# PV-Powered Electric Vehicle Charging Stations: Preliminary Requirements and Feasibility Conditions
###### Abstract  
Environmental benefits lie in halting direct air pollution and reducing greenhouse gas emissions. In contrast to thermal vehicles, electric vehicles (EV) have zero tailpipe emissions, but their contribution in reducing global air pollution is highly dependent on the energy source they have been charged with. Thus, the energy system depicted in this paper is a photovoltaic (PV)-powered EV charging station based on a DC microgrid and includes stationary storage and public grid connection as power source backups. The goal is to identify the preliminary requirements and feasibility conditions for PV-powered EV charging stations leading to PV benefits growth. Simulation results of different scenarios prove that slow charging with long park time could increase PV benefits for EVs and may reduce the charging price, therefore, EV users should be more willing to stay at charging stations. Whereas, for fast charging, EV users should accept the high charging price since it depends on the public energy grid. Energy system distribution and EV's energy distribution are well presented. charging station; electric vehicle; energy distribution; feasibility conditions; photovoltaic energy; power flow management; microgrid +
Footnote †: journal: Applied Sciences  
APPLEMENTARY  
Nevertheless, the charging of EVs will become a serious issue and will increase the burden on the public grid, as EV stock continues to grow and expand. The charging of EVs during the day will increase the peak load, as shown in Figure 1a. However, EVs are considered a flexible load unlike uncontrollable loads; therefore, the charging of EVs can be controlled and shifted to other times to prevent the peak load by implementing a smart charging framework, for example, overnight charging as shown in Figure 1b. However, this can constrain EV users, whose behavior is hard to predict and control. To overcome this constraint, the EVs can charge with photovoltaic (PV) energy which is a reliable and effective option, to reduce the burden on the public grid [2]. Thus, while the EVs are being charged with green energy [3; 4], the EV market will be encouraged since EVs contribute to minimizing the impact of transportation on the environment [3; 5; 6]. Different charging/discharging frameworks of EVs exist [7]:  
1. Uncontrolled charging: the EV starts charging immediately until its battery is fully charged or the EV user unplug their vehicle [8]. This framework can be expressed as uncoordinated charging or immediate charging where the EV is charged at maximum power with no restrictions [9; 10]. In this framework, there is not any interaction between the EV users and the electrical grid. This is the worst scenario since it charges the EV with the maximum power to be fully charged in the shortest time imposing difficulties on the grid and peak load [11]. 2. Delayed charging: when the park time (time duration for an EV parked in a station) is longer than the actual required time of charging, therefore, the EV charging can be delayed taking into account the time of use price and can be charged during the low-cost and off-peak energy period [8; 9]. 3. Average charging: the EV is charged at constant power depending on the park time in which the EV is able to meet the requested state of charge (SOC) or full SOC, where it is not necessary to charge with full power [9; 10; 11]. 4. Smart charging: the EV users provide the public grid with information regarding the park time and the requested charge that must be supplied before leaving the station. Therefore, renewable energies are used first to supply the load then the public grid will control and shape the EV charging profiles and minimize the charging costs [8]. 5. Smart discharging: known as vehicle-to-grid, the EVs act as stationary storage allowing to discharge power back to the public grid [8]. This will improve the electrical grid efficiency and reliability.