# Design and Development of Bladeless Vibration-Based Piezoelectric Energy-Harvesting Wind Turbine
## 5 Experimental Results  
This section presents the results of the prepared experimental setup shown in Figure 8 for the simple cylinder and in Figure 9 for the modified cylinder. The data are related to the three locations of the piezoelectric component, i.e., top, middle, and bottom of that component, and for two different angles of attack, i.e., 0 and 5 degrees, and are presented in Tables A1-A4. As predicted by numerical results, increasing velocity increases the amount of applied force on the vortex generator. Furthermore, adding complexity increases the lift force slightly; however, this change was extensive in the numerical results, which could be related to the non-precise shape of the object added to the primary geometry and the accuracy of the measurement. Similarly, placing the piezoelectric component farther from the vortex generator object induces more electrical voltage in the piezoelectric element. Nevertheless, this phenomenon cannot be observed when the piezoelectric member is in the middle of the mast. The mast becomes an obstacle in the turbulent wind flow, which is neglected in the numerical simulation. This effect probably affects the wind flow around the mast and vortex generator object and enhances the vibrations of this part of the mast. Additionally, considering a constraint for the mast movement and fixing the mast to the ground changes the mast vibration pattern. Finally, it should be noted that the angle of attack almost does not impact the exerted lift force. Maximum attainable power for each case when the piezoelectric sensor is located near the vortex generator utilizing Equation (5) is presented in Table 4. The amount of power obtained experimentally at different locations of the piezoelectric element is plotted in Figure 10. \begin{table}
\begin{tabular}{l c} \hline \hline
**Experimentally Tested Case** & **Maximum Attainable** \\  & **Power (nW)** \\ \hline Case 1: Simple cylinder at v = 10 m/s & 0.00011974 \\ Case 2: Simple cylinder at v= 15 m/s & 0.0010777 \\ Case 3: Simple cylinder at v= 20 m/s & 0.0043108 \\ Case 4: Modified cylinder at v= 10 m/s & 0.00026942 \\ Case 5: Modified cylinder at v= 15 m/s & 0.0024248 \\ Case 6: Modified cylinder at v= 20 m/s & 0.0187100 \\ Case 7: Modified cylinder: real-life dimensions at v = 10 m/s & 0.0681910 \\ Case 8: Modified cylinder: real-life dimensions at v = 15 m/s & 0.7946900 \\ Case 9: Modified cylinder: real-life dimensions at 20 = 10 m/s & 3.1247000 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Calculated power attained for the piezoelectric component located at the top of the mast. Figure 9: The proposed modified cylinder design experimental setup in a wind tunnel with piezoelectric sensors positioned at the tested locations. In addition, when the piezoelectric component is located at the bottom of the mast, more power can be harvested, as seen in Figure 11. The results are reported in Table 5 and plotted in Figure 11. The maximum harvested amount of energy is 212.473 nW at a wind speed of 20 m/s using a modified cylinder with real-life dimensions. This result is promising for small electronic devices and can later be improved to generate more power. Figure 11: Output power for the piezoelectric component located at the bottom of the mast. Figure 10: Output power attained for the piezoelectric component located at the top of the mast. Figure 14: Experimental results for the complex cylinder case with the angle of attack at 0 deg. Figure 13: Experimental results for the simple cylinder case with the angle of attack at 5 deg. Figure 15: Experimental results for the complex cylinder case with mast angle of attack at 5 deg. Figures A1-A3 present measured voltage from the piezoelectric sensors located at the top, middle, and bottom of the mast at different wind speeds with a mast angle of 0 degrees. The mast is now facing the flow stream with no deviation. Figure A4 displays the measured voltage of all simple cylinders using the sensors located at the top, middle, and bottom of the mast at an angle of 0 degrees.