Clean energy journalism for a cooler tomorrow

Harnessing the heat beneath our feet: Geothermal’s past and future

It’s been a niche power source for over a century, but advanced techniques drawn from the oil and gas industry could help geothermal energy hit the mainstream.
By Michael Thomas

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A large industrial site in a desert valley with mountains in the distance. A tall metal tower is seen at center.
An enhanced geothermal system in Utah (Utah Forge)

This story was first published by Distilled.

Geothermal power is having a bit of an unexpected moment.

After two decades of slow growth, most energy experts wrote the technology off as an unrealistic way to generate large amounts of electricity. In an era dominated by incumbent energy sources such as natural gas and cheap emerging technologies including solar, geothermal was expensive and, more importantly, geographically limited. Few saw it ever generating more than 1% of America’s electricity.

But recently there has been a series of breakthroughs in enhanced geothermal systems, an advanced method of generating electricity from the earth’s heat. 

If these developments continue, geothermal could generate between 10 and 20 percent of the country’s electricity in the coming decades, according to recent studies from the Department of Energy and Princeton.

Enhanced geothermal could also solve one of clean energy’s biggest problems: intermittency. Unlike solar and wind, geothermal power plants can operate at all hours of the day, no matter the weather or time of year. 

In this story, I’ll cover the past, present and future of enhanced geothermal and look at what needs to happen in order for the technology to play a large role in decarbonizing America’s power sector. I’ll cover:

  • The history of traditional geothermal power.
  • Why traditional geothermal entered a period of stagnation in the 1990s.
  • The story of the nuclear weapons scientists at Los Alamos who launched a side project that led to the first enhanced geothermal tests in the 1970s.
  • How recent developments in fracking technology led to renewed interest and innovation in geothermal.
  • How current government incentives could pave the way for this technology.
  • The barriers that could prevent geothermal’s growth.

As with my recent article on battery storage, I went really deep on this one trying to understand geothermal’s history and why there’s been such a surge in progress lately.

So with that, let’s dive in. 

Traditional geothermal’s boom and bust 

The first thing you need to know about geothermal energy is that the earth is very hot. 

The core of the earth is about as hot as the surface of the sun, reaching temperatures in excess of 6,000 degrees Celsius or 10,800 degrees Fahrenheit. Even a few thousand feet beneath the surface, the temperature of the earth can be a few hundred degrees Fahrenheit. This heat reaches the surface in volcanically active places like Japan and near tectonic plates (think Iceland).

For thousands of years, humans have been using some of this heat to bathe and cook. But it wasn’t until the beginning of the 20th century that anyone figured out how to use geothermal energy to generate electricity. 

In 1904, Piero Ginori Conti, an Italian aristocrat, was put in charge of his family’s boric-acid extraction firm. For more than a century, Italians had been using geothermal power and boric-acid-rich steam in the region to produce everything from ceramics to insecticides. Shortly after taking over the family business, Conti wondered if it would be possible to use the steam to produce a different product entirely: electricity. 

That year, Conti successfully built the world’s first geothermal power engine. At its peak, the 4-kilowatt system could power five light bulbs. 

In an old black and white photo, a man in a coat and fedora stands next to a car-sized mechanical device
Piero Ginori Conti and his geothermal engine

Geothermal technology has developed significantly since Conti built his first power plant over 100 years ago — today, the world’s largest geothermal power plant can produce 225,000 times more electricity than Conti’s engine —but the fundamental technology is still the same.

Boiling water is basically the foundation of most of our legacy electricity generation,” Wilson Ricks, a clean-energy researcher at Princeton, told me. With geothermal, we’re literally just going and finding boiling water in the real world. Then all you do is drill a well, extract that steam or superheated water, and then you pass it through a turbine.”

By the 1920s, geothermal power technology began to spread around the world. In 1921, the owner of a geothermal spa in an area of Northern California known as The Geysers drilled a well in hopes of generating electricity. But it didn’t work out as planned. 

