Grant Awarded for Advanced Solar Technology

Weight is everything when it comes to sending something into space. In fact, at a cost of US$50,000 per kilogram, it’s no wonder that NASA has taken great interest in the solar power advances that Texas-based Entech has achieved.

Keller, Texas – October 17, 2002 [SolarAccess.com] Using an advanced system of concentrating lenses, coupled with high-efficiency solar cells, Entech has achieved unprecedented efficiency with their solar arrays while dramatically cutting down overall weight, according to the company. Both are major prerequisites for NASA’s solar needs. For their successes, Entech was recently awarded a US$195,000 contract sponsored jointly by the National Science Foundation (NSF), NASA, and the Electric Power Research Institute (EPRI), to investigate advanced technologies for future space solar power applications. According to Mark O’Neill, Entech’s president, the contract will go toward improving their solar arrays, which achieved their success by magnifying available light through lenses onto high-efficiency PV cells. Thanks to the magnification of the lenses, less PV is needed to generate a comparable amount of power. “The cells we use are triple-junction solar cells, made by Spectrolab and Emcore, with measured cell efficiencies above 30 percent for space sunlight under our lens concentration,” O’Neil said. “Our lenses are over 90 percent efficient in capturing and focusing sunlight onto the solar cells, resulting in an overall lens/cell efficiency of more than 27 percent.” The lenses, known as Fresnel lenses, are made of thousands of tiny prisms within a 1/6000 inch sheet that magnify the available light nine times onto the cell surfaces. The lenses are much lighter and cheaper to manufacture than the solar cells said O’Neill. The solar cells achieve their uncommon efficiency by capturing more of the light spectrum than traditional PV. While most PV captures the middle of the light spectrum, mostly visible light, the triple-junction cells that Entech incorporates are able to use the low and high ends of the light spectrum as well, O’Neill said. This technology has been successfully tested in outer space on a NASA missions. Entech made the 720 lenses used on the award-winning solar array on NASA’s Deep Space One spacecraft, launched in October 1998. With the solar arrays performing flawlessly, Deep Space One visited the Asteroid Braille in July 1999, and the Comet Borrelly in September 2001. The grant will go toward a next generation of Entech PV systems that are even better then those today and dramatically better than those that powered Deep Space One. Those first generation PV systems were putting out 45 watts-per-kilogram. Entech’s most current arrays are already generating 180 watts-per-kilogram, and O’Neil expects that to be greatly surpassed within couple years. “With this new contract we’ll be looking for a similar leap ahead,” O’Neil said. This technology is still far from the mainstream terrestrial market but will probably make inroads within the next five to 10 years said O’Neil. “Just like in space, efficiency rules at the end of the day,” O’Neil said. “It won’t happen overnight, but eventually the terrestrial market will be much bigger.”