The Solar Energy Generating System (SEGS) solar trough plants in Kramer Junction, California have been operating for decades, and will last at least that much longer without requiring replacement costs as other electricity generating technologies require.
The operating and maintenance (O&M) costs of SEGS are only 2 cents per kilowatt-hour (kWh), which includes cleaning the collectors and periodic refurbishing of the steam turbines. Cost reduction work on one of the plants has lowered O&M costs to 1.22 cents per kWh, and future plants will have O&M costs below 1 cent per kWh (< US $ 0.01 / kWh).
A solar trough power plant with 30 MW turbine was built in 1985 in Dagget, California, followed with solar trough power plants built in Kramer Junction during the late 1980s that power five more 30 MW turbines. The same design was then used in 1989 and 1990 to build solar trough arrays that power two 80 MW turbines at Harper Lake. All of these plants continue to operate successfully, requiring only maintenance.
An earlier 14 MW plant built in 1984 in Dagget used a different design. That first plant used oil tanks for heat storage which were destroyed by fire. The subsequent 8 plants did not use heat storage. Solar trough plants being built now use molten salt heat storage (instead of oil storage) to generate electricity at night. Molten salt stores heat safely and efficiently.
The plants at Kramer Junction are numbered III through VII:
Solar trough plants can use turbines that generate 250 MW to 500 MW of electricity per turbine, including the General Electric D Series steam turbine (up to 375 MW) and the Siemens
Collectors extend in the north-south direction, along a constant longitude (a longitudinal meridian).
The most effective method of cleaning the collectors is to point them upward when rain or snow is predicted. Snow is reported to do an especially good job. However, the site is sunny 98 percent of each day, so other cleaning methods are required.
Washing is done once per week during peak summer season, using demineralized water. The water is demineralized on site. Two washing methods are used: the classic deluge wash, and the twister method which is more effective, but takes longer and costs more, so it is not done every cleaning. Both methods use less than one liter (less than one-fourth gallon) of water per square meter of collector area for each washing.
The twister method is almost as good as natural snow cleaning. It uses a tractor with twirling nozzles, towing a water tank:
For the deluge method, the collectors face each other so that two rows of collectors are washed at once. A large tanker truck with fixed sprayers drives between the collectors:
The cost of deluge washing is US $ 0.14 per square meter of collector area per year.