Concentrating Solar Power (CSP)

Considering that the energy in sunlight reaching the Earth in just 70 minutes is equivalent to annual global energy consumption, the potential for solar power virtually is unlimited. With concentrating solar power (CSP) capacity expected to double every 16 months over the next five years, worldwide installed CSP capacity will reach 6,400 megawatts in 2012-14 times current capacity.

Unlike solar photovoltaics (PVs), which use semiconductors to convert sunlight directly into electricity, concentrating solar power (CSP) plants generate electricity using heat. Much like a magnifying glass, reflectors focus sunlight onto a fluid-filled vessel. The heat absorbed by the fluid is used to generate steam that drives a turbine to produce electricity. Power generation after sunset is possible by storing excess heat in large, insulated tanks filled with molten salt. Since CSP plants require high levels of direct solar radiation to operate efficiently, deserts make ideal locations.

Two big advantages of concentrating solar power (CSP) over conventional power plants are that the electricity generation is clean and carbon-free and, since the sun is the energy source, there are no fuel costs. Energy storage in the form of heat also is significantly cheaper than battery storage of electricity, providing CSP with an economical means to overcome intermittency and deliver dispatchable power.

The U.S. and Spain are leading the world in the development of solar thermal power, with a combined total of more than 5,600 megawatts of new capacity expected to come online by 2012. Representing over 90% of the projected new capacity in that span, the output from these plants would be enough to meet the electrical needs of more than 1,700,000 homes. The largest solar thermal power complex in operation today is the Solar Electricity Generating Station in the Mojave Desert in California. Coming online between 1985 and 1991, the 354-megawatt complex has been producing enough power for 100,000 homes for almost two decades. In June 2007, the 64-megawatt Nevada Solar One plant became the first multi-megawatt commercial CSP plant to come online in the U.S. in 16 years.

Today, more than a dozen new CSP plants are being planned in the U.S., with some 3,100 megawatts expected to come online by 2012. Some impressive CSP projects in the planning stages include the 553-megawatt Mojave Solar Park in California, the 500-megawatt Solar One and 300-megawatt Solar Two projects in California, a 300 megawatt facility in Florida, and the 280-megawatt Solana plant in Arizona.

In Spain, the first commercial-scale concentrating solar power plant to begin operation outside the U.S. since the mid 1980s came online in 2007: the 11-megawatt PS10 tower. The tower is part of the 300-megawatt Solucar Platform, which, when completed in 2013, will contain 10 CSP plants and produce enough electricity to supply 153,000 homes while preventing 185,000 tons of carbon dioxide emissions annually. All told, more than 60 plants are in the pipeline in Spain, with 2,570 megawatts expected to come online by 2012.

Economic and policy incentives partly are responsible for the renewed interest in concentrating solar power plants. The incentives in the U.S. included a 30% Federal Investment Tax Credit (ITC) for solar through the end of 2008, which has good prospects for being extended. Moreover, the Renewable Portfolio Standards hold sway in 26 states. California, for instance, requires that utilities get 20% of their electricity from renewable sources by 2010, and Nevada requires 20% by 2015, with at least five percent from solar power.

In the Southwest, the cost of electricity from CSP plants (including the Federal ITC) roughly is 13 to 17 cents per kilowatt-hour, meaning that CSP with thermal storage is competitive today with simple-cycle natural gas-fired power plants. The Department of Energy aims to reduce CSP costs to seven to 10 cents per kilowatt-hour by 2015 and to five to seven cents by 2020, making CSP competitive with fossil-fuel based power sources.

Outside the U.S. and Spain, regulatory incentives in France, Greece, Italy, and Portugal are expected to stimulate the installation of 3,200 megawatts of CSP capacity by 2020. China anticipates building 1,000 megawatts by that time. Other countries developing CSP include Australia, Algeria, Egypt, Iran, Israel, Jordan, Mexico, Morocco, South Africa, and the United Arab Emirates.

A study by Ausra, a solar energy company based in California, indicates that more than 90% of fossil fuel-generated electricity in the U.S. and the majority of U.S. oil usage for transportation could be eliminated using solar thermal power plants - and for less than it would cost to continue importing oil. The land requirement for the concentrating solar power plants would be roughly 15,000 square miles (the equivalent of 15% of the land area of Nevada). While this may sound like a large tract, CSP plants use less land per equivalent electrical output than large hydroelectric dams when flooded land is included, or than coal plants when factoring in land used for mining. Another study, published in Scientific American, proposes using CSP and PV plants to produce 69% of U.S. electricity and 35% of total U.S. energy, including transportation, by 2050.

parabolic solar reflector