Developments in the synthesis of flat plate solar selective absorber materials via sol–gel methods: A review

There is a great demand for low-cost and environmentally friendly techniques for synthesizing high quality solar selective absorber (SSA) coatings. Such coatings are capable of absorbing most of the incoming solar radiation (high absorptance) without losing much of the thermal energy through re-radiation from heated surface (low emittance). Sol–gel techniques are promising synthesis methods for these SSA coatings. The optical properties and durability of the SSA coating can be easily controlled by fine-tuning relevant design parameters such as heating temperature or precursor concentrations in the synthesis process. In light of this, there are many knowledge gaps that need to be filled in the context of technicalities regarding the sol–gel processes and the optical and morphological characteristics of these coatings. Comprehensive understanding of these characteristics is a vital component in the optimal design of SSA coatings and therefore, the aim of this paper is to identify these technical issues and review developments in the synthesis of flat-plate SSA materials produced by sol–gel methods.