GPU-based Monte Carlo ray tracing simulation considering refraction for central receiver system

The heliostat in the central receiver system usually adopts silvered-glass reflectors, where a glass layer covers a specular reflection layer. Previous flux density distribution simulation methods ignored the refraction effects caused by the glass layer. This paper proposes a more accurate Monte Carlo ray-tracing simulation method considering refraction and total internal reflection (TIR) effects caused by the ray transmission in the glass layer. The proposed simulation method is fully designed and implemented on a graphics processing unit (GPU), which enables the algorithm performance to remain effective even when the simulation is more consistent with the real situation. Experiments and simulations reveal that refraction has non-negligible effects on the simulation results. Compared with the classical Monte Carlo ray-tracing simulation method that only considers the ray's reflection, refraction reduces the maximum radiative flux and total energy by up to 80% and 50%, respectively. Refraction also causes the flux spot reflected on the receiver panel to spread greatly. In several extreme cases, the ray is trapped in the glass due to TIR.