An abandoned gas well in Illinois has been converted into a geothermal energy storage system, repurposing a once-polluting extraction site into a huge underground battery. An industrial-scale geothermal energy storage battery that uses no harsh chemicals and has no risk of fire.
Researchers from the University of Illinois Urbana-Champaign were able to harness the deep subsurface structure, even though it does not actually produce geothermal energy by itself.
As a result, they built an artificial geothermal energy storage reservoir there, which stores heat as energy. The team used the abandoned oil well to inject water heated to 122 degrees Fahrenheit into a layer of porous sandstone 3,000 feet below the surface.
As reported in Tech Explore by Lois Yoksoulian, of the University of Illinois at Urbana-Champaign, many of the same properties that make subsurface rock formations ideal for oil and gas extraction also make them ideal for geothermal storage. The test site is a former gas well, which means most of the infrastructure is already in place. Like gravity energy storage sites using abandoned mining shafts, repurposing existing infrastructure ensures that the projects are less expensive to set up and deploy and quickly provide a return on investment.
The highest cost is the implementation of a heat exchanger and steam-powered generation unit.
In the long run, storing excess heat from nearby industries underground will be possible and releasing it as electric power when demand is high. The underground reservoir serves as an underground battery while repurposing abandoned oil and gas wells.
In the Illinois Basin, a large geological feature that stretches under almost the entire state, spongelike rocks and minerals provide excellent thermal conductivity. These insulating layers keep heat from dissipating into the surrounding structure.
The process can sustain 82 percent thermal storage efficiency based on field results and numerical modelling making it an economically viable and even profitable system, producing electricity at a competitive $0.138 per kilowatt-hour.
The study concluded that the Illinois Basin can store excess waste heat energy from industrial sources, making these industries more efficient while offsetting their grid energy consumption, thereby reducing their carbon footprint.