Scaling Up Electric-Vehicle Battery Swapping Services in Cities: A Joint Location and Repairable-Inventory Model
74 Pages Posted: 22 Jul 2020 Last revised: 25 Oct 2021
Date Written: June 19, 2020
Battery swapping for electric vehicle refueling is reviving and thriving. Despite a captivating sustainable future where swapping batteries will be as convenient as refueling gas today, tensions are mounting in practice (beyond the traditional “range anxiety” issue): On one hand, it is desirable to maximize battery proximity and availability to customers. On the other hand, power grids for charging depleted batteries are not accessible everywhere. To reconcile this tension, some cities are embracing a “swap-locally, charge-centrally” infrastructure network. In this paper, we aim to understand whether and how to design such a network. This task is complicated by non-Poisson swaps (observed from real data), and by the intertwined stochastic operations of swapping, charging, stocking and circulating batteries among facilities. We tackle these complexities by deriving analytical models, which enrich the classical batched repairable-inventory theory. We next propose a model for citywide deployment of hub charging stations, which jointly determines the location, allocation and reorder quantity decisions with a non-convex non-concave objective function. We solve this problem exactly by exploiting submodularity and combining constraint-generation and parameter-search techniques. Even for solving convexified problems, our algorithm brings a speedup of at least three orders of magnitude relative to Gurobi solver. The major insight is twofold: The benefit of inventory pooling alone is not enough to justify centralized charging; Instead, the main justification is the capacitated urban grid that curbs decentralized charging at slow speed. We also identify planning and operational flexibilities such as order splitting. In a broader sense, this work deepens our understanding about how mobility and energy are coupled towards enabling smart cities.
Keywords: battery swapping, electric vehicles, sustainable operations, non-convex optimization algorithms, facility location, smart cites
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