Researchers at The University of New Mexico are exploring more efficient, sustainable and reliable ways of extracting heat from the Earth for geothermal energy.
The Department of Energy recently committed $12 million to seven research projects focusing on developing enhanced geothermal systems (EGS). A UNM team led by John Stormont, a professor in UNM’s Department of Civil, Construction and Environmental Engineering, is receiving $2 million of the grant. The UNM team includes Nick Carroll (UNM), Mahmoud Reda Taha (UNM) Pania Newell (Univ. of Utah) and Stephen Bauer (Sandia National Laboratories).
“Tapping into geothermal energy — a clean and reliable energy source underneath our feet that is available in all corners of this country — is a key part of our plan to expand and diversify America’s clean energy market,” said U.S. Secretary of Energy Jennifer M. Granholm. “The ground-breaking solutions we’re anticipating from the selected national laboratory and university research teams will help America achieve a clean energy economy while creating good-paying jobs and bolstering America’s energy workforce.”
In addition to the UNM team, the DOE funded researchers from Cornell University, Lawrence Berkeley National Laboratory, Missouri University of Science and Technology, Montana State University, Oklahoma State University and Pennsylvania State University.
Geothermal energy is an affordable and sustainable source of energy. Naturally, the Earth produces its own heat. Geothermal energy can be obtained by injecting water into a hot rock. This rock then heats up the water and turns it into steam energy.
“It would be great if we could drill a hole, get hot water or steam from the well, and use that to produce electricity. But very few resources like that are accessible,” Stormont explained. “The idea of enhanced geothermal involves finding a naturally heated rock that also has fractures in it. Using two wells drilled from the surface, we inject cold water into the rock and let that water flow through the fractures, collecting heat. Then the heated water is collected in the second well, pumped to the surface and used to produce electricity.”
If enhanced geothermal systems are properly developed, geothermal energy will be a significant source of energy for the world. As a renewable energy source, geothermal energy will not make the same negative impact on the planet as fossil fuels.
The DOE funding will be used to develop technologies and techniques for EGS. This includes the development of innovative materials that can be injected into rock fractures and improve the extraction of heat energy from the rock.
“The big challenge here is creating a good circulation pattern for the water that you inject and having it move through the rock in a way that is predictable and efficiently collects the heat from the rock,” Stormont said.
Different fracture sizes impact the rate at which water flows through the rock. When water is injected into the rock the bigger fractures naturally take in more water, causing the rock to cool faster around certain larger fractures. As the fractures cool quickly, they expand and take in even more water – creating thermal short circuiting, a failing point in EGS efficiency and reliability.
“We’re researching ways to manipulate or modify fractures that are contributing to thermal short circuiting,” he said. “We’re using microcapsules to carry materials into the fractures. Those capsules then dissolve, and the materials mix to form a porous polymer material.”
The polymer material adheres itself to the rock inside the fracture, constricting water flow in the larger cracks. Since the material is porous, it still allows water to flow through the fracture but at a slower rate. By constricting waterflow in the bigger fractures, scientists can create a more diverse network of fractures, increasing the internal surface area of the rock, maximizing water heating time, increasing efficiency, and decreasing rock cooling time.
“Instead of pushing the water through just one fracture, if you push it through twenty fractures you have twenty times the surface area and your resource will last much longer,” Stormont explained.
Overcoming thermal short circuiting is an essential step to ensuring EGS is an economic way of providing energy.
“The capability to modify fracture permeability and thereby limit thermal short-circuiting addresses one of the most critical challenges that must be overcome in order for EGS to be economically successful,” Stormont said.
John Stormont is available for media interviews. Contact Rachel Whitt (email@example.com) to set up an interview.