Pumping up the Geysers
NREL and a California utility increase the efficiency of the world’s largest geothermal power plant
By Kevin Eber
With its 750-megawatt power output, the geysers in California is this largest producer of geothermal energy in the world. But a drop in steam pressure threatens to reduce power production from the plant’s 14 units. NREL is helping Pacific Gas & Electric (the local utility) to solve this problem by applying innovative cooling techniques. In addition to compensating for the drop in steam pressure, the new strategies will help conserve the geothermal resource and reduce the amount of water used in the cooling process.
Focusing on the condensers
At the geysers, steam produced by heat found deep under the ground is brought to the surface and pumped directly through a turbine to generate electricity. The steam must then be condensed. About half the units at the geysers use direct contact condensers, which channel the steam into the bottom of the condensing chamber. Here is comes into direct contact with a spray of cool water. The resulting warm water is then piped to cooling towers and cooled for reuse. NREL’s direct contact condenser increases efficiency by using “structured packings.” Designed like a three-dimensional maze, these innovative packings offer more surface area on which the coolant can do its job. In some sections of the condenser, structured packings also channel the noncondensible gases upward for efficient collection and removal. Under a cooperative research agreement with pacific gas & Electric, NREL is developing ways to design and predict the performance of the new condensers. The new methods consider factors such as the plant’s operating temperatures, flow rates, the types of noncondensible gases, and the accompanying chemistry. The goal is to produce a fully optimized condenser, which will be used to upgrade one unit at the geysers by 1996. Researchers believe that the improved design will reduce steam consumption by as much as 5%.
The Geysers…and beyond
NREL’s method for designing direct contact condensers could have applications beyond the geysers. For example, the technology may open up new fields with marginal geothermal resources or in water starved areas. Increasingly stringent siting regulations may make the improved condensers useful in fossil-fuel plants as well. For more information on NREL’s innovative condensers, contact Desikan Bharathan at (303) 275-3618
Above: The geysers in northern California is the world’s largest producer of geothermal energy.
Right” NREL researchers have tested these structured packing samples for direct contact condensers such as those at the geysers
NREL in Review Winter 1994-95
Researchers believe that the improved design will reduce steam consumption by as much as 5%
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