## 2 Harvesting System
### Model and Test Results Comparison and Proposed System Verification  
In order to verify the mini wind harvester proposed model, the simulations results were compared with the prototype measured values. Figure 18 summarizes the performance of the system for two load conditions, 10 \(\Omega\) and 100 \(\Omega\), and two wind flow velocity conditions, 3 m/s, and 10 m/s. The load changes the output voltage and the frequency. If the load remains constant and the wind flow changes the system behaves the same. Thus, the decrease in the load or the wind flow leads to reduced output AC voltage amplitude and frequency. \begin{table}
\begin{tabular}{c c c} \hline \hline \(\mathbf{x_{0}}\) & \(\mathbf{x_{2}}\) & \(\mathbf{\delta}\) \\ \hline
0.169 & 0.153 & 0.0215 \\ \hline \(\mathbf{x_{0}}\) & \(\mathbf{x_{6}}\) & \(\mathbf{\delta}\) \\ \hline
0.169 & 0.129 & 0.0195 \\ \hline \(\mathbf{x_{0}}\) & \(\mathbf{x_{10}}\) & \(\mathbf{\delta}\) \\ \hline
0.169 & 0.0965 & 0.0243 \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Coefficient of frictional torque calculation values. Figure 17: Damping ratio of mini wind harvester. Figure 18: Linear Technology Spice (LTspice) model and real test results with 10 and 100 \(\Omega\) loads and with 3 and 10 m/s wind flow velocities. (**a**) LTspice model results with 10 \(\Omega\) loads and 3 m/s wind flow velocity. (**b**) LTspice model results with 100 \(\Omega\) loads and 3 m/s wind flow velocity. (**c**) Real test results with 100 \(\Omega\) load and 3 m/s wind flow velocity. (**d**) Real test results with 100 \(\Omega\) load and 3 m/s wind flow velocity. (**e**) LTspice model results with 10 \(\Omega\) loads and 10 m/s wind flow velocity. (**f**) LTspice model results with 100 \(\Omega\) loads and 10 m/s wind flow velocity. (**g**) Real test results with 10 \(\Omega\) load and 10 m/s wind flow velocity. (**h**) Real test results with 100 \(\Omega\) load and 10 m/s wind flow velocity. However, the mechanic limitations of the present prototype bearings set the maximum wind velocity to 10 m/s wind velocity. Table 16 and Figure 19 show a comparison of measures and simulations of the model under different wind flow powers with a load matching condition (27 \(\Omega\)). The measurements have a maximum voltage and power relative error, for a wind velocity of 3 m/s, of 3.43% and 7.21%, respectively; regarding the frequency, the error is 8.98% for a wind velocity of 6 m/s, which is less overall. The obtained results confirm that the model met the requirements and can be used in the research, as long as the three results that have an error higher than 5% occurring only in \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{\(R_{load}\) = 27 \(\Omega\)} \\ \hline \hline \multirow{3}{*}{_v_ **(m/s)**} & \multicolumn{3}{c}{**Results**} & \multicolumn{3}{c}{**Statistics**} \\ \cline{2-10}  & \multicolumn{3}{c}{**Real**} & \multicolumn{3}{c}{**Model**} & \multicolumn{3}{c}{**Relative Error (\%)**} \\ \cline{2-10}  & \(V_{p}\) **(V)** & \(P_{out}\) **(mW)** & \(f\) **(kHz)** & \(V_{p}\) **(V)** & \(P_{out}\) **(mW)** & \(f\) **(kHz)** & \(V_{p}\) & \(P_{out}\) & \(f\) \\ \hline
3 & 0.525 & 15.28 & 1.9 & 0.543 & 16.381 & 1.899 & 3.43 & 7.21 & 0.05 \\
4 & 0.745 & 31.16 & 2.569 & 0.729 & 29.525 & 2.548 & 2.15 & 5.25 & 0.82 \\
5 & 0.998 & 55.49 & 3.452 & 0.977 & 53.029 & 3.425 & 2.10 & 4.44 & 0.78 \\
6 & 1.413 & 111.02 & 5.047 & 1.437 & 114.721 & 5.5 & 1.70 & 3.33 & 8.98 \\
7 & 1.702 & 160.72 & 6.093 & 1.732 & 166.657 & 6.075 & 1.76 & 3.69 & 0.30 \\
8 & 2.085 & 239.69 & 7.311 & 2.079 & 240.125 & 7.301 & 0.29 & 0.18 & 0.14 \\
9 & 2.207 & 272.54 & 7.794 & 2.224 & 274.788 & 7.809 & 0.77 & 0.82 & 0.19 \\
10 & 2.451 & 333.15 & 8.766 & 2.469 & 338.665 & 8.65 & 0.73 & 1.66 & 1.32 \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Comparison of results between the real measurements and model simulation under different wind conditions with a load impedance matching condition.