Optical and Thermal Analysis of a Parabolic Trough Solar Collector through Coupling MCRT and FVM Techniques

Abstract

Concentrating solar power (CSP) technologies are one of the most promising renewable energy sources for clean electricity generation. The parabolic trough is the proven technology for power generation of all the CSP technologies available up to now. The optical performance of typical Parabolic Trough Collector (PTC) is strongly related to the heat flux distribution around the absorber tube. In order to maximize energy collection the PTC tracks the sun from sun rise to sunset. Therefore, during a day, the incidence angle varies, with maximum values at sunrise and sunset and a minimum of 0° at solar noon for East-West oriented parabolic trough collectors. Subsequently the heat transfer fluid temperature in a cross section of the absorber will not be uniform due to the flux distribution. The present study is focused on the effect of incidence angle on the performance of the PTC taking into account the non-uniformity of solar flux. Firstly, a 3D optical model based on the Monte Carlo Ray Tracing method (MCRT) written in MATLAB software has been developed and validated with previous published studies. This model is then used to determine the circumferential flux distribution around the absorber tube and the resulting optical efficiency of the PTC. The developed model has been applied to analyze the LS2 collector of Solar Thermal Electric Generation Systems (SEGS). In the second part, the results of the MCRT code has been coupled with FVM method using ANSYS software to analyze the heat flux distribution on the absorber tube. This technique allows understanding the thermal performance of the PTC under nonuniform solar flux. A detailed information can be obtained when coupling the MCRT and FVM methods, particularly the 3D solar ray's distribution around the absorber tube. Such a coupling technique is very helpful for analyzing both the optical and thermal performance of the PTC and therefore, provides a comprehensive study including optical efficiency, thermal efficiency and heat losses.