AUTHORS: Luce Engérant and Jeff Turner
Vehicle to grid (V2G), or the ability for EVs to return power to the grid, is getting closer to reality with the launch of the new all-electric Ford-150 Lightning earlier this spring. Ford has announced that the iconic pickup will not only run on electricity but will also be able to power customers’ tools or homes. In this article, we zoom in on V2G technology: the benefits it can bring to the grid, and key regulatory considerations for deploying it at scale.
WHAT IS VEHICLE TO GRID?
Vehicle to grid (V2G) is a form of vehicle-grid integration (VGI) – broadly defined as solutions that allow EVs to interact with the power grid. Vehicle-grid integration can potentially alleviate stresses EVs could cause to the grid (e.g., peak load impacts) and generate benefits (e.g., potentially synchronize EV charging with renewables). We recognize two forms of vehicle-grid integration:
- Smart charging (V1G), also known as controlled uni-directional charging, optimizes when and how much an electric vehicle is charged by enabling communication between the vehicle and the grid.
- Bi-directional charging, allows EVs to return energy to plug loads or the grid. While vehicle-to-grid (V2G) is the only form of bidirectional charging that is truly grid interactive, these two terms are often used interchangeably. There are different types of bi-directional charging:
- Vehicle to Load (V2L), where an EV powers a device (e.g., a tool at a worksite)
- Vehicle to Home (V2H) or Building (V2B), where an EV powers a home or building that is not connected to the grid (e.g., during an outage)
- Vehicle to Grid (V2G), where an EV returns electricity back to the grid. The key difference between V2H and V2G is whether the home is grid-connected. Returning energy to a grid-connected home is technically considered V2G.
So far, the electric F-150 is set to include both V2L and V2H features from the get-go – e.g., allowing customers to power tools (V2L) or a home during an outage (V2H). However, Ford has announced that the electric pick-up will eventually be able to power grid-connected homes during peak energy hours: a form of V2G.
V2G ON THE HORIZON: BENEFITS & HURDLES
While V2G has been discussed with excitement for many years, it has not always been clear whether it would get support from automakers to move beyond limited trials and demonstrations. But with V2L and V2H capabilities trumpeted as headline features of the electric version of North America’s best-selling vehicle, V2G has suddenly come much closer to reality. With bidirectional charging capability already integrated into the electric F-150, we can focus on what is needed to make the incremental step from V2H to V2G: utility programs.
Vehicle to Grid can provide several benefits to utilities and stakeholders at large. Like energy storage, V2G-enabled vehicles could:
- Enable energy arbitrage, allowing vehicles to charge when electricity rates are low (e.g., overnight) and discharge when rates are high (e.g., during peak demand events).
- Allow distribution congestion relief for system operators.
- Help to defer necessary investments in new grid capacity.
As seen with the all-electric F-150 (and hybrid F-150, released last year with V2L capability), customers see significant value in providing worksite power or backup power from their vehicle. However, the benefits of V2G are less obvious to customers. V2L and V2H can bring bidirectional charging capabilities to the market, but there won’t be significant demand for V2G functionality until utilities recognize the value of V2G for the grid, and design programs that provide a sufficient incentive for EV owners to participate. With the right programs and incentives in place, we can expect customer demand to drive automakers to incorporate V2G capabilities into their products.
Utilities and regulators, therefore, need to consider some important questions: What is the value of V2G to the grid? How does it compare to other distributed energy resources? What is the best way to incentivize V2G to get desired grid benefits?
WHAT CAN UTILITIES AND REGULATORS DO TO SUPPORT V2G?
To support V2G, utilities and regulators can find inspiration from other distributed energy resources. In other words, look at the processes they have in place to allow customers to install rooftop solar or energy storage on their property and adapt them for EVs. For example, utilities could clearly define and streamline interconnection / V2G charger approval processes or establish incentive policies (e.g., strong Time of Use signals, other demand response incentives creating savings opportunities).
Utilities and regulators need to pay careful attention to an important distinction between AC and DC charging, two common types of EV charging that require different approaches for enabling and regulating V2G capabilities. V2G requires bidirectional power conversion equipment (a bidirectional “charger” or “inverter”), and the use of either AC or DC charging will determine whether that equipment is integrated in the charging station or in the EV.
For DC charging, the conversion between AC grid power and DC battery power happens in the charging station. With a stationary inverter, bi-directional DC chargers can therefore be treated similarly to stationary energy storage or solar PV systems. The energy storage in a vehicle may be mobile, but the critical grid interface (the inverter) remains in a fixed location.
On the other hand, AC charging relies on the vehicle’s on-board charger, and V2G functionality would include a bidirectional charger/inverter that is integrated into the vehicle. This would turn the EV into a truly mobile distributed energy resource, introducing additional risk and complexity from a grid management perspective. As opposed to stationary devices, utilities will have a harder time verifying inverters located in each customer’s EV, especially if that vehicle can just as easily relocate and discharge into the grid in an entirely new location. To ensure inverters meet safety and interoperability requirements, utilities could require EVs to follow industry standards being developed for V2G, such as SAE J3072. The SAE J3072 standard defines interconnection requirements for mobile inverter systems. It defines communication norms between the EV and the charging station to allow the EV to safely discharge at a given site.
CONCLUSION: THE KEY ROLES OF UTILITIES
To conclude, V2G is a technology that can bring significant benefits to the grid but will require utility programs and incentives to deploy at scale. Recent V2L and V2B offerings on the market suggest that the necessary technical developments are at our doorstep. Utilities and regulators in Canada should start thinking now how best to incentivize V2G to meet grid objectives, building on experience with distributed solar and storage, and adapting as needed to accommodate the mobile nature of V2G-enabled EVs.