Investigation of concentrated solar collector with discretized flat mirrors in parabolic arrangement

Abstract

Parabolic Trough Concentrators (PTC) and Linear Fresnel Concentrators (LFC) are widely used for solar thermal applications. LFC's were developed as an alternative to counter the high manufacturing cost of parabolic collectors. The manufacturing cost of LFC is lower but it either reduces the output power or is larger in size. A hybrid collector combining the beneficial features of both PTC and LFC, which is compact and efficient, is proposed in this paper. Discrete Linear Fresnel plates are pivoted with their midpoints lying on a parabola and the performance is compared with LFC and PTC. A mathematical model is developed to calculate the projected area of the hybrid solar collector. The optical performance is estimated, considering the shading, blocking, cosine effect and end loss of the mirrors and is compared with a similar sized PTC and LFC. The optical performance at 8 a.m. for a hybrid collector is 58% of a similar sized PTC. The optical performance ratio increases with time, reaching a maximum of 93% at noon and decreases thereafter reaching 58% by 4 p.m. The comparison with LFC shows that the hybrid collector performs better than LFC by 5% between 10 a.m. and 2p.m and only 2% when averaged over the day. This has been found to increase to about 3.5% with modifications in hybrid collector design. The results were also calculated by solar ray tracing using SolTrace and were found to be in good agreement with the proposed model.