Impact of the variation of the receiver glass envelope transmittance as a function of the incidence angle in the performance of a linear Fresnel collector

Abstract

In this paper, we focus on the variation of the transmittance of the receiver glass envelope as a function of the incidence angle and we measure its impact on the annual optical efficiency of a LFR plant using ray-tracing techniques. For this purpose, we draw up a detailed model of the LFR collector installed on the roof of the School of Engineering of the University of Seville, Spain. We also calculate the optical efficiency with and without a secondary reflector and with constant or variable transmittance receiver glass envelope properties. We run simulations using a clear-sky annual 1-min synthetic data set as input and calculate an average annual optical efficiency using efficiency matrices and Incidence Angle Modifiers (IAM) obtained from ray-tracing simulations. We find that the effect of the variation of the receiver glass envelope optical properties, as a function of the incidence angle, reduces the annual optical efficiency by 2.5%when the LFR plant has a basic secondary reflector and by 0.7% when there is no secondary reflector, according to the results obtained when using constant optical properties. We also evaluate the performance of the system with an optimised secondary reflector design.