In the past fifty years, innovations adapted from oilfield technologies have led to the creation of enhanced geothermal systems (EGS), unlocking the potential to access deep natural heat reserves in a much wider array of locations.
Roland Horne, a professor of energy science and engineering at the Stanford Doerr School of Sustainability, remarked, "There is a lot of excitement about enhanced geothermal energy," during the 50th Stanford Geothermal Workshop. The event gathered over 450 engineers, scientists, and managers from 28 countries to share insights and project results.
Horne noted that nearly all EGS applications so far have been confined to experimental, small-scale projects. He was tasked with leading a team to produce a review for the February 2025 issue of Nature Reviews Clean Technology, which examines the possibility of scaling EGS for broader energy production.
Reflecting on the evolution of the field, ancient Romans once utilized subterranean heat for warming, and Italy inaugurated the world's first geothermal power plant over a century ago. Today, while geothermal supplies up to 45% of electricity in countries like Kenya, its global share remains under 0.5%, with solar and wind offering more than 25 times the capacity. EGS now presents a promising avenue to significantly expand geothermal's contribution to worldwide energy needs.
Additional strategies, such as drilling multiple wells from a single pad and using synthetic diamond drill bits to penetrate hard rock, have further reduced drilling times from months to just weeks, improving overall project economics.
Horne, the Thomas Davies Barrow Professor at Stanford and a member of an enhanced geothermal development company's scientific advisory board, stated, "Drilling faster makes an enormous difference to the whole economics of EGS," underscoring the financial benefits of these technological advances.
Modeling led by PhD student Mohammad Aljubran and co-authored estimates indicate that faster drilling could bring the cost of EGS down to approximately $80 per megawatt-hour, making it competitive with average electricity prices across much of the United States by 2027.
In California, where geothermal currently supplies about 5% of the state's electricity, researchers predict that EGS could boost capacity tenfold to 40 gigawatts by 2045, potentially replacing fossil fuels for baseload power. This increase would provide steady support to complement intermittent renewable sources like wind and solar, thereby enhancing grid stability.
Commenting further, Horne said, "With EGS, we can meet the load," at a review session co-authored with experts including Tim Latimer, Jack Norbeck, and former student Mark McClure, along with collaborators William Ellsworth, Eva Schill, and Albert Genter. Their collective work spans fields from geophysics to international geothermal development.
Mitigating induced seismicity remains a key challenge, as the fracturing process used to access deep reservoirs can trigger earthquakes, much like those seen in oil and gas fracking.
One straightforward risk reduction measure is careful site selection; avoiding regions with high seismic activity, such as areas along the San Andreas Fault, is essential, Horne warned.
Another approach involves continuous seismic monitoring using a traffic-light protocol. Under this system, minor tremors prompt a slowdown in drilling, while larger seismic events trigger an immediate halt and a comprehensive review before operations can resume.
Horne explained that by creating many smaller fractures instead of one or a few large ones, the risk of significant seismic events can be minimized. He noted, "A drip-drip-drip instead of a fire hose approach can significantly reduce the risk and size of induced seismicity," highlighting the benefits of a more controlled drilling method.
Optimists in the field hope that the new study will encourage further research into EGS as a sustainable and reliable energy source. He added, "EGS could be a game changer for green energy production not just in California but across the US and worldwide," and continued, "Safely harnessing Earth's internal heat could substantially contribute to powering our future."
Research Report:Enhanced geothermal systems for clean firm energy generation
Related Links
Stanford Doerr School of Sustainability
Powering The World in the 21st Century at Energy-Daily.com
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