Next-generation geothermal technologies are gaining steam as a source of clean, renewable energy and an alternative to fossil fuels. With demonstration projects across the globe now showing strong potential, enhanced geothermal (using ever-present and bountiful heat found deep within the Earth) could one day offer energy to millions of homes, businesses and cities.

But geothermal currently makes up just a fraction of global energy produced, at less than 1%. That’s because conventional geothermal methods require special conditions, including permeable land, subsurface heat, plus available water with which to tap into this energy resource.

This trifecta means that, while geothermal is exploited in slightly more than 30 countries — led by the U.S., Indonesia, the Philippines and Turkey — actual production is miniscule, a mere 16,318 megawatts of installed capacity. By contrast, installed global wind capacity tipped 1 million MW over the last year.

But next-gen geothermal seems poised to take a great leap forward, expanding its capacity massively because all that’s needed is underground heat and economical access to it. Instead of tapping surface hot springs, next-gen tech aims to drill deep into hot rocks to create permeability. It then injects water or other fluids, such as brackish water or treated wastewater, into the Earth to construct artificial subsurface reservoirs heated by the surrounding hot bedrock.

These innovative approaches, once perfected, could drive geothermal use far higher.

In the U.S. alone, it’s estimated that next-gen geothermal could provide 8.5% of the country’s energy by 2050; that’s enough to power 65 million homes, with its ultimate potential dwarfing that several times over.

Unpacking next-gen geothermal

Within the box known as next-gen geothermal, there are multiple tech solutions, often involving procedures akin to hydraulic fracturing (also known as fracking), the controversial technique used by the oil and gas drilling industry. This suite of technologies is known as enhanced geothermal systems, or EGS.

While EGS tech can vary, these advanced systems generally use boreholes instead of fractures to create a closed loop for water transfer. Other approaches — variously known as superhot rock or super critical geothermal — aim to drill extremely deep to reach subsurface rock with constant temperatures above 374° Celsius (705° Fahrenheit). EGS methods vary, but generally the heated rock creates steam, which then turns an electric turbine, producing energy.

Some next-generations systems aim to drill at depths of around 5,000 meters (16,400 feet). Oil and gas fracking wells are within this range, going down 2,000-6,000 m (5,000–20,000 ft).

Reaching superhot subsurface rock will mean drilling far deeper, up to and beyond 12,500 m (41,000 ft) at some locations. To date, the deepest drilling operation ever carried out on Earth is Russia’s Kola Superdeep Borehole (KSB), which in 1989 sank a hole 12,262 m (40,230 feet).

Superhot rock is in early stages of development, facing issues such as the technological challenge of drilling to record depths into rock layers that are at very high temperatures, where fracking would be used to crack hot rocks to create subterranean artificial water reservoirs.

The technology has enormous potential, say experts. Tapping into just 1% of the world’s total superhot rock potential could generate as much as 63 terawatts, or million MW, of energy, according to modeling by the Clean Air Task Force, an NGO. Currently, total energy usage at the global level is estimated at around 17.7 TW.

“The goal in each case is to create a geothermal reservoir where none exists naturally,” says Joseph Moore, principal investigator at the Frontier Observatory for Research in Geothermal Energy (FORGE) project in Utah. “Right now, virtually all geothermal reservoirs are associated with hot springs at the surface.”

But next-gen geothermal is not without its challenges, which presently include high cost and the threat of environmental harm. Induced seismicity can come as a consequence of drilling deep into Earth’s crust and injecting fluids, though industry experts say that risk can be managed and mitigated. Also, substantial technological advances still need to be made before superhot rock becomes a safe, potentially limitless energy source.

Geothermal energy for a circular economy

National governments worldwide are investigating possibilities of ramping up next-gen geothermal, with commercial-scale projects under development in some countries. Many European Union nations have produced geothermal road maps, including next-gen systems that underline the technology’s circular potential. Germany, for example, is home to a commercial-scale closed-loop advanced system operated by Eavor, a geothermal company based in Canada. China plans to increase its own exploitation of significant geothermal potential.

