# Electrification in Maritime Vessels: Reviewing Storage Solutions and Long-Term Energy Management
## 2 Electrification of Marine Vessels
### Battery Management Systems (BMSs) for Marine Vessels  
All-electric ships have become a standard configuration in marine propulsion and energy systems. The strategy for managing battery operations significantly impacts energy efficiency and marine vessels' safety. Battery management systems (BMSs) are essential for battery packs' safe and efficient operation, particularly crucial in maritime applications where substantial energy storage capacities are required. These BMSs are not just systems but meticulously engineered solutions designed to perform several critical functions precisely. These functions include continuous monitoring of battery health, precise management of charging and discharging cycles, and ensuring optimal conditions for battery systems' safety, stability, and longevity [48; 49]. Similar to an EMS, a BMS is tasked with a suite of critical functions. These include state of charge (SoC) estimation, which predicts the current capacity of the battery to prevent issues such as overcharging and deep discharging. State of health (SoH) prediction involves continuous monitoring of battery health to identify problems such as cell imbalance or gradual battery degradation. Thermal monitoring is conducted to check the battery's temperature and implement precautions against overheating. Safety protection mechanisms are in place to monitor and mitigate risks such as overvoltage, undervoltage, overcurrent, and short circuits. Additionally, balancing control is crucial for maintaining uniform charge levels across cells, enhancing the battery's stability, and prolonging its lifespan [50]. BMSs play a pivotal role in naval platforms and systems deployed on vessels such as hybrid and electric ships, where they oversee extensive battery clusters used in propulsion and auxiliary systems to ensure optimal safety and stability. Additionally, BMSs are integral in managing backup power systems, such as uninterruptible power supplies (UPSs) on ships, and maintaining critical operations during power outages. They also optimize the integration of renewable energy sources into the battery systems to enhance environmental safety and extend the lifespan of the batteries. Furthermore, a BMS is crucial in emergency systems, providing reliability and stability during critical scenarios, such as sudden power failures or lighting issues [51; 52]. BMSs are also deployed across various use cases in maritime vessels. A critical application is within hybrid propulsion systems, where a BMS meticulously monitors and manages the interaction between battery usage and conventional engines. This allows for an optimized balance that minimizes fuel consumption and emissions [53]. In scenarios where high power demand arises due to challenging maritime conditions, a BMS can provide supplemental power from the battery components, alleviating the generator load and reducing fuel consumption [54]. A BMS also ensures that battery components are consistently ready to supply additional power in diverse emergency scenarios within maritime environments, thus enhancing vessel safety [55]. Additionally, for maritime vessels equipped with regenerative braking technology, a BMS efficiently manages and stores the energy captured during braking operations, making it available for future use [56]. In conclusion, a BMS significantly contributes to maritime vessels by enhancing energy efficiency through optimized usage of battery components, tailored to varying maritime environmental conditions. They also provide an additional layer of safety and reliability by continuously monitoring the state of charge of each battery component to prevent overcharging and deep discharge situations.