| Solar Energy Generating Systems | |
|---|---|
Part of the 354 MW SEGS solar complex in northern San Bernardino County, California. | |
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| Country | United States |
| Location | Mojave Desert |
| Coordinates | 35°01′54″N117°20′53″W / 35.0316°N 117.348°W /35.0316; -117.348 |
| Status | Operational |
| Construction began | 1983 |
| Commission date | 1984 |
| Owner | NextEra Energy Resources |
| Solar farm | |
| Type | CSP |
| CSP technology | Parabolic trough |
| Collectors | 936,384 |
| Site resource | 2,725 kWh/m2/yr |
| Site area | 1,600 acres (647.5 ha) |
| Power generation | |
| Units operational | 2 |
| Units decommissioned | 7 |
| Nameplate capacity | 160MW |
| Capacity factor | 19.2% |
| Annual net output | 539 GW·h (2015) |
Solar Energy Generating Systems (SEGS) is aconcentrated solar power plant inCalifornia, United States. With the combined capacity from three separate locations at 354megawatt (MW), it was for thirty years the world'slargest solar thermal energy generating facility, until the commissioning of the even largerIvanpah facility in 2014. It was also for thirty years the world's largest solar generating facility of any type of technology, until the commissioning of thephotovoltaicTopaz Solar Farm in 2014. It consisted of ninesolar power plants in California'sMojave Desert, whereinsolation is among the best available in the United States.
SEGS I–II (44 MW) were located atDaggett (34°51′45″N116°49′45″W / 34.86250°N 116.82917°W /34.86250; -116.82917); they have been replaced with a solar photovoltaic farm.
SEGS III–VII (150 MW) were installed at Kramer Junction (35°00′43″N117°33′32″W / 35.01194°N 117.55889°W /35.01194; -117.55889); all five SEGS have undergone demolition.[1][2][3]
SEGS VIII–IX (160 MW) are located atHarper Lake (35°01′55″N117°20′50″W / 35.03194°N 117.34722°W /35.03194; -117.34722).[4]NextEra Energy Resources operates and partially owns the plants located at Kramer Junction. On January 26, 2018, the SEGS VIII and IX at Harper Lake were sold to renewable energy company Terra-Gen, LLC.
A tenth plant (SEGS X, 80 MW) had been in construction and SEGS XI and SEGS XII had been planned byLuz Industries, but the developer filed for bankruptcy in 1992, because it was unable to secure construction financing.[5] The site of SEGS X was later licensed for a solar photovoltaic farm, Lockhart Solar PV II.[6]
Most of the thermal facilities were retired by 2021,[7] and photovoltaics were built on the same sites.
Before retirement and replacement of SEGS I-VII with solar photovoltaics, the plants had a 354 MW net (394 MW gross) installed capacity. The nameplate capacity, which operating continuously, would dеliver the samе net power output, coming only from the solar source was around75MWe —, representing a 21%capacity factor. In addition, the turbines could be utilized at night by burningnatural gas.
NextEra claimed in 2009 that the solar plants could power 232,500 homеs (during the day, at peak power) and displace 3,800 tons of pollution pеr year that would have been produced if the electricity had been providеd by fossil fuels, such as oil.[8]
The facilities had a total of 936,384 mirrors and cover more than 1,600 acres (647.5 ha). Lined up, the parabolic mirrors would have extended over 229 miles (369 km).
As an example of cost, in 2002, one of the 30 MW Kramer Junction sites required $90 million to construct, and its operation and maintenance cost was about $3 million per year (4.6 cents per kilowatt hour).[9]

The installation usesparabolic trough,solar thermal technology along withnatural gas to generateelectricity. About 90% of the electricity is produced by thesunlight.[citation needed] Natural gas is only used when the solar power is insufficient to meet the demand fromSouthern California Edison, the distributor of power in southern California.[10]
The parabolic mirrors are shaped like quarter-pipes. The sun shines on glass panels, 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 3,000 mirrors 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. The term "field area" is assessed as the actual collector area.
