Geothermal Heat Extraction Process Takes Advantage of New Liquid

The molecular makeup of one of several MOHCs. (PNNL)

Scientists at the Department of Energy's Pacific Northwest National Laboratory have come up with an innovative approach that can safely and economically extract and convert heat from untapped geothermal resources. The heat recovery method makes the most of low-temperature “hot rock” resources.

The PNNL researchers developed a new liquid called biphasic fluid with rapid expansion and contraction capabilities, which the new conversion system will use. 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, the scientists added nanostructured metal-organic heat carriers - or MOHCs - which boost the power generation capacity to near that of a conventional steam cycle. PNNL Laboratory Fellow Pete McGrail cited PNNL's nanotechnology and molecular engineering expertise as an important factor in the development.

"Some novel research on nanomaterials used to capture carbon dioxide from burning fossil fuels actually led us to this discovery," says McGrail. "Scientific breakthroughs can come from some very unintuitive connections."

"By the end of the calendar year, we plan to have a functioning bench-top prototype generating electricity," McGrail predicts.

Watch McGrail describe the process in the video below.