Design of self-calibrating controllers for heliostats in a solar power plant

A self-calibrating controller is developed for reducing installation and drive errors in a heliostat (steerable mirror used in solar/electric energy conversion). In this scheme, the heliostat periodically tracks the sun, which serves as a precision position reference. The difference between commanded and actual drive angles is used to estimate the coefficients of a model representing installation and drive errors. The calibrated model is then used to correct the drive actuator commands for these error sources when the heliostat is in a tracking mode (its principle mode of operation). Simulation results are given for a typical heliostat configuration with realistic errors. The algorithm is very effective in reducing beam steering errors. The concept is demonstrated using a prototype test apparatus and is shown to achieve an error reduction of more than 5:1.