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Large-scale solar plants ‘greening the grid’

Matthew Charles and Bill Sepmeier
Vail, CO, Colorado

When most people hear the words “solar power” they think of modules soaking up sun on a neighborhood roof, but modern technology has taken solar applications into increasingly powerful roles.

One of the most important advancements in solar technology today is “Concentrated Solar Power.” which uses the sun to generate massive amounts of power for commercial power plants. This is done by using mirrors to concentrate solar thermal energy onto a central focal point to run conventional steam turbines that otherwise would have to use coal and natural gas. This clean method of power production is responsible for a widespread “greening of the grid.”

Concentrated solar power is being rapidly developed in Europe, Israel and the American southwest. Two companies are now building a 59 million-watt hybrid solar generation plant near Barstow, California. According to the builders, this plant employs the latest design of improved tried-and-true concentrated solar power technology using twin parabolic collectors (mirrors) with twin parabolic tubes as energy receivers and thermal energy storage for eight hours of off-peak or nighttime power generation. The plant is a hybrid, which means it also has conventional steam generators to provide reliable 24-hour electricity when cloudy days restrict solar energy production. Additionally, some 354 megawatts of concentrated solar power are produced in the Mojave Desert in California, a plant that has been in operation for the past decade.

Concentrated solar power can provide electricity to the grid well after the sun has set because the energy is stored in a liquid salt solution at 800 degrees Celsius.

According to Dr. Arnold Leitner, chief executive officer of Sky Fuel Inc. of Albuquerque, a firm that is planning a concentrated solar power facility in New Mexico, the total electrical energy needed by a family of four over several days can be stored in the equivalent of a five-gallon bucket of liquid salt solution at these temperatures.

During operation, the salts are heated by a transfer fluid that passes through the focal point of long lengths of large horizontal parabolic mirrors. The hot fluid directs energy to the storage medium where it is eventually extracted using heat exchangers that boil water into high-temperature, high-pressure steam. The steam spins conventional turbines and generators, thus creating electricity. It’s a solar hot water system on steroids.

Concentrated solar power is important because it can be a practical source of 24 hour-a-day energy. People have gotten used to having power available when they need it, so a constant source is vital. As more conventional power producers adopt concentrated solar as a primary or secondary energy source, dependence on the fossil fuels which presently provide nearly half of the electricity we use here in the west can be drastically reduced, along with carbon emissions.

The 59 megawatt plant under construction in Barstow will, when running in solar mode, produce power for 5,000 homes with no production of carbon greenhouse gasses. And 59 megawatts is a small facility in the conventional power production world where 1,000 and 2,000 megawatt plants are common. Since the sun delivers about 5 million watts of free energy per acre, it won’t take much desert land to deliver clean power to western US customers.

Concentrated solar power’s costs of production, apart from plant construction and operating costs, which are similar to fossil fuel fired plants, are low enough to make this technology viable today. The greening of the grid through concentrated solar power energy production, combined with individual home solar heat and electric systems, will play an important role in preserving our climate and lifestyles in the coming years. Encourage your local utility to consider adding concentrated solar power to its energy mix.

Bill Sepmeier is the chief technical officer and Matthew Charles is a design and sales specialist for Grid Feeders, a renewable energy firm in Eagle-Vail. For more information, call 688-4347, or go to http://www.gridfeeders.com.


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