Harnessing the power of just one per cent of superhot rocks could provide more than eight times the current global electricity generation.
Deep beneath the Earth’s surface lies an immense source of energy that scientists believe could help power a low-carbon future.
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A growing number of researchers and energy companies are now racing to unlock ‘superhot’ geothermal energy, a very old – but also novel – form of power that could provide constant, carbon-free electricity almost anywhere on Earth.
Earlier this year, the International Energy Agency (IEA) highlighted superhot geothermal in its State of Energy Innovation report, describing it as a promising source of “clean, firm power” capable of supporting the transition away from fossil fuels.
Now, one of the sector’s most closely watched projects is breaking ground in the US state of Oregon, where startup Quaise Energy says it plans to build what it calls the world’s first superhot geothermal power plant by 2030.
What is superhot geothermal energy?
Geothermal energy uses heat from beneath the Earth’s surface to generate electricity or provide heating.
Its role as a power or heating source isn’t necessarily new.
In Iceland, geothermal water has been used to heat homes for nearly a century. Today, around 30 per cent of the country’s electricity comes from geothermal sources.
According to the IEA, traditional geothermal plants rely on naturally occurring underground reservoirs of hot water or steam, which are typically concentrated in volcanically active regions or along the boundaries of the Earth’s tectonic plate.
Superhot geothermal aims to go deeper.
The technology targets rocks that are hotter than 300°C, where water reaches a supercritical state and can carry significantly more energy than conventional geothermal systems.
According to the US-based non-profit Clean Air Task Force, tapping just one per cent of these resources could provide more than eight times the current electricity generation globally.
Why is it difficult?
The main challenge, until now, has been drilling deep enough to reach these extreme temperatures.
According to various energy agencies, conventional drilling systems – many adapted from the oil and gas industry – face major challenges under the extreme heat and pressure found several kilometres underground. Costs also rise as wells get deeper.
That has led researchers to explore alternative drilling technologies.
Quaise Energy plans to use conventional drilling for the upper sections of its Oregon wells before switching to millimetre wave technology developed at the Massachusetts Institute of Technology, where the startup was spun out of research projects.
The system uses high-frequency electromagnetic waves, similar to microwaves, to melt and vaporise rock rather than cutting through it mechanically.
If successful, the process could allow wells to reach much deeper geothermal resources than existing technology permits.
Water would then be pumped underground, heated by the surrounding rock and returned to the surface as steam to generate electricity before being recycled back into the system.
Quaise says this system would offer 50 megawatts of always-on, renewable power – enough to supply tens of thousands of homes. The company hopes to expand the project to 200 megawatts soon after coming online, a potential game-changer for a world struggling to cut emissions while keeping up with rising energy demand.
Why does it matter?
Unlike solar and wind power, geothermal energy can run continuously regardless of weather conditions. However, the plummeting cost of battery storage is helping renewables provide around-the-clock electricity at prices that rival fossil fuels, according to a new report from the International Renewable Energy Agency (IRENA).
Supporters also point to geothermal’s relatively small land footprint compared with large solar or wind farms.
It’s little surprise that interest in superhot geothermal is growing globally.
In Iceland, researchers recently secured €10 million in EU funding to develop similar projects. Last year, New Zealand also entered a cooperative agreement with Iceland to develop geothermal technology as part of its long-term energy security plans.
Experts believe this type of power could eventually expand beyond volcanically active regions. According to the IEA, advances in deep drilling could make it viable across larger parts of Europe, Asia and North America.
Promising as it may be, the technology has a long way to go until it transforms power grids globally.
No commercial superhot geothermal plant is operating yet, and researchers still need to prove that drilling systems, underground rock formations and power infrastructure can withstand the extreme conditions over long periods.
There may be environmental concerns, too.
Researchers say geothermal drilling can trigger small earthquakes – a phenomenon called induced seismicity. While most are too small to be felt, some can be serious.
In 2017, an earthquake measuring 5.4 on the Richter scale struck near a geothermal site in Pohang, South Korea, causing widespread damage. It was believed to be caused by induced seismicity, after high-pressure fluid was injected into the ground at the site.
Still, its advocates argue, the potential returns are difficult to ignore.
According to the Clean Air Task Force, about two per cent of the geothermal energy located between three and 10 kilometres beneath the Earth’s surface could provide the equivalent of 2,000 times the current energy demand of the United States alone.
