Multi-Stage Dynamic Programming Design and Life-Cycle Economic Analysis of a Photovoltaic-Storage-Charging System in the Hasuhai Expressway Service Area

To improve the long-term adaptability of photovoltaic-storage-charging systems under rapidly increasing electric vehicle charging demand, this study develops a multi-stage dynamic programming and life-cycle economic assessment framework for the Hasuhai expressway service area in Inner Mongolia, China. A SARIMA-Holt-Winters hybrid forecasting model was used to predict future load growth, and a phased capacity expansion scheme was established for photovoltaic generation, energy storage, and charging facilities. The results show that the annual average load is projected to increase by approximately 11.22 times from 2026 to 2045, indicating that the one-time construction scheme may face long-term supply insufficiency despite its favorable short-term economic performance. Compared with the initial scheme, the multi-stage planning scheme improves long-term adaptability by dynamically expanding photovoltaic capacity, energy storage capacity, and charging ports according to load growth. The optimized scheme increases the net present value from 33.094 million CNY to 57.347 million CNY, reduces the levelized cost of charging to 0.171 CNY/kWh, and increases the 25-year carbon emission reduction to 62,490 tCO2. Sensitivity analysis indicates that the charging service fee has the greatest influence on project economics, followed by the grid electricity price and discount rate. The proposed framework provides a practical reference for the phased construction and investment decision-making of photovoltaic-storage-charging systems in expressway service areas with rapidly growing charging demand.