Have enhanced geothermal, will travel

Naturally occurring hydrothermal systems have always been a limited, localized energy source, offering steady production that doesn't vary with the weather or time of day – as long as there are very specific conditions of heat, water, and permeable rock. These specific conditions do not always occur where energy is needed, which is a primary reason why geothermal power provides less than 1% of global renewable energy capacity.

Recent advances in the emerging technology of enhanced, or manmade, geothermal systems have the potential to dramatically increase locations for clean energy production of this type.

Enhanced geothermal tech

Manmade geothermal energy, or enhanced geothermal systems (EGS), have been around since the 1970s, but with recent advancements, geothermal may finally graduate to being part of the suite of globally viable renewable energy options.

Hydraulic fracturing techniques are now being used to split relatively solid rock at depths much greater than naturally occurring geothermal wells. Water is then injected into these rocks to generate steam, which subsequently drives turbines to produce electricity.

The technology is not without risks, with the scientific community divided on how hydraulic fracturing could affect seismic activity. While some believe earthquake risks are minimal, a 2017 incident in South Korea was linked to an enhanced geothermal project.

AltaRock Energy

The U.S. Geothermal Technologies Office EGS program supports research, development, and demonstration projects that aim to make geothermal power viable beyond traditional hydrothermal regions, extend geothermal energy production nationwide and make it economically competitive with solar and wind.

Washington-based AltaRock Energy is one of a handful of companies and labs advancing pilot projects and research in the field.

AltaRock's two categories of projects include creating well access to hot rock with no hydrothermal circulation and increasing the efficiency of existing commercial geothermal systems by creating new adjacent fracture zones – expanding the size and heat transfer efficiency of the geothermal reservoir.

This previously untapped energy production, coined 'Super Hot Rock' geothermal, drills deep down to rock where naturally occurring temperatures are above 400 degrees Celsius, or 750 degrees Fahrenheit.

"The next generation of geothermal power, Super Hot Rock geothermal, will require development of engineered reservoirs in deep basements where hotter 'supercritical' temperatures can yield up to 10 times more energy than a conventional geothermal well," said Geoff Garrison, vice president of research and development at AltaRock. "Once proven in the field, Super Hot Rock geothermal resources will ultimately provide competitively priced, carbon-free power to far greater markets than can currently be reached by affordable geothermal power."

Utah FORGE

DOE is funding Utah's Frontier Observatory for Research in Geothermal Energy (FORGE), demonstrating significant improvements in drilling rates and successful rock stimulation.

Led by the University of Utah, FORGE lab is the only dedicated field site of its kind used to research, test, and accelerate EGS technologies and tools whose development can be de-risked and advanced.

Its latest project, geothermal greenhouses, is inspired by functional applications of naturally occurring hydrothermals worldwide. (For instance, Türkiye is the location of one-third of the world's geothermal greenhouses.)

Harnessing round-the-clock geothermal energy in agriculture allows for more space-efficient farming, lower produce costs, improved community food security, fresher products and increased year-round yields. Most importantly, it has the potential to eliminate the field's consumption of fossil fuels.

"We are excited to collaborate on these new R&D projects," said Joseph Moore, Ph.D. and managing principal investigator of the Utah FORGE project. "This research will be invaluable. Each breakthrough brings us another step closer to realizing the potential of geothermal energy, and the ability to generate EGS-based electricity anywhere in the world."

In its year-end report, Utah FORGE Lab described its research progress in 2023. This includes more than 10 miles of drilling in eight wells, as well as a state-of-the-art seismic monitoring system for understanding the creation and growth of the reservoir fracture network and for mitigating hazards.

Fervo Energy

Fervo Energy successfully tested an EGS system last year in Nevada that demonstrated it can create flexible geothermal power capable of adjusting output up or down as needed. The project proves EGS are essentially giant underground batteries, a commercially viable counterpart to other clean energy grid solutions.

By building up and relieving pressure in the wells, energy is saved up and utilized on demand. The company will next be building in Utah, with an ambitious goal of providing constant, clean power by 2026.

For more information on DOE-funded enhanced geothermal projects, click here.