Lindsay Kalter
GHG Monitor
04/27/12
The University of Minnesota has sold intellectual property that merges geothermal energy production and carbon capture and sequestration technology to a South Dakota-based startup company, which will employ new technological concepts developed at the University that could help to mitigate prohibitive costs of CCS projects, according to project researchers. The launch of Heat Mining Company LLC is the most recent development in a three-year research effort that has investigated the use of sequestered carbon dioxide, rather than water, to extract heat from underground to be used for electricity generation—a practice that scientists say could also increase the efficiency of renewable electricity production.
The idea behind the so-called CO2 plume geothermal system (CPG) was conceived during a road trip, when earth sciences faculty member Martin Saar and then-graduate student Jimmy Randolph discussed the possibility of combining their existing research projects, Randolph told GHG this week. “Dr. Saar and myself had been doing basic research on geothermal energy and CCS separately, and we hit on the idea that maybe they could be directly merged,” said Randolph, now a postdoctoral fellow in the University’s earth sciences department and scientist at Heat Mining Company LLC. “After doing a bit of investigating, we determined that would actually make sense.”
Project Began With $600K from University
In 2009, the project received a $600,000 grant from the Initiative for Renewable Energy and the Environment, a program within the university’s Institute on the Environment. The financial support allowed Randolph and Saar to organize a team of geologists, mechanical engineers, policy specialists and economists to help determine the technology’s feasibility from several angles.
The use of CO2 in geothermal processes presents a number of advantages, according to researchers, one being a decrease in the amount of energy required to sufficiently mobilize CO2 for the purpose of heat extraction. “It turns out the energy conversion is actually more efficient with CO2 than with water,” Thomas H. Kuehn, a mechanical engineering professor and co-developer of the technology, told GHG this week. “CO2 has higher mobility than water, so there’s basically less pumping power needed, and that increases the amount of power you can provide.” Kuehn added that most of the eligible locations for conventional geothermal projects are in hotspots in the western United States, but CO2 allows for a broader range of application, along with a greater number of rock formations in which it can be used.
Can Technology Offset CCS Costs?
According to project advocates, CPG could serve to offset the high costs of CCS—a barrier that has significantly increased public and federal resistance to CCS technologies worldwide. Steven J. Taff, associate economics professor at the university who is conducting financial modeling for the technology, said CPG could provide a financial boost to CCS projects in the absence of a carbon pricing scheme. He said the physical nature of CO2 creates a thermal syphon that reduces the need for injection and extraction pumps, which cuts costs.
But, he said, there are still several economic components that have yet to be investigated. “We think we’re in the same ball park as a whole lot of other renewable systems, but it really depends on the heat of the resource and the rate at which it comes out,” he told GHG. “All renewable costs depend on the resource. Context is everything.” He added that a single CPG system may not be large enough to defray the cost of CCS by any sizeable amount, but “if one were to chain several CPG systems into a single CCS system, we may be able to make a dent.”
The next step is to settle on a site location, which would ideally be one with a reserve of CO2 that has already been sequestered, said Steve O’Rourke, president of the privately-funded Heat Mining Company LLC. An alternative would be an enhanced oil recovery site, which may require high-cost equipment due to the more complex fluid created by a the mixture of CO2 with hydrocarbons and water. The third and probably least feasible option, O’Rourke said, is a wind and solar farm where the excess energy during high generation periods would be used to inject CO2 into the ground. "That one gets a bit more difficult just because of the source of CO2," said O’Rourke, who previously served as president of global exploration for BHP Billiton Petroleum. "That might entail some sort of drilling of both injection and production wells." Co-creator Randolph said a CCS site located in Canada is currently a front-runner, but no commitments have been made. The CCS injections for the project would begin in about two years, he said. But Taff said the project planning process will be a long one, given all of the moving parts. “Even if it proves to be the world’s greatest idea, we wouldn’t see it for a number of years,” he said.
