Heliostat Field Performance Testing Guideline - A Step Forward in the Measurement of Distributed Concentrator Systems

The final quality of each individual heliostat and its interaction as a heliostat field is an important factor which determine the final performance and economic success of a solar tower system. The total energy reaching the receiver is influenced by the operation and interaction of all heliostats functioning as a heliostat field. The Heliostat Field Acceptance Guideline was developed in the German national project HELIODOR to assess the quality of heliostat fields. The guideline is a step forward in the measurement of distributed concentrator systems. The new field guideline builds upon the SolarPACES Guideline for Heliostat Performance Testing which allows the characterization of individual heliostats. The field quality is influenced by several factors like intelligent positioning of the individual heliostat units, their interaction (blocking/shading), light attenuation to the receiver, receiver optical acceptance angles, and operational parameters like calibration quality, aimpoint strategies, heliostat availability and reliability. Although the guideline gives several options for acceptance testing, the level-2 approach, based on statistical sampling of some heliostats and consecutive raytracing with measured and extrapolated values is recommended. The guideline offers various standardized test and qualification procedures, providing an objective method to facilitate the field acceptance testing after construction, making it easier for suppliers and customers to negotiate contracts and ultimately reduce risks and costs.