## 5 Discussion  
From the results in Section 4, it is clear that the proposed dynamic VESS operation by **P1** provides more benefits to the VESS service participants and utility grid than the existing VESS operation using **P0**. Based on the results, the following recommendations can be made for VESS operation in SECs:  
* The proposed dynamic VESS operation considering the usage-limited constraint is more cost-effective than the existing VESS operation with a capacity constraint, as shown in Figure 3. The effective peak demand reduction in the proposed VESS operation represents significant savings on the demand bill, as shown in Figure 4. This shows that the peak demand dominates the VESS operation and the proposed VESS operation more adaptively operates the VESS to maximize social welfare compared to the existing VESS operation.
* When the proposed VESS operation is applied, more units can participate in the VESS service, as shown in Figure 6. The reason is that it is possible to obtain not only the benefit from the reduction in the service cost according to the existing economics of scale but also the benefit of savings on the demand bill according to the additional decrease in the peak demand.
* The PLCC results of the proposed VESS operation have a higher correlation with the characteristics of the participants, as shown in Figure 7. This means that the proposed VESS operation accurately reflects the characteristics of the participants compared with the existing VESS operation.
* In all the cases where the implemented VESS capacity is changed, the peak demand is considerably reduced by the proposed VESS operation compared with the existing VESS operation, as shown in Figure 5. Peak demand affects the system operation  
Figure 8: Return of investment of participants with varying the price factor.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Price Factor**} & \multicolumn{3}{c}{**Energy Price (USD/kWh)**} \\  & **Off-Peak** & **Mid-Peak** & **On-Peak** \\ \hline \(0.0=\left(\begin{array}{c}0\\ 0.0290\end{array}\right)\) & 0.0799 & 0.0799 & 0.0799 \\ \(0.5=\left(\begin{array}{c}0.0145\\ 0.0290\end{array}\right)\) & 0.0638 & 0.0870 & 0.0973 \\ \(  
performance of the utility grid as well as the electricity bill of the units. The peak demand reduction increases the benefits for both the units and utility grid.
* With increasing the variance of the electricity tariff, the economic benefit, i.e., ROI, is improved, as shown in Figure 8. This means that the VESS is dynamically operated according to the electricity tariff. This study presents a dynamic VESS operation strategy for SECs, and the following future research directions can be suggested:
* This study has considered passive units to be the energy consumers. However, with demand-side management programs such as the demand response and peer-to-peer energy transactions, a unit can be operated as an energy consumer that acts as both the consumer and producer. A VESS operation problem can be formulated by considering an active unit with demand-side management programs.
* By using the proposed VESS operation, more units can participate in the VESS service. However, the benefits of the VESS service vary from participant to participant. The fairness problem can be considered to ensure fairness in the VESS operation.
* Flexible resources, such as electric vehicles, can be considered as resources. An increase in the implemented VESS capacity increases the benefits of the VESS operation. However, increasing the fixed VESS capacity reduces the ROI. Therefore, a problem considering fixed and flexible ESS resources can be formulated for dynamic VESS operation.
* This study has not included the costs of energy distribution and transmission to the ESS. This is because the energy community exists within close distance, usually at the same distribution line. The system can be extended to large-scale grid connection cases with the cost.