NREL/PG&E Condensation System Increases Geothermal Power Plant Efficiency
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Golden, Colo., June 17, 1997 -- The world's largest producer of geothermal power has improved its power production efficiency thanks to a new technology developed under a research partnership between the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory and Pacific Gas and Electric Company (PG&E).
PG&E announced test results today confirming that it has gained 5% efficiency in Unit 11 of the Geysers Power Plant in northern California. Unit 11 is one of 14 power producing units that comprise the plant. The Geysers complex generates 750 megawatts of electrical power, supplying 5 percent of California's residential electricity.
Geothermal power plants like The Geysers produce energy by collecting steam from underground reservoirs and converting it to electricity with turbine generators. Over time, pressure from geothermal reservoirs falls, decreasing power output. The goal of the PG&E/NREL partnership was to increase process efficiency, maximizing use of the resource and minimizing power production costs.
Under the $935,000 three-year program, NREL and PG&E engineers used computer modeling to enhance condensation of spent steam using optimal geometric frameworks, commonly termed "packings" or "fills". The renovation of Unit 11's condensation system reduced vapor pressure in the condenser, helping "pull" steam through the turbines. The result is more efficient power production.
"We've proven that advanced direct contact condensation makes a big difference," said Desikan Bharathan, NREL's lead researcher. "It shows that the renovation is worthwhile for existing direct contact condensation systems, a good investment for new geothermal plants and may be economically viable for conventional condensation systems for fossil-fuel plants."
NREL plans to license the advanced direct contact condenser technology to manufacturers interested in building condensers for new plants or retrofits and to service companies interested in renovating existing condensers.
The laboratory is also interested in demonstrating the technology in a fossil-fuel power plant. To use a direct contact condenser in a fossil-fuel plant, it is necessary to also use intermediate heat exchangers. Because these exchangers can be modular, they may be cleaned individually without shutting down the entire plant, as must now be done to clean conventional surface condensers. According to the Electric Power Research Institute, condenser cleaning outages cost the utility industry more than $ 1 billion in down time per year.
PG&E is expected to renovate five additional units at The Geysers with advanced direct contact condenser technology. Technical information about advanced direct contact condensers is available from Desikan Bharathan at 303/384-7418 or email: Desikan_Bharathan@nrel.gov.