Automatic determination of heliostat orientation using an auxiliary mirror

Abstract

In this paper a new method is presented which can be used to determine the heliostat orientation and improve the tracking accuracy in solar thermal power towers during operation. A small mirror attached to every heliostat, the auxiliary mirror, reflects the sunlight onto the target. The resulting spot is used to determine the orientation of the heliostat, which can be used to adjust the heliostat orientation with respect to the assigned aim point. Tracking accuracy of the heliostats can be improved by applying a correction based on the determined orientation. In the study presented the applied method is described and analyzed in detail. Furthermore, restrictions of the method are discussed. Simulations and a short test performed to evaluate the accuracy are presented.