A limitless supply of heat exists beneath our feet within the Earth’s crust, but harnessing it at scale has proved challenging. Now, a combination of new techniques, government support and the pressing need to secure continuous clean power in an era of climate crisis means that geothermal energy is finally having its moment in the US.
Until recently, geothermal has only been viable where the Earth’s inner heat simmers near the surface, such as at hot springs or geysers where hot water or steam can be easily drawn to drive turbines and generate electricity.
While this has allowed a limited number of places, like Iceland, to use geothermal as a main source of heating and electricity, it has only been a niche presence in the US, providing less than 1% of its electricity. But this could change dramatically, offering the promise of endless, 24/7 clean energy that can fill in the gaps of intermittent solar and wind generation in the electricity grid.
“Geothermal has been used for over 100 years, limited to certain geographic locations – but that is now changing,” said Amanda Kolker, the geothermal laboratory program manager at the National Renewable Energy Laboratory (NREL).
“As we penetrate the grid with renewables that are not available all the time, we need to find a base load, which is currently taken up by gas. There aren’t really many options for zero-emissions base load power, which is why geothermal is entering the picture.”
Geothermal capacity could increase 20-fold by 2050, generating 10% of the US’s electricity, according to a recent road map released by the US Department of Energy. Joe Biden’s administration has also funded new projects aimed at pushing forward the next generation of geothermal that aim to make the energy source available anywhere on America’s landmass, not just easy-to-reach hot springs.
“The US can lead the clean-energy future with continued innovation on next-generation technologies, from harnessing the power of the sun to the heat beneath our feet, and cracking the code to deploy them at scale,” said Jennifer Granholm, the US energy secretary, who added that she saw “enormous potential” in geothermal.
Expanding the geothermal footprint to the entire US will take time, as well as plenty of money – the department of energy estimates as much as $250bn will be needed for projects to become widespread across the country, providing a major source of clean power.
But advocates of geothermal say that such growth is within reach, because of a wave of geothermal technologies as well as government support. In February, the Biden administration announced $74m for up to seven pilot projects to develop enhanced geothermal systems that, the government said, hold the potential for powering 65m American homes.
Ironically, enhanced geothermal uses similar fracking techniques currently used to extract oil and gas, which must be phased out if the world is to avoid climate disaster. In the geothermal version of fracking, fluid is injected deep underground, causing fractures to open up, with the liquid becoming hot as it circulates. The hot water is then pumped to the surface, where it can generate electricity for the grid.
This, and other new techniques that allow deeper and horizontal drilling, in some cases down to eight miles deep, allows geothermal energy to be drawn from hot rocks found anywhere underground, rather than select spots that have hot water near the surface. This vastly expands the potential of the technology.
“Anywhere in the country, if you drill, it gets hotter and hotter with each mile you go deeper,” said Koenraad Beckers, an NREL thermal sciences researcher.
“In the western United States, that temperature increases fast. If you drill just one to two miles deep, you have temperatures hot enough for electricity. To get those temperatures in eastern states, you might need to drill miles and miles down, but you can use lower temperatures to directly heat or cool campuses, neighbourhoods and even towns.”
Dozens of new companies are looking to push ahead with geothermal plans, buoyed up by incentives offered by recent legislation passed in the US, although only a few have so far managed to complete full projects in the US, such as Eavor, a Canadian firm that successfully drilled a three-mile hole in New Mexico to prove it could access heat in deep, granite rock.
At play for these companies is an inexhaustible energy supply. Just one type of next generation geothermal – called superhot rock energy, where deep drilling reaches temperatures 400C or hotter – is abundant enough to theoretically fulfil the world’s power requirements. In fact, just 1% of the world’s superhot rock potential could provide 63 terawatts of clean firm power, which would meet global electricity demand nearly eight times over.
“While this modelling is preliminary, our findings suggest an enormous opportunity to unlock vast amounts of clean energy beneath our feet,” said Terra Rogers, the director for superhot rock energy at Clean Air Task Force, which produced the modelling tool to measure the potential of this approach.
“Energy security backed by always available zero-carbon energy isn’t a far-off dream.”
