SkyFuel’s Parabolic Trough Shines in NREL Tests

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NREL confirm that SkyFuel’s parabolic trough solar concentrator meets the highest standard for efficiency in its class.

Tests conducted by scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) confirm that SkyFuel’s parabolic trough solar concentrator meets the highest standard for efficiency in its class. Utility scale parabolic trough solar concentrators harness the sun’s energy to make steam for electricity generation. Patterned after the best of previous, time proven designs, the SkyTrough® is a breakthrough in cost and constructability resulting from significant design and material innovations. The SkyTrough® is the first utility scale solar concentrator to employ lightweight ReflecTech® Mirror Film, developed collaboratively by SkyFuel and NREL, in place of the fragile glass mirrors traditionally used.

A view along the focal line of the SkyTrough® parabolic solar collector at Solar Energy Generating Station II in Daggett, California: the receiver is glowing with concentrated sunlight.

Thermal efficiency is the proportion of available sunlight that is converted into heat and available to generate electricity in the power block. It is used to predict the performance of a given parabolic trough and compare competing technologies. NREL tests show the SkyTrough’s thermal efficiency at 350 °C (662 °F) to be over 73%, meaning that nearly three quarters of the solar radiation striking the trough surface is converted into thermal energy. NREL’s results confirm that the SkyTrough® delivers performance comparable to or exceeding that of the previous, proven, utility‐grade trough systems at a cost that is well below industry standards. “A lot of thoughtful engineering went into the SkyTrough® so we were confident our efficiency would be high, but NREL’s confirmation really validates our technology. We couldn’t be more pleased with NREL’s assessment”, said Randy Gee, SkyFuel’s Chief Technology Officer.

NREL scientists combine the results of two tests to establish a collector’s thermal efficiency.

Performance of the optical elements of the SkyTrough was measured at the Optical Efficiency Test Loop in Golden, Colorado. The test facility design allows study of the optical performance independent of the receiver’s heat loss characteristics. Optical efficiency is a direct gauge of the design elements that set the SkyTrough® apart ‐ mirror reflectance, parabolic accuracy, receiver alignment to the focal line of the trough, and the system’s tracking precision. “The SkyTrough solar collector is a new, low‐weight design that takes advantage of the patented reflector film jointly developed by SkyFuel and NREL,” said Chuck Kutscher, Principal Engineer and Manager of NREL’s Thermal Systems Group.” Helping industry achieve higher efficiencies and lower costs is central to the mission of our Concentrating Solar Power (CSP) research program.”

In a separate test at NREL’s Parabolic Trough Receiver Heat Loss Test Stand, scientists measured the heat loss from the SkyTrough’s SCHOTT PTR80 receiver. This is crucial because, no matter how well the SkyTrough’s optical elements perform, the overall ability of the system to deliver usable heat for power generation depends on how well the receiver retains the heat it collects. The new 8 cm diameter SCHOTT PTR80 performed well ‐ on par with SCHOTT’s 7 cm PTR70, the current industry standard for utility grade parabolic trough systems.

A white paper on thermal efficiency measurement is available for download at

SkyFuel, Inc. is a solar thermal power technology and service provider founded in 2007. SkyFuel’s advanced, glass‐free parabolic trough concentrators (the SkyTrough®) harness solar radiation to produce steam for electricity generation and industrial applications. It is the highest performance, lowest‐cost utility‐scale Concentrating Solar Power (CSP) system in the world. SkyFuel’s wholly owned subsidiary, ReflecTech, Inc., holds the exclusive license to manufacture and market ReflecTech® Mirror Film. SkyFuel is also developing next‐generation, high‐temperature parabolic trough and linear Fresnel systems.

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