Outdoor Surface Slope Measurement of Large Heliostats

Precise heliostat optics are an essential part of any well performing solar thermal plant, especially as higher solar concentration plants are designed for Gen3 concentrated solar power (CSP) and high temperature solar heat for industrial processes (SHIP). Accurate optical measurements of operating heliostats can reveal important information about their performance over time, which can inform design changes, maintenance operations, and qualification of the field. This has been challenging with existing metrology tools, though it has been accomplished at different research institutions with a variety of techniques. In the last year, a new adaptation of Reflected Target Nonintrusive Assessment (ReTNA) method has been used to measure large heliostats outdoors. ReTNA leverages advancements in consumer cameras and computer vision tools. Recent advancements allow for in-situ measurement on a mobile platform with relatively little equipment and new image stitching techniques. This presentation describes the basic measurement setup and reviews results collected on outdoor heliostats. Measurement uncertainty is estimated for a generic outdoor setup. ReTNA can also be paired with other metrology tools such as beam characterization systems, UAS-based methods like NIO, and photogrammetry, to gain a more complete understanding of the heliostat. We will discuss efforts to pair these techniques for measurement verification and to address metrology gaps identified in the HelioCon roadmap.