In the U.S., the federal government is striving to drive down geothermal costs from around $450 per megawatt-hour to $45 by 2035 via an initiative that also supports demonstration projects. Fervo Energy, a private company, is using that program to move forward with a 2,000 MW EGS installation able to power up to two million homes; the operation also benefits from a partnership with Google. The goal is to drill straight down, then horizontally into hot dry rock, then use fracking to open up fractures and create geothermal reservoirs with pumped-in water. The target date for completion is 2028.

Sage Geosystems recently announced a deal with Meta to produce 150 MW of energy in the U.S. using its next-gen system. The company has also sealed deals with the U.S. Department of Defense to power military installations. The firm plans to launch its first commercial-scale plant in 2027, according to Sage Geosystems CEO Cindy Taff.

“The potential is there, but we, as an industry, need to get the cost down,” she explains. “I think the challenge right now for next-generation geothermal is that we need to get that cost to a point where people are willing to pay for that clean power.”

Earlier this year, the government of Aotearoa New Zealand backed research into early-stage superhot rock geothermal. U.S.-based company Quaise Energy plans to have a superhot rock demonstration project up and running by 2026, using technology developed at the Massachusetts Institute of Technology to retrofit existing fossil fuel infrastructure.

Next-gen approaches aside, many countries are exploring conventional geothermal to achieve cleaner power generation. Kenya is already meeting nearly half its energy needs from geothermal, and the nation plans to expand this even further. Other projects in Europe and elsewhere have, or are exploring, the use of abandoned coal mines as already existing underground reservoirs to generate geothermal power.

Unlocking this potential could push forward local-scale circular economies, says Terra Rogers, the program director for superhot rock energy at the Clean Air Task Force (CATF). She points to Iceland as an example, where the HS Orka geothermal site uses heat produced by the facility and water to power a local tourist spa along with other industries, even using this geothermal power source to provide materials for the cosmetics industry.

“We find that the opportunities to engage in this cascading heat stream [offer] a lot of follow-on jobs and value to communities, when done with enough strategy and forethought,” she says. Geothermal energy production “could really change the economy of certain regions.”

Steaming ahead, with caution

As already noted, geothermal energy offers many benefits in its favor, but like most renewables, it faces hurdles, not least of which is the precarious task of working deep beneath Earth’s surface.

A primary concern for next-gen geothermal companies is the risk of triggering harmful and costly earthquakes, which is particularly true for projects relying on hydraulic fracturing. Oil and gas fracking operations worldwide have run into this problem, with fracking inducing quakes worldwide that have led to loss of life, physical injuries and serious damage. Ole Kaven, a research geophysicist at the U.S. Geological Survey’s Earthquake Science Center, sees earthquakes as a “major risk” for developing geothermal projects.

In 2006, an EGS project near Basel, Switzerland set off a 3.4-magnitude earthquake that caused $9 million in damage, likely because the project was sited near an active fault. More than a decade later, a project in Pohang, South Korea, caused a 5.5-magnitude quake; 90 people were injured and $52 million in damage was done.

“Seismicity has been a problem in the past,” says Moore from FORGE. “I can’t tell you whether it’ll be a problem again, but several projects have been shut down because of seismicity.”

At the FORGE site in Utah, his group is gaining valuable knowledge to inform future commercial-scale projects, specifically where and where not to drill, and when to stop if problems arise. The FORGE project has carried out commercial-scale drilling, resulting in hundreds of thousands of seismic events, but they’ve all been small-scale. One key lesson: The particular geology of a region matters; a fact that may necessarily exclude some areas of the world from exploring next-gen geothermal.

To be successful, companies also need to engage in continual transparent community engagement from the planning process forward, say Moore and others. “Effective communication [matters] because at the end of the day, it’s not just about managing the risks. It’s also about managing the perceptions of the risks,” says Ryan Schultz. His team recently published a paper laying out geothermal project guidelines for others to follow.

