[xendipity]

"EGS are engineered reservoirs, created beneath the surface, where there is hot rock but limited pathways through which fluid can flow. During EGS development, the injection of fluid into the hot rock enhances the size and connectivity of fluid pathways by re-opening fractures. Once completed, EGS function just as natural geothermal systems do: fluids circulating through the hot rock carry energy to the surface through wells, driving turbines and generating electricity. EGS could provide up to 100+ GWe of economically viable capacity in the United States. This potential could supply green electricity to over 100,000,000 American homes, and represents a domestic energy source that is clean, reliable, flexible and renewable."

[IgorPartola]

I can see the headlines from 40 years in the future: Geofracking Responsible for Devastation of the State of Tennessee as Record Breaking Earthquake Shakes the Eastern Seaboard”

Also how exactly is extracting heat from underground renewable? What exactly renews the constantly cooling core of our planet?

[burlesona]

The core of the earth is essentially a fission reactor with quite a lot of fuel available. While this heat source is technically finite, so is the sun, and the universe itself. If you somehow live to see the heat death of the universe, you’re probably SOL.

But for humans living on earth today, and in timescales we care about (millions of years), the Earth’s core won’t run out of heat.

[kragen]

Not the core, which is made of stable elements like iron, but the crust. You'd think that uranium and thorium would settle to the core because they're heavy, but they're not siderophilic, so most of them stays in the crust. About two thirds of the geothermal heat flux is from fission in the crust: https://en.wikipedia.org/wiki/Geothermal_gradient

Non-sustainable heat extraction is much more likely, because the sustainable resource is only about 44 TW, while world marketed energy consumption is already 18 TW (https://en.wikipedia.org/wiki/World_energy_supply_and_consum...). By contrast, there are about 100 000 TW of solar energy available. There are billions of years of fossil heat locked up in the crust, amounting to conservatively many millions of times the total oil supply, and by extracting it faster than it was produced you can get much higher power.

Like (above-ground) nuclear energy, this is not currently an economically competitive source of exergy because of the cost of the heat engines required, except in unusual cases. It was until only a few years ago, but PV has gotten much cheaper since then. It probably won't be again until a revolution in manufacturing technology.

[burlesona]

Thanks for the clarification! I was under the impression that the heavier elements would be found toward the center. I appreciate the links :)

[martythemaniak]

As others have pointed out, nothing is renewable on long enough timelines. The earth will burn out, the sun will burn out, eventually the universe will burn out.

[Lammy]

Try “from 2019” https://news.ycombinator.com/item?id=30139155

[baremetal]

radioactive decay.

[jeffbee]

In other words it isn’t renewable, it’s just very long-lived.

[connicpu]

There's no such thing as infinite energy in this universe. There's enough deuterium in the oceans to power humanity at our current pace until well after the sun expands and makes earth uninhabitable, but that is still a limit where we'd run out.

[colechristensen]

So is the Sun.