## 3 Results
### Flow Rate's Influence on Discharging Performance  
After being converted into chemical energy, electrical energy is typically stored in external tanks in the form of an electrolyte solution, and electrolyte transport occurs through pipes, with the flow aided by pumps. The flow rate of the electrolyte is directly proportional to the efficiency of the battery's operation [44]. A higher electrolyte flow rate improves the overall performance of VRFBs. A high increase in flow rate, on the other hand, may result in high energy consumption during loading, reducing the VRFB's energy efficiency [31]. As a result, it is critical to determine an appropriate electrolyte flow rate in order to balance system capacity acquisition with efficiency loss [45]. It should be noted that the discharging in this step used charged reactants produced by 1.7 V of the charging voltage. The electrochemical polarization curves determined during the charging period illustrated that the performance of the VRFBs was increased with an increase in the electrolyte flow rate (Figure 8). The polarization curves show that the ohmic and concentration losses increased when electrolytes were fed at the lowest rate of 5 mL/min. On the other hand, in the areas of activation, ohmic, and concentration losses, the highest rate offered the slower rate of voltage decay. The performance gain at the focus loss was the most striking among these improvements. The concentration gradient between the concentration of \begin{table}
\begin{tabular}{c c c} \hline \hline
**Applied Voltage** & **Maximum Power (mW)** & **Voltage Efficiency (\%)** \\ \hline
1.6 V & 30.28 & 53.45 \\
1.7 V & 38.46 & 50.46 \\
1.8 V & 27.40 & 48.38 \\
1.9 V & 30.80 & 45.64 \\
2.0 V & 31.27 & 43.57 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Maximum power and voltage efficiency obtained from polarization curves. Figure 7: (**a**) Polarization curves and (**b**) power vs. current density plots obtained from the discharging process following electrolyte preparation with various applied voltages. the bulk electrolyte and the concentration of the electrode surface is what is thought to be responsible for the restricted mass transit [44]. As a result, feeding electrolytes into the VRFB cell at an appropriate flow rate can alleviate this limitation and improve the reaction capability on the electrode surface. The lower the flow rate, the lower the mass transport coefficient and the wider the Nernst diffusion layer [11]. The link between the flow rate and the current produced on the electrode is shown in Equation (8) [46]. Along with affecting concentration loss, the electrolyte flow rate also has an impact on the liming current density. Electrolyte flow rates can be split into two categories: the flow rate of the electrolyte reactant diffusing through porous electrodes, and the flow rate of the electrolyte reactant flowing into a flow battery. The electrode structure and design affect the electrolyte diffusion through porous electrodes. During operation, the electrolyte flow rate going into the battery can be changed. \[\mathrm{i}=0.9783\frac{\mathrm{nFD_{\mathrm{c}}}}{\mathrm{L}}\int\limits_{0}^ {\mathrm{L}}\left(\frac{\mathrm{u}_{\mathrm{f}}}{\mathrm{hDx}}\right)^{1/3} \mathrm{dx} \tag{8}\]  
where L is the length of the flow channel, u\({}_{\mathrm{f}}\) is the averaged electrolyte flow velocity along the flow channel, h is the distance between the electrode and one flat plate, c is the bulk concentration, D is the diffusion coefficient, F is Faraday's constant, n is the number of elementary charges transferred by each ion, and i is the current. Additionally, the electrolyte flow rate affects both the pressure and retention time of the reactant reaction in the VRFB system, as well as the electrolyte velocity. In reality, the flow rate in the VRFB system is only one factor in determining pressure; another is the flow behavior in the electrode structure. A porous electrode's fluid flow is explained by the Navier-Stokes equation.