The sunlight bounces off the mirrors and is directed to a central tube filled withsynthetic oil, which heats to over 400 °C (750 °F). 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 theRankine cycle steam turbine,[11] thereby generating electricity. Synthetic oil is used to carry the heat (instead of water) to keep the pressure within manageable parameters.
The SEGS power plants were built byLuz Industries,[11][12] and commissioned between December 20, 1984 and October 1, 1990.[13] After Luz Industries'bankruptcy in 1991 plants were sold to various investor groups as individual projects, and expansion including three more plants was halted.[5]
Kramer Junction employs about 95 people and 45 people work at Harper Lake.[citation needed]
| Plant | Year built | Location | Turbine capacity | Field area | Oil temperature | Gross solar production of electricity (MWh) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Net (MW) | Gross (MW) | (m2) | (°C) | 1985 | 1986 | 1987 | 1988 | 1989 | 1990 | |||
| SEGS I | 1984 | Daggett | 14 | 14 | 82,960 | 307 | 19,261 | 22,510 | 25,055 | 16,927 | 23,527 | 21,491 |
| SEGS II | 1985 | Daggett | 30 | 33 | 190,338 | 316 | 25,085 | 23,431 | 38,914 | 43,862 | 39,156 | |
| SEGS III | 1986 | Kramer Jct. | 30 | 33 | 230,300 | 349 | 49,444 | 61,475 | 63,096 | 69,410 | ||
| SEGS IV | 1986 | Kramer Jct. | 30 | 33 | 230,300 | 349 | 52,181 | 64,762 | 70,552 | 74,661 | ||
| SEGS V | 1987 | Kramer Jct. | 30 | 33 | 250,500 | 349 | 62,858 | 65,280 | 72,449 | |||
| SEGS VI | 1988 | Kramer Jct. | 30 | 35 | 188,000 | 390 | 48,045 | 62,690 | ||||
| SEGS VII | 1988 | Kramer Jct. | 30 | 35 | 194,280 | 390 | 38,868 | 57,661 | ||||
| SEGS VIII | 1989 | Harper Lake | 80 | 89 | 464,340 | 390 | 114,996 | |||||
| SEGS IX | 1990 | Harper Lake | 80 | 89 | 483,960 | 390 | 5,974 | |||||
| Total | 354 | 394 | 2,314,978 | 19,261 | 47,595 | 150,111 | 244,937 | 353,230 | 518,487 | |||
| Sources: Solargenix Energy,[14] KJC Operating Company,[15]IEEE,[16]NREL[17][18] | ||||||||||||
| Gross solar production of electricity (MWh) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | average 1998–2002 | Total |
| SEGS I | 20,252 | 17,938 | 20,368 | 20,194 | 19,800 | 19,879 | 19,228 | 18,686 | 11,250 | 17,235 | 17,947 | 17,402 | 16,500 | 348,950 |
| SEGS II | 35,168 | 32,481 | 36,882 | 36,566 | 35,853 | 35,995 | 34,817 | 33,836 | 33,408 | 31,207 | 32,497 | 31,511 | 32,500 | 571,696 |
| SEGS III | 60,134 | 48,702 | 58,248 | 56,892 | 56,663 | 64,170 | 64,677 | 70,598 | 70,689 | 65,994 | 69,369 | 66,125 | 68,555 | 995,686 |
| SEGS IV | 64,600 | 51,007 | 58,935 | 57,795 | 54,929 | 61,970 | 64,503 | 71,635 | 71,142 | 63,457 | 64,842 | 70,313 | 68,278 | 1,017,283 |
| SEGS V | 59,009 | 55,383 | 67,685 | 66,255 | 63,757 | 71,439 | 75,936 | 75,229 | 70,293 | 73,810 | 71,826 | 73,235 | 72,879 | 1,014,444 |
| SEGS VI | 64,155 | 47,087 | 55,724 | 56,908 | 63,650 | 71,409 | 70,019 | 67,358 | 71,066 | 68,543 | 67,339 | 64,483 | 67,758 | 878,476 |
