Thermal performance analysis of a line-focus Fresnel lens solar collector using different cavity receivers

In this paper, a line-focus Fresnel lens solar collector using different cavity receivers are studied and compared. Thermal performance of the line-focus Fresnel lens solar collector with each cavity receiver is studied experimentally at different temperature levels. The efficiency factors and heat removal factors of Fresnel lens solar collectors using different kinds of line-focus cavity receivers are obtained both theoretically and experimentally. Eight kinds of cavity receivers, namely: triangular, arc-shaped, rectangular, semicircular, positive trapezoidal, reverse trapezoidal, hetero trapezoidal and convex, are tested and analyzed. It is found that the theoretical results agree well with the test results. For the line-focus Fresnel lens solar collector, the triangular cavity receiver shows the best thermal performance. The highest experimental heat removal factor is about 0.805 when the operation temperature is 180 °C. Results show that under given operation conditions, the optimum width of cavity aperture, the optimum inside diameter of the receiver tube and the optimum vertex angle of the cross section of the receiver are 50 mm, 18 mm and 60°, respectively. It is recommended that the geometrical concentration ratio of the studied Fresnel lens solar collector should be more than 55. The experimental heat removal factors for triangular cavity receivers are increased to 0.879 (using rectangular pipelines as the absorber plate) and 0.873 (using tube bundles as the absorber plate) respectively, after optimization.

► We studied a line-focus Fresnel lens solar collector using different cavity receivers.
► The collector heat removal factors are derived to find out the optimal cavity shape.
► Theoretical and experimental analysis shows that the triangular cavity receiver is better.