A Holistic Approach for Low Cost Heliostat Fields

Hinge and overturning moments due to unsteady heliostat pressure distributions in a turbulent atmospheric boundary layer

“…by Pfahl et al (2015) and Emes et al (2017). Furthermore, the peak drag and lift coefficients on normal and stowed heliostats have been shown to depend on both the turbulence intensity and the longitudinal integral length scales of the energy-containing eddies in the longitudinal and vertical directions, respectively (Jafari et al 2018;Jafari et al 2019a).…”

“…The vertical profiles of turbulence intensities and length scales of the longitudinal 𝑢 and vertical 𝑤 velocity components in Figure 2 are taken from ESDU 85020 (2001) using similarity theory formulations of full-scale ABL data as a function of 𝑧 0 . A flat "open country" terrain is commonly assumed as the surroundings of a heliostat field (Peterka and Derickson 1992;Pfahl et al 2015), where the wind characteristics are derived from the 10-m reference height defined in design wind codes and standards (Holmes 2007). However, the expected loads for the single turbulence…”

Progress in heliostat development

“…42). Due to the rims, the loads on the drives are small and the backlash of the drives can be relatively high because of the long lever arms (distance between drives and centre of rotation), which enables the usage of low cost drives (Pfahl et al 2013) (Pfahl et al, 2015). A further advantage of the rims is the additional rigidity they provide, which leads to higher resonance frequencies and thus to lower dynamic loads.…”

Turbulence length scales in a low-roughness near-neutral atmospheric surface layer

“…The average sizes of the energycontaining eddies in the longitudinal direction of the lower surface layer can be represented by the Eulerian integral length scale , following Taylor's hypothesis that the turbulent flow field is translated downstream with uniform horizontal velocity in the longitudinal direction. The magnitude of relative to the characteristic length of a physical structure has a significant effect on the fluctuating pressures and unsteady forces on physical structures [8,9], which can result in galloping and torsional flutter when the turbulence length scales and characteristic length scale of the physical structure are the same order of magnitude [10]. Small eddies result in wind loads on various parts of a structure that become uncorrelated with distance of separation, however large eddies whose size is comparable with the structure result in well correlated pressures over its surface as the eddy engulfs the structure, leading to maximum wind loads [1,11].…”