Sputter Deposited Nanostructured Coatings as Solar Selective Absorbers

Renewable energy is in critical need throughout the world. The use of solar energy therefore represents one of the most important ways for seeking green, renewable energy. The use of solar energy is either through a solar photovoltaic or thermal system. In this chapter, we present and discuss a key component in the solar thermal system, namely Solar Selective Absorber Coatings. Solar selective absorber coatings play an important role in not only absorbing the sunlight but also conserving the thermal energy. To meet this purpose, an ideal solar selective absorber is required to exhibit high solar absorptance (α) in the solar spectrum range and low thermal emittance (e) in the infrared (IR) range. Moreover, the increasing demand for pumping up the conversion efficiency pushes the working temperatures higher than before; thus, high temperature stability of solar selective absorber is becoming a critical challenge. Herein, we will first introduce solar thermal system and the optical properties of solar selective absorber coatings. This is followed by the categorization of the solar selective absorber coatings, including conventional and state-of-the-art materials. Finally, we report high temperature (≥ 650°C) absorber coatings.