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NREL Researchers Test Solar Thermal Technology

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Golden, Colo., September 23, 1997 -- Motorists who look north while driving on Interstate 70 may notice a large, alien-looking device on the mesa-top above the main research facilities of the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL). The 40-foot high, mirror-laden machine actually is a heliostat, a down-to-earth way of converting the sun's heat into electricity.

Researchers at the lab are testing the prototype heliostat developed by Science Applications International Corporation's (SAIC) Golden office under DOE's Solar Manufacturing Technology (SolMaT) initiative. The heliostat at NREL's mesa-top facility will help researchers learn more about installation of the equipment and its control system.

The SAIC effort incorporates a number of design and manufacturing modifications that could make the heliostat less costly and make power tower systems cost competitive with conventional sources of electricity. Power towers, a type of solar thermal power plant, use a field of heliostats to focus sunlight onto a fluid-filled receiver mounted on a tower. The fluid, heated to temperatures greater than 1000 degrees Fahrenheit, is used to create steam for driving a turbine to produce electricity.

SAIC says improvements in the heliostat include: A larger reflective area. The mirror now measures 1831 square feet. And a lower-cost mirror design, in which thin glass mirror tiles are adhered to a membrane of stretched stainless steel. The test heliostat has 22 sets of mirrors, each measuring 10 feet in diameter.

The SolMaT program helps manufacturers cut the costs of solar thermal hardware and paves the way for earlier use of the technology. As much as 60 percent of the cost of solar thermal power plants results from the field of heliostats.


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