Sequential Multi-Pad Inductive Power Transfer for Autonomous Heavy Duty Electric Drayage: Electromagnetic Design, Thermal Dynamics, Stochastic Grid Modeling, and 10-Year Total-Cost-of-Ownership Analysis

Abstract

This paper introduces and rigorously analyzes a Sequential Multi-Pad Inductive Power Transfer (SMP-IPT) architecture engineered for  autonomous heavy-duty battery-electric yard tractors (BEYTs) operating inside enclosed intermodal container terminals. The research  develops four coupled analytical frameworks—each novel in application to port-class power levels—and integrates them into a unified system  design: (i) a parametric electromagnetic coupling model for Double-D (DD) coil pairs at air gaps of 150–400 mm and lateral offsets up to  200 mm, validated against published finite-element and field data; (ii) a lumped two-body RC thermal model for 250–500 kW Litz-wire coil  assemblies under port-realistic duty cycles, including closed-form steady-state solutions and numerical ODE integration for transient analysis;  (iii) a stochastic Poisson-arrival fleet demand model that yields analytic closed-form expressions for peak grid power percentiles, confirmed  by a 90-day Monte Carlo simulation spanning 10,000 synthetic traversals; and (iv) a net present value (NPV) total-cost-of-ownership (TCO)  framework comparing WPT and conductive DC fast charging (DCFC) over a 10-year horizon at fleet scale.

Key quantitative findings: η ≥ 88% across ±150 mm lateral envelope at 300 mm air gap with active liquid cooling required at all port-class  power levels; 95th-percentile peak grid demand of 4,635 kW (analytical) vs. 4,340 kW (Monte Carlo); staggered demand-control reduces the  demand coefficient of variation from 0.48 to 0.18 (62% reduction); WPT achieves positive cumulative NPV relative to conductive DCFC  under base-case assumptions at Year 3.8, with a sensitivity range of 2.1–6.1 years across pad cost, labor rate, grid upgrade cost, and failure  rate scenarios; and cumulative CO₂ avoidance of 27,610 tonnes over 10 years per 60-truck terminal. This work additionally presents, as  secondary contributions, (C6) an Adaptive Digital-Twin (ADT) pad health monitoring framework based on Unscented Kalman Filtering, and  (C7) a structured human-centered equity analysis quantifying workforce transition impacts and community health co-benefits. All results are  analytical and simulation-based, calibrated against published field data from WAVE Charging and InductEV deployments; experimental  prototype validation is the primary identified future work priority.