# Application of Simultaneous Symmetric and Cambered Airfoils in Novel Vertical Axis Wind Turbines
## 4 Results and Discussion
### Power Production  
The power coefficients of four types of turbines are displayed in Figure 6 for different TSRs from 1.5 to 4. In TSRs higher than 4, all analyzed VAWTs cannot produce power. Since symmetric blades have higher power coefficients than non-symmetric blades, it is predictable that the HT-NACA0018 turbine produces power in the broader range of TSRs, while the HT-S815 turbine produces lower power within a small range of TSRs. NSA-2 extracts power in a broader range of TSRs compared to other VAWTs and approximately performs like a VAWT with symmetric airfoils in terms of power extraction range. Apart from NSA-2, NSA-1 produces power in a broader range of wind velocity than a VAWT with cambered airfoils. For TSR > 3, NSA-1 and HT-S815 turbines cannot generate power,  
Figure 5: Validation: (**a**) dynamic simulation; (**b**) static simulation; (**c**) error analysis. and their power coefficient is almost zero (not shown in Figure 6). In other TSRs, the power coefficient of NSA-2 is bigger than that of NSA-1. In TSR = 1.5, Figure 6a shows that due to the type of airfoils and their placements, VAWTs have a different number of repeated cycles in one rotation. HT-NACA0018 has four of them, and NSA-1 has two of them. Nevertheless, NSA-2 does not have a repeated cycle in 360\({}^{\circ}\). Therefore, NSA-2 has the maximum \(\mathrm{C_{p}}\) in one rotation compared to other VAWTs. HT-NACA0018 experiences the highest and lowest \(\mathrm{C_{p}}\) in this TSR. Although HT-NACA0018 yields the lowest \(\mathrm{C_{p}}\) four times in one rotation, it has the highest \(\mathrm{C_{p}}\) with the same number of repeats. Maximum \(\mathrm{C_{p}}\) is higher than the minimum in terms of value, so HT-NACA0018 has the highest average \(\mathrm{C_{p}}\) in this TSR. For NSA-1, the maximum \(\mathrm{C_{p}}\) is lower than HT-NACA0018 and NSA-2. It happens two times, and also its lowest \(\mathrm{C_{p}}\) is lower than NSA-2 and higher than HT-NACA0018. The maximum \(\mathrm{C_{p}}\) of HT-S815 is lower than half of the highest \(\mathrm{C_{p}}\) of NSA-2 and HT-NACA0018. Figure 6: Power coefficient of VAWTs with TSRs of (**a**) 1.5, (**b**) 2, (**c**) 2.5, (**d**) 3, (**e**) 3.5, and (**f**) 4; for zero azimuth angle (\(\theta\) = 0\({}^{\circ}\)), see Figure 1.  
In TSR = 2 (Figure 6b), NSA-2 has the highest C\({}_{\text{p}}\), about 1.65 times higher than that of HT-NACA0018. HT-NACA0018 in about 240\({}^{\circ}\) of a cycle has a power coefficient close to its highest, and also its lowest C\({}_{\text{p}}\) is close to zero and higher than those of NSA-2 and NSA-1. NSA-1 has the highest C\({}_{\text{p}}\) close to HT-NACA0018, and at 160\({}^{\circ}\), its C\({}_{\text{p}}\) is about half of its maximum. HT-S815 has the lowest oscillation, and its C\({}_{\text{p}}\) is always between 0.1 and 0.23, roughly about half of the other VAWTs' maximum values. In TSR = 2.5 (Figure 6c), NSA-2 and NSA-1 have the highest C\({}_{\text{p}}\). Additionally, a similar pattern and C\({}_{\text{p}}\) variation can be seen when their power coefficient is not as high as their maximum value. HT-NACA0018 has a maximum C\({}_{\text{p}}\) lower than NSA-1 and NSA-2. HT-S815 has the lowest range of power coefficient. In TSR = 3 (Figure 6d), the average power coefficient of HT-S815 is zero; therefore, it is not plotted. Unlike NSA-1 and NSA-2, HT-NACA0018 does not have a negative power coefficient in this TSR, and its fluctuation is slight and varies between 0.3 and 0.4. NSA-2 has the highest and lowest C\({}_{\text{p}}\) compared to other VAWTs. NSA-2's highest power coefficient is roughly equal to that of NSA-1. In TSR = 3.5 (Figure 6e), like HT-S815, NSA-1 does not produce power, so it is not shown. Again, HT-NACA0018 has a slight fluctuation, and its C\({}_{\text{p}}\) varies between 0.2 and 0.32. If signs of power coefficients are ignored, the minimum C\({}_{\text{p}}\) of NSA-2 will be bigger than its maximum. Finally, in TSR = 4 (Figure 6f), only HT-NACA0018 can produce power and oscillates between 0.04 and 0.22.