Solar-blind pyrometric temperature measurement under concentrated solar irradiation

Abstract

The surface temperature distribution of high temperature solar materials is a key parameter in concentrating solar thermal applications. As contact thermometry is often not appropriate in the presence of high-flux solar irradiation, pyrometric techniques can be adopted. However, depending on the optical properties of the sample, special measurement treatments are required to eliminate the bias in the pyrometric measurement resulting from the single and multiple surface reflections of incoming solar radiation. Several pyrometric methodologies for particular applications have been reported in literature. In this paper a more general approach to this technique and its adaptation for the use in high temperature solar receivers is presented. The measurement requirements including the necessity and type of a selective filter are obtained from the analysis of the spectral bi-directional reflectance and the operational range of temperature. According to these conditions a classification of materials encountered in solar receivers is given and adequate measurement methodologies are suggested for each type of receiver and temperature range.