(87f) Exploring the Role and Value of Bidirectional Electric Vehicle Dispatch in Low-Carbon Power Systems

To ensure resiliency across low-carbon, renewables-dominated power systems, adequate dispatchable power and reserve capacity is critical to balancing intermittent variable renewable energy (VRE) supply with the demands of an increasingly electrified world. To this end, vehicle-to-grid (V2G) servicing has been proposed as a form of flexible load and decentralized energy storage for future “smart grids”. Within a V2G framework, grid-connected electric vehicles (EVs) can both draw power and discharge to the grid. Operationally, a V2G aggregator coordinates and optimizes the charge and discharge of individual vehicles to function as a synergistic, bulk energy resource and load.

Here we are the first to assess V2G potential through the lens of its long-run system value and implications for future generation and stationary storage requirements in the context of the high EV, low carbon futures it would service. Informed by regional load, weather, and performance datasets, our integrated simulation framework both elucidates where and how V2G derives value and provides insights to optimal V2G dispatch and region-level infrastructure requirements.

We introduce a custom V2G storage class to an open source capacity expansion model (CEM) and quantify its impact via the greenfield buildout and operation of a New England-sized power system in 2050. Akin to an independent system operator (ISO), the CEM makes system-wide investment and operational decisions for least-cost optimization of meeting forecasted electricity demand over the course of one year at an hourly resolution. The V2G class, which is configured to provide power injection, demand response, and ancillary services, interfaces with the power system model at a clustered vehicle resolution and is governed by time-dependent power, energy, and demand constraints that account for degradation costs associated with EV battery cycling. We also employ a unique, destination-based system topology (i.e. homes, workplaces) that enables us to independently quantify the system value and storage displacement specifically derived from (1) location-specific charging infrastructure investments (2) overall and destination-based V2G participation, and (3) specific services offered to the grid.

With high EV penetration (60% of the light duty vehicle fleet) and emissions targets informed by 2050 decarbonization goals of the New England states (50 gCO2/kWh load), we find that V2G impact on generation capacity and system value is substantial. In our base case, 23.1% EV participation (13.9% of the LDV fleet) entirely displaces 14.7 GW of stationary storage capacity (6h duration) and reduces overall system cost by 12.5% relative to the non-V2G baseline. At 80% participation, savings increase to 20.9% and carbon emissions are reduced from 50 to 44 gCO₂/kWh load. The monetary value of V2G servicing is primarily driven by the displacement of stationary storage, followed by reductions in firm generation capacity and shifts in renewable generation portfolios.

At low V2G participation rates, large uncontrolled evening charging peaks are partially offset by EV power injection. As participation increases, more of the EV demand is controlled, allowing it to be dispersed to periods with smaller baseloads and higher VRE availability, which in turn reduces peak gas firing and requires less frequent peak shaving services. This load shifting is a critical aspect of V2G servicing and its realized value, as the unsupervised EV demand, on average, constitutes 32% of peak evening loads. Likewise, increased V2G storage availability also lends to more efficient VRE utilization while also reducing thermal starts and required generation capacity, as renewables generation is shifted from periods of high availability to those of low availability and high net loads. And while V2G injection to the grid constitutes only 2-3% of total generation, the conferred reduction to stationary storage and gas is substantial. By comparison, demand response alone, with no bi-directional capabilities, offers storage displacement and cost savings at 40-50% of the bi-directional V2G rate. Finally, we demonstrate that the value of bidirectional charging infrastructure in commercial areas is minimal, as value is primarily derived from servicing residential loads, where unsupervised evening load peaks are most prevalent and are complementary to high daytime VRE generation.