International regulations and market demand for zero-emission transportation are accelerating the adoption of sustainable solutions in the shipping industry. Wind-Assisted Propulsion Systems (WAPSs) present a promising alternative, as elaborated on in the EU-funded Orcelle Wind project. This paper deals with the integration of wing sails into the conceptual design of a Very Large Crude Carrier (VLCC) using a parametric, multi-objective optimization framework. The results reveal that optimized VLCC designs with WAPSs can achieve over 20% reductions in fuel consumption and greenhouse gas emissions compared to conventional designs. Additionally, the obtained optimized designs exhibit notable differences in the main design characteristics and hull form compared to conventional designs, highlighting the importance of multi-objective optimization in the early design stage to tap the potential of WAPS technologies and wind propulsion.

The maritime industry faces growing pressure to reduce greenhouse gas (GHG) emissions, reflected in the progressive adoption of stricter international energy regulations. Wind-Assisted Propulsion Systems (WAPS) offer a promising solution by significantly contributing to decarbonization. This paper presents a versatile simulation and optimization platform that supports the conceptual design of WAPS-equipped vessels and evaluates the viability of such investments. The platform uses a steady-state force equilibrium model to simulate vessel performance along predefined routes under realistic weather conditions, incorporating regulatory frameworks and economic assessments. A multi-objective optimization framework identifies optimal designs across user-defined criteria. To demonstrate its capabilities, the platform is applied to a bulk carrier operating between China and the USA, optimizing for capital expenditure, net present value (NPV), and CO₂ emissions. Results show the platform can effectively balance conflicting objectives, achieving substantial emissions reductions without compromising economic performance. The final optimized design achieved a 12% reduction in CO₂ emissions, a 7% decrease in capital expenditure, and a 6.6 million USD increase in net present value compared to the reference design with sails, demonstrating the platform’s capability to deliver balanced improvements across all objectives. The methodology is adaptable to various ship types, WAPS technologies, and operational profiles, offering a valuable decision-support tool for stakeholders navigating the transition to zero-carbon shipping.

The operational profiles of both commercial and naval ships encompass a range of speeds below the service speed. On the way to estimating their performance at these speeds, the varying effect of hull roughness should be quantified. Roughness constitutes a significant resistance component superimposed on skin frictional resistance, which deteriorates ship performance by increasing power requirements and CO₂ emissions to retain a specified speed or, equivalently, by reducing attained speed at a given power. This paper exploits the single available full-scale records of a naval combatant and the Computational Fluid Dynamics (CFD) calculations for a well-known containership to compose a methodology to derive the speed dependence of fouling on ship performance at reduced speed based on the respective effect at service speed. Sailing at reduced speed, either imposed by the charter contract for fuel economy (slow steaming) or due to adverse sea conditions, resulting in excessive ship dynamic responses and/or added resistance in waves, is a quite common situation, occurring for the whole period of charter contracts or a significant portion of it, respectively. This study concluded that the roughness effect reduces drastically with speed, supporting shipowners to compose a more reliable charter contract and shipping companies to derive a realistic dry-docking plan.