Heliostat surface deformation and encoding under gravity and wind loads for optical performance analysis

In solar power tower systems (SPT), the heliostats will be deformed by external loads such as gravity and wind, significantly influencing the radiative flux density distribution (RFDD) on the receiver. In this paper, an optical performance of deformed heliostat caused by these external loads is analyzed comprehensively and in detail. First, finite element analysis is performed to compute heliostat deformation under external loads. Then the deformed heliostat surface is compactly represented using surface encoding method. Finally, the compact representation of deformed heliostat surface is adopted as input for Monte Carlo ray tracing simulation to obtain the high-fidelity RFDD. The detailed simulations, validation and, analysis show that under wind conditions of 20 m/s, the slope error of heliostat can reach up to 2.97 mrad, leading to a 310.7% increase in the flux spot size compared to gravity-only conditions. Furthermore, the results reveal that among various surface encoding methods, the Gaussian mixture model is the most feasible surface encoding method for RFDD simulations of both single heliostat and heliostat fields. The proposed work provided a comprehensive approach for analyzing the effects of gravity and wind on heliostat surface deformation and RFDD, offering potentials for optimizing heliostat design and enhancing SPT performance.