Scientists have created a unique system that will help them harness energy from deep below the ground.

The Stimulation and Flow System, the newest rock star from Pacific Northwest National Laboratory and its partners is designed to study how water travels underground through very hot rocks and then transmits heat to surface.

Several components, one unique system

This mine was once the largest and deepest in North America. It is now used for various scientific purposes. One project is investigating how geothermal energy could one day power 10,000,000 homes.

The EGS Collab is using the underground facility as a test bed where water and other fluid mixtures will be pumped under high pressure into one of five boreholes–four-inch-wide “tunnels” drilled into the rock–and then pumped out of the other boreholes. The team is investigating how fluids break down the rock between boreholes and how they get heat from the energy contained within the rock. This heat can then be used to generate electricity.

The team created the system to support the EGS Collab’s efforts. It includes several instruments that are crucial for their study.

Chris Strickland (PNNL scientist) said, “The uniqueness this system is that combines several components required to glean valuable data for geothermal research into one system.” This is unique.

These components include two injection pumps, which can each inject fluids at high pressures into the rock. The one pump can be used to control flow and pressure, while the second can be used when flow rates are high.

The fluid chiller produces cold water, which allows the team to study the effect of water temperatures on the thermal properties and rock. The reverse osmosis system is used to extract data from the fluid flow by altering the saltiness or salinity of the fluid.

A set of five “packers”, which are inserted into boreholes, is also included in the system. Sensors are installed on the packers to provide pressure and temperature measurements. The packers are equipped with pressurized bladders that seal the boreholes.

Strickland stated that the best thing about the system is its autonomy. This means we can use a laptop or smartphone at home to operate it and collect data above ground. “This way, we don’t have to spend as much time underground.”

In pieces, going deep

Strickland said, “We assembled the system and tested it in an above-ground laboratory to ensure that everything was working.” “Then, we disassembled it, transported it a mile underground in pieces measuring 4 x 4, and then reassembled it.

It took three weeks to construct the entire system underground, measuring 7 feet high, 7 feet wide, and 30 feet long. The system was built and tested underground by PNNL and EGS Collab Partners from Sandia National Laboratories and Idaho National Laboratory.

Strickland said, “One might believe that working in a 7-foot underground tunnel would be difficult. To maintain a constant temperature of 70 degrees in the tunnels and to provide fresh air, air is constantly pumped in from above. The workday is long and starts at 6:30 am and ends at 6:30 pm. There are limited opportunities to return to the surface.