New laboratory data confirm the potential for geothermal energy’s “holy grail”: tapping into superhot, superdeep rock miles beneath the Earth’s surface, which could generate a clean, renewable energy source capable of replacing a substantial portion of the fossil fuels driving global warming. The findings, published in Nature Communications, are among the first to demonstrate that such rock can form fractures that connect and increase permeability. Until now, geologists were unsure whether this was even possible.
These fractures are crucial because water passing through them can become supercritical, a steam-like phase that most people are unfamiliar with. (Common phases include liquid water, ice, and vapor, like the kind that forms clouds.) Supercritical water, in turn, “can penetrate fractures faster and more easily and can carry far more energy per well to the surface—roughly five to ten times the energy produced by today’s commercial geothermal wells,” according to the 2021 report “Superhot Rock Geothermal, A Vision for Zero-Carbon Energy ‘Everywhere,’” by the Clean Air Task Force.
The data also show that rock that fractures at superhot conditions can be ten times more permeable than rock that fractures at conditions closer to the Earth’s surface, and can also deform more readily. Those factors could make this geothermal resource “much more economic,” says Geoffrey Garrison, Vice President of Operations for Quaise Energy, one of the funders for the work. Quaise is working on a novel drilling technique for accessing superdeep, superhot rock.
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