Site Selection for Hillside Central Receiver Solar Thermal Plants

Problem: Despite the precedence of utilizing hillsides as sites for heliostat fields and the advantages of hillside heliostat fields with ground-level receivers (e.g. elimination of tower capital costs reduced capital and operations costs of high pressure pumps etc.) no tools exist for locating suitable sites. Technology: The purpose of this invention is to locate suitable sites in any terrain for central receiver solar thermal plants based on a simplified model of heliostat field efficiency. It is intended in particular to locate hillside sites for ground-level receivers such as described by the CSPonD concept (MIT Case 13251). The tool consists of designating candidate receiver locations on a grid layout of uniform spacing. At each iteration in which a receiver location is evaluated the heliostat field is sampled by selecting points within the extents of the heliostat field boundary using digital elevation data to determine position relative to the receiver from which the average annual efficiency is calculated for each location. Then the total field efficiency corresponding with each receiver location is approximated as the average of the efficiencies of the sampled locations. The field efficiency or ratio of radiation incident to the receiver to direct normal solar radiation is maximized as a result of factors including projection losses and interference between heliostats also known as cosine efficiency shading and blocking. By iteratively defining the receiver location and evaluating the corresponding site efficiency by sampling elevation data points from within the defined heliostat field boundary efficiency can be mapped as a function of the receiver location and optimal sites found.