Development and evaluation of several models for precise and fast calculations of shading and blocking in heliostats field

We propose an accurate method to calculate the shading and blocking of a heliostat from the integration of an analytical function, then we demonstrate the calculation from solar central ray tracing to the discrete area is also an accurate method. Present codes apply the approximate projection method to obtain the blocking and shading factor. We propose a new method to precisely calculate the projection positions of neighbors on the analyzed heliostat through the actual focus ray, and develop two methods to calculate the blocking and shading from the actual projections of heliostat's single vertex and four vertices (quadrilateral model). We apply the solar central ray tracing method to evaluate modified Helios and Lipps models, as well as single vertex and quadrilateral models. The results show that the single vertex and quadrilateral models with actual focus ray projection have better precision and less computation time than modified Helios or Lipps model in PS10 heliostat field. The average absolute error is <0.05%, 0.1-0.2%, 0.2-0.5% and 0.5-1.2% respectively for quadrilateral, single vertex, modified Helios and Lipps models in calculating the shading and blocking factor of the PS10 field at a moment. (C) 2013 Elsevier Ltd. All rights reserved.