“Geothermal is really prime time ready,” says Tim Latimer, founder and CEO of Fervo, the EGS startup.
The appeal of geothermal energy has to do with consistency: while the electricity production of wind and solar plants varies with the weather and the time of day, geothermal energy is always on, providing a stable source of electricity.
“It’s really the only renewable base load,” says Jody Robins, a geothermal engineer at the National Renewable Energy Laboratory. Nuclear power (which is carbon-free but not renewable) can play a similar role, although cost, waste issues, and public perception have limited its implementation.
Modern geothermal power plants have been operating in the US since the 1970s. These plants generally pump hot water or steam from underground to the surface to drive a turbine and generate electricity. The water is then pumped down to maintain the pressure underground, so the process can continue.
Major geothermal sites share certain characteristics: heat, fractured rock, and water, all close to each other and within a couple of miles of the surface. But now more accessible geothermal resources have been tapped (in the US, they are mainly concentrated in the west). Although researchers believe there are still many more potential sites to find, it is difficult to know where they are. And in most of the eastern US and many other places in the world, underground rock isn’t the right kind for traditional plants to work, or the water isn’t there.
Some researchers and startups are trying to expand geothermal to new places. With EGS, they are trying to engineer what is underground by pumping fluid into the impermeable rock to force open the cracks. This creates a space where water can move freely and heat, producing the steam needed to generate power. The process has the potential to trigger earthquakes, as the first projects in South Korea and Switzerland have shown. However, EGS is similar to fracking, which is widespread in the US, and the risks are likely to be manageable in most places, Robins says.
This approach could expand geothermal to places that don’t have the groundwater or rock types needed for traditional plants.
Still, reaching these resources will not be easy. Commercial drilling is typically not much deeper than seven kilometers (four miles), for cost reasons it is often even less than that, and many places that could benefit from geothermal energy are not hot enough at that depth to reach 150 ° C needed to generate electricity economically. Reaching sufficient temperatures may mean going deeper, which would require new techniques and technologies that can withstand high temperatures and pressures.
Fervo is working on some of those details on his own projects, including one announced earlier this year with Google to install geothermal capacity near the company’s data centers in Nevada. He also recently became involved in a DOE project in central Utah called FORGE (Frontier Observatory for Research in Geothermal Energy).
FORGE academic and industry researchers are trying to find best practices for implementing EGS, including drilling and reservoir maintenance. The site was chosen because its geology is fairly representative of places where other EGS plants could be built in the US, says Lauren Boyd, EGS Program Manager in DOE’s Office of Geothermal Technologies.
With the new funding from the infrastructure bill, the DOE will fund four additional demonstration sites. That will broaden what the researchers understand about installing EGS facilities, as they will be able to work in different locations and with different types of rocks. At least one plant will be built in the eastern United States, where geothermal energy is less common.
But technological barriers are not all that have slowed the progress of geothermal energy, says Susan Hamm, director of DOE’s Office of Geothermal Technologies. Building a geothermal plant can take up to a decade due to all the permits involved. Simplifying that paperwork could cut that time in half and double projected geothermal capacity by 2050.