The well blew up like a volcano, according to one account. The following year, another well was drilled. Mud, tools, rocks and steam” blew out of the second well with force before it was finally tamed to create the first successful geothermal system outside of Italy. 

The first geothermal power plants at The Geysers were small even by the standards of the time. But they proved that generating electricity from the earth’s heat in the region was possible. 

It would take another few decades until the modern geothermal power industry took shape. In 1955, utility Pacific Gas & Electric Company a contract to purchase power from a geothermal developer in The Geysers. Five years later, the first unit of what would eventually become the largest geothermal power plant in the world went live. 

A black and white photo of a small power plant in forested mountain terrain topped by clouds of billowing steam
A geothermal power plant at The Geysers (Calpine)

At this point, fossil fuels still reigned as king in America and much of the world. Coal, oil and gas were all cheap, densely packed with energy and easily transported over long distances. But the era of cheap and abundant energy eventually started to wane.

In the early 1970s, geothermal received a boost when energy prices skyrocketed due to the first oil crisis. The U.S. federal government signed a series of bills incentivizing the construction of geothermal power plants. Half of all America’s geothermal capacity was built in the decade that followed. 

This period of growth for geothermal was short-lived. Incentives and supportive policies came and went quickly. By the end of the 1980s, energy prices fell and interest in renewable energy dropped off. The geothermal industry also encountered a problem that would plague its development for decades: a severely limited supply of usable resources. 

Three key ingredients are necessary to build a traditional geothermal power plant: heat, permeable rock and water. The geothermal industry quickly learned that while there’s a nearly infinite amount of heat beneath the earth’s surface, naturally occurring permeable rock and water are rarer. 

But the key phrase there is naturally occurring.” If it were possible to create fissures in the rock beneath our feet and then pump water through them, a vast amount of energy would suddenly be available. 

Enhanced geothermal began as a side project at Los Alamos 

The most significant early enhanced geothermal research was never really supposed to happen in the first place. 

In the 1960s, a group of engineers working on nuclear weapons technologies at the Los Alamos National Laboratory in New Mexico decided to begin tinkering with a side project. One of them, Bob Potter, had been reading a fantasy novel called At the Earth’s Core when he decided to deviate from some of his research on bombs and weapons. 

A book cover illustration showing a partially unclothed man with a bow and arrow battling a flying dragon
A 1922 edition of Edgar Rice Burroughs' fantasy novel At the Earth's Core

When he wasn’t designing nuclear weapons, Potter, who was interested in everything,” according to one colleague, also liked to read nonfiction books about geophysics, hydrology, rock mechanics, and other areas related to drilling. 

Potter stumbled upon research from the oil and gas industry on hydraulic fracturing technology. He learned that offshore drilling companies were blasting rock beneath the surface with high-pressure water to create fissures and unlock new oil and gas reservoirs. 

Around that time, he and a few other scientists at Los Alamos began to discuss another related idea. What if, they wondered, it was possible to harness the vast amount of heat under the surface of the earth to create electricity? They concluded that the vast thermal reservoir represented by [hot dry rock] at accessible depths in the earth’s crust was an energy supply that could and should become extremely important in the world’s energy future.”

Thus, the Los Alamos Hot Dry Rock Program was born. The program received no funding or official recognition for the first few years. It was informal in every respect, including financial support, and was carried on largely on a volunteer basis,” according to Morton Smith, a Los Alamos scientist involved in the project and the author of The Furnace in the Basement: The Early Days of the Hot Dry Rock Geothermal Program, 19701973.

In December 1971, the unofficial group began drilling their first boreholes near the lab’s Fenton Hill Observatory, an astronomical research facility in the Jemez Mountains of New Mexico. The environment was harsh, and the group had little to no relevant experience. We were handicapped by subfreezing temperatures, several heavy snowfalls, and the fact that — in undertaking novel and difficult experiments — not everything worked the first time we tried it,” Smith wrote.

