A bidirectionally coupled multi-energy and route optimization framework for low-carbon maritime transport

Energy-efficient and low-carbon maritime transport remains challenging because routing decisions and onboard energy systems are often optimized separately. This study proposes a bidirectionally coupled multi-energy optimization framework that integrates route planning with wind-assisted propulsion, solar photovoltaic generation, and main-engine waste heat recovery. High-resolution meteorological data and vessel dynamic responses are incorporated to establish a closed-loop interaction between navigation decisions and energy-system performance. A representative very large crude carrier operating on a transoceanic route is used to evaluate the proposed framework under realistic operating conditions. Results show that the framework reduces fuel consumption by up to 11.29 %, corresponding to cost savings of 7.25 %, while decreasing CO2 emissions per nautical mile by approximately 11–12 %. Beyond these performance improvements, the study identifies a relatively consistent contribution structure among the integrated clean-energy technologies under the investigated VLCC operating profile: wind-assisted propulsion, solar photovoltaic generation, and waste heat recovery contribute approximately in a 3:1:6 ratio. This pattern highlights waste heat recovery as the dominant energy-saving pathway during long-duration high-load operation, while wind and solar energy provide complementary route-dependent benefits. These findings indicate that ship decarbonization should be treated as a system-level optimization problem governed by nonlinear coupling among routing decisions, environmental exposure, and onboard energy conversion, providing a methodological basis for integrated low-carbon maritime energy management.