Analysis of Wind and Load Variations in a Full-Scale Operational Heliostat Field

A field of heliostats surrounding a central receiver of a concentrating solar thermal (CST) plant is impacted by turbulent wind that imparts bending and torsional loads on the supporting structure of individual heliostats. Depending on a heliostat's orientation and position in the field and the characteristics of the approaching wind, the resulting loads can deform the heliostat's support structure and the reflecting mirror facets. Design wind loads are typically estimated from wind tunnel tests and numerical simulations on a single, isolated heliostat. However, localized turbulence and wake effects from upstream and neighboring heliostats and the resulting wind loads in the interior of the field can significantly deviate from an individual heliostat. To understand wind loading in real-world conditions, NLR conducted field measurements of wind and resulting structural loads on heliostats in an operational CST plant. We equipped three heliostats: two at the perimeter of the collector field, and one in the interior, with an array of load sensors for measuring forces and torques on the pedestal, torque tube and mirror facet supports. The main objective is to understand the variation of structural wind loads, including lift forces, hinge moments, overturning moments and azimuth moments, on heliostats in the exterior and interior of the heliostat field. In this talk, we will present results from analysis of load measurements in a full-scale operational collector field in operating and stow positions and compare non-dimensional load coefficients to published findings on single heliostats in open field environments and heliostat arrays in wind tunnel tests.