# PV-Powered Electric Vehicle Charging Stations: Preliminary Requirements and Feasibility Conditions
## 5 PV-Powered EV Charging Station Simulation Results and Analyses
### Discussion  
In scenario 1, only one EV is charged in slow mode with a private charger. It is shown that the known park time could bring PV benefits and reduce public grid dependency, which will decrease the charging price for the EV user. In Scenario 2, there are five EVs that are charged with public chargers. Regarding scenario 2a versus 2b, where all EVs are charged in slow mode, it is shown that scenario 2b may be superior to scenario 2a, where PV benefits are greater since the park time is known for each EV. Regarding scenario 2c versus 2d, where three EVs are charged in slow mode and two EVs are charged in fast mode, it is shown that EVs charged in fast mode depend mainly on the public grid and stationary storage energy while EVs charged in slow mode depend on PV energy. However, when the park time is known and longer than the time actually needed to charge, PV benefits could increase and public grid dependency could be reduced. Regarding scenario 2e, the same conditions as for scenario 2c are applied but EV2 requests full charge (100%) in fast mode. It is shown that EV2 affects negatively EV1 and EV3 since they coincide some of the time, this will reduce PV benefits for EV1 and EV3. Moreover, EV2 is largely dependent on the public grid and stationary storage energy. The stationary storage power is limited to 7 kW, so it will not be emptied quickly if some EVs want to charge in fast mode. The simulation results show, for fast charging mode, that EVs depend mainly on public grid energy. Moreover, the public grid energy tariff is dynamic in reality and it is high in peak times. Therefore, EV users who want to charge in fast mode are supposedly willing to pay higher bills. However, knowing that charging the EV in fast mode is costly, EV users will tend to change their behavior and choose to charge in slow mode since it is cheaper. Hence, an economic model is necessary for the PV-powered charging station to optimize the EV charging power, have the best power distribution for energy sources, and have the lowest cost for charging EVs, which is the key factor to influence EV users. Nevertheless, uncertainties always exist in the real world. However, in the present study, the uncertainty of the demand profile by EVs is always ensured by first, the stationary storage and then by the public grid when there is uncertainty in PV generation to ensure power at all times. Regarding the EV's capacity, it is assumed that all EVs are the same. For EV's SOC and operating schedules, these are taken as hypotheses, where they represent the data and choices of EV users that they choose through the human-system interface. The demand profile of EVs is hard to predict as it depends on various factors (type of user,  
Figure 25: EVs energy distribution for Scenarios 2c and 2e. charging preference, and energy demand). Therefore, the arrival time of the EV, SOC of the EV at arrival, and its requested SOC at departure are assumed arbitrarily but cover many cases. Finally, to increase PV benefits, the preliminary requirements and feasibility conditions for a PV-powered charging station may be summarized as follows:  
1. Slow charging is characterized by: * Charging power up to 7 kW; * Based on PV energy and stationary storage, which is charged by PV sources only; * Stationary storage should be well designed and its power should be limited; * EV battery filling up to 6 kWh; * User acceptance for long and slow charging. 2. For fast charging mode: * Charging power from 7 kW up to 22 kW; * Based on public grid energy; * Stationary storage should be well designed and its power should be limited at 7 kW; * User acceptance for high charging price. Moreover, PV power generation depends on the geographical location and weather conditions, as solar irradiation and the temperature of the PV modules. Proper sizing of the stationary storage is required. A user interface is required to facilitate the interaction between the EV users and the charging station and to take into consideration EV user choices.