A new project aimed at sequestering CO2 and at the same time extracting energy from geothermal resources is being developed by Berkeley Lab researchers. Their plan is to build a CO2-enabled geothermal system in Cranfield, Mississippi a year from now.
“This is the first project intended to convert geothermally heated CO2 into useful electricity,” says Barry Freifeld, a mechanical engineer in Berkeley Lab’s Earth Sciences Division who leads the project.
The researchers want to inject high-pressure CO2 underground at a depth of three kilometers, where temperatures reach 125 degrees Celsius. There, the CO2 gas reaches a state called “supercritical,” having both liquid and gas properties. It is then ejected right into a turbine that turns heat into electricity.
The CO2 is afterwards recycled, pumped back into the earth and part of it stays there forever, doing the sequestration part of the equation, and making place for more CO2 to be injected. People used to do this with water, and observed the same phenomenon happening.
“Our approach relies on this gradual loss as a way to store a power plant’s CO2 underground rather than emitting it into the atmosphere. Our planned demonstration is the first attempt at proving that we can simultaneously mitigate greenhouse gas induced climate change and generate clean baseload power using geothermal energy,” says Freifeld
“Carbon storage takes a lot of power – large pumps and compressors are needed. We may be able to bring down its costs by generating electricity on the side,” he adds.