Application of On-Axis General Sun-Tracking Formula in Open-Loop Sun-Tracking System for Achieving Tracking Accuracy of below 1 mrad

Abstract

A novel on-axis general sun-tracking formula has been derived and integrated into an open-loop azimuth-elevation sun-tracking system for improving the tracking accuracy. The installation defect of a 25 m2 solar concentrator prototype has induced significant sun-tracking errors, range from 12.12 to 17.54 mrad. With the use of CCD camera for recording the solar image, three misaligned angles from ideal azimuth-elevation axes have been determined and corrected by changing of the general formula parameters’ values to better the tracking accuracy to 2.99 mrad, which reach the encoder resolution limit of 4.13 mrad. Further fine-tuning has been made to attain the tracking accuracy up to 0.96 mrad, by including the motor step count, 1.64 × 10–4°/step, which is beyond the encoder resolution. The general formula has been demonstrated to be capable of achieving reasonably high tracking accuracy cost effectively without complicated sun-tracking solutions.