Solar Energy Generating Systems

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Sketch of a Parabolic Trough Collector

Solar Energy Generating Systems (SEGS) is the name given to nine solar power plants in California's Mojave Desert, where insolation is among the best available in the United States. Florida Power and Light (FPL) operates and partially owns the plants. The Kramer Junction location receives an average of 340 days of sunshine per year, which makes it an ideal location for solar power generation. The average direct normal radiation (DNR) is 7.65, one of the best in the nation.^{[citation needed]} SEGS III-VII are located at Kramer Junction, with SEGS VIII-IX at Harper Lake and SEGS I-II at Daggett respectively.^[1]

The installation uses parabolic trough solar thermal technology along with natural gas to generate electricity. Ninety percent of the electricity is produced by the solar panels. Natural gas is only used when sunlight is insufficient to meet the demand from Southern California Edison, the distributer of power in southern California. FPL claims that their solar plants displace 3800 tons of pollution per year, they power 232,500 homes, and their energy displaces 815,000 barrels of oil annually.^[2]^[3]

The plants have a 354 MW installed capacity, making it the largest installation of solar plants of any kind in the world.^[1] By comparison, the largest photovoltaic plant, which is in Spain, produces 23 MW, although a 62 MW PV installation (Moura photovoltaic power station) is under construction in Germany^[4] and a 154 MW PV Solar power station in Victoria, Australia, is planned.^[5]

The SEGS power plants were commissioned between 1984 and 1991. The facilities have a total of 936,384 mirrors and cover more than 1,600 acres (6.4 km²). Lined up, the parabolic mirrors would cover 229 miles. SEGS VIII (80 MW) and SEGS IX (80 MW) are the largest solar power plants individually and collectively in the world.^[6]

The parabolic mirrors are shaped like a half-pipe. The sun shines onto the panels made of glass, which are 94% reflective, unlike a typical mirror, which is only 70% reflective. The sun bounces off the mirrors and is directed to a central tube filled with synthetic oil, which heats to over 400 degrees. The intensity of the reflected light is equal to 71 to 80 suns. The synthetic oil transfers its heat to water, which creates steam to turn the turbine and generate electricity. Synthetic oil is used to carry the heat (instead of water) to keep the pressure within managable parameters. The mirrors automatically track the sun throughout the day. The greatest source of mirror breakage is wind, with 3000 typically replaced each year. Operators can turn the mirrors to protect them during intense wind storms. An automated washing mechanism is used to periodically clean the parabolic reflective panels.