# Electrification in Maritime Vessels: Reviewing Storage Solutions and Long-Term Energy Management
## 1 Introduction
### The Benefits and Challenges of Hybrid Marine Vessels  
All-electric marine vessels rely solely on electric power for propulsion and onboard systems, eliminating direct emissions and significantly reducing the environmental impact [22]. These vessels use electric motors powered by batteries to drive the propellers or water jets. Common battery types include Li-ion and Li-polymer batteries, which store the electrical energy necessary for propulsion and other systems. Charging these vessels is accomplished through shore power connections or onboard generators, making the development of charging infrastructure at ports essential for their operation. The advantages of electric marine vessels are numerous: they produce zero emissions at the point of use, have lower operating costs due to reduced fuel and maintenance expenses, operate more quietly, and can integrate with renewable energy sources. However, they also face challenges such as limited range due to battery capacity, longer charging times compared to traditional refueling, and the need for significant initial investment in charging infrastructure [23]. Additionally, hybrid marine vessels combine internal combustion engines (typically diesel) with electric propulsion systems, offering greater operational flexibility and efficiency improvements. These vessels can operate in different modes: pure electric mode, hybrid mode (using both engines and electric motors), or internal combustion engine mode. This adaptability allows for optimized fuel efficiency and reduced emissions. Hybrid vessels also have batteries that store energy from regenerative braking, surplus engine power, or shore charging. The advantages of hybrid systems include improved fuel efficiency, reduced emissions, silent operation in electric mode, and the provision of backup power in case of engine failure, which also reduces wear and tear on the main engines. However, hybrid systems are more complex to design and maintain compared to traditional power systems, and the initial investment cost is higher due to the integration of multiple technologies [23; 24]. Leading maritime companies and shipyards are now investing in electric and hybrid propulsion systems, exploring their application across various vessel types, from small ferries and leisure boats to large cargo ships and tankers. Pilot projects and commercial deployments demonstrate the viability and advantages of electrification, paving the way for broader adoption in the coming years [25; 26]. However, this shift towards electrification presents several challenges, including the need for substantial infrastructure development, high initial costs, and technological hurdles related to energy storage and power management. Despite these challenges, ongoing research and development efforts are actively addressing these issues, ensuring a smooth and effective transition to a more sustainable future for the maritime industry [27]. The electrification of marine vessels is not just a critical component but an urgent necessity in the maritime industry's evolution towards sustainability and efficiency. As technological advancements continue and the regulatory landscape evolves, electric propulsion systems are poised to play a central role in the future of marine transportation, significantly contributing global efforts to reduce environmental impact and promote sustainable development [28]. Table 1 summarizes the key characteristics and advantages of electric and hybrid marine vessels, highlighting their potential to transform maritime transportation into a more sustainable and efficient industry [29].