A detailed study on the optical performance of parabolic trough solar collectors with Monte Carlo Ray Tracing method based on theoretical analysis

The optical performance of a parabolic trough solar collector (PTC) is studied comprehensively based on Monte Carlo Ray Tracing method (MCRT) and theoretical analysis. The MCRT models are established, and the theoretical equations of several critical parameters are derived firstly. And then the effects of different geometrical parameters on the optical performance are discussed in detail. It is revealed that the distribution of local concentration ratio around the absorber tube changes greatly, and cannot be divided into four parts as previous studies showed for some special parameter conditions. The theoretically derived parameters explain very well the different properties for the critical conditions. The variations of those parameters with different geometrical configurations are further displayed. Accordingly, the optical properties for different critical parameters are discussed. The size relationship between the reflected light cone and the absorber diameter affects the optical efficiency significantly because of the rays escaping effect. Practically, the absorber diameter should be larger than the size of the reflected light cone to avoid great optical loss caused by rays escaping. All the findings in this paper establish the foundation for further research on the optical-to-thermal energy conversion in the PTC system, and provide a reference for designing and optimizing PTC's structure.