Concentrating efficiency loss of heliostat with multiple sub-mirrors under wind loads

As an important design load for heliostat, wind load crucially affects the safety and concentrating performance. Herein, an evaluation method is proposed to study the impacts of wind loads on concentrating efficiency loss of the heliostat with multiple sub-mirrors. In particular, the computation method and evaluation index of the concentrating efficiency are established for the heliostat. Moreover, the finite element model of an on-site heliostat with multiple sub-mirrors is developed and the wind-induced responses of the heliostat are analyzed. Subsequently, the concentrating efficiency loss is investigated in detail when subjected to varying pitch angles and wind directions. Results show that the wind loads may induce the heliostat vibration to significantly decrease its concentrating efficiency. The imposition of wind loads makes the average concentrating efficiency decrease from 95.5% to 72.2%. The mean concentrating efficiency decreases with decreasing pitch angle, particularly at the sub-mirror edge. Furthermore, it is found that the increase of the wind direction angle enhances the concentrating efficiency loss of the heliostat when the pitch angle is small, while the influence is insignificant if the pitch angle is large. This work may provide theoretical guidance for evaluation and optimization of the concentrating efficiency loss of heliostat.