| SEGS VII | 58,373 | 46,940 | 54,110 | 53,251 | 61,220 | 70,138 | 69,186 | 67,651 | 66,258 | 64,195 | 64,210 | 62,196 | 65,048 | 834,986 |
| SEGS VIII | 102,464 | 109,361 | 130,999 | 134,578 | 133,843 | 139,174 | 136,410 | 137,905 | 135,233 | 140,079 | 137,754 | 138,977 | 137,990 | 1,691,773 |
| SEGS IX | 144,805 | 129,558 | 130,847 | 137,915 | 138,959 | 141,916 | 139,697 | 119,732 | 107,513 | 128,315 | 132,051 | 137,570 | 125,036 | 1,594,852 |
| Total | 608,960 | 538,458 | 613,798 | 620,358 | 628,674 | 676,091 | 674,473 | 662,631 | 636,851 | 652,835 | 657,834 | 662,542 | 654,539 | 8,967,123 |
| Sources: Solargenix Energy,[14] KJC Operating Company,[15]IEEE,[16]NREL[17][18] | ||||||||||||||
| Net solar production of electricity (MWh) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | average 2003–2014 | Total |
| SEGS I | 6,913 | 8,421 | 6,336 | 5,559 | 0 | 10,705 | 9,033 | 10,648 | 11,164 | 11,666 | 9,403 | 8,583 | 8,203 | 98,431 |
| SEGS II | 11,142 | 14,582 | 13,375 | 7,547 | 5,445 | 28,040 | 18,635 | 22,829 | 26,198 | 25,126 | 23,173 | 7,611 | 16,975 | 203,703 |
| SEGS III | 59,027 | 64,413 | 56,680 | 51,721 | 59,480 | 69,012 | 62,971 | 60,029 | 61,350 | 56,877 | 56,824 | 54,407 | 59,399 | 712,791 |
| SEGS IV | 58,100 | 62,006 | 56,349 | 52,439 | 59,799 | 69,338 | 63,563 | 63,084 | 57,684 | 62,414 | 58,317 | 54,321 | 59,785 | 717,414 |
| SEGS V | 61,921 | 67,717 | 62,309 | 53,471 | 59,547 | 69,316 | 59,820 | 54,328 | 60,451 | 62,877 | 57,758 | 56,354 | 60,489 | 725,869 |
| SEGS VI | 50,504 | 53,618 | 51,827 | 45,076 | 65,832 | 67,156 | 62,750 | 63,576 | 59,327 | 56,082 | 52,539 | 50,547 | 56,570 | 678,834 |
| SEGS VII | 49,154 | 50,479 | 46,628 | 42,050 | 58,307 | 65,185 | 58,950 | 58,836 | 57,378 | 54,147 | 48,183 | 46,762 | 53,005 | 636,059 |
| SEGS VIII | 119,357 | 124,089 | 120,282 | 117,451 | 122,676 | 135,492 | 131,474 | 155,933 | 152,463 | 145,247 | 141,356 | 145,525 | 134,279 | 1,611,345 |
| SEGS IX | 115,541 | 123,605 | 120,915 | 117,310 | 122,699 | 150,362 | 139,756 | 163,899 | 160,506 | 164,203 | 154,082 | 147,883 | 140,063 | 1,680,761 |
| Total | 531,659 | 568,930 | 534,701 | 492,624 | 553,785 | 664,606 | 606,952 | 653,162 | 646,521 | 638,639 | 601,635 | 571,993 | 588,767 | 7,065,207 |
| Net solar production of electricity (MWh) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Plant | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | Total | Total 1985–2021 |
| SEGS I[19] | 12,562 | dec. | (PV) | (PV) | (PV) | (PV) | (PV) | 12,562 | 459,943 |
| SEGS II[20] | dec. | dec. | (PV) | (PV) | (PV) | (PV) | (PV) | 0 | 775,399 |
| SEGS III[21] | 52,073 | 46,582 | 44,115 | 43,849 | 38,242 | 0 | dec. | 224,861 | 1,933,518 |
| SEGS IV[22] | 53,117 | 49,034 | 43,182 | 44,406 | 41,865 | 0 | dec. | 231,604 | 1,969,301 |
| SEGS V[23] | 52,646 | 50,142 | 43,934 | 47,383 | 41,424 | 0 | dec. | 235,529 | 1,975,842 |
| SEGS VI[24] | 46,937 | 40,923 | 36,380 | 34,262 | 0 | 0 | dec. | 158,502 | 1,715,812 |
