We’ve had at least one prior thread on this, but David Roberts at Volts recently did a podcast on it recently and I learned quite a bit.
I’d post a link but the nanny filter got drunk on power and decided a portion of the URL was offensive EVEN THOUGH THE LINK WAS EMBEDDED AND NO ONE CAN SEE IT.
Anyway, conventional geothermal is nice in that it is carbon free, but it is obviously constrained by geography, and another problem is that it typically must provide baseload power to be cost effective. In a world with increasing intermittent sources like wind and solar, dispatchable sources become more and more important. So not a ton of potential there.
But there’s a lot of potential for enhanced geothermal, which is basically fracking hot, dry rock, injecting water, and recovering the steam to generate electricity. Several reasons why this is exciting. One is that geographically, a much larger area is now theoretically suitable. A second is that by throttling back the recovery leg, you increase the pressure in the reservoir, which means you are effectively storing the energy which makes it dispatchable.
Because of the intermittent nature of wind and solar, these sources need lots of capacity to provide a 100% carbon-free grid. Most of the time that excess capacity is wasted. But if you had a carbon-free dispatchable source, you need less excess capacity, and the cost of the whole system comes way down.
That’s the theory. In practice, as of right now there is barely any enhanced geothermal so the economics aren’t well understood. But there are several utility scale projects in the works, including one with Google. There is a really good animation at the link that shows why load following geothermal is so beneficial for going carbon free. Interesting space to watch.