Water use and contamination are other concerns, particularly in areas prone to water shortages, such as the U.S. West. Geothermal requires substantial amounts of water, though industry reps emphasize this doesn’t need to be freshwater. And unlike the fossil fuel industry, the water for next-gen geothermal is continuously reused.

A recent paper by the World Resources Institute (WRI) says these impacts are, in general, less severe when compared to oil and gas development, and even compared to other clean energy tech such as solar and wind.

WRI’s analysis notes that geothermal can offer health benefits because it supplants polluting power sources; it reduces air pollution by eliminating the need for fossil fuel power plants that can release harmful particulates, nitrogen oxides and sulfur dioxide.

However, some geothermal projects, such as the Puna plant in Hawai‘i, report the opposite, with local residents complaining the local geothermal plant is a continual source of noise and air pollution due to its operation. In 2016, the U.S Environmental Protection Agency found that the Puna plant was releasing harmful chemicals, including hydrogen sulfide, a toxic gas that can be present with hydrocarbons in underground oil and natural gas formations, and which can be released to the surface by hydraulic fracturing. However, the Puna plant says it doesn’t employ fracking to create fissures; it only exploits naturally occurring fissures.

When hydraulic fracturing is used in next-gen geothermal, it’s much cleaner than the process used by the oil and gas industry. Fossil fuel fracking uses frac fluids, a mix of chemicals, some toxic, to help release underground hydrocarbons; frac fluids can pollute groundwater. But geothermal fracking uses mostly highly pressurized water rather than frac fluids. However, hot water traveling back to the surface can carry salt and other contaminants leached from subsurface rock, which could potentially pollute aquifers and drinking water if not fully self-contained within the geothermal system. Oil and gas wells, for example, with poorly made casings can leak and pollute.

When considering key indicators such as land use, water use, emissions, waste and critical mineral usage, “geothermal performs as well as, or better than, other clean electricity technologies on a life cycle basis,” according to WRI.

“Geothermal can provide really important grid benefits while performing relatively well on environmental criteria,” says Katrina McLaughlin, report author and an associate on the U.S. energy team at the World Resources Institute. “There are impacts that do need to be managed, and the two primary ones are induced seismicity and concerns around water use and consumption.”

Geothermal on the up

The list of positives for tapping into Earth’s heat are tantalizing, though potential negatives are serious enough to warrant caution.

For now, next-gen technologies have yet to become mainstream. Should commercial-scale ventures prove successful, geothermal could grow quickly and become a key component of clean grids, say experts.

“I think we’re going to make incredible strides in the next five to eight years,” says Moore, adding that superhot rock development will take longer. “We need demonstration projects in a variety of different environments so that we can learn how to mitigate these [varied] issues, and I think that’s happening very quickly.”

To achieve “liftoff,” experts say next-gen geothermal needs to advance to commercialization, achieving 2,000-5,000 MW of installed capacity by 2030, at a cost of $20-$25 billion, according to a recent report. Scaling up to 125,000 MW by 2050 could cost an estimated $250 billion.

Critically, in the U.S. it remains to be seen if the slated federal funding to step up next-gen demonstrations will carry over from the Biden administration into the second Trump presidency. “We are hopeful that the promise of abundant, low-cost, homegrown energy is appealing to the new administration, just as it was the previous,” says Rogers.

Geothermal appears to have major potential as a renewable and circular energy solution, provided those pushing it forward do so with care. “If you manage the earthquakes well, you can have … the best of both worlds. You can manage the … risks, but you can also have this green economy,” Schultz says.

Next-gen geothermal could be a really important part of a reliable, relatively clean, cost-effective energy grid if rolled out in a responsible way, adds McLaughlin. But “Making sure it continues to have a good amount of transparency, proactive education and communication with local communities and stakeholders is really key to the industry maintaining that social license to operate.”

Banner image: Advocates of next-gen geothermal note that using already-designed oil and gas industry technology can bring socioeconomic benefits, allowing fossil fuel industry personnel to be retrained to work for the renewables industry. Image courtesy of Eric Larson, Flash Point SLC.

Calls for caution as enhanced rock weathering shows carbon capture promise

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