Optical and thermal performance of double receiver compound parabolic concentrator

Conventional solar compound parabolic concentrators are normally fitted with one tubular receiver positioned along the axis of the two parabolas. This work investigates the potential of using either two tubular receivers in one compound parabolic concentrator or an elliptical single receiver. Using advanced ray tracing technique, the optical efficiency of a compound parabolic concentrator with two tubular receivers aligned horizontally and vertically was predicted. Results showed that the horizontal configuration outperforms both the single and the vertical configurations by up to 15%. Also, a horizontally aligned elliptical single tube showed an increase in the average daily optical efficiency by 17% compared to the single tube configuration. The thermal performance of the single and double horizontally aligned tubular receivers was determined using a thermosyphon heat pipe experimentally tested utilising the heat flux obtained from the optical simulation at different acceptance angles. Results show that double tube configuration thermally outperforms the single one in terms of heat transferred to the cooling water by 21%, 19.8% and 18.3% for acceptance angles of 30°, 40° and 60° respectively. This work highlights the potential of using either two tubular receivers or single elliptical one aligned horizontally in one concentrator to improve the optical and thermal efficiencies of compound parabolic collectors.