# Effect of Wind Direction and Velocity on PV Panels Cooling with Perforated Heat Sinks
## 5 Results and Discussion
In these figures, the values displayed on the plots (35, 45, 55, 65, 75 and 85) represent the scale for the average operating temperatures of the PV panel measured in \({}^{\circ}\)C. The tendency registered for 1 m/s is also manifesting for higher velocities: 2-5 m/s, with the highest temperatures recorded for the base case (T front PV BASE) and the lowest ones for the horizontal heat sink with 30 mm perforations (T front PV HORIZ 30 MM). A remarkable result is found for the convective heat transfer coefficients. Therefore, the global air circulation determined by the presence of the heat sinks with horizontal fins is also improving the heat transfer coefficients \(h_{c}\) on the front of the PV. In this case, the \(h_{c}\) in front of the PV panel have closer values to the ones recorded on the back. This phenomenon is less intense for the vertical fins. The wind direction seems to change the best configuration (Case 2--horizontal 30 mm) only for particular cases. The temperature reduction determined for this case is presented in Table 5.  
A general tendency of the data obtained showed that the horizontal (transversal fins) are superior to those vertical (longitudinal) for each wind direction and velocity, while the best wind direction for improving the cooling of the PV panel-heat sink ensemble is towards the back of the PV panel. Also, if analyzed separately, the smaller holes (\(\Phi\) = 30 mm) determine better results for horizontal fins, while the larger ones (\(\Phi\) = 60 mm) are suitable for the vertical ones. The cooling effect over the global energy production is quantified as efficiency improvement, taking into account the data available from the producer data sheet--a linear reduction of the efficiency by \(-\)0.37%/\({}^{\circ}\)C [32]. Therefore, for these disadvantageous external conditions (\(t_{air}\) = 35 \({}^{\circ}\)C, \(G\) = 1000 W/m\({}^{2}\)), the normalized power generation was calculated--as the ratio of the maximum theoretical power \(P_{STC}\) obtained in Standard Test Conditions. The results regarding the power production are normalized and presented as a fraction of maximum theoretic power (320 Wp in STC conditions). Therefore, each degree of temperature above the standard test conditions temperature \(t_{STC}\) = 25 \({}^{\circ}\)C determines lower efficiencies compared to the STC one (\(\eta_{STC}\) = 19.30%) [32]. The visual effect over the improvement of the PV panel power generation determined by the heat sinks is presented in Figures 11-13. These figures present the normalized power productions as a ratio of the power produced in STC (considering the STC power as equal to 1). Each figure shows the amount of power produced in each case (from Case 0 to Case 6) for different wind directions (Figure 11--back wind, Figure 12--front wind and Figure 13--side wind. These charts present the results obtained for each case for the air velocity of 1 m/s. This trend is maintained for higher velocities, Table 6, but the effect compared to the base case is attenuated. Figure 11: Normalized power production for **back wind**, \(v_{\text{back}}=1\) m/s, \(t_{\text{air}}=35\), \(G=1000\) W/m\({}^{2}\).