Heliostat Size Optimization Regarding Component Cost and Yield

Abstract

At DLR, an innovative heliostat of low cost and high accuracy is being developed. Finding the optimal mirror size considering the specific costs (€/m²) and the field efficiencies, is an im-portant next step. In this study, three heliostats with mirror sizes of 2 m², 6.4 m², and 12.8 m² were designed. The sub-components were dimensioned and parts selected, so that the helio-stats can operate as required and withstand the maximum wind loads. Based on the final di-mensions and parts used, the cost of each heliostat could be estimated. Additionally, field effi-ciencies for nine exemplary solar tower systems using the three different heliostats were cal-culated. For each case the field layout was optimized and the effect of the mirror size on the energy yield analysed. Preliminary cost approximations reveal that the medium sized heliostat has the lowest specific cost. While the drives account for large proportion of the specific costs for the smallest heliostat, the steel structures make up an increasing proportion for the larger sizes. Higher efficiencies were observed for fields with smaller heliostats, especially for small plants and high concentrations. However, the optimal heliostat size decreases only slightly in these cases. For large plants and medium concentrations, the size has a negligible effect on efficiency.