# Thermal Effects on Photovoltaic Array Performance: Experimentation, Modeling, and Simulation
## 1 Introduction  
It is well established that photovoltaic (PV) efficiency is dependent on temperature. The temperature of PV arrays is affected by factors such as ambient temperature and wind speed [1, 2, 3, 4]. In recent years, there has been significant interest in studying the influence of the aforementioned factors on PV temperature. Although it is well known that higher temperature will negatively affect PV performance, there is no consensus on the quantitative results [1]. In general, there are three approaches to study the effects of ambient temperature and wind speed on PV temperature: wind tunnel experiments, field measurement, and simulations. In these approaches, researchers aim to determine the heat transfer coefficient directly or obtain a dimensionless Nusselt number from these experiments. A brief summary of some of the existing correlations for flat plates is shown in Table 1. Note that the purpose of Table 1 is not to provide a comprehensive review of available correlations, as a comprehensive list of equations can be found in the review work by [PERSON] [5]. Rather, the purpose is to illustrate two points. First, many of these empirical correlations are basedon structured equation forms (e.g., linear, power law, boundary layer equation forms) [4], and that the constants/coefficients are determined empirically. Second, these empirical constants/coefficients can differ significantly and depend on the PV orientation relative to the wind, material roughness, solar irradiance, etc. In general, these correlations can become very inaccurate once the setup deviates from the original experiment's conditions. As a result, [PERSON] [6] concluded that determining an empirical equation for general application is likely not possible. More recent studies have focused on developing models to capture the effects of tilt angle, wind direction, turbulence intensity, solar irradiance, ambient temperature on surface temperature, and subsequently, PV performance using modeling and experimentation. [PERSON] et al. [4] studied the effects of tilt angle on the convective heat transfer coefficient and developed a new empirical equation based on experimental and computational fluid dynamics (CFD) results. [PERSON] and [PERSON] [1] conducted wind tunnel experiments to quantify the influence of turbulence intensity on local and average heat transfer coefficients. Subsequently, a field experiment by [PERSON] and [PERSON] [13] concluded that wind direction has a significant effect on the production output of a PV solar plant. The layout of rows of PV arrays can significantly affect the turbulent intensity as air flows through the PV plant. [PERSON] et al. [14; 15] conducted wind tunnel experiments and CFD simulations to study the temperature distribution on a PV module, and the results of this work were used by [PERSON] et al. [16]. It was found that wind flow contributed to an increase in heat transfer on PV modules, thus leading to greater production. [PERSON] et al. [17] analyzed how solar module orientation and tilt angle can be optimized to maximize solar radiation reception. Furthermore, [PERSON] et al. [18] and [PERSON] et al. [19] concluded that solar irradiance and ambient temperature are key contributing factors that affect PV performance. It is interesting to note that [PERSON] et al. examined various mathematical models to assess the ability to accurately predict the surface temperature of a solar module under varying environmental conditions. They concluded that wind velocity did not play a significant role in solar module efficiency. Numerous thermal models have been developed to estimate the effect of heat load on temperature, and consequently, the energy yield. [PERSON] et al. [20] performed wind tunnel experiments that indicated that the spatial temperature variations caused by wind should be considered for accuracy yield evaluation. [PERSON] et al.