System-Level Analysis of Rigid Wing Sails as Wind-Assisted Ship Propulsion Technologies Over Given Ship Routes

Kurzfassung

The shipping industry contributes significantly to global greenhouse gas (GHG) emissions, with a share of 2.89% in 2018. As maritime trade continues to grow, this share is projected to increase according to the International Maritime Organization (IMO) Greenhouse Gas Study 2020, estimating a 90-130% rise in emissions by 2050 compared to 2008. Consequently, urgent action is required to control these emissions. The IMO is taking initiatives by setting GHG reduction targets and implementing policies to achieve them. One recommended approach to reduce emissions in the shipping industry is the utilization of Wind-Assisted Propulsion Systems (WAPS). This master’s thesis aims to provide a comprehensive understanding of different wind propulsion technologies and develop a generic framework to assess the benefits of integrating WAPS devices on ships. The thesis consists of two main parts. Firstly, it explains a Python program, jointly developed with other projects, that extracts hourly average wind data (speed and direction) based on the Automatic Identification System (AIS) data of the selected ship and route, provided as input for the program. Secondly, a Matlab-based Performance Prediction Program (PPP) is developed with one Degree of Freedom (DoF) to simulate sail forces, engine load, fuel savings, CO2 savings, and Energy Efficiency Operational Index (EEOI) along a given route, with and without the WAPS device. The PPP incorporates an aerodynamic model of the rigid wing sail, a hydrodynamic model of the ship, a sail trim optimization module, and various saving estimation modules. Although the hydrodynamic module’s detailed design is beyond the scope of this study, hydrodynamic information for a typical bulk carrier ship is integrated into the framework. The WAPS device considered in this study is a detailed model of a rigid wing sail with a symmetric airfoil cross-section and a constant chord throughout its height. The sail is assumed to be fully or partially retractable based on the wind conditions for optimal sail thrust generation. To evaluate the framework’s effectiveness and the impact of the rigid wing sail on ship performance, a case study is conducted using a bulk carrier ship and a specific route for the entire year of 2019. Simulation results indicate significant achievements, including 8.75% fuel savings, CO2 savings of 705.34 tons, and a 2.25% reduction in EEOI compared to the ship’s performance without the rigid wing sail when sailed during the year 2019. These results are validated against another PPP study using the same input parameters. This study serves as an initial step, by DLR, towards developing a comprehensive performance prediction program, including a weather data extraction module. With further integration of models for different WAPS devices, a more resolved weather prediction, a detailed hydrodynamic module, and a route optimization module, the program can serve as a valuable tool for assessing the techno-economic feasibility of WAPS during the early stages of projects.