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Solar Trough Plants
Kramer Junction, California

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. Operating and maintenance cost is only 2 cents per kilowatt-hour (US $ 0.02/kWh), and will be lower for future solar trough plants (< $ 0.01/kWh).

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. That plant now operates without heat storage. The subsequent 8 plants did not use heat storage (and still don't). Solar trough plants being built now will 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:

Figure 1 [ SAND99-1290 ]

Figure 2. One of the five 30 MW turbines at Kramer Junction. NREL ]

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 SST-5000 (up to 500 MW). Future solar trough plants will use turbines that generate 500 MW to 1000 MW of electricity per turbine.

Figure 3:  Solar trough power plants in the United States. The 30 and 80 Megawatt (MW) plants were originally designed to use larger turbines (160 MW each turbine for plants VIII and IX), but were scaled back to comply with anti-solar laws. 

Figure 4:  Actual 1997 operating and maintenance (O&M) cost of plant VI (US$ 107 per kilowatt per year, which is 1.22 cents per kilowatt-hour), and Sandia Labs 1997 estimates for planned solar trough plants (all less than 1 cent per kWh). The subsequent U.S. plants were not built.

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