A New-Mexico-based company has developed receivers for small- to medium-scale use that are as much as 20% better at absorbing light than current technology
Concentrating solar power (CSP) plants, using massive arrays of mirrors (heliostats) to reflect sunlight onto receivers, are in most cases large facilities built across desert landscapes. Now, engineers from Sandia National Laboratories have figured out how to downsize such facilities, by designing a new receiver that can absorb greater amounts of sunlight than todayâ€™s technology.
Traditional receiver panels are made up of tubes arranged in flat panels or cylinders, but can absorb only 80-90% of light directed towards them. To boost receiver efficiency, the engineers came up with a fractal shape to capture more of the incoming sunlight (previous research has just focused on special coatings applied to the receiver). â€œWhen light is reflected off a flat surface, itâ€™s goneâ€, says Cliff Ho, a mechanical engineer at Sandia. â€œOn a flat receiver design, 5% or more of the concentrated sunlight reflects away. So we configured the panels of tubes in a radial or louvered pattern that traps the light at different scales. We wanted the light to reflect, and then reflect again toward the interior of the receiver and get absorbed, sort of like the walls of a sound-proof room.â€
The receivers, 3D-printed with a high-temperature nickel alloy named Iconel 718, were tested at the National Solar Thermal Test Facility (NSTTF), the only test facility of this type in the US. 3D printing allowed the team to test several fractal designs in an economical manner this way, finding those that work best for each application. According to Ho, it would have been difficult to create the complex geometries with casting, welding, or extrusion.
The receivers were designed and studied as part of a laboratory-directed Reseach and Development project and have also been included to the Solar Energy Research Institute for India and the United States (SERIIUS) project. SERIIUS is a five-year project co-led by the governments of the two countries that focuses on cost-effective solar power technology by addressing the barriers and challenges of each market. Sandia has led the groupâ€™s research in concentrating solar power, with an emphasis in scalable systems.
Source: Sandia Labs