# PV-Powered Charging Station with Energy Cost Optimization via V2G Services
## 6 Conclusions  
In conclusion, a PVCS with energy cost optimization and V2G service can provide a sustainable and cost-effective solution for EV charging/discharging, which can help grid operators by discharging EV batteries via with V2G services, leading to a more efficient system. The focus of the paper is to minimize energy costs, prevent EV penalization and PV shedding, and consider prediction errors in real-time simulations. Additionally, the paper analyzes energy distribution for the system and each EV to gain a better understanding of the system's functionality. However, there are still some challenges to be addressed in order to optimize the energy cost of the charging station. One of the main challenges is the optimal scheduling of the charging and discharging of the EV batteries to minimize the energy cost and to maximize the charging of EVs with PV power. Furthermore, the cost of implementing and maintaining a PVCS and V2G system can be high, and there is a need to establish standardization and protocols for integration with the existing public grid and communication networks. In addition, the type of an EV can affect the energy cost in the case of V2G because each type of EV has a different battery size, charging and discharging power characteristics, and energy efficiency. Battery EVs have larger batteries with higher power ratings than plug-in EVs and hybrid EVs, which means they can provide more flexibility for charging/discharging operations, and eventually they provide more energy to support the electricity grid. Although V2G operation is possible for FCEVs, the consumption/production of hydrogen can be inefficient compared to battery-based vehicles due to the low efficiency of fuel cells and electrolyzers. The simulation results show that variable charging and discharging power have major advantages over constant charging/discharging, as no penalization was imposed, and the EV users were satisfied. In addition, optimizing the charging/discharging power is cost-effective because EVs are charged during off-peak hours and discharged during on-peak hours into the public grid, resulting in greater profitability. Furthermore, the energy that EVs inject into the public grid during V2G service is significant, accounting for over 75% of the total energy injected into the public grid during V2G service. The optimization problem is applicable to both private (domestic, work) charging stations and public ones, regardless of their size. By participating in V2G services, EV owners and/or charging station operators can generate revenue and reduce the total energy cost of EV charging, while also providing grid services to improve the reliability and efficiency of the public grid. The HMI allows for the operation of both a single EV and multiple EVs, and the number of EVs that can be operated is only limited by the number of charging terminals. However,the size of the charging station can affect the applicability of optimization problems for V2G services. For example, a small charging station (e.g., one EV in a residential building) can participate in V2G service to support the electricity grid and earn revenue in return for its services; however, it will have limited power support capacity, and hence it may not be able to provide significant aid individually. In contrast, a large charging station (e.g., 100 EVs in a university parking lot) will have more power capacity, which can enable more significant V2G services for the electricity grid based on its requirements. For future research, the degradation impact on EV batteries will be studied, as well as the environmental impact. Moreover, more case studies will be conducted to validate the optimization method and demonstrate its feasibility in real-time experimental tests under the concept of power hardware in the loop. Furthermore, annual simulation will be considered where optimization and real-time simulation take into account annual irradiation profiles, temperatures, and EV profiles. Conceptualization, S.C.-M., B.C., M.S. and F.L.