Shape effects on aerodynamic loading of heliostats

The effect of the shape of the mirror of a heliostat is studied through wind tunnel tests in uniform smooth and turbulent flow conditions. Three shapes are investigated: square (reference case), octagonal and circular geometries. The forces and moments are measured on reduced scale models of heliostats in low, medium and strong turbulence wind conditions in a uniform wind profile. The turbulence intensity of the flow is adjusted in the wind tunnel test section by the adjunction of passive grids upstream the model. The experimental results are presented for several elevation and azimuth angles. The results showed that: in smooth flow conditions, the geometry of the mirror has very limited effect on the mean force coefficient, while impacting the fluctuating part of the aerodynamic loads. In turbulence flow conditions, the circular mirror/panel is advantageous for the aerodynamic design of the elevation drive and mirror support structure