250326123552/en/XGS...

Fervo's advances in drilling technology would go well with this other company's technology.

> even in the frigid cold of Alaska

Well (ha!), actually...the permafrost in Alaska can be up to 2000ft deep, though the populous areas of Alaska have minimal permafrost.

I'd like to see a calculation for how long the world could rely on geothermal before they needed to stop to prevent the Earth's interior from cooling so much that Earth loses its protective magnetic field.

Don't worry. There's so much heat, we little humans could never affect any significant change /s

EDIT But seriously. I remember years ago going to a residential GT workshop encouraging private heat sink wells hosted by some boomer reformed hippies. When I asked if there were any studies on the effect of subsurface heat exchange on things like ground water temperatures or different subsurface materials one of the presenters waved it off saying it was probably fine and the other honestly admitted that they didn't know, and that that should probably give us pause before encouraging 200 homes in a square mile all sink wells.

this hole goes 5km out of 6.378km. So 0.1% of the way. Even if we drilled all over the surface (and see floor) it would make very little difference. There is just a lot of Earth and the heat conducts very slowly.

Atmosphere on the other hand is very thin and mostly concentrated close to surface (half is under 5km) so it's much easier for humans to fuck it up

I want to believe this. But it just seems like every generation of humans has their "would make very little difference" moment. When it comes to energy, it turns out there's just no such thing as a free lunch.

To me it looks like there are several free lunches available, just because the sun produces so mich energy compared to what we could possibly use.

It's no different from using a solar cell though. It's all sunlight at the end of the day!

... no?

geothermal heat is harnessing energy from nuclear decay and energy left over from the formation. It is not from the sun.

If anything, it would increase convection (slightly) in the core by increasing the temperature drop there and hence increase the magnetic field (slightly).

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