| SEGS VII[25] | 37,771 | 30,480 | 32,601 | 27,956 | 0 | 0 | dec. | 128,808 | 1,599,852 |
| SEGS VIII[26] | 138,149 | 140,849 | 123,451 | 132,871 | 120,530 | 114,557 | 81,699 | 852,106 | 4,189,538 |
| SEGS IX[27] | 145,863 | 142,867 | 131,268 | 137,564 | 124,375 | 122,045 | 116,013 | 919,995 | 4,161,294 |
| Total | 539,118 | 500,877 | 454,931 | 468,291 | 366,254 | 236,602 | 197,712 | 2,754,405 | 18,780,499 |
| Starting 2017, SEGS I was replaced byPV system Sunray 2, and SEGS II by PV system Sunray 3 | |||||||||
UntilIvanpah Solar Power Facility was commissioned in 2014, SEGS VIII and SEGS IX, located at35°01′55″N117°20′50″W / 35.031815°N 117.347270°W /35.031815; -117.347270 (SEGS VIII and IX) were the largest solar thermal power plants individually and collectively in the world.[28] They were the last, the largest, and the most advanced of the nine plants at SEGS, designed to take advantage of theeconomies of scale. Construction of the tenth plant in the same locality was halted because of the bankruptcy of Luz Industries. Construction of the approved eleventh and twelfth plants never started. Each of the three planned plants would have had 80 MW of installed capacity.[29]Abengoa Solar recently constructed the 280MWMojave Solar Project (MSP) adjacent to the SEGS VIII and SEGS IX plants.[30] The MSP also uses concentrating solar thermal trough technology.
Starting in February 2020, SEGS VIII no longer burned natural gas. The last production month was October 2021. SEGS IX stopped burning natural gas starting October 2020, except for January 2021.

This location (35°00′48″N117°33′38″W / 35.013218°N 117.560531°W /35.013218; -117.560531 (SEGS III–VII)) receives an average of 340 days of sunshine per year, which makes it an ideal place for solar power generation. The averagedirect normal radiation (DNR) is 7.44 kWh/m2/day (310 W/m2),[15] one of the best in the nation[citation needed]. This was the location of SEGS II - VII, which were retired in 2019. As of 2021, they were going to be replaced with a new solar photovoltaic array called Resurgence I.[2][3]
SEGS I and II were located at34°51′47″N116°49′37″W / 34.8631°N 116.827°W /34.8631; -116.827 (SEGS I and II) and owned by Cogentrix Energy (Carlyle Group).[31] SEGS II was shut down in 2014 and was replaced by Sunray 3 (EIA plant code 10438), a 13,8 MW photovoltaic system. SEGS I was shut down one year later and replaced by 20 MW PV system Sunray 2 (EIA plant code 10437).[32][33] Sunray 2 and Sunray 3 started production in 2017 as per EIA data.
In February 1999, a 900,000-US-gallon (3,400 m3)mineral oil storage tank exploded at the SEGS I (Daggett) solar power plant, sending flames and smoke into the sky. Authorities were trying to keep flames away from two adjacent containers that heldsulfuric acid andsodium hydroxide. The immediate area of 0.5 square miles (1.3 km2) was evacuated.[34]
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