High-Temperature Solar Selective Absorber Material Using Surface Microcavity Structures

The spectral properties of thermal radiation can be controlled by surface microstructures with feature size in the optical wavelength range. We applied this technology to solar selective absorbers for concentrated solar power (CSP) generation systems. We investigated the spectral properties and thermal stability of two-dimensional periodic microstructures on a tungsten (W) surface to develop solar selective absorbers for high-temperature applications. The developed absorbers exhibited good spectral selectivity and sufficient thermal stability under vacuum. Although we could verified that the microstructured solar selective absorbers improved CSP efficiency, this method cannot be put into practical use because of cost and time, and also because there is currently no technology for fabricating surface gratings on high melting point materials over a large area. Therefore, we used W–Cu alloys to investigate an approach to mass production of surface microcavity structures over a large area. We then confirmed that the absorptivity in the visible light range could be increased by using this simple method.