Context and motivations
Solar thermal technologies rely on the collection of the solar radiation to generate heat (by heating a fluid) that can be used for domestic, residential and industrial purposes. If solar irradiance is concentrated using mirrors, this heat can in turn be used to produce electricity via a turbine. These technologies call for optically efficient components with complex and sometimes conflicting optical behaviors. In particular, the solar receiver should be highly absorbing in the solar range (0.28 – 4 µm) to harvest as much solar radiation as possible, but also lowly emissive in the infrared range (1 – 50 µm) to limit radiative thermal losses. This spectral selectivity can be achieved using multilayered coating architectures, associating lowly emissive (e.g. metals) and highly absorptive materials (e.g. dielectric/ metal/dielectric multilayers or metal-ceramic composites), that need to be optically designed and optimized in terms of layer thicknesses and compositions, to guarantee their high optical performance.
A judicious preselection of materials is also paramount, as the solar receivers should also be resistant to harsh operating conditions such as high temperatures, high solar irradiation, oxidant and erosive atmospheres and high thermomechanical stress for long durations, while remaining optically efficient.