There's enough heat flowing from inside the earth to meet total global energy demand twice over. But harnessing it requires drilling deep underground and transforming that heat into a usable form of energy. That's difficult and expensive, which is why geothermal power--sometimes called the forgotten renewable--makes up only about 0.3% of electricity generation worldwide. 

Now, though, it's getting a boost. The recently passed US infrastructure bill set aside $84 million for the Department of Energy to build four demonstration plants to test enhanced geothermal systems, an experimental form of the technology.

The funding is only a tiny fraction of the DOE's $62 billion allocation in the infrastructure bill, which also includes money to build more long-distance transmission lines, strengthen the supply chain for batteries, and help nuclear power plants stay afloat. But geothermal researchers say even these limited funds could go a long way in helping transition enhanced geothermal systems (EGS) to commercial use.

"Geothermal is really ready for prime time," says Tim Latimer, founder and CEO of the EGS startup Fervo.