For some innovations, such as calculators and computers, the key to success was in finding a way to make things smaller. The future of concentrated solar power, on the other hand, depends on making the product deliverable on a grand scale. A team of government and private sector scientists in Colorado has achieved a breakthrough, which they believe will launch the technology as a major provider of domestic power.
Scientists from the National Renewable Energy Laboratory (NREL) and the Arvada, Colo.-based SkyFuel, have developed a thin silver polymer film to substitute for bulkier glass mirrors on solar-collecting troughs. The massive curved sheets of metal have the potential to be 30 percent less expensive than today’s best collectors of concentrated solar power.
Concentrated solar technology has been around for more than 30 years. The parabolas distort the sun’s rays, concentrating the heat onto a tube filled with heat-transfer fluid, which carries the heat to boilers in a power station, which generates electricity. The original collectors were roughly the size of a typical rooftop solar panel, about 7 feet wide and 20 feet long. Lined up, six or more in a row, they were designed to collect the sun’s rays, with a motorized system turning the mirrors as the sun moved across the sky.
However, to be a cost-effective and marketable producer of utility-scale quantities of electrical power, the challenge was to find an alternative to glass, the primary material in the parabolas, which has been known to shatter under operating conditions, resulting in considerable cost. The replacement material needed to be cheaper, lighter and easier to install, but still durable in the hot sun.
Instead of glass, the glossy film developed by the Colorado scientists, known as ReflecTech Mirror Film, uses several layers of polymers, with an inner layer of pure silver. The collectors using the new materials, called SkyTrough, are longer than football fields and look like gigantic funhouse mirrors. They are constructed of a revolutionary rib-and-panel design that provides high optical accuracy and results in a mirrored surface for each parabolic trough module that is continuous from rim to rim. They also include a lightweight aluminum space frame that assembles quickly in the field and a helical drive and wireless controller for tracking the sun’s movement. In commercial use, the SkyTrough measures 375 feet long and 20 feet high. One SkyTrough can supply enough electricity for at least 50 homes.
A prototype SkyTrough is currently capturing the sun’s rays atop South Table Mountain overlooking NREL’s Golden, Colo., campus; a larger pilot system also has been installed at SkyFuel’s location a few miles north of NREL.