Comparative Study of a Fixed-Focus Fresnel Lens Solar Concentrator/Conical Cavity Receiver System with and without Glass Cover Installed in a Solar Cooker

Abstract

The glass cover is often situated at the aperture of a cavity receiver in concentrating collectors to reduce heat dissipation. However, the decrease in optical efficiency due to the reflection loss on the surface of the glass cover will directly reduce the thermal efficiency of a collector, especially for a fixed-focus solar concentrator, whose optical axis is generally not coincident with the central axis of the receiver. To fundamentally evaluate the effect of a glass cover on the efficiency of a fixed-focus Fresnel lens solar concentrator/conical cavity receiver system, its performances with and without a glass cover considered under different incidence angles were comparatively investigated. To obtain the optical performance, optical models of the system were first built with TracePro® 7.0 software. An experimental setup was then constructed to test the thermal performance of the system. The results show that the optical efficiency of a system without a glass cover is much higher than that with a glass cover. The difference between them remains unchanged for incidence angle at a range of 0–20°. The time constant of the system with a glass cover is much less than that without a glass cover, in the ranges of 29–33 s and 48–59 s, respectively. The system with a glass cover for a wide range of higher temperature differences also has better thermal efficiency.