Sandia National Laboratories, a contractor for the U.S. Department of Energy’s National Nuclear Security Administration (NNSA), has designed a set of efficient solar power receivers using 3D printing.
Multiple complex prototype designs for receivers, which receive solar energy and feed it into an electricity generator, were produced using powder bed fusion 3D printing of a high temperature nickel alloy.
The receivers have been produced as part of a project for the Solar Energy Research Institute for India and the United States (SERIIUS), a government-sponsored collaboration between the Indian Institute of Science and the US National Renewable Energy Laboratory.
One of the project’s aims is to develop cost-effective solar power facilities capable of generating one megawatt or less for Indian villages, and to replace the polluting diesel generators that many of the villages still use.
Addressing inefficiency and scalability
Conventional commercially available solar power receivers consist of flat panel of tubes or tubes arranged in a cylinder. While these designs can absorb between 80 and 90 percent of the concentrated sunlight directed at them, this is still neither cost effective enough nor scalable enough for the desired applications.
One option to address this problem is to apply special coatings, containing nano-crystals, to improve efficiency of energy absorption. These coatings may, however, be damaged over time and are expensive to maintain.
Cliff Ho, a Sandia engineer working on the project, explained that “on a flat receiver design, five percent or more of the concentrated sunlight reflects away.” Sandia’s engineers instead designed, produced and perfected a set fractal-like receiver designs.
“We configured the panels of tubes in a radial or louvered pattern that traps the light at different scales,” Ho explained. “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.”
From small scale prototypes to working models
To find the most effective and cost-efficient design, the Sandia team 3D printed a set of prototype designs for tests, using powder bed fusion technology. The material used for the eventual bladed design was a nickel alloy called Iconel 718, ideal for withstanding the high temperatures of solar energy conduction.
3D printing the prototypes, according to Ho, “enabled us to generate complex geometries for the receiver tubes in a small-scale prototype.” According to the Sandia engineer, these geometries would not have been possible to configure using “extrusion, casting or welding.”
Each set of receivers was tested at National Solar Thermal Testing Facility, where mirror-like heliostats are aimed at a tall building with the receiver at the top. The receivers absorb the sunlight’s heat, and transfer them to the fluids inside. Fluids tested include molten salts, steam, air, carbon dioxide and helium.
Sandia’s specific test involves combining receivers with with supercritical carbon dioxide Brayton cycles, a turbine generator system powered by pressurized “semi-liquid” carbon dioxide that is heated above its normal critical temperature and pressure.
Sandia National Laboratories was also the testbed for Laser Engineering Net Shaping (LENS) technology. Optomec, known for 3D printing smartphones, began to apply LENS technology to additive manufacturing after former Sandia scientist David Keicher joined the company in 1997.
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Featured image shows Sandia intern Jesus Ortega inspecting one of the new bladed receivers. Photo via Sandia/Randy Montoya.