How one could really use geothermal energy for the energy transition

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Enough heat reaches the surface from the earth’s interior to cover the entire global energy demand – even twice. But in order to make this resource usable, firstly, one usually has to drill deeply and, secondly, convert this heat into a usable form. This is difficult and expensive, which is why geothermal systems – sometimes referred to as “forgotten renewables” – only make up around 0.3 percent of global electricity generation.

That could change soon in the US. The new infrastructure law recently passed by the Biden government provides for $ 84 million for the US Department of Energy to build four demonstration plants in which so-called Enhanced Geothermal Systems (EGS), experimental forms of technology, are tested.

The funds are only a tiny fraction of the $ 62 billion total available to the Department of Energy under the Infrastructure Act, which also provides funds for building new long-distance transmission lines, strengthening the battery supply chain, and maintaining nuclear power plants. However, geothermal researchers believe that even these limited resources could make the transition from EGS to commercial use much easier. “Geothermal energy is really ripe for prime time,” says Tim Latimer, founder and CEO of the EGS start-up Fervo.

The attraction of geothermal energy lies in its persistence: While the electricity production of wind and solar systems fluctuates depending on the weather and time of day, geothermal energy is always in operation and provides a stable source of electricity.

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“It’s really the only renewable base load supply,” says Jody Robins, geothermal engineer at the National Renewable Energy Laboratory. Only nuclear energy – which is carbon-free but non-renewable – could play a similar role, although costs, the disposal problem and public perception limit its use.

Modern geothermal power plants have been in operation in the USA since the 1970s. In these systems, hot water or steam is usually pumped from the subsurface to the surface in order to drive a turbine and generate electricity. The water is then pumped back down to maintain the pressure in the subsurface so that the process can continue.

The best geothermal locations have certain characteristics: geothermal energy, permeable rock and water – all in close proximity to one another and not too far from the surface. However, the most accessible locations – in the US they are mainly concentrated in the west – have already been developed. While researchers believe there are many more potential locations to be found, it is difficult to pinpoint where they are. And in most of the eastern regions of the United States and many other places around the world, the underground rock is not made in the way that conventional systems work – or there is a lack of water.

Some researchers and start-ups are therefore trying to use geothermal energy in new places. With EGS, they want to change the subsurface by pumping liquid into impermeable rock and opening up the necessary paths. This creates space in which the water can move freely and heat up, creating the steam required to generate energy. This is not entirely unproblematic: The process can 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 should be manageable in most cases, says Robins. With this approach, geothermal energy could be extended to locations that do not have the groundwater or the types of rock required for traditional installations.

However, it will not be easy to reach these resources. Commercial wells usually do not go much deeper than seven kilometers – often even less for reasons of cost – and many regions that could benefit from geothermal energy are not hot enough at this depth to reach the 150 degrees Celsius required for one economic electricity generation are required. In order to achieve adequate temperatures, one may need to go deeper, which requires new techniques that can withstand high heat and pressure.

Fervo worked out a couple of issues on its own projects, including a venture announced earlier this year with Google to install geothermal capacity near the company’s Nevada data centers. Fervo recently joined a US Department of Energy project in central Utah called FORGE (Frontier Observatory for Research in Geothermal Energy).

As part of FORGE, scientific researchers and colleagues from industry are trying to find the best ideas for using EGS, including drilling and maintaining the reservoirs. 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 department’s Geothermal Technologies Office.

More from MIT Technology Review

More from MIT Technology Review

More from MIT Technology Review

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With the new funds from the Infrastructure Act, the authority will finance four more demonstration plants. This will expand the researchers’ knowledge about the construction of EGS systems, as they can work in different locations and with different types of rock. At least one system will be built in the east of the USA, where geothermal energy has so far been less widespread.

But not only technological obstacles have slowed the progress of geothermal energy, says Susan Hamm, director of the Geothermal Technologies Office at the US Department of Energy. The construction of a geothermal system can take up to ten years due to the large number of permits required. By simplifying the bureaucracy, this time could be cut in half and the forecast geothermal capacity doubled by 2050.

Financing geothermal projects can also be a challenge. They have a higher cost of capital than solar or wind projects: $ 3,000 to $ 6,000 per kilowatt, compared to $ 1,700 to $ 2,100 per kilowatt for wind and solar systems. (However, a geothermal system produces two to four times as much electricity as a wind or solar system with the same capacity.)

In some regions, geothermal energy is now receiving similar tax breaks as other renewable forms of energy. However, since, as mentioned, it can take nearly a decade to begin construction on a project, developers cannot rely on the tax breaks to remain in effect until the facility is operational.

With a combination of new political frameworks and technological advances, geothermal power generation in the US could reach up to 60 gigawatts by 2050, according to a report by the US Department of Energy in 2019. That would mean geothermal energy would make up nearly 9 percent of all electricity generation in the US, compared to 0.4 percent today.


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