Comparative Study of Two Integrated Solar Collectors with Symmetric and Asymmetric CPC Reflectors Based on a Ray Trace Analysis

This paper presents a ray trace analysis in order to compare two integrated solar collectors. The first one is an ICS solar water heater based on symmetric CPC reflectors (ICS_SCPC), and the second one is an ICS solar water heater based on asymmetric reflectors (ICS_ACPC).

ICS_ACPC is a new model which is designed to improve the optical performances of an existing system by increasing the quantity of absorbed energy. ICS_AFCPC consists of an integrated collector storage (ICS) solar water heater combined with an asymmetric compound parabolic concentrator (CPC) with two concentrating stages. The upper part contains two symmetrical parabolic sections with focal axes tilted at ±48° from the vertical plane. The lower part is constituted of three involute reflectors. Its cylindrical storage tank covers the triangle formed by the three involute part centers, and its geometric concentration is about 1:34. This design has a strong connection with a previous study, where an ICS system was designed and tested (Helal et al. 2011a). In this study, the ICS solar water heater based on symmetric CPC reflectors (ICS_SCPC) was modeled, realized, and experimentally tested. It consisted also of two concentrator stages: the first one, which was common to both systems, and the second one was a parabolic reflector placed in the exit aperture of the first stage. In both systems, the absorber of cylindrical design has a total stored water volume V_ab = 100 l.

A ray-tracing model was developed via a code written on Matlab to simulate the reflection of the solar radiation on the CPC reflectors at different angles of incidence and compute the absorbed solar radiation distribution on the absorber surface. The obtained results, when compared with the experimented model, showed a significant improvement in optical efficiency and the distribution of the absorbed energy regarding the angle of incidence.