ECOLEAF: Understanding Solar Thermal Energy (CSP) a Renewable Energy

renewable solar thermal power energy

Ecoleaf Understanding Solar Thermal Power

Solar thermal power plants operate in a similar fashion to conventional power plants in that they use high-temperature steam or gas to drive a turbine and subsequently an electric generator. The difference is that the sun is used to create the steam instead of fossil fuels being burned to create it.

In the mid-1970s, the Department of Energy began investing heavily in R&D projects. One of them was a CSP facility built and tested at Sandia National Labs in Albuquerque, New Mexico. This facility validated CSP technology and paved the way for the first-ever installation of a fully-operational test facility in Barstow, CA. Solar One was built in 1982 and provided 10MW of electricity over a period of 6 years at a cost of nearly $28,000/kW ($2.0/kWh).

From 1985 to 1990, a series of solar thermal facilities—called Solar Electric Generating System or SEGS—were installed in California. A total of nine unique systems (covering over 2,500 acres) with 1 million mirrors were installed. These systems have a capacity of 354MW of utility-scale power and have been in continuous commercial production since early December of 1985. SEGS solar reflectors—and supporting and tracking structures—account for 50% of the cost. SEGS also burns natural gas to provide energy when the sun is absent. As of 2007, these nine systems have produced more than 12,000 GWh of electricity and netted over $2 billion; however, their profitability is questionable since their initial equipment installation costs were remarkably high.

From 1996 to 1999, CSP technology was tested and validated in Solar Two. This testing proved that molten salt could be used as a viable heat transfer medium, thus providing stored energy when the sun is not shining. The salt is a combination of sodium and potassium nitrate and has a melting temperate of 460 degrees Fahrenheit. When the molten salt liquefies and runs at a higher operating temperature of 1000 degrees F, it can achieve higher thermodynamic cycle efficiencies of 40%.

Global Solar Thermal Energy Capacity in 2005: 0.4GW

US Solar Thermal electricity consumption in 2005: 350 GWh

The electro-mechanical systems that made CSP systems cost-prohibitive in the past have become cheaper, thus enabling it to come off the dormant technology shelf. In 2007, the first solar thermal facility to be built in 16 years was constructed. It has a production capacity of 64MW. Currently, it’s estimated that by 2012, there will be a national capacity of 3.1GW. This figure includes installations in California capable of producing 553MW, 500MW, and 300MW respectively; a facility in Florida with 300 MW of production; and one located in Arizona that would have an output of 280MW.

In 2005, solar thermal power had a .4GW worldwide capacity; the U.S. represented 100% of that production. The current cost of power from these systems is estimated to be $7,200/kW of capacity ($0.16kWh).

NOTE ON SOLAR DISH TECHNOLOGY: An older dish/engine technology—CSP—is being revitalized. Initially introduced in 1901 as a solar motor, it utilizes an array of mirrors shaped into a dish to concentrate sunlight onto a receiver at its focal point. The receiver converts the absorbed solar radiation (heat) into mechanical motion to produce electricity. This type of solar dish uses a Stirling heat engine (invented in 1816 by Dr. Robert Stirling) to track the sun along two axes. In 1984, a 25kW [dish] was optimized to work at an efficiency of 29.4%. As of 2008--nearly 25 years later--a group known as Stirling Engine Systems (SES) has reached an efficiency of 31.25%. The 82 mirrors utilized by this new system are 38ft in diameter and are concentrated onto a Stirling engine. SES has two sites in California: San Diego Gas & Electric and Southern California Edison. Since 2005, these have provided up to 1,750 MW of power with 70,000 solar-dish engine units. The electricity produced by these installations has cost 0.06$/kWh. New construction will begin on a 1MW test facility that will employ 40 (25kW) dish systems. It will involve 5 to 6 systems per acre; each system will be capable of producing up to 60,000 kWh of electricity.

RECENT UPDATES: The Nevada Solar One plant (which runs on CSP technology) went live in June 2007 with 64MW of nominal production capacity. At a cost of $266 million, it boasts a price of $4,156 per KW of capacity. It is the largest CSP plant to have been built since 1991 and is located 40 miles west of Las Vegas in Boulder City, NV. It took 16 months to build, employs 28 green-collar workers, and covers 400 acres. The 180,000 mirrors reflect solar radiation onto 760 parabolic concentrators; these concentrators then heat the transfer liquid to 735° F.

In 2007, the world’s first CSP facility outside of the U.S. began operations. Spain’s initial 11MW-output tower will grow to a 300MW-facility by 2013. In February of 2008, Spain’s Abengoa Solar announced their intention to build a 280-MW CSP plant—the Solana Generating Station—70 miles southwest of Phoenix, Arizona. The plant will go live in 2011 and will have six hours of energy storage. Solana will cover three square miles (7.8 sq km) and will have 2,700 collectors; the cost is estimated at more than $1.2 billion ($4,285 per KW of capacity). The collectors are 25 feet wide, 450 feet long and 10 feet wide. When the facility is fully operational, Solana will employ 85 green-collar workers.

•Ausra plans to build a linear fresnal 177 MW power plant to be completed in 2010 with PG&E.
•Solel Solar Systems with PG&E plans to build a 553 MW, by 2011, a solar-trough system in the Mojave Desert in Southern California.
•Solel plans to build a 10 MW system in Spain by 2010 at a cost of $103 million for EMPE solar.
•FPL Energy LLC plans to build a 250MW CSP facility in California.
•BrightSource Energy Inc plans to build a 400 MW CSP facility in California.