Characterisation of Edge Canopy Flow Within a Linearly Staggered Heliostat Array

Abstract: Wind flow characteristics were measured throughout a 7 row linearly staggered heliostat array (49 heliostats) in the University of Adelaide large wind tunnel. The flow was captured using a Turbulent Flow Instrumentation multi-hole pressure probe affixed to a 3-axis traverse, allowing for vertical profiles to be measured at the midpoint between each of the 7 rows. From analysis of the changes in flow throughout the array, canopy flow characteristics were identified such as; primary and secondary flow velocity inflection points, decreases in velocity further downstream, an increase in flow velocity standard deviations, and matching to literature shear length scales normalised to shear velocity at canopy height. These findings will aid in heliostat wind load estimations within an array by evaluating variations in wind loading based on canopy flow characteristics, with the goal to reduce the capital cost of concentrated solar power plants. Further investigation is required to measure wind loads on the heliostats directly and correlate the loads to the flow characteristics. Keywords: Canopy flow, Boundary-layer, Turbulence, Kelvin-Helmholtz rollers, Heliostats