# Wind Loads on a Solar Panel at High Tilt Angles
## 1 Introduction  
Renewable energy is an integral part of the worldwide measures to address climate change and reduce environmental pollution. Power generation from photovoltaic (PV) systems is one of the most promising substitutes to the use of fossil fuel. The total capacity in operation was 303 GW in 2016 and 402 GW in 2017, which corresponds to energy supplies of 375 TWh in 2016 and 494 TWh in 2017 (20.4% of the global renewable energy supply) [1]. PV panels are usually mounted on the rooftops of residential or commercial buildings. The systems are generally smaller than ground-mounted PV systems, for which land occupancy is a potential problem. PV systems that float on reservoirs or lakes use a pontoon structure for buoyancy, and there is a reduction in water evaporation and the temperature of solar cells. Trapani and Santafe [2] reviewed projects with floating PV systems from 2007 to 2013, and more installations are expected in the near future. Oceans cover approximately 71% of the Earth's surface, and offshore environments can take full advantage of solar energy. Offshore PV systems have been proposed recently [3, 4]. However, these installations are subject to greater wind loads in severe sea wave environments. A PV system consists of tilted panels. Any PV system design requires an accurate estimation of wind-induced loads in order to ensure proper function. Many studies determine the aerodynamic characteristics of tilted panels or their supporting structure. [PERSON] et al. [5] showed that the most critical parameter is the angle at which the panel is tilted, \(\alpha\). Wind-induced loads are primarily due to pressure equalization for small angles of tilt and turbulence for large angles [6, 7]. For a stand-alone panel that faces the direction of flow, [PERSON] et al. [8] showed that an increase in \(\alpha\) (15\({}^{\circ}\)-25\({}^{\circ}\)) results in a decrease in the unit sectional uplift coefficient in a uniform flow. There are strong suction forces nearthe front edge on the upper surface and slight wind-induced pressure on the lower surface. The mean spanwise pressure distributions have an inverted U-shape, which corresponds to the corner vortices. For the extreme cases of open terrain exposure, [PERSON] et al. [9] showed that an increase in \(\alpha\) (20\({}^{\circ}\)-45\({}^{\circ}\)) leads to greater suction, and peak suction occurs at \(\alpha=45^{\circ}\). An increase in the intensity of the freestream turbulence results in the upstream movement of a separation bubble and side-edge vortices. More intense pressure fluctuations and bending moments have been observed [10]. [PERSON] [11] also showed that discrepancies in the available wind tunnel data may be due to the characteristics of the inflow turbulence. [PERSON] et al. [12] studied the effect of wind direction, \(\beta\). When \(\beta=15^{\circ}\)-60\({}^{\circ}\), there is greater suction on the upper surface near the windward corner. [PERSON] and [PERSON] [13] showed that the maximum wind load occurs at \(\beta=45^{\circ}\). There are maximum overturning moments for \(\beta=45^{\circ}\) and 135\({}^{\circ}\)[14]. A sheltering effect was reported by [PERSON] et al. [15]. The wind loads on the tilted panels are significantly reduced by the presence of neighboring upwind panels, and the degree of reduction decreases quickly. [PERSON] et al. [16] also had similar results. To harness solar energy, the performance of a PV system depends significantly on the angle at which the PV panels are tilted, their orientation, and shadowing [17; 18; 19]. The optimal value for \(\alpha\) is achieved when the sunlight is perpendicular to the surface of the PV panels. Designs for a PV system often use wind loading standards, such as the American Society Civil Engineers (ASCE 7) [7; 20], in order to calculate wind loads. However, wind loads can be larger than the ASCE 7 standard [21]. For PV panels floating directly on the surface of water, [PERSON] et al.