Computational Investigation of Wind Loads on Tilted Roof-Mounted Solar Array

Abstract

A detailed computational investigation of the wind field around tilted solar modules mounted on a large building roof has been undertaken, utilizing the Reynolds-Averaged Navier-Stokesv (RANS) approach supplied with the SST k − ω turbulence model. The study investigated the flow field for various tilt angle of modules at normal wind directions relative to the wall. Then the shape factors and moment coefficients of modules were explored. The results show that the recirculation vortex generated by the building edge is disintegrated to smaller local vortices. With the increasing of the tilt angle, an increasing number of local vortices emerged at the leading rows, leading to a relatively large wind pressure and shape factor at the corner of the array. In most tilt angles at 0° and 180° wind direction the shape factors are negative. However, for the 40° and 55° tilt angles at 180° wind direction, the shape factors on the lower surfaces are positive, due to the dominating of approaching flow rather than the local vortices. The array is divided into six zones based on the distribution of shape factors. As the shape factors on upper and lower are similar, the shape factors in most zones for tilt angles from 5° to 55° are quite small. However, shape factors in the leading row for 30°, 40° and 55° are relatively large. This indicates that the shading effect of front rows can significantly reduce the shape factors of the rear rows. Compared to the values calculated by Chinese, American and Japanese standards, the shape factors by simulation are quite small. The moment induced by nonuniform wind pressure, which is often ignored in the literature and standards, is quite large at the leading zones, with a maximum of 0.28 for 55° tilt angle. Ignoring the wind induced moment on the leading zones may make the wind resistance design of the solar module support structure unsafe.