Closed loop control system for a heliostat field

Abstract

The alarming energy crisis, heightened by the continuing depletion of fossil fuels, accentuates the need for the development of renewable energy technology, knowledge, and infrastructure. A Central Receiver (Power Tower) Solar Energy system uses heliostats (motorized planar reflectors) to continuously reflect direct radiation from the sun onto a central receiver. This paper discusses a novel closed loop control system for a heliostat field. In this system, rough adjustment of the heliostat is performed using an Inertial Measurement Unit (IMU). Precision adjustment of the heliostat is performed by inducing a small mechanical vibration in the heliostat's reflective surface, using a piezoelectric actuator. This vibration creates time-dependent changes in the light waves reflected from the heliostat, which can be detected by photo-sensors surrounding the thermal receiver target. The position of misaligned heliostats can be corrected once they are identified by FFT analysis of the light waves received by the photo-sensors. This technique can, in principle, control thousands of heliostats simultaneously. The control system is coded using MATLAB.