Wind Loads of Solar Water Heaters: Wind Incidence Effect

For applications of solar thermal energy, solar water heaters (SWHs) are becoming common. In this study, the effect of a crosswind on the aerodynamic characteristics of residential (an inclined flat plate with a horizontal cylinder) and large-scale SWHs (an inclined flat plate only) is experimentally investigated. The tests are conducted in a low speed wind tunnel and the relative wind direction with respect to the test model, , ranges from 0 to 135？deg. Measurements of the mean and fluctuating pressures are presented. These results demonstrate that higher suction and fluctuating pressure are observed near the upwind corner, particularly for the test case of ？deg. 1. Introduction The use of renewable energy technologies represents an opportunity to reduce global warming. In this respect, SWHs are rapidly becoming an integral part of worldwide measures to combat the effects of climate change. Previous studies [1, 2] found that the wind loads on solar collectors are significantly reduced by the sheltering effect of the first row of collectors and of the building itself. For a residential SWH (an inclined solar collector with a horizontal water storage tank), normal to the direction of smooth uniform wind, the study by Chung et al. [3, 4] demonstrated that localized wind loads at a tilt angle？α of 15–30？deg. are significant near the front edge and reach a minimum value at a distance of approximately one-third of the total length from the leading edge. Reynolds number independence was also noted. For a large-scale SWH (inclined solar collector or flat plate only), Chung et al. [5, 6] indicated that there is a higher suction force on the lower surface over the first half of the inclined solar collector and a stronger positive mean longitudinal differential pressure coefficient is observed. Kopp et al. [7] further pointed that the presence of the building changed the aerodynamic loads substantially compared to ground-mounted systems. There is a complex interaction between building generated vortices and the flow induced by solar arrays. Wind incidence has an important influence on the aerodynamics of bluff bodies [8]. Certain oblique wind directions, , correspond to the critical case for wind loads. Wood et al. [9] demonstrated that the orientation of the solar collectors with respect to the wind direction and the proximity of the panels to the leading edge have a significant effect on the pressure distributions measured. Kopp et al. [7] found that the largest wind loads are associated with vortex shedding from in-line solar collectors. The peak system torque