Phased Planning of Heavy-Duty Electric Vehicle Charging Stations: An Optimization Framework Under Grid Capacity Constraints

The electrification of heavy-duty vehicle fleets is an important component of the clean energy transition in the transportation sector. However, this process presents challenges, including high power demand from electrified vehicles, limited charging station (CS) availability, and long grid upgrade timelines. Existing studies focus on light-duty vehicles, overlooking the impact of grid constraints and phased fleet expansion on heavy-duty electric vehicle (HDEV) CS planning. Here, we present a novel optimization framework to show that depot-based HDEV CSs can operate within existing grid capacity limits, thus eliminating costly and time-consuming grid upgrades. Specifically, we evaluate three potential CS configurations for a phased HDEV rollout: fully renewable energy (FRE)-based CSs, partially renewable energy (PRE)-based CSs, and storage buffer (SB)-based CSs. These are evaluated within three potential grid capacity limits – 500 kW, 1 MW, and 5 MW – in a real-world case study in California. Our results show that SB-based CSs offer the lowest total annual cost, reducing costs by 59% compared to FRE-based CSs, while PRE-based CSs provide greater grid independence with larger land requirements. Phased expansion planning reduces costs by up to 69% in early stages. This study provides insights for policymakers and fleet operators to accelerate cost-effective, large-scale HDEV electrification.