Electric vehicles are promising and essential to reduce the carbon footprint from the transport sector. Grid power is the primary source to charge the EV. Currently, grid power which comes from burning fossil fuel is not environmentally benevolent. Solar-powered electric vehicles are promising as the required power to charge the EV comes from the PV system, which generates benign energy. PV system can be installed in the car shed or rooftop of a building. For commercial buildings, vehicles are mainly parked during the peak solar radiation time, which can be utilised to charge the EV by employing PV.
Green power generation from PV technology is extremely promising. In 2017, 500 TWh benign electricity was produced globally from a PV system. In 2019, 500 GW PV was installed, 90 times higher than in 2006 . The use of renewable solar energy is accessible to a wider audience due to the falling cost of the PV systems. Hence, the PV has potential to be source for the EV. A PV powered EV is only suitable for the BEV which can be considered a complete zero emission technology, as nonrenewable and renewable are both still considered as a source.
The inclusion of the EV into the grid-powered charging station enhances the grid instability . A grid-connected charging station that can supply more than 100 kW to fully charge a 36 kWh battery in 20 min can impose energy losses in the grid if it charges ten vehicles simultaneously (imposing 1000 kW load) with the same capacity . The PV system can supply charging power to EVs as a standalone system. The BEV is a particularly well-suited potential candidate which can be powered directly by the PV. The PV generation system is a complete set where components such as the PV generator, battery, charge controller, inverter, and system load are interconnected and directly convert solar irradiance into electricity. These PV power generation plants are not connected to any utility grid. This system possesses several advantages, for example, grid dependency will be reduced, which in turn reduces the risk of grid failure due to EV penetration; and the EV battery can increase the storage facility and can supply everything in the form of vehicle-to-everything (V2E/V2X) which includes vehicle-to-grid (V2G), vehicle-to-home (V2H), vehicle-to-building (V2B), vehicle-to-load (V2L), and vehicle-to-vehicle (V2V) .
A standalone PV system can be installed at office buildings, domestic house rooftops, factories, industrial areas, universities, and car parking areas for EV charging (as shown in Figure 1) . Generally, employees park their vehicle for a minimum of 8 h during daytime when solar radiations are available and grid electricity demand is also high. Without the need for battery storage, this charging is possible and can mitigate the negative impact of excessive PV-generated power . This “charging while parking” is a very popular concept nowadays . It is also possible to install a PV-powered charging station at a remote location where a large grid is not available . A 10.5 kW AC PV array and a 9.6 kWh lithium-ion battery was employed to power lightweight EVs in university campuses .
Figure 1. Concept of a solar powered EV charging station .
Variability of PV power generation can be an obstacle for a PV–EV combination. Due to the diurnal nature of PV power generation, load charging is often performed during daytime at universities, offices, etc. . Using an open source model, it was predicted that nonPV generation may require EV charging to serve the afternoon hours, as only a small portion of transportation demand can be achieved from the high capacity of photovoltaic power generation . Variability can be predicted by employing a probabilistic- or a deterministic-enabled prediction a day ahead of real-time PV output, or a combined state of charge (SOC)-based fair EV charging strategy incorporating a noniterative PV output based on the historical PV ramp data and the real-time measurement . Voltage fluctuation from the PV system was controlled using a large capacity connected in parallel with the PV module .
Vehicle to grid (V2G) concept perceives an EV not as load but as a source from where its battery power can be supplied to grid . Hence, the EV can provide the grid support by regulating voltage and frequency, peak power shaving and spinning reserve . Parked vehicles during grid-connected charging or idle mode can be employed to let active and reactive power flow from the car to the to the grid and power lines. Large-scale deployment of EVs enhances the uncontrolled charging and discharging, significantly influening the power system which can be controlled using a V2G system . For V2H, EV batteries supply energy to a building when the main source of building power cannot meet the building energy demand .
A bidirectional converter is an essential power electronics component which allows an EV to be a source for the grid, load, other vehicles and homes. The use of unidirectional converters allows EVs to charge using the charging station (which is primarily powered from the grid), whereas the bidirectional converter allows vehicle to be a source of power and supply to others (grid, load, homes, etc.), hence electricity can flow in both directions. A new topology was investigated where voltage source converters converted solar farm generated power (200 kWh) and further voltage level was modified using a buck boost converter and harmonics, and transients were removed using a low pass filter. A bidirectional converter between the battery storage and DC microgrid maintained the power flow by charging and discharging the battery power . The investigation was also performed using PV system battery storage which was directly connected into a medium voltage direct current bus, and with the grid for EV charging. The medium voltage direct current bus voltage played a key role in controlling the system . For Irish climate, the performance of a 6.65 kW PV to charge four EVs was simulated, and the results indicated that in summer, an EV with 90% SOC using home charging facility can run 100 km daily. The performance was also compared for AC and DC distribution systems which showed that the AC system efficiency was 4.67% lower than the DC system over a year . A highly efficient and power-dense three-port converter was developed to integrate the EV, PV and grid to meet the standard of the combination of the CHAdeMO and the Combined Charging System (CCS) .
A variety of charging methods utilising PV have been explored suggesting that, subject to local energy tariffs, solar workplace roofs are a favourable solution. However, with the advancement of thin film PV technology, a concept described by Bhatti et al. as a vehicle integrated PV (VIPV) has been suggested as another elegant solution to charging EVs. However, VIPV as the sole power source of a BEV has been shown to be limited due to several factors, including the low power density available. Similarly,  deduced that in the study location of Newark which has an array with a peak power of 300 WP and an inverter efficiency of 90%, the VIPV could account for just over 12% of the yearly miles of a Chevy Volt. The study concludes that due to the limited space available on commercial passenger vehicles and subsequent low power density, VIPV may only be considered as a supplement to plug-in charging techniques. The feasibility of VIPV, particularly for large commercial vehicles with big roof surfaces, was conducted using diesel energy equivalent, payback time, potential savings of costs, and CO2 parameters. It was shown that a 1 m2 monocrystalline-based VIPV system integrated into a truck can save up to 1100 litters of diesel in a vehicle with a lifetime of ten years . It was predicted that VIPV is a solution but low light condition and rainy season EV still needs power from external charging station which can be grid powered or SPV system .