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Use Cases for Communication Between Plug-in Vehicles and the Utility Grid: An Overview of SAE J2836-1-2019
SAE J2836-1-2019 establishes a structured set of use cases for communication between plug-in electric vehicles (PEVs) and the electric power grid. This information report defines the communication pathways, actor roles, and interaction flows necessary to support energy transfer and grid services. The 2019 revision expands the scope to include indirect communication via third-party aggregators and mobile service providers, reflecting the evolving ecosystem of electric vehicle charging.
Direct and Indirect Communication Pathways
The standard distinguishes two primary communication architectures: direct and indirect. In direct communication, the PEV communicates directly with the utility or energy service interface (ESI), allowing real-time exchange of pricing, load, and charging commands. Indirect communication introduces intermediary actors such as third-party energy service providers or mobile platforms, enabling additional services like charging station reservation and location-based optimization.
| Aspect | Direct Communication | Indirect Communication |
|---|---|---|
| Primary actors | PEV, Utility, ESI | PEV, Third-Party Provider, Mobile Service, Utility |
| Data flow | Direct PEV ↔ Utility | PEV ↔ Third-party ↔ Utility |
| Use cases | Smart charging, emergency demand response | Charging station location, reservation, aggregated response |
| Security requirements | End-to-end authentication with utility | Trust delegation to third parties |
🔍 The inclusion of indirect communication allows flexible business models, such as aggregator-managed charging and mobile app integration, without requiring direct utility connectivity for every vehicle.
Additionally, the standard defines how the Home Area Network (HAN) and Energy Management System (EMS) interact with the EVSE and utility, covering three distinct cases: the EMS as the primary utility interface, the EVSE as the interface, or the vehicle using a scheduled charging approach independent of real-time utility communication.
The EVSE: Bridge or Gateway? 🛠️
One of the critical design decisions in any vehicle-to-grid (V2G) implementation is the role of the Electric Vehicle Supply Equipment (EVSE) in the communication chain. SAE J2836-1-2019 clarifies that the EVSE can function as either a bridge or a gateway to the energy service interface (ESI).
| Function | Description | Example |
|---|---|---|
| Bridge | Passes data between vehicle and ESI without protocol translation; acts as a transparent relay. | Vehicle sends SEP 2.0 messages through EVSE to HAN. |
| Gateway | Translates between different communication protocols (e.g., CAN to Wi-Fi) and may perform local control logic. | EVSE converts J2847-1 messages to Smart Energy Profile for the utility. |
Engineering design insight: The modularization of communication segments—vehicle-to-EVSE, EVSE-to-utility, and EVSE-to-EMS—allows each interface to evolve independently. A gateway architecture introduces greater flexibility and support for legacy systems but also adds complexity and potential single points of failure. The choice between bridge and gateway depends on the existing network infrastructure, security requirements, and the need for protocol adaptation.
The standard provides several system diagrams illustrating the placement of these functions, including configurations where the EVSE interacts with the EMS or utility directly.
Standardized Use Cases and Optimization Strategies
SAE J2836-1-2019 employs a rigorous use case methodology derived from EPRI Intelligrid and UML. Each use case is described as a “package” containing a textual description, scenario matrix, equipment diagram, communication path diagram, activity diagram, and sequence diagram. This structure ensures unambiguous implementation guidance for both top-level use cases (defining actors and goals) and detail use cases (including specific scenario attributes and communication flows).
The standard covers key operational scenarios such as:
- Bulk charging: Simple time- or energy-based charging without advanced optimization.
- Optimized charging: Incorporates distributed energy resources (DER), user preferences, and price signals to minimize cost or integrate renewables.
- Reservation and location: Uses indirect communication to allow drivers to find and reserve charging stations via mobile providers.
These use cases form the requirements that must be supported by SAE J2847-1, the companion recommended practice for communication protocols.
⚠️ Common implementation pitfall: assuming direct PEV-to-utility communication is mandatory. The standard explicitly enables indirect paths when third-party or mobile providers offer equivalent functionality. Another frequent error is confusing the bridge and gateway roles of the EVSE, leading to architecture mismatch.
Frequently Asked Questions
- What is the difference between direct and indirect communication? Direct communication involves a direct logical path between the PEV and the utility, while indirect communication passes through one or more intermediary actors such as a third-party aggregator or mobile service provider.
- When should the EVSE operate as a bridge versus a gateway? A bridge is suitable when the vehicle and ESI use compatible protocols and no translation is needed; a gateway is used when protocol conversion or local intelligence is required to bridge different communication stacks.
- What are the key use cases covered in SAE J2836-1-2019? They include bulk charging, optimized charging (with DER and user preferences), charging station location and reservation, and emergency demand response, among others.
- How does optimized charging differ from bulk charging? Optimized charging considers real-time price signals, renewable availability, and user preferences to schedule charging, while bulk charging follows a fixed schedule (e.g., charge immediately or at a preset time) without optimization.
By standardizing these use cases, SAE J2836-1 provides a foundation for interoperable V2G communication systems that can adapt to diverse market and infrastructure conditions.
