# Wind Loads on a Solar Panel at High Tilt Angles
## 2 Experimental Setup  
Experiments were conducted in a wind tunnel at the Architecture and Building Research Institute. The tunnel is a closed-loop type with a contraction ratio of 4.71. The constant-area test section is 2.6 m (height) \(\times\) 4 m (width) \(\times\) 36.5 m (length). For a stand-alone panel (60%-scale commercial module), the test configuration is shown in Figure 1. The length (\(L\)) and width (\(W\)) are 120 cm and 60 cm, respectively. At \(x\)/\(L=1.0\), the panel is 3 cm above the tunnel floor. The blockage ratio is up to 6.3%. Note that a blockage correction is required for the mean surface pressure for a tilted panel if the blockage ratio is more than 10% [22]. This study determined the effect of \(\alpha\) and \(\beta\). Meteorological data (wave, wind, tide, and current) were collected from three near-shore buoys in Taiwan (Qigu, 23\({}^{\circ}\)05\({}^{\prime}\)42\({}^{\prime}\)N, 120\({}^{\circ}\)00\({}^{\prime}\)27\({}^{\prime}\)E; Hsinchu, 24\({}^{\circ}\)45\({}^{\prime\prime}\)19\({}^{\prime}\)N, 120\({}^{\circ}\)50\({}^{\prime}\)12\({}^{\prime}\)E; and Longdong, 25\({}^{\circ}\)05\({}^{\prime}\)48\({}^{\prime}\)N, 121\({}^{\circ}\)55\({}^{\prime}\)19\({}^{\prime  
Figure 1: Test configuration for a stand-alone model. the period of 2013-2017, and is shown in Figure 2. The most common values of \(\beta\) are 210\({}^{\circ}\)-225\({}^{\circ}\) and 315\({}^{\circ}\)-360\({}^{\circ}\). Note that the wind direction is 30\({}^{\circ}\)-45\({}^{\circ}\) in Hsinchu, and 0\({}^{\circ}\) in Longdong. The inclination of the PV panels depends on the waves. The historical data for typhoons shows that the maximum wave height and wind speed in Longdong are 17.12 m (mean period = 12.5 s during typhoon Soudelor, 2015) and 26.7 m/s (mean period = 11.8 s during typhoon Soulik, 2013), respectively. The variation in \(\alpha\) for the PV panels with respect to wind is \(\pm\)45\({}^{\circ}\). Therefore, the setup for \(\alpha\) is 10\({}^{\circ}\)-80\({}^{\circ}\) (in increments of 10\({}^{\circ}\)). The value for \(\beta\) ranges from 0\({}^{\circ}\) (facing the direction of the wind) to 180\({}^{\circ}\) (in increments of 15\({}^{\circ}\)). Note that the angle between the PV panels and their base is not changed in sea wave environments, which is not exactly the same as the case for the experimental setup. The experiments were conducted in a uniform flow. The freestream velocity was set at \(14.5\pm 0.1\) m/s, measured using a Pitot-static tube, and the turbulence intensity was 0.3%. [PERSON] et al. (2014) showed that there is greater expansion on the upper surface, and more positive pressure on the lower surface of a tilted panel when the intensity of the turbulence increases. The front edge of the test model was located 2.8 m from the inlet of the working section. A Reynolds number of \(1.17\times 10^{6}\) is based on the length of the tilted panel. [PERSON] et al. (2015) reported that a tilted panel is not affected by the Reynolds number. A total of 330 pressure taps were drilled on the test model and were connected to flexible polyvinyl chloride tubing that is 1.1-mm in diameter and 60-cm in length, so the phase distortion has little effect on the measured peak pressure ([PERSON], 2013). As there are strong pressure gradients (flow separation and reattachment) near the front edge of the tilted panel, 92% pressure taps were machined on the first two-thirds of the upper and lower plate surfaces. SCANVALVE multichannel modules (Model ZOC 33/64 Px 64-port; Model RAD3200 pressure transducer) were used for the surface pressure measurements. The full-scale range of the sensors was \(\pm\)2490 Pa, with an accuracy of \(\pm\)0.15% full scale. The sampling rate was 250 Hz and each record contained 32,768 data points. A Pitot-static tube, which was at the same height as the front edge of the tilted panel and 2.8 m from the inlet of the working section, was used to measure the static pressure, \(p_{\infty}\), and the dynamic pressure, \(q\), of the incoming flow.