Sandia National Laboratories engineers designed the receivers as part of a Laboratory Directed Research & Development (LDRD) program backed by the US government. The findings are being applied to Sandia’s work for SERIIUS, the joint Solar Energy Research Institute for India and the United States. While most concentrating solar power facilities throughout the world are large, India is interested in developing 1MW or smaller facilities to provide power for small villages and communities. Improving the efficiency of these smaller receiver designs is a key step toward making that goal a reality.
Sandia engineers developed and tested the new receivers at the National Solar Thermal Testing Facility in Albuquerque, New Mexico. They studied the receivers’ ability to withstand high temperatures and pressures while absorbing sunlight as heat that can be stored or transferred to a power cycle to generate electricity. Some previous attempts at improving the efficiency of solar receivers has focused on special coatings that are applied to the receiver. According to Sandia, many of these coatings are susceptible to breaking down over time, which reduces the ability of the receiver to absorb sunlight and the potential lifetime of the solar receiver itself while increasing costs due to reapplication and repair. Sandia says its new fractal-like receiver designs have increased solar absorption efficiency without the need for special coatings.
The Sandia team has pioneered the use of a 3D printing technique called powder-bed fusion to print their small-scale receiver designs from Iconel 718, a high-temperature nickel alloy. For the high-temperature testing, they used both Inconel 718 and alumina. However, the alumina is white and not conducive to solar receivers unless it is painted or coated, said Sandia engineer Cliff Ho.
Their claim of a 20% improvement was based on the increase in effective solar absorptance over the intrinsic material solar absorptance due to the novel geometric features that allowed light to be reflected toward other absorbing surfaces of the receiver, Ho said. ‘The 3D printing allowed us to generate these complex geometries,’ he said. ‘For the small prototypes that we constructed, we did not compare the cost with other traditional methods, which would have required extrusion, machining, and welding, but the cost of printing the one-of-a-kind prototypes was pretty expensive. We anticipate that for larger-scale, higher production components, the cost savings could be significant.’
Sandia sees 3D printing playing a role in not only solar thermal receivers, Ho said, ‘but other CSP components as well, including heliostat structures, heat exchangers, headers, valves, turbomachinery, and other components with complex features or geometries.’