# Effect of Wind Direction and Velocity on PV Panels Cooling with Perforated Heat Sinks
## 5 Results and Discussion  
The present simulations have a higher level of accuracy compared to the majority of literature, because the air circulation around the PV panel-heat sink ensemble causes a change in temperatures distribution and non-homogeneous heat transfer. While the majority of existent studies are realized by using a constant convective heat transfer coefficient (\(h_{c}\)) in order to replace the air circulation around an object [18], in the present paper, the airflow near the photovoltaic panel and heat sink ensemble is also considered. This approach produces more realistic results and could represent a good starting point for future research in the literature, representing the connection between air velocity, direction and the power production obtained for these conditions. The PV panel operating temperature and normalized power production were obtained. In Figures 8-10, there are presented qualitative and quantitative results regarding the average temperatures of the photovoltaic panels obtained for each model of the heat sink and various wind velocities and directions. These results are obtained by varying the set-up: \(t_{air}\) = 35 \({}^{\circ}\)C, \(v_{air}\) = 1-5 m/s and \(G\) = 1000 W/m\({}^{2}\) and three wind directions (Table 5). Figure 6: Validation of the numerical simulation—base case—PV panel without heat sink. Figure 7: Validation of the numerical simulation—PV panel with heat sink. Figure 10: Variation of average operating temperature for \(v_{air}\) = 5 m/s. Figure 9: Variation of average operating temperature for (a) \(v_{air}\) = 3 m/s; (b) \(v_{air}\) = 4 m/s. These values could represent a good marker in order to choose, when possible, the right positioning of the PV panels related to the dominant wind in a certain geographical area. The best temperatures of the heat sinks were obtained when the wind was towards the heat sink--in the backside of the PV panel--determining a decrease of the average  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multirow{2}{*}{\(\mathbf{v_{air}}\)} & \multicolumn{2}{c}{**Back Wind**} & \multicolumn{2}{c}{**Front Wind**} & \multicolumn{2}{c}{**Side Wind**} \\ \cline{3-8}  & & \multicolumn{3}{c}{**Drop of \(\mathbf{t_{PV}}\) Compared to Base Case, for \(\mathbf{t_{air}}\) = 35 \({}^{\circ}\)C**} & \multicolumn{1}{c}{} & \\ \cline{3-8}  & & \({}^{\circ}\)**C** & **\%** & \({}^{\circ}\)**C** & **\%** & \({}^{\circ}\)**C** & **\%** \\ \hline
0. Base Case & & 70.1 \({}^{\circ}\)C & - & 70.7 \({}^{\circ}\)C & - & 80.4 \({}^{\circ}\)C & - \\ \hline  
\(-\)7.58 \({}^{\circ}\)C & \(-\)14.8\% & \(-\)5.59 \({}^{\circ}\)C & \(-\)10.9\% & \(-\)10.03 \({}^{\circ}\)C & \(-\)17.5\%operating temperature of approximately 15 \({}^{\circ}\)C. On the other hand, the best cooling effect was registered for the side wind, due to the higher temperatures resulted in the base case--when no cooling is applied. Although the lowest temperatures were achieved for the back wind, the cooling effect was more intense for the side wind. If, in the case of wind velocity, the effect of cooling evolves almost linearly from 1 m/s to 5 m/s, in terms of the wind direction, there is a slightly different behavior. Therefore, there are present some recirculation areas that modify the distribution of velocities and temperatures on the PV panel-heat sink ensemble. The worst wind direction, from this point of view, is the side one, causing a non-uniform temperature distribution, which is influencing the entire PV panel efficiency. The quantitative results for \(v_{air}\) = 1 m/s, air temperature \(t_{air}\) = 35 \({}^{\circ}\)C and solar radiation \(G\) = 1000 W/m\({}^{2}\) for each case are presented in the following graphs: Figures 8-10.