Geothermal energy could surpass current boundaries. A team of researchers has shown that ductile rocks, previously unexplored, can be fractured.
About 87% of the Earth's internal heat comes from the radioactive decay of minerals such as uranium and thorium. These rocks, located deep underground, could become a significant source of energy.
Geothermal power plant.
Illustrative image Pixabay
Currently, geothermal energy is limited to volcanic regions. However, new discoveries are paving the way for the exploitation of supercritical geothermal resources, present almost everywhere across the globe. Companies like Quaise Energy are attempting to drill deeper than ever before to reach these rocks. Boreholes would have to reach depths of up to 10 kilometers (roughly 6 miles), where the temperature exceeds 500°C (932°F).
Ductile rocks, compared to soft caramel, deform under high pressures. Nevertheless, they could be fractured, allowing water to circulate and transport energy.
Researchers first need to recreate in the lab the extreme conditions of temperature and pressure similar to those found at the heart of the Earth's crust. Gabriel Meyer, from EPFL, led an experiment revealing that even at these extreme depths, supercritical water can flow through ductile rocks. A discovery that could transform the future of geothermal energy.
Marie Violay, project leader, highlights the importance of this breakthrough for exploiting deep geothermal reservoirs, which have been inaccessible until now.
Supercritical water: an ideal state of water for geothermal energy
Supercritical water is a phase of matter that occurs when water exceeds its critical temperature and pressure (374°C [705°F] and 221 bars). In this state, it is neither fully liquid nor fully gas. It combines properties from both states, allowing large amounts of thermal energy to be extracted.
Supercritical water has a density close to that of a liquid but a viscosity similar to that of a gas. It becomes an excellent conductor of heat, efficiently transporting energy from the deep Earth's crust to the surface. This unique ability makes it ideal for geothermal power plants, as it can multiply energy output compared to regular water.
Supercritical geothermal reservoirs are underground zones where the temperature exceeds 400°C (752°F) and water reaches a supercritical state. These reservoirs are typically found at depths of about 5 to 10 kilometers (3 to 6 miles), near the boundary between the Earth's crust and the mantle.
In these reservoirs, supercritical water can transport vast amounts of thermal energy. This phenomenon could dramatically increase electricity production, up to ten times more than traditional geothermal methods that rely on lower temperature water.
The exploitation of supercritical geothermal reservoirs depends on deep drilling techniques and the ability to maintain water circulation through ductile rocks. These reservoirs present a technical challenge due to the extreme conditions of pressure and temperature, but recent advances, like those from EPFL, show that these resources could be accessible and promise to revolutionize geothermal energy.
Article author: Cédric DEPOND