High-Temperature Solar Thermal Energy Conversion Enhanced by Spectrally-Selective Metafilm Absorber under Concentrated Solar Irradiation
Abstract
Concentrating solar power, particularly parabolic trough system with solar concentrations less than 50, requires spectrally selective solar absorbers that are thermally stable at high temperatures of 400°C above to achieve high efficiency. In this work, the solar-thermal energy conversion performance of a selective multilayer metafilm absorber with excellent thermal stability is characterized along with a black absorber for comparison by a lab-scale experimental setup that measures the steady-state absorber temperature under multiple solar concentrations. Heat transfer analysis is employed to elucidate different energy conversion modes and validate the solar-thermal experiment. The solar-thermal efficiency was measured to be 38% from the experiment and projected to be 86% without parasitic heat losses for the selective metafilm-on-Si absorber at the temperature of 336°C under 9.1 suns, in comparison with measured 30% and projected 55% efficiency for the black absorber at a lower temperature of 266°C under the same solar concentration. In addition, the metafilm absorber deposited on the flexible cost-effective stainless steel foil achieves the solar-thermal efficiency 57% at a steady-state temperature of 371°C under 10 suns during the lab-scale experiment with losses, while a highest efficiency of 83% was projected under the same conditions for practical solar thermal applications. The results here will facilitate the research and development of novel solar materials for high-efficiency solar thermal energy conversion.