Performance evaluation of a linear Fresnel collector with catoptric subsets

Abstract

In this paper, the optical, thermal and overall performance of a linear Fresnel collector with catoptric subsets is reported. Subsets consist of mirrors which focus on the receiver while they maintain their relative positions with respect to each other. Ray tracing modelling is used for the estimation of the optical performance of the collector. A thermal analysis is performed in order to assess the thermal and the overall efficiency of the collector. A comparison is attempted between the specific collector and a more typical one, which involves mirrors strips, uniformly distributed to the same land area. Two materials with different reflectivity values and optical errors, i.e. glass mirrors and aluminium sheets, are considered for the reflecting surface of the primary mirrors.Results indicate that the performance of the collector with the catoptric subsets is similar to that of the collector with the uniformly distributed mirrors for sun positions close to solar noon and lower for large sun inclinations. Each design gives its own temperature distribution on the receiver but similar thermal performance. However, the catoptric-subset design provides a robust configuration which requires a lower number of rotating parts; therefore, it deserves further techno-economic analysis, to better evaluate its potential.