With mammoth CSP plants in varying states of operation all across the world, the search for the true ‘world’s largest’ plant generally points to either California, Nevada, or Morocco. But which is really the biggest?
What is Concentrated Solar Power
Using mirrors to concentrate the sun’s energy, CSP technologies upgrade traditional steam turbines or engines to create electricity from heat. And, in a recent upgrade to early CSP technology, newer plants are now employing thermal energy storage of the heat that is generated. Thermal energy is effectively stored by running the heat through molten salts which are able to hold the heat for up to eight hours. This allows electricity to be produced as needed, even during the night.
The application of concentrating mirrors and receivers can take shape in a variety of configurations, including:
Numerous parallel east-to-west rows of curved mirrors focus the sun’s energy onto a receiver tube running down the center of each trough for its entire length, typically 300-450 feet. A synthetic oil able to support temperatures higher than 750°F is stored in the receiver tubes. When transferred through a heat exchanger, this fluid heats up water, producing steam. The steam then drives a conventional turbine system to produce electricity.
Compact Linear Fresnel Reflectors (CLFR)
Similar to parabolic troughs, CLFRs also employ numerous parallel rows of troughs but generally use more economical flat mirrors. The sun’s energy is focused onto receiver tubes filled with water. The water boils, generating highly pressurized steam which is then used to produce electricity.
Distributed over the surface of parabolic dishes that rotate on two axes to track the sun, mirrors concentrate the sun’s energy onto fixed focal point receivers. Hydrogen stored within each receiver is heated up to 1,200°F and used to drive an engine, thus generating power.
Heliostats to Power Tower
Heliostats are electronically-controlled flat mirrors tracking the sun along two axes. The top of the Power Tower serves as a central receiver for every heliostat’s focused solar energy. A transfer fluid in the tower receives the concentrated solar power, heating it to over 1,000° F. This heated fluid is then used to produce steam which drives a central power generator. Salts optionally heated in the tower are held in tanks and utilized for thermal energy storage.
Where is the World’s Largest CSP Plant
Now that we have a better idea of what to hunt for, let’s focus on the ‘where’ to find the prize-winning CSP plant from among the major contenders:
Cresent Dunes – Tonopah, Nevada
At 110 MW, Crescent Dunes is not the big winner for size. Nevertheless, it does wins the prize for America’s first commercial-scale CSP Power Tower with molten salt thermal energy storage. With 10,000 heliostats beaming solar energy to a 640-foot tower, the project can power 75,000 US homes. Instead of using synthetic oil to receive and transfer solar heat, Crescent Dunes uses molten salt heated in the central tower. It is pumped through a heat exchanger, to boil water which creates steam for driving an electricity-producing turbine. Cooling salt returns to its storage tank then moves to the tower to again receive heat from the heliostats, continuing the cycle. Full operation of the 1,600-acre site started just last month.
Mojave Solar One – Mohave Desert, California
Ranking as the second largest CSP plant in the US, Mojave Solar is a 280 MW parabolic trough CSP plant without thermal energy storage. Spanning 1,765 acres, this plant provides energy equal to powering 90,000 Southern California homes. Mojave Solar went into operation in January 2015.
Ivanpah SEGS – Mojave Desert, California
At 392 MW, Ivanpah is the big prize winner for the largest CSP plant in the United States. Spanning 3,500 acres of the Mojave Desert in California, Ivanpah CSP plant utilizes 173,500 heliostats and three power towers, without thermal storage. With a stated capacity of enough power for 100,000 homes, this project has nevertheless not yet reached full capacity, despite being in operation two and a half years.
NOOR – Ouarzazate, Morocco
At 580 MW, Morocco’s NOOR CSP plant definitely wins the big prize as the World’s Largest CSP Plant. Noor is a three phase parabolic trough CSP plant with half a million mirrors and molten salt thermal energy storage technology. The storage will provide thermal heat for up to eight hours. Officially inaugurated in early February 2016 by Morocco’s King Mohammed VI, Noor 1, with 160 MW is now operational, and construction of Noor 2 is underway. Noor 3 will follow to complete the 6,178-acre installation, beginning operation in 2018. At full capacity, Noor can supply clean, renewable solar power to 1.1 million Moroccan homes while reducing CO2 emissions by 760,000 tons per year.