Figure 5.

Electricity system generation capacities: the total available generation capacity divided by the total (EV + main) load is shown for unidirectional (V1G) and bidirectional (V2G) EV for the full range of EV-to-main load fraction ($E{V}_l/M_l$). Grid-battery capacity is delineated in kW by dividing the kWh capacity by the charging/discharging time (h). As $E{V}_l/M_l$ in both V1G and V2G increases, the Natural Gas system capacity significantly reduces at modest EV penetration levels, and remains relatively constant as EV penetration increases. The capacity expansion in VRES + Battery systems significantly reduces at modest EV penetration levels, and gradually continues to decrease as more EVs are added to each system. In V1G, the grid-battery remains present, while V2G rapidly substitutes for the grid-battery. In all cases, cost and total non-curtailed generation decrease monotonically with increased EV penetration, but capacities deployed can increase due to differing capacity factors across technologies.