A black and white photo of two men wearing eyeglasses and lab coats looking closely at a piece of granite
Morton Smith and Francis West examine a core sample taken from a depth of 3,700 feet at the Fenton Hill geothermal test site in the Jemez Mountains west of Los Alamos. (American Institute of Physics)

Then, in 1973, the group got lucky. That year, as energy prices surged during the oil crisis, the federal government took an interest in alternative-energy research programs. The group received official recognition and funding. So far as we were concerned, the timing of all this couldn’t have been better,” Smith wrote. 

But funding alone wasn’t enough to solve the program’s biggest problem. While the researchers could create fissures in the rock, they struggled to connect two wells. This was a problem, given that they needed to pump water down into the hot rock and then have it travel back out. A single well meant sending water down never to return. 

It would take a decade and a half for the researchers at Fenton Hill to prove that building an enhanced geothermal system was possible. In May 1985, the group created a system that generated between 4 and 10 megawatts of power. That spring, one scientist had everyone on the team over to his house for a Thank God It’s Connected party.”

But while the researchers at Fenton Hill proved the viability of enhanced geothermal, they also proved that it was difficult — and more importantly, expensive — to harness the earth’s heat. In 1995, the Department of Energy killed the Fenton Hill project and plugged the boreholes, beginning a long winter for the technology. 

Fracking for clean energy 

The same year that researchers at Fenton Hill created their first successful enhanced geothermal system, George Mitchell, an oil baron, was trying to solve a similar problem 600 miles to the west in northern Texas.

At the time, his oil fields were drying up, threatening to take down his company, Mitchell Energy. Mitchell, inspired by research similar to what had piqued the interest of Bob Potter in Los Alamos, saw an opportunity to drill into shale rock and fracture it with highly pressurized fluids to free natural gas and bring it to the surface.

Like the researchers at Los Alamos, Mitchell’s team of engineers initially struggled. For 15 years, Mitchell personally looked for well sites and visited his engineering department daily looking for updates. As one of his employees told The New York Times, For George Mitchell…this was survival, this was need.” 

Finally, in 1997, Mitchell created the first financially viable fracking well. In doing so, the so-called father of fracking” transformed America’s oil and gas industry and its role in the global energy trade. 

Soon after Mitchell drilled his first successful well, other companies followed suit. Some of these companies combined another technique, horizontal drilling — which had been around for more than 100 years — to make their wells even more productive. Combined, the two techniques made it possible to extract fossil fuels where no one had previously thought it could be done. Over the next decade, the cost of drilling wells using these techniques fell rapidly.

The fracking boom was a disaster for the environment and many people living near projects. But if there was a silver lining, it was the fact that much of the technology could also be used to create enhanced geothermal systems. 

As fracking transformed the energy industry in America, several people interested in geothermal energy began to take notice. One such person was Tim Latimer, who would later become the founder and CEO of Fervo Energy. While at Stanford, he and a few colleagues at the school’s geothermal research program started exploring whether fracking technology could be used to create enhanced geothermal systems.

In 2015, Latimer, who started his career as a drilling engineer in the oil and gas industry, went to his first geothermal conference. There, he met a well-respected researcher and proposed his idea. He told me that enhanced geothermal systems would never work,” Latimer recently recounted on David Roberts’ Volts podcast.

But Latimer continued working on his idea to use hydraulic fracturing and horizontal drilling to create advanced geothermal power plants, launching Fervo Energy in 2017

He hypothesized that creating an affordable enhanced geothermal system would be possible using off-the-shelf oil and gas technology. Anytime that you want to build a new tool, you extend your development timeline by years or decades,” he told Roberts. Latimer saw how quickly drilling costs fell in the previous decade and bet his company could hitch a ride on the learning curve. 

A large piece of mechanical equipment topped by a tall metal tower. Gray clouds and snowcapped mountains are in background.
Fervo Energy's enhanced geothermal drilling rig (Fervo Energy)

Earlier this year, Latimer’s bet paid off when Fervo completed its first successful enhanced geothermal power plant using the technology. In May, the company proved in a 30-day test that its system could generate 3.5 megawatts of clean power at all hours of the day.

