Wind Loading on Heliostats in an Operating Power-Tower CSP Plant

Heliostats that accurately track the sun are crucial for the performance of a concentrating solar power (CSP) power-tower plant. Both optical performance and structural integrity of heliostats are impacted by wind approaching the heliostat field. Depending on a heliostat's location in the field, its orientation, and the characteristics of the approaching wind, the resulting wind loads can deform the heliostat's support structure and the reflecting mirrors, impacting optical efficiency. On the other hand, the heliostat's structural design must be optimized for typical and extreme wind conditions to avoid costly overdesign and structural failure. Commonly, wind loads in a heliostat field are estimated from wind tunnel tests and numerical simulations. However, wind conditions and resulting wind loads experienced in the field can significantly deviate from idealized conditions. To understand wind loading in real-world conditions, NLR is conducting field measurements of wind and resulting structural loads on heliostats in an operating power-tower plant. We equipped three heliostats: two at the edge of the collector field, and one in the interior, with an array of load sensors for measuring forces and moments on the support structure, mirror deformations and dynamic accelerations. Our main goals are understanding how static and dynamic wind loads, such as lift forces and overturning moments, differ between heliostats at the edge and in the interior of the heliostat field. Another focus is the transfer from turbulent wind fluctuations to load fluctuations over a wide range of frequencies. In this talk, we will present results from our load measurements in an operating collector field and compare them to previous findings from wind tunnel tests. A heliostat's location in the field, its orientation, and the characteristics of the approaching wind influence the static and dynamic wind loads and resulting deformation of the heliostat's support structure and the reflecting mirrors. Heliostat wind loads have commonly been estimated based on wind tunnel tests and numerical simulations in idealized conditions. To understand wind loading in real-world conditions, NLR is conducting field measurements of wind and resulting structural loads on heliostats in an operating power-tower plant. Two heliostats at the edge of the field and one heliostat in the interior of the field were equipped with an array of load sensors for measurement and characterization of heliostat wind loads. This talk will present analysis of loads measurements at an operational solar collector field and compare them to previous findings from wind tunnel tests.