Geothermal power plant — Photo by Sam Bark on Unsplash
You might think that geothermal power is limited to highly volcanic locations like Ice Land, but you’d be mistaken. This super clean elemental energy is widespread. Take the US; it has an estimated 15 billion GWh of thermal power availability, and 5,157 GW of accessible geothermal power just sat there waiting to be used. That is the equivalent of 450% of the current US energy consumption. If the US can tap into this energy source, it could revolutionise its energy infrastructure and even the economy by becoming a clean energy exporter. But there is a problem: harnessing this non-volcanic geothermal energy is incredibly challenging and expensive. But all that might be about to change thanks to Fervo energy.
So why is it hard to tap into these geothermal reserves? You might think they are too deep to be commercially used. While that is true for many potential geothermal sites, that isn’t what’s happening here. That estimate of 5,157 GW of accessible geothermal power is for Enhanced Geothermal Systems (EGS) (also known as Hot Dry Rock), which is at the same depth as normal geothermal power, but requires different technology to extract energy. Let me explain.
Typical geothermal sites need highly permeable rocks to function. They work by drilling two boreholes down to the geothermal site. Water is injected into one borehole, and at the bottom, it permeates through the super-hot porous rock. This dramatically increases the surface area between the rock and water, which in turn speeds up the heating of the water, turning it to steam quicker. This builds up pressure, forcing steam up the other borehole, and once at the surface, this steam drives a turbine to make power before it is cooled and condensed back into water and reinjected.
These porous rocks tend to occur near volcanic sites. But geothermal reserves away from volcanic sites tend to have non-porous rocks. This can dramatically slow the rate at which water is heated and turned to steam, rendering geothermal power useless. As such, Enhanced Geothermal Systems were invented. These use multiple wells/boreholes and hydraulic…