Integrated AHP–TOPSIS model for renewable energy planning in low-carbon port Cities: Implications for marine pollution mitigation

An integrated Analytic Hierarchy Process–Technique for Order Preference by Similarity to Ideal Solution (AHP–TOPSIS) framework is developed to support renewable energy planning in low-carbon port cities, with explicit attention to marine-pollution mitigation. The approach is applied to Ningbo–Zhoushan Port, China, using a criteria system organised into four main groups and twelve sub-criteria. Judgements from 50 experts indicate that environmental and marine-pollution impacts (weight = 0.36) dominate over technical performance (0.24), social/policy acceptance (0.22), and economic feasibility (0.18), with emission reduction and marine-pollution pressure together accounting for almost 0.29 of the total weight. Combining these weights with normalised performance scores, TOPSIS identifies offshore wind farms (closeness coefficient = 0.83) and hybrid systems with storage and hydrogen-readiness (0.80) as the most suitable options for Ningbo–Zhoushan, followed by coastal onshore wind and port-area solar photovoltaic. At the same time, waste-to-energy/biomass CHP ranks lowest. Scenario analysis confirms the robustness of these findings under varying environmental, cost, and reliability priorities, highlighting portfolios centred on offshore wind and hybrid systems as key to reducing port-related emissions and pressures on coastal waters.