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Extracting More Power From Geothermal Sources

Metal-organic heat carrier
The molecular makeup of one of several MOHCs
(cc) Pacific Northwest National Laboratory

A new 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 will determine if their innovative 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 PNNL Laboratory Fellow Pete McGrail. “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 new 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, which 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 lab.

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

PNNL is receiving $1.2 million as one of 21 DOE Energy Efficiency and Renewable Energy grants through the Geothermal Technologies Program. Some of the research was conducted in EMSL, DOE’s Environmental Molecular Sciences Laboratory on the PNNL campus.

EMSL, The Environmental Molecular Sciences Laboratory is a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. EMSL’s technical experts and suite of custom and advanced instruments are unmatched. Its integrated computational and experimental capabilities enable researchers to realize fundamental insights and create technologies for energy, the environment, and human health.

Pacific Northwest National Laboratory is a Department of Energy Office of Science national laboratory where interdisciplinary teams advance science and technology and deliver solutions to America’s most intractable problems in energy, national security and the environment. PNNL employs 4,250 staff, has a $918 million annual budget, and has been managed by Ohio-based Battelle since the lab’s inception in 1965.

Read Geothermal Power Plants: Principles, Applications, Case Studies and Environmental Impact from Amazon.

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