## 5 Discussion  
From Section 4, it is evident that the proposed community solar operation strategy achieves near-optimal electricity bill savings and distributes the benefits of electricity bill savings to the members in relation to the optimal operation of P0 using the information on the future time. Based on these results, the following key points were derived for community solar operation in SECs.  
* The central objective of the community solar operation strategy in P0 is to maximize the overall electricity bill savings of the members; however, the strategy requires information on the future time. The proposed distributed strategy with partial information has a slightly less electricity bill savings compared to P0, as shown in Table 2. However, the optimal gap was less than 10% without the consideration of a small community solar capacity of 50 kWp, as shown in Figure 7. Moreover, the proposed strategy distributes the electricity bill savings of the members more fairly than the strategy in P0. This verified the effectiveness of the proposed community solar operation strategy.
* The electricity bill savings per community solar capacity in Figure 8 and Jain's fairness index in Figure 9 exhibit completely opposite shapes. This implies that there is a trade-off between the electricity bill savings and guarantee of fairness.
* The savings on the electricity bill were directly proportional to the community solar capacity, as shown in Table 2. However, the efficiency, measured as the electricity bill savings per capacity, was reduced with increasing community solar capacity, as shown in Figure 8. Moreover, increasing the community solar capacity requires additional investment from the SEC members; thus, an appropriate community solar capacity implementation is required when configuring a community solar system for the SEC.
* The fixed proportional operation strategy presented as PP has a large optimal performance gap compared to the centralized and proposed operation strategies, as shown in Figure 7. However, the electricity bill savings per community solar capacity in the PP strategy were decreased with increasing community solar capacity, as shown in Figure 8. Particularly, the Jain's fairness index of PP was closest to the optimal value (c.f., the optimal Jain's fairness index is 1), as shown in Figure 9. This implies that the PP strategy can be used as a baseline community solar operation strategy for SECs. This study also presents a distributed fair community solar operation for SECs, and the following future research directions are suggested.
* In this study, the implementation cost of community solar power was neglected. As discussed above, by increasing the community solar capacity, the benefits of electricity bill savings and cost of generation are also increased. Therefore, the community solar  
Figure 10: Distribution of the electricity bill savings per allocated capacity of each member when the community solar capacity is 100 kWp. (**a**) The P0 case. (**b**) The proposed strategy case. (**c**) The PP case.  
implementation issue can be investigated in future research considering the trade-off between the benefits and costs.
* This study assumed a case in which the SESP implemented and operated community solar generation and distribution. This can be extended to a case where third-party service providers such as a community solar service providers (CSSP) are used to implement community solar generation and the SESP rents the community solar capacity. In the extended case, the benefit distribution between the CSSP and members of the SEC can be formulated as a new problem.
* This study did not consider the energy transaction constraints such as transmission and distribution congestion and cost because the SEC consists of members in close proximity to each other. Therefore, this study can be extended to large-scale grid connection systems by considering the energy transaction constraints.