A method for capturing significantly more heat from low-temperature geothermal resources holds promise for generating virtually pollution-free electrical energy. Scientists at the Department of Energy's Pacific Northwest National Laboratory, Richland, Wash., will determine if their approach can safely and economically extract and convert heat from vast untapped geothermal resources. The goal is to enable power generation from low-temperature geothermal resources at an economical cost. In addition to being a clean energy source without any greenhouse gas emissions, geothermal is also a steady and dependable source of power.
“By the end of the calendar year, we plan to have a functioning bench-top prototype generating electricity,” predicts Pete McGrail, a PNNL laboratory fellow. “If successful, enhanced geothermal systems like this could become an important energy source.” A technical and economic analysis conducted by the Massachusetts Institute of Technology estimates that enhanced geothermal systems could provide 10 percent of the nation’s overall electrical generating capacity by 2050.
PNNL’s conversion system will take advantage of the rapid expansion and contraction capabilities of a liquid developed by PNNL researchers called biphasic fluid. When exposed to heat brought to the surface from water circulating in moderately hot, underground rock, the thermal-cycling of the biphasic fluid will power a turbine to generate electricity.
To aid in efficiency, scientists have added nanostructured metal-organic heat carriers, or MOHCs, that boost the power generation capacity to near that of a conventional steam cycle. McGrail cited PNNL’s nanotechnology and molecular engineering expertise as an important factor in the development, noting that the advancement was an outgrowth of research already underway at the laboratory.
PNNL produced a video that shows PNNL's Pete McGrail describing the process. It is available on the organization's web site.