U.S. Department of Energy - Energy Efficiency and Renewable Energy
Geothermal Technologies Office
New Working Fluids Cut a Wider Swath of Geothermal Reserves
December 17, 2013
Scientists at the Energy Department’s Pacific Northwest National Laboratory (PNNL) have made a commercially viable discovery—how to capture substantially more heat from low-temperature resources. In a market where binary working fluids are costly and traditionally inefficient, this advance harnesses a much larger sector of near-term geothermal potential through inventive, low-cost solutions. Payback on this novel technology is now estimated in certain operational conditions at under 36 days, and DOE expects a commercialization plan by first quarter 2014.
PNNL developed the innovative liquid—called biphasic fluid—with the capability for rapid expansion and contraction and added tiny nano structured metal-organic heat carriers (MOHC s) to boost power generation capacity near to that of a conventional steam cycle. The team found that the new working fluid has significantly exceeded performance requirements at lab scale, with a 15% increase in power generation and capital cost reductions at existing plants. Put all these pieces together, and this innovation creates a new energy producing cycle that allows developers to exploit low-temp geothermal sources for more economical power production.
To engineer this innovation, PNNL’s expertise in nanotechnology and molecular engineering adapted advancements already underway at the lab. Nano fluids offer unique potential to improve efficiency of working fluids without major modifications to equipment or operating conditions – they increase thermal conductivity, improve heat transfer, and interact at the molecular level by increasing effective latent heat. Molecular stimulation of low-temperature resources from this project reduces capital costs, increases efficiency of the cycle, and expands the range of geothermal resources suitable for economic power production and waste heat recovery.
Read more about low temperature resources.