Solar Electric Generating Systems
SEGS, Solar Electric Generation Systems, was originally conceived and constructed by Luz Industries between 1983 and 1991. It is now partially owned by FPL Energy, a Florida Power & Light affiliate. FPL has formed a green energy group called NextEra Energy Resources that is operating across the USA and Canada.
SEGS consists of nine solar power plants in California's Mojave Desert where insolation, suns intensity, is among the best available in the United States. Here the suns radiation is perpendicular, very little reflected energy, to earth and is very near 1000 Watts/sq yard. SEGS III-VII (150 MW) are located at Kramer Junction, SEGS VIII-IX (160 MW) at Harper Lake, and SEGS I-II (44 MW) at Daggett respectively. Connected directly to the grid, SEGS sells the 354 megawatts to Southern California Edison.
These parabolic mirror lined troughs are about 18 feet in diameter and follow the sun through out the day. The tracking system focuses the sun light on a central tube. While a good quality mirror is 70% reflective, these industrial models are made with polished glass that attains a 93% reflectivity. Maintenance consists of washing, alignment and replacement. SEGS reports to replace 3000 mirrors annually.
The central tube is a special insulated creature. The tube assembly is actually two high tech glass tubes, one inside the other, where an insulating vacuum is maintained between the tubes. The inner tube is filled with synthetic oil that is pumped through a closed loop that includes the mirrors and a heat exchanger. The concentrated sun light heats the oil to 750 degrees fahrenheit before it is sent to the heat exchanger. The heat exchanger generates steam that drives a turbine and generates three phase electricity. The last step is a voltage and phase relationship adjustment before it is fed to Southern California Edison's transmission lines.
Here is California's latest. Here's the federal governments (Bureau of Land Management, S. California) latest. Arizona and Nevada have each designed twenty four hour/day operations. Twenty four hour/day generators store excess heat in water/salt vaults during the day, then utilize that heat at night. France has this. Spain's Torresol company operates these twenty four hour plants. Cool stuff.