Scalable-manufactured metal–insulator–metal based selective solar absorbers with excellent high-temperature insensitivity

Abstract

Solar absorbers, harvesting solar irradiance in the form of heat, are extensively applied in the solar hot water systems and concentrated solar thermal systems such as concentrated solar power plants, solar thermoelectric generators, and solar thermophotovoltaics. It is of great significance to incorporate spectrally selective solar absorbers into solar thermal systems, especially at high operational temperatures to depress the thermal loss due to the thermal re-emission of high-temperature solar absorbers. This work computationally and experimentally demonstrates a new spectrally selective solar absorber consisting of a multilayered stack made of silica/alumina/tungsten/alumina/tungsten based on metal–insulator–metal resonance structures and fabricated by the magnetron sputtering method, which are angular insensitive and polarization-independent. The relationship between solar conversion efficiency, cut-off wavelength, operational temperatures, and concentration factor is theoretically investigated. An overall absorptance of 88.1% at solar irradiance wavelength, a low emittance of 7.0% at infrared thermal wavelength, and a high solar-to-heat efficiency of 82.5% are identified. Additionally, it shows the annealed samples maintain an extremely high absorption in solar radiation regime over at least 800 °C and a high concentration factor of over 100. The SEM topography images of the absorbers after thermal annealing at various temperatures demonstrates that the surface blisters and cracks result in the thermal degradation of the absorbers due to the dissimilarity between thermal expansion coefficients of tungsten and silica. The high-temperature insensitivity of the multilayer metal–insulator–metal-based selective solar absorbers will shed light on an alternative novel photonic metamaterial structure that can be scalable-manufactured to improve the energy conversion efficiency of solar thermal engineering.