An improved flux density distribution model for a flat heliostat (iHFLCAL) compared with HFLCAL

The simulation of the flux spot reflected by a flat heliostat is one of the fundamental problems in the central receiver system. In this paper, we propose an improved model based on Gaussian distribution assumption to more faithfully depict the flux density distribution on the receiver reflected by a flat heliostat, which is also the basis for study of the focusing heliostat. First, an imaginary flux density distribution is modeled by an elliptical Gaussian function in the image plane coordinate system. The relationship between the standard deviations of the Gaussian function and the heliostat length and width is revealed. Shading and blocking effects are carefully considered and addressed. Then, this distribution is mapped to the receiver plane through oblique parallel projection along the reflection direction of the heliostat based on the law of energy conservation and calculus. A state-of-the-art GPU-based ray tracing simulation method is adopted, and satisfactory consistency between the proposed model and the ray tracing result is found. The experiments and comparisons demonstrate that the proposed model is as efficient as but more accurate than the related Gaussian models. (C) 2019 Elsevier Ltd. All rights reserved.