In the quest for energy sources that reduce carbon emissions to stave off global warming, geothermal energy is coming into the spotlight—and it should. Virtually limitless, “always on” and widely available across all 50 states, geothermal resources offer a tantalizing opportunity to provide affordable, carbon-neutral electricity, heating and cooling for every American without disrupting our economy.
Several thousand feet below the Earth’s surface, rock can reach temperatures that exceed 300 degrees Fahrenheit. Passing fluids through the rock at this temperature harvests enough heat to spin turbines and generate electricity. Enhanced geothermal systems are a promising technology that could make this energy source available. As demonstrated by Reykjavik, Iceland, smart use of geothermal can dramatically improve air quality while also reducing heating and cooling bills.
Until recently however, significant barriers have stood in the way. One particularly concerning problem is induced seismicity, where enhanced geothermal systems could cause tremors in the Earth unless solutions are found to prevent these shakes. At Los Alamos National Laboratory, we recently discovered a promising new approach, called fracture caging, to solve this induced seismicity problem. In a nonobvious twist, fracture caging is achievable using existing tools and expertise refined over the decades by the oil and gas industry. Adopting caging merely requires a shift in thinking.
Earthshot for geothermal
Long before modern civilization, people began taking advantage of natural geothermal energy in the form of hot springs and steam vents for heating and bathing. The magic that powers these resources is nearly everywhere, if only we can find a way to responsibly tap into it.
In the 1970’s, Los Alamos pioneered a modern geothermal-energy harvesting method in the Jemez Mountains. While this test successfully demonstrated the core concept of what is now called enhanced geothermal systems, funding priorities shifted in the ensuing decades.
Today, interest in geothermal has bounced back to a new high. Our research with fracture caging synergizes with a much larger effort, the Department of Energy’s Enhanced Geothermal Shot. It’s part of the department’s Energy Earthshots Initiative to help break down the biggest remaining scientific and technical barriers to tackling the climate crisis. The Enhanced Geothermal Shot aims to slash the cost of geothermal by 90%, to make it competitive with traditional energy sources.
The payoff of geothermal is huge. The United States alone has enough geothermal resources to meet the electricity needs of the entire world. Using just a fraction, the Earthshot aims to help geothermal affordably power more than 40 million American homes by 2050. Beyond electricity, geothermal offers a plentiful opportunity for widespread use of high-efficiency ground-source heat pumps to help homes, businesses and entire communities decarbonize.
In fact, the Los Alamos-led I-WEST initiative will be expanding its scope to assess the potential for geothermal as an energy transition pathway toward carbon neutrality in the Intermountain West, while protecting local jobs, tax revenues and ways of life. I-WEST has learned through community engagement that revitalizing local economies is just as important to regional stakeholders as achieving carbon neutrality. Overlap with traditional fossil fuel technologies and its skilled workforce makes geothermal a good fit for the energy transition away from fossil fuels.
What about safety?
In conventional geothermal systems, the induced seismicity problem is often sidestepped by working far out in remote areas to mitigate impacts and by reducing the pressure and flow rate of the working fluid when shaking exceeds tolerable limits. However, this approach does not solve the problem for people in rural areas and it brings a high risk of economic losses for investors, developers, operators and the communities that these developments could have otherwise benefitted.
Fortunately, our proposed solution to induced seismicity is surprisingly simple and holds promise to be robust for ensuring safe, sustainable and responsible development of geothermal resources. With fracture caging, we preemptively drill boundary wells to “cage” around each injection well so the developed reservoir can be contained and managed.
If successful, this cage will capture virtually all the injected fluid, which controls seismicity, reduces water use and maximizes heat-mining efficiency. Our preliminary investigation indicates that caging could be economic, or even highly profitable, without requiring yet-to-be-discovered technologies and skills.
Our experiments, models and analysis show that fracture caging is more promising and more robust than we had dared to believe was possible. Even so, we are working to discover the limits and unique challenges of this new approach—we don’t expect any solution to induced seismicity to flawless. In fact, identifying and quantifying safe operating limits is the No. 1 goal for our ongoing research.
In the future, we hope to reduce development costs for geothermal energy and improve tools for resource exploration and characterization. Ultimately, the long-term goal is to enable geothermal to reach its full potential as a widely available, always-on, clean and carbon-neutral energy source.
Luke Frash is an engineer and scientist working in geothermal research at Los Alamos National Laboratory. The research was funded by the Department of Energy Office of Science — Basic Energy Sciences with additional support provided by the Laboratory Directed Research and Development program at Los Alamos.
