Marine Hybrid Propulsion Systems - Overview, Feasibility, and a Case Study of a High-Speed Passenger Vessel
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- Institutt for marin teknikk 
The increased awareness on the climate creates a new increased demand for more environmentally friendly solutions when it comes to the powering and propulsion of different modes of transport. Environmental concerns, financial incentives, and support schemes, in addition to operational life-cycle cost, are three of the main drivers behind a currently ongoing effort to reduce emissions and fuel consumption in all transportation sectors, including maritime transportation.This master thesis aims at building a comprehensive understanding of marine hybrid propulsion systems and assesses the feasibility of this propulsion system in a high-speed passenger vessel through a case study analysis with real vessel operational data. The research starts with a thorough investigation of the state-of-the-art for marine propulsion systems through an extensive literature review. It emphasizes the understanding of the system designs through a structured categorization of different configurations of the hybrid propulsion system. This is followed by an investigation of the hybrid system on a component level with a review of the relevant subsystems and components comprising the hybrid propulsion system. The properties and key design elements characteristic for the hybrid propulsion system is assessed.The next part discusses relevant marine system design considerations and important general factors to consider in a marine design process. This part also includes maritime project considerations important for the feasibility of a green low-emission propulsion system project, and challenges associated with the implementation of a hybrid propulsion system, such as component integration, charging infrastructure and relevant regulatory framework.The case study is a structured feasibility study of the hybrid propulsion system in a high-speed passenger vessel. By comparing the hybrid system with two other relevant propulsion systems in a technical, environmental, and economic framework, this analysis provides valuable insights related to the implications of implementing a hybrid propulsion system in an existing high-speed vessel. The work includes a rough sizing of relevant components in the hybrid propulsion system, including batteries and electric motors.A key finding regarding the propulsion system design is that the design must be assessed on a case by case basis and it must be adapted to the vessel's operating profile and route. Furthermore, it was found that an increased proportion of electric propulsion out of the hybrid vessel's overall operation is beneficial in several ways. First, it will lead to lower fuel consumption compared with diesel propulsion, thus reducing emissions and fuel costs. The electric propulsion also increases the comfort onboard the vessel by reducing noise, vibrations, and local emissions. Several different ship segments are relevant for partial or full electrification, but the effect of this will vary depending on the vessel's operating profile. A challenge lies in adapting the hybrid vessel s propulsion system design to implement as much electric operation as possible, and to facilitate battery charging during operation. For a high-speed passenger vessel, low weight is a crucial factor in maintaining the required high service speed, while batteries are associated with high weight. It is, therefore, a trade-off between operational performance on the one hand, and economy and emissions on the other hand.