Heliostat Beam Characterization System

The Beam Characterization System utilizes video radiometer techniques to quantitatively describe the solar energy projected by a heliostat. This system is designed to evaluate prototype heliostats and to improve the performance of the Central Receiver Test Facility heliostats. The system consists of a beam target, video camera, analog image analyzer, calibration system, video digitizer and a minicomputer system. The calibration technique corrects for background illumination, target irregularities, vidicon shading and camera dark currents. A computer code corrects for off-axis camera angle and converts calibration and beam data into a map of screen irradiance. Post test data analysis provides the geometric centroid, energy versus radius, iso-flux contours, intensity cross sections and 3-D intensity diagrams which are determined from the data map. The system has a fast data capture mode which can be used to study wind loading and short term tracking errors. The capabilities of the Beam Characterization System make it a useful heliostat evaluation tool.