Impact of Atmospheric Turbulence on Dynamic Wind Loads on Heliostats

This study analyses the turbulent wind properties in the lower 10 m of the atmospheric surface layer close to the ground where heliostats are located. Power spectral densities of streamwise and vertical components of wind are analysed, and the frequencies associated with the peak of the spectra are determined using field data collected at two open-country terrains in addition to spectral models of ESDU85020. Variations of the peak frequencies with height from the ground, terrain type and average wind speed are discussed and the impact on heliostat wind loads are described. It is found that while the peak frequency of the streamwise turbulence is between 0.01–0.1 Hz, the peak of the vertical turbulence occurs at frequencies in the range of 0.1–1 Hz. It is shown that smaller heliostats that are located closer to the ground are exposed to turbulent wind fluctuations at a higher frequency and are thus expected to experience wind loads with a higher dominant frequency compared to larger heliostats located higher above the ground. These frequencies need to be considered in design of heliostat drives and structural components