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Solar Energy Generating Systems

Solar Energy Generating Systems (SEGS) is the largest solar energy generating facility in the world. It consists of nine solar power plants in California's Mojave Desert, where insolation is among the best available in the United States. FPL Energy operates and partially owns the plants. 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.

Plants' scale

The plants have a 354 MW installed capacity, making it the largest installation of solar plants of any kind in the world. 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 Portugal and a 154 MW PV Solar power station in Victoria, Australia, is planned. The average gross solar output for all nine plants at SEGS is around 75 MWe. In addition, the turbines can be utilized at night by burning natural gas.

Land footprint

The facilities have a total of 936,384 mirrors and cover more than . Lined up, the parabolic mirrors would extend over .

Fossil fuel equivalent

FPL claims that their solar plants displace 3,800 tons of pollution per year, they power 232,500 homes, and their energy displaces 815,000 barrels of oil annually.

Principle of operation

The installation uses parabolic trough solar thermal technology along with natural gas to generate electricity. 90% of the electricity is produced by the sunlight. Natural gas is only used when the solar power is insufficient to meet the demand from Southern California Edison, the distributer of power in southern California.

Mirrors

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 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.

Heat transfer

The sun bounces off the mirrors and is directed to a central tube filled with synthetic oil, which heats to over . The reflected light focused at the central tube is 71 to 80 times more intense than the ordinary sunlight. The synthetic oil transfers its heat to water, which boils and drives the Rankine cycle steam turbine, thereby generating electricity. Synthetic oil is used to carry the heat (instead of water) to keep the pressure within manageable parameters.

Individual locations

The SEGS power plants were built by Luz Industries, and commissioned between 1984 and 1991. Kramer Junction employs about 95 people and 45 people work at Harper Lake.

SEGS plant history and operational data
Plant	Year built	Location	Net turbine capacity	Field area	Oil temperature	Gross solar production of electricity (MWh)
			(MW)	(m²)	(°C)	1996	average 1998–2002
SEGS I	1984	Daggett	14	82,960	307	19,900	16,500
SEGS II	1985	Daggett	30	165,376	316	36,000	32,500
SEGS III	1986	Kramer Jct.	30	230,300	349	64,170	68,555
SEGS IV	1986	Kramer Jct.	30	230,300	349	61,970	68,278
SEGS V	1987	Kramer Jct.	30	233,120	349	71,439	72,879
SEGS VI	1988	Kramer Jct.	30	188,000	391	71,409	67,758
SEGS VII	1988	Kramer Jct.	30	194,280	391	70,138	65,048
SEGS VIII	1989	Harper Lake	80	464,340	391	139,174	137,990
SEGS IX	1990	Harper Lake	80	483,960		141,916	125,036
Sources: Solargenix Energy, KJC Operating Company, IEEE, NREL

Harper Lake

SEGS VIII and SEGS IX, located at , are the largest solar power plants individually and collectively in the world. They were the last, the largest, and the most advanced of the nine plants at SEGS, designed to take advantage of the economies of scale. SEGS VIII and IX have operated continuously and have been commercially successful since the very beginning.

Kramer Junction

This location receives an average of 340 days of sunshine per year, which makes it an ideal place for solar power generation. The average direct normal radiation (DNR) is 7.44 kWh/m²/day (310 W/m²), one of the best in the nation.