Development of high performances solar absorber coatings

Abstract

In order to improve the efficiency of a solar receiver, the operating temperature has to be increased, from 500°C in the 1st generation (direct steam generation solar receivers) to 700°C in the current generation (molten salt solar receivers) and up to more than 800°C in the next generation (higher temperature molten salt solar receivers). This very high operating temperature requires the employment of a solar absorber coating showing high optical performances and good stability at high temperature in order to guarantee the nominal solar receiver performances. The absorber coating currently used exhibits lower performances at such temperatures. For this reason, the development of a new absorber coating having the required high performances at high temperature is sought. The development of high performances (high solar absorbance and high lifetime) solar absorber coatings is one of the developments programs which CMI has been working on for several years in order to increase the performances and reliability of its Solar Receiver and to keep a leadership in the very competitive CSP market. The results of these developments are two new solar absorber coatings: the first one is a high performance “Silicon-based Black Paint”, which will provide high absorptance (97.2% vs 96.2% for current technology) with an increased efficiency of the solar receiver and an increased lifetime (3 years) and the second one is a patented “Plasma Sprayed Coating” that will provide good optical performances (similar absorptance and lower emissivity than current technology) with higher durability (>3 years) useful in the next generation of solar receivers.