“Geothermal is really ready for prime time,” says Tim Latimer, founder and CEO of EGS startup Fervo.
The attractiveness of geothermal energy lies primarily in its durability: While the power output of wind and solar systems varies with the weather and the time of day, geothermal energy is always switched on and provides a stable power source.
“It really is the only renewable base load system,” says Jody Robins, geothermal engineer at the National Renewable Energy Laboratory. Nuclear energy (which is carbon-free but not renewable) can play a similar role, although costs, waste problems and public perception have limited its use.
Modern geothermal power plants have been running in the USA since the 1970s. These systems usually pump hot water or steam from underground to the surface to move a turbine and generate electricity. Then the water is pumped back down to maintain the pressure underground so the process can continue.
First-class geothermal locations have certain properties in common: heat, rock with fractures in them, and water, all close together and only a few kilometers from the surface. But now the most accessible geothermal resources – in the US they are largely concentrated in the west – have been developed. While researchers believe there are many more potential locations, it is difficult to figure out where they are. And in most of the eastern United States and many other places around the world, the bedrock isn’t the right type for traditional plants or the water isn’t there.
Some researchers and startups are trying to expand geothermal energy in new places. With EGS, they try to manipulate the subsurface by pumping liquid into impermeable rock to open cracks. This creates a space in which the water can move freely and heat, creating the steam required for electricity. The process has the potential to trigger earthquakes, as the first projects in South Korea and Switzerland have shown. EGS, however, is similar to fracking that is widespread in the United States, and the risks are likely manageable in most places, Robins says.
This approach could extend geothermal energy to locations that do not have the groundwater or the types of rock needed for traditional plants.
Still, reaching these resources will not be easy. Commercial wells typically go no deeper than seven kilometers (four miles) – often even less for cost reasons – and many places that could benefit from geothermal energy are not hot enough at this depth, around 150 ° C. needed to generate electricity economically. Reaching sufficient temperatures can mean going deeper, which would require new techniques and technologies that can withstand high heat and pressure.
Fervo is working out some of these details in its own projects, including one announced earlier this year with Google to install geothermal capacity near the company’s Nevada data centers. It also recently got involved in a DOE project in central Utah called FORGE (Frontier Observatory for Research in Geothermal Energy).
FORGE academic and industrial researchers are trying to identify best practices for using EGS, including drilling and reservoir maintenance. The site was chosen because its geology is fairly representative of places where other EGS facilities could be built in the U.S. says Lauren Boyd, EGS program manager in the DOE’s Geothermal Technologies Office.
With the new financing from the Infrastructure Act, the DOE is financing four additional demonstration sites. This will expand researchers’ understanding of how to set up EGS facilities as they can work in different locations and with different types of rock. At least one plant is being built in the eastern United States, where geothermal energy is less common.
But not only technological barriers have slowed the progress of geothermal energy, says Susan Hamm, director of the DOE’s Geothermal Technologies Office. The construction of a geothermal system can take up to a decade due to all the necessary permits. Streamlining this paperwork could cut that time almost in half and double forecast geothermal capacity by 2050.
