Geothermal energy is cheap and clean and having its 'moment'

Efficient energy sources are pivotal to our thriving modern society, and the continuous quest for “greener” energy alternatives has focused attention on geothermal energy.

Accessing this vast reservoir of natural heat from Earth has always been limited by one principle of real estate: location, location, location.

Conventional geothermal power plants rely on the presence of hot, porous rocks and abundant subsurface fluids.

This requirement has limited the application of geothermal systems to areas of recent volcanic activity, like Japan, Kenya, Iceland, and the western United States, among others.

Understanding geothermal energy – the basics

Geothermal energy taps into Earth’s natural heat to generate electricity and warm buildings. Deep beneath the surface, the planet’s core stays scorching hot, heating underground reservoirs of water.

When we drill into these hot spots, we can release steam or hot water to spin turbines and produce power.

Some places, like Iceland and parts of the U.S., sit on top of prime geothermal real estate, making it easier to harness this renewable energy.

Unlike fossil fuels, geothermal doesn’t rely on the weather, so it provides a steady, reliable source of power year-round.

This technology cuts down on energy bills and reduces reliance on gas or coal. Plus, geothermal plants have a much smaller carbon footprint compared to traditional power sources.

Enhanced geothermal systems (EGS)

But things might be changing. For the past half-century, adapted techniques, originally designed for oilfields and now utilized for enhanced geothermal systems (EGS), have raised the prospects of extracting natural heat from a wider geographical range.

“There is a lot of excitement about enhanced geothermal energy,” noted Roland Horne, a professor of energy science and engineering from the Stanford Doerr School of Sustainability.

He was at the forefront of bringing together engineers, scientists, and managers from 28 countries at the Stanford Geothermal Workshop, and encouraging the exchange of innovative thinking and insights from ongoing geothermal projects worldwide.

Historical evolution of geothermal energy

Geothermal power has historically been an integral component of the evolution of society.

Subterranean heat was used by the ancient Romans to heat their structures thousands of years ago, and the world’s first geothermal power plant was started in Italy, more than a century ago.

Geothermal power, in contemporary times, accounts for up to 45% of the electricity supply in certain nations, such as Kenya.

But it accounts for less than half of 1% of the global energy production.

The rise of EGS, though, could potentially redefine the role of geothermal sources in fulfilling our energy needs.

Rapid drilling, lower costs

Among the most promising developments in EGS are techniques borrowed from the shale gas boom in the early 2000s.

These include horizontal drilling and hydraulic fracturing, or “fracking,” which involve pumping fluids at high pressures into wells dug thousands of feet underground into rock formations.

The pressure opens up existing fractures in the rock or forms new ones, facilitating the flow of fluids, including hot water, to the surface.

Moreover, drilling multiple wells from a single pad enhances efficiency and keeps costs in check.

Synthetic diamond drill bits that can chew through hard rock faster are also crucial.

“Drilling faster makes an enormous difference to the whole economics of EGS,” noted Horne.

Cost-competitive geothermal energy systems

Recent studies by a group of authors, including Ph.D. candidate Mohammad Aljubran, indicate that by 2027, enhanced geothermal system costs may be comparable with the average cost of electricity throughout the United States, which is around $80 per megawatt-hour.

For instance, in California, which currently produces about 5% of its electricity from geothermal energy, EGS could potentially increase its geothermal capacity tenfold, to 40 gigawatts, by 2045.

This significant increase could replace fossil fuels for baseload power and add stability to a decarbonized power grid, complementing intermittent renewables like wind and solar.

“With EGS, we can meet the load,” confirmed Horne.

Balancing the seismic risks

Despite the immense potential, EGS is not without its challenges.

For example, fracking, a key component of EGS, is known to trigger earthquakes, thus posing a serious risk.

Mitigation tactics include avoiding seismic-prone regions for drilling, and implementing a traffic-light protocol – a monitoring system that dictates the pace of drilling based on seismic activities.

A recent development also involves creating many smaller fractures during drilling, instead of just one or a few massive fractures, to reduce the risk and size of induced seismicity.

“A drip-drip-drip instead of a fire hose approach can significantly reduce the risk and size of induced seismicity,” shared Horne.

EGS could power the future

The scientific community is optimistic about EGS’s potential.

Horne, along with his colleagues, hopes that the new study promotes further research and development of EGS as a sustainable and reliable energy source.

“EGS could be a game changer for green energy production not just in California but across the U.S. and worldwide. Safely harnessing Earth’s internal heat could substantially contribute to powering our future,” he concluded.

The full study was published in the journal Nature Reviews Clean Technology.

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