Over the next decade, the company plans to scale the technology. Recently, Fervo signed a contract with Google to sell it 24/7 clean electricity to power its data centers.

Geothermal gets a boost from policymakers 

Private companies like Fervo aren’t the only ones taking notice of geothermal’s potential. Over the last three years, policymakers at both the federal and state levels have passed bills encouraging the emerging technology.

In 2021, as part of a broader procurement order, the California Public Utilities Commission issued a mandate requiring utilities and other load-serving entities to secure 1 gigawatt of zero-emissions resources“ able to generate when needed, for as long as needed” — a definition that would include geothermal power. 

California’s law is similar to bills passed on the East Coast to encourage offshore wind development. New Jersey and New York have said [they] want to mandate a certain amount of offshore wind because we know this is going to be a potentially important long-run industry,” Ricks, the Princeton researcher, told me. This classic form of industrial policy aims to offer protection from cheap fossil fuels and intermittent renewables, giving the industry an early boost. 

Two other recent major government policies could provide the funding needed to improve and build out enhanced geothermal.

The Bipartisan Infrastructure Law, passed in 2021, provides up to $84 million for geothermal pilot projects, and the Department of Energy recently announced that up to $74 million of that funding would be made available for seven enhanced geothermal projects.

In 2022, the geothermal industry received more federal support when President Biden signed the Inflation Reduction Act into law. Unlike past legislation that singled out renewables such as solar and wind, the IRA allows geothermal developers to use the generous tax credits.

One month after the IRA was signed, Biden’s Department of Energy announced its Enhanced Geothermal Shot program. The effort aims to reduce the cost of enhanced geothermal by 90 percent by 2035. Geothermal advocates hope that the technology can follow in the footsteps of the solar industry. 

In 2011, Obama’s administration announced a similar program, the SunShot Initiative, at a time when solar was far more expensive than incumbent technologies. Over the next decade, the cost of solar fell faster than even the most bullish analysts thought possible. The goals of the SunShot Initiative were reached three years ahead of schedule. 

A chart showing the steep global decline in solar PV module costs from 1975 to 2020

The barriers standing in the way of cheap, abundant power 

To play an important role in the power sector, enhanced geothermal must still overcome significant barriers. The obvious ones are things like technology risks,” Ricks told me. Fervo Energy’s milestone is important, but whether or not the system can scale and move down the cost curve is still an open question. 

Even if enhanced geothermal costs 90% less in the future, developers will face similar challenges to those plaguing the solar and wind industry. They will likely struggle with the same transmission and grid-connection delays that many say are their most formidable barriers to growth. 

Geothermal developers will also face a challenge unique to their technology. On public land — where most wells are likely to be drilled — environmental reviews take between seven and 10 years. By contrast, oil and gas companies, which are granted a categorical exclusion from these lengthy reviews, can permit new wells in just a few years’ time. 

It’s effectively the exact same activities for an objectively cleaner use,” Ricks says. But the geothermal lobby doesn’t have the same sway in Washington as fossil fuel companies. 

Slower permitting processes also drive up the cost of projects. Financing costs make up 30% of a geothermal project’s already high cost of capital, compared to wind and solar’s 2% to 7%, according to the think tank Third Way.

But if enhanced geothermal can overcome these barriers, it could transform the energy industry in America and globally. In the most optimistic scenario in Ricks’ recent study, he shows how the technology could provide enough power to supply up to 45% of the electricity needed in some regions of the U.S. In this scenario, the cost of wholesale electricity would also fall by 25%, reducing utility bills for individuals and businesses. 

This is subject to many caveats,” Ricks says. But the question of if we develop this, will it matter? The answer is yes. Quite a lot.” 

Michael Thomas is the founder and author of Distilled, a newsletter with deeply researched stories about the politics of climate change.