Grid Impacts of Electric Vehicles and Managed Charging in California

Deep changes are occurring in both the transportation and electricity sectors with the adoption of plug-in electric vehicles (PEVs) and the addition of renewable energy (RE) resources to the generation mix. We use California as a case study to examine the synergies of these two energy transitions, by evaluating the economic value and RE grid integration impacts of different penetration levels of PEVs (ranging from 0.95 million to 5 million PEVs) under various charging strategies. We consider the effects of smart charging and time-of-use (TOU) charging, under a State mandate requiring that utilities produce at least 50% of electricity from renewable sources by 2025. Previous studies that have evaluated such managed PEV charging strategies have shown them to help integrate RE into power grids but have not demonstrated feasibility by fully representing constraints imposed by the mobility requirements and charging choices of PEV drivers. We fill this gap by linking high-resolution travel behavior and grid production cost models that more accurately characterize charging infrastructure, travel demand, and grid dispatch constraints. We find that the flexibility inherent in PEV smart charging patterns can provide substantial benefits to the power sector, primarily in lowering grid operating cost and the amount of RE that must be curtailed (turned down or off from the level that they would otherwise be producing) to avoid over-generation when supply and demand are mismatched. For example, if treated as flexible loads, 2.5 million smart charging PEVs avoid about 50% of incremental system operating costs annually and reduce renewable energy curtailment by about 30% annually relative to when the same number of unmanaged charging PEVs are added to the grid. Overnight TOU charging provides similar cost savings, though not curtailment reductions, without incurring smart charging implementation costs. Both smart and overnight TOU charging can defer system infrastructure expansion at PEV deployment of 5M, which is the State’s goal for 2030.