We can drill down and pump out oil and natural gas from anywhere in the world, even building refineries on massive rigs in the middle of the ocean.
We can dig down and extract coal through endless tunnels that stretch out under the sea.
Why is it not feasible to just drill down far enough to pump water down and allow steam to rise up and power turbines? I know some parts of the world have the required heat closer, but surely tapping into the heat that perpetually sits under our feet is a huge contribution to the solution of replacing fossil fuels?
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In short, it’s too far down generally. Drilling wells is expensive. Maintaining deep wells is expensive too. We might end up spending more energy drilling and maintaining a couple of wells than the energy expected to be produced over the lifetime of those wells.
Most human settlements are in places where the crust of the earth is many miles thick, and the necessary heat sources are buried beneath thirty miles of solid rock.
The costs and engineering challenges of boring and maintaining huge numbers of the world’s deepest boreholes (current record is short of 8 miles) have so far been prohibitive.
Most of the thin points in the crust are inconveniently located in ocean trenches, and prone to seismic activity that would damage your delicate miles-long geothermal piping.
There’s a few hot spots like Iceland where upwelling magma have brought heat much closer to the surface and we do build geothermal plants there.
Massive upfront costs and uncertain returns. Basically, what every capitalist is told to avoid in the money making bible.
My family built our home 12 years ago. We have a geothermal heating and cooling system. We were the first home on our area to.
There’s a company trying to drill deep wells to do this. The idea includes drilling next to existing fossil fuel plants so they can reuse the infrastructure, turbines, grid connections etc.
https://www.quaise.energy/
If you drill the average place, you can get heating for a house at 30-300m. 30 is economical, 300 is not.
If you drill to 3000m you can get something around 50-100 C degrees. That’s not enough to run a electric power plant. You can use a stirling engine but: you drilled 3000m to get 5 horsepower per 1000kg of engine, that’s not even gonna cover the water pumping of the well., let alone spinning a generator for electricity.
In specific places you can drill a 100m hole and get 200-1000 C degrees. That’s reasonably ok for getting steam and spin a turbine that then spins a generator. But rock is a good insulator. As soon as you run the system the drill hole cools down to 100-500 C. So you can get some power, but not a lot of power. It’s ok in Iceland, there’s few people, little power demand, and geothermal costs less than importing electricity. Geothermal powerplant does have an excess of heat as every powerplant, so in Iceland you get free heating for houses too. But let’s say you are in the middle of france, summer, you find an epically good spot, you make your plant and all you get is excess heat that is useless and 1 Megawatt of electricity… in a place where a nuclear plant makes 1000 megawatts… is it worth it?
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