Sandia National Laboratories

Solar Thermal Technology at Sandia

Sandia's Work in Solar Thermal Technology
Sandia National Laboratories works with users and manufacturers of solar thermal electric systems to increase acceptance of the technologies as cost-competitive candidates for power generation and to further their commercialization. Sandia’s work focuses on evaluating and improving solar thermal systems and providing design assistance. SNL works with industry, organizations and government agencies and it makes the results available through workshops, publications, seminars and private communications.

Sandia operates the Solar Thermal Design Assistance Center as part of its overall program in renewable energy. The center specializes in evaluating solar thermal systems for given applications, and provides technical assistance in the design and installation of solar thermal systems. The center can often predict the performance of different components in a solar thermal system, and it can estimate how well an entire system might operate. In order to stay current on trends in the solar thermal industry, the center’s staff frequently visits operating solar thermal systems throughout the United States. The center is often asked to serve as a technical resource for state and federal agencies and for the military in developing energy and energy-related programs.

Examples of recent projects include:

Testing and validation of a solar oven large enough for a village's needs;

Testing of a solar-powered refrigerator/ice maker that can be used in rural health-care facilities and fishing villages;

Teaming with a consortium of nine utilities led by Southern California Edison, industry, and the DOE in the construction of Solar Two, which will be the world's most advanced central receiver solar thermal power plant. The project, a $48 million, five-year retrofit of the 10-megawatt Solar One Pilot Plant near Barstow, Calif., will use molten salt to transport heat. The facility should begin operating in 1995 and is expected to lead to the first 100-megawatt commercial solar power tower plant by the end of the decade;

Targeting worldwide remote power markets in a four-year, $14 million joint venture program with Cummins Engine Company. The work is expected to lead to commercially available seven-kilowatt systems within two to three years.

Another big component of Sandia's efforts in renewable energies is the National Solar Thermal Test Facility, which Sandia operates for the U.S. Department of Energy. The facility’s central feature is the 200-foot "Power Tower," which is surrounded by 220 heliostats on eight acres. The heliostats focus sunlight on the tower, producing temperatures of more than 500 degrees centigrade. The test facility is used for numerous tests that require intense heat or the ability to direct high heat onto a small target. Examples include testing the effects of heat on materials or components used in a nuclear power plant, and the simulation of the aerodynamic heating that occurs when a missile travels through the atmosphere.

Fundamentals
Solar thermal power systems convert sunlight to heat, which is then used to generate electricity. The systems use mirrored surfaces to concentrate the sun’s energy to create the heat, which is then used to heat water, generate steam or power an engine that generates electricity. Three types of collector systems are used, each incorporating tracking mirrors to reflect and concentrate sunlight onto a receiver where it is converted to high temperature thermal energy.

Trough systems use parabolic reflectors in a trough configuration and are the most mature solar thermal technology. Troughs concentrate the sun up to 100 times onto a fluid-filled receiver tube positioned along the line of focus in the trough. Temperatures up to 400 degrees centigrade can be produced and used as heat or to generate electricity.

Power tower, or central receiver systems, use heliostats (highly reflective mirrors) that track the sun and reflect it to a central receiver atop a tower. The sun heats a fluid in the receiver typically to temperatures up to 650 degrees centigrade. The heated fluid is converted to steam that drives a turbine to produce electric power.

Dish systems use parabolic reflectors in the shape of a dish to focus the sun’s rays onto a receiver mounted above the dish at its focal point. The solar energy heats a fluid powering a small engine/generator mounted at the focal point. The systems operate at about 800 degrees centigrade and can generate up to 50 kilowatts of electric power.

Applications
Solar thermal systems are used to produce electricity, steam, hot water, or heat. Hot water for institutions, industrial processes, and refrigeration are areas where solar thermal systems can make sense economically and practically.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy.

Media Contact
Chris Miller
cmiller@sandia.gov

Last modified: August 6, 1997

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