Scientists test a unique geothermal energy system 4,100 feet underground.

The group collaborates to build and test the “rock star” system. 4100 feet beneath, a team of scientists has devised a one-of-a-kind gadget to help them find out how to capture energy from deep underground.

The Stimulation and Flow System is the latest “rock star” from Pacific Northwest National Laboratory (PNNL) and its collaborators, and it was created to learn how water travels underground through extremely hot rock and then transmits heat to the surface.

The new system is part of the EGS Collab, a collaboration comprising multiple national laboratories, universities, and industrial partners to advance geothermal technologies.

The mine, which was formerly known as North America’s largest and deepest gold mine, is now used for a variety of scientific reasons. One study is investigating how geothermal energy could eventually power 10 million homes.

Water and other fluid combinations will be pushed under high pressure into one of five boreholes—four-inch-wide “tunnels” driven into the rock—and subsequently pumped out of the other boreholes as part of the EGS Collab’s subterranean facility. The researchers are looking at not just how the fluids break apart the rock between the boreholes, but also how they gain heat from the energy stored within the rock, which can then be injected above ground to generate power.

The team created the system, which is made up of various instruments that are crucial to the EGS Collab’s research.

“The novelty of this system is that it combines multiple components required for geothermal data collection into a single system,” said the researcher.

Two injection pumps, each capable of injecting fluids into the rock at high pressures, are among those components. One pump can be utilised for extremely fine flow and pressure control, while the other can handle enormous flow rates.

A fluid chiller produces cold water, allowing the scientists to investigate how water temperatures affect the rock’s thermal properties. The team uses a reverse osmosis method to gather information about the water’s flow path by altering the salinity—or saltiness—of the injected fluid.

A set of five “packers” is also included in the system, which are placed into the boreholes. The packers are equipped with sensors that measure temperature and pressure. The boreholes and control pumps are sealed by pressurized bladders on the packers.

“The best aspect is that the system is self-contained, which means we can control it and collect data above ground from the comfort of our own homes,” said Strickland. “This allows us to spend less time underground.”

“We built and tested the system in an above-ground lab first to make sure everything worked,” Strickland explained. “Then we dismantled it, moved a mile below using 4-foot by 4-foot components in a train car, reassembled the system, and retested it.”

The entire system took three weeks to construct underground, measuring 7 feet tall by 7 feet wide and 30 feet long. Sandia National Laboratories, Idaho National Laboratory, and Lawrence Berkeley National Laboratory collaborated with PNNL to build and test the system.

“One might imagine that operating in a 7-foot tunnel a mile deep would be uncomfortable,” Strickland continued. However, new breathing air is regularly pumped in from the surface to keep the tunnels at a constant 70 degrees. Working days are lengthy, starting at 6:30 a.m. and finishing at 6:30 p.m., with only a few chances to return to the surface.”

The EGS Collab’s infrastructure and research are supported by the Department of Energy’s Geothermal Technologies Office. The system will offer data for months, if not years. The findings of this study will aid in the development of new geothermal energy solutions for industry.

“Each component brings in good, critical data,” Strickland continued. “The EGS Collab will receive the most comprehensive data to aid in the progress of geothermal energy as a unified system.”