Numerical investigation on reducing wind load by enclosing solar dish concentrator with membrane structure

Abstract

The exposed steel skeleton on the back of the traditional dish concentrator (TDC) results in poor aerodynamic shape, and the superposition of wind pressure on both the front and back surfaces of each mirror unit can significantly deteriorate optical accuracy or cause damage. This paper proposes using membrane structure to enclose the steel skeleton forming a membrane-enclosed dish concentrator (MDC) with a new streamlined aerodynamic shape to reduce the wind loads. Only the mirror's working surface (concave side) to withstand the wind pressure, while the mirror backside within the membrane enclosed area without wind pressure. The wind load (including aerodynamic six-component and wind pressure load) and flow-around characteristics of MDC (a 17.7 m diameter dish concentrator) are investigated by CFD numerical simulation, 35 sets of wind conditions with the combination of wind direction angle θ = 0°–180° (wind speed of 17.1 m/s) and concentrator elevation angle β = 0°–90° are considered, and compared these results with those of TDC. The results indicate that the MDC demonstrates excellent load reduction effects in most conditions, especially when the concentrator's back (convex side) faces the wind. The load reduction effect is most pronounced for drag load, with the drag coefficient is reduced by up to 0.50, and the average reduction rate of the drag load is up to 22.53 % at β = 0°. The average reduction rates for horizontal total load and total wind load at β = 0° can be up to 18.14 % and 17.91 %, corresponding to the reductions of 7990 N and 7891 N. The wind pressure on each mirror in MDC is significantly reduced, with the PWS coefficients ranging only from −0.5 to 1.1 for all conditions. At β = 0° and β = 45°, the PWS coefficient can be reduced on average of 0.570 and 0.412, equivalent to reduction wind pressure by 102.25 Pa and 74.16 Pa, providing an excellent comprehensive load reduction effects.