Glittering across the dry expanses of the Nevada desert is an unusual kind of power plant that harnesses energy not from the sun or wind, but from the Earth itself.
Known as Project Red, the facility pumps water thousands of feet into the ground where rocks are hot enough to roast a turkey. Around the clock, the power plant siphons heated water back into the generator. Since last November, carbon-free, earth-based power has been flowing into Nevada's local power grid.
Although geothermal energy is continuously released from the Earth's ultra-hot core, it has long had a relatively niche use, largely confined to volcanic regions such as Iceland, where hot springs bubble up from the ground. But geothermal enthusiasts have dreamed of getting power from the Earth in places without special geological conditions, such as the Nevada site of Project Red, developed by energy startup Fervo Energy.
These next-generation geothermal systems have been in the works for decades, but have proven expensive, technically challenging, and sometimes even seismic. Some experts hope that new efforts like Project Red will finally signal a turning point by leveraging technologies now honed in oil and gas extraction to improve reliability and cost efficiency.
These developments have given rise to hope that, with enough time and money, geothermal power, which currently produces less than 1% of the world's electricity and 0.4% of America's electricity, could become a mainstream energy source. Some hypothesize that geothermal could be a valuable tool in transitioning our energy system away from fossil fuels because it can provide a continuous backup to intermittent energy sources such as solar and wind. “This has been the most promising energy source for me for a long time,” says Roland Horne, an energy engineer at Stanford University. “But now that we’re moving toward a zero-carbon power grid, geothermal is very important.”
a rough start
Geothermal energy works best with two things: rock that is permeable enough to transport heat and water. Where molten rock sizzles close to the surface, water seeps through the porous volcanic rock, becomes warm and bubbles upward in the form of hot water, steam, or both.
If the water or steam is hot enough (ideally around 300 degrees Fahrenheit), it can be extracted from the ground and used in an electric generator. In Kenya, nearly 50% of the electricity produced comes from geothermal sources. Iceland gets 25% of its electricity from this source, New Zealand gets about 18% and the state of California gets 6%.
Some natural geothermal resources, such as those in the western United States, remain untapped, says geologist Ann Robertson-Tait, president of GeothermEx, the geothermal energy consulting division of oil field services company SLB. But overall, natural, high-quality geothermal resources are being depleted, leading experts to consider ways to extract geothermal energy in areas where energy access is much more difficult. “There is too much heat on Earth,” she says, Robertson-Tait. But she added, “Most of it is trapped within impermeable rock.”
Tapping that heat requires deep drilling and creating fractures in the non-volcanic, dense rock to allow water to flow. Since 1970, engineers have been developing “enhanced geothermal systems” (EGS) to do this by applying methods similar to hydraulic fracturing, or fracking, used to suck oil and gas from deep rocks. Water is pumped at high pressure into wells up to several miles deep to fracture the rock. The cracked rock and water create underground radiators where the water is heated before rising to the surface through a second well. Dozens of these EGS facilities have been built in the United States, Europe, Australia, and Japan, most of them experimental and government-funded, with mixed success.
Famously, an EGS plant in South Korea closed suddenly in 2017 after a magnitude 5.5 earthquake. Fracking of any kind can put pressure on nearby tectonic faults. The other problem was technical. Some plants did not create enough fractures to facilitate heat exchange, or the fractures moved in the wrong direction and failed to connect two wells.
However, some efforts have been converted into viable power plants, including several German and French systems built in the Rhine Valley between 1987 and 2012. There, engineers took advantage of cracks in the rock.
But overall, there hasn't been enough interest in developing EGS into a more reliable and profitable technology, says Dimitra Teza, a geophysicist at the energy research institute Fraunhofer IEG in Karlsruhe, Germany, who helped develop part of the Rhine Valley EGS system. “It’s been quite a struggle for the industry.”