Developments towards the heliostat field performance testing guideline

The final quality of each individual heliostat and its interaction as a heliostat field are important factors which determine the final performance and economic success of a solar tower system. 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.

The Heliostat Field Acceptance Guideline is currently being developed to assess the quality of heliostat fields. This article gives background information and experiences which have been fed into the draft version of the new guideline for the heliostat field. The draft document will be shared with the community and will be a step forward in the measurement of distributed concentrator systems. It complements and builds on the existing SolarPACES Guideline for Heliostat Performance Testing, which allows the characterization of individual heliostats. The article discusses several options for heliostat field acceptance testing. The level-2 approach, based on statistical sampling of some heliostats and subsequent raytracing with measured and extrapolated values is recommended. The draft guideline also suggests various standardized tests 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.