Joint Optimization of Route and Speed for Energy-Efficient Wind-Assisted Shipping

Wind-Assisted Propulsion Systems (WAPS) are increasingly recognized as a promising means of exploiting the abundant wind resource, particularly given the high cost and limited availability of renewable fuels. WAPS can contribute significantly to the decarbonization of the shipping sector. Contemporary systems are tightly integrated with onboard energy systems to meet stringent supply chain requirements, with recent developments focusing on larger sail configurations and the integration of hydro-generators to enhance overall efficiency.

Unlike conventionally powered ships, which typically search for the shortest navigational safe route at nearly constant speed, wind-assisted vessels benefit from a more flexible operational paradigm in which routing and speed adaptation are key to realizing their full potential. In the present study, the benefit of jointly optimizing route and speed for a cargo vessel equipped with WAPS is demonstrated. A four-degree-of-freedom steady state simulation model is employed to evaluate vessel performance under varying environmental conditions based on ERA5 data. To identify energy-optimal routes between ports, a dedicated algorithm is developed and presented that combines probabilistic roadmap techniques with dynamic programming.

The proposed framework is highly flexible with respect to the integration of diverse meteorological datasets and ship performance models. A key novelty is its ability to accommodate negative power and energy values, thereby enabling the optimal recuperation of energy through hydro-generator operation. The results indicate a substantial reduction in energy consumption through the combined optimization of routing and speed adjustment across multiple transport routes over a one-year operational period Moreover, by avoiding harsh weather conditions, routing enabled numerous routes that would have been unviable without it. The case study demonstrated average energy savings of approximately 75%, and up to 100% for selected low-speed trans-Atlantic crossings.