Blockchain architecture for multi-site electric vehicle charging coordination

Electric Vehicle (EV) charging management in buildings is constrained by dynamic tariffs, power caps, contractual limits, and user requirements, while isolated building-level schemes often underutilize available grid capacity. Blockchain enables trusted multi-site coordination but faces scalability challenges due to high update rates, telemetry overhead, and smart-contract limits. This paper introduces a platform-agnostic, event-driven architecture for multi-level EV charging coordination across several buildings. The framework satisfies building-level constraints, grid import limits, and individual EV requirements while leveraging diversity in EV arrivals and energy needs to maximize delivered energy. The architecture uses blockchain for cross-site coordination and immutable event logging, and employs a lightweight off-chain MILP scheduler to overcome data-rate, throughput, and smart-contract limitations. A threshold-triggered event mechanism, paired with a profitability metric, links operational savings to per-event fees and exposes a configurable trade-off between responsiveness and cost. Simulations show that delivered energy increases from 222 kWh to 387 kWh and served EVs rise from 11 to 44, while maintaining grid import limits. Rebased savings reach 17% and exceed blockchain transaction fees incurred by event-triggered updates at a 1 kW threshold.