Battery Systems in Maritime Applications
Battery systems are becoming an integral part of modern maritime technology, driven by the global push for sustainable energy solutions and stricter environmental regulations [1]. These systems offer a promising alternative to traditional fossil fuel-based engines by providing cleaner and more efficient power sources for various maritime applications, including propulsion, auxiliary power, and hybrid energy solutions. Advances in battery technology, such as lithium-ion batteries, have made it possible to develop high-energy-density systems capable of meeting the demanding power requirements of maritime operations.
From the statistical point of view, there are 944 battery ships in operation and 448 ships on order. These ships are divided into hybrid, plug-in hybrid, and pure electric with a contribution 64%, 17%, and 19% of the total number, respectively. Figure 1 shows the distribution of battery ships (in operation and on order) per ship type [2].
Battery systems bring several key benefits to the maritime industry. First, they reduce greenhouse gas emissions and pollutants, supporting compliance with regulations from organizations like the International Maritime Organization (IMO) [3]. This makes battery-powered or hybrid vessels particularly suitable for operations in emission-controlled areas. Additionally, batteries enable significant fuel savings by providing electric propulsion and power for auxiliary systems, thus lowering operational costs. Their use also leads to reduced noise and vibration levels, which can enhance crew and passenger comfort, as well as minimize underwater noise pollution affecting marine life. The hybridization of battery systems with the main engines onboard can follow three different operation modes: spinning reserve, peak shaving, and dynamic load transition ramps.?
The use of batteries in place of an auxiliary engine that is idle in standby mode or fails is known as spinning reserve. When there is an unexpected spike in the demand for electricity, such as when a big crane or pump starts up unexpectedly, the spinning reserve mode can be used. The battery system in this mode can be applied as a buffer against unexpected circumstances and abrupt engine failure. For example, a typical ship has two auxiliary engines to cover the hoteling load, these engines are working in a low load (typically below 40%). In this configuration, the battery system can be used instead of one auxiliary engine with the operation of the other one at high load. In this way, energy efficiency is expected to increase and reduce fuel consumption, operating expenses, and maintenance.??
The engine peak shaving with the support of a?battery system offers another opportunity for cost reduction. This operation mode offers the opportunity to keep the engine at a steady average load while the battery covers the peak power (discharging) and to be charged when the required load demand is lower than the average load of the engine (charging). This operation mode leads to a significant reduction in operation expenses like spinning reserve mode. The installation of a shaft generator is necessary for this operation mode to shave main engine peak loads.??
On the other hand, the goal of dynamic load transition ramps is to lessen the abruptness of a load shift. In low-pressure gas engines, very abrupt load shifts can cause banging and significant particle emissions, both of which could be detrimental to the engine. Additional advantages and a decrease in fuel usage can result from delivering electricity from a battery to smooth the load change.
Moreover, the battery systems can be used to propel the ship during the departure phase from the port which leads to a significant reduction of harmful emissions in the port areas. Then, the engine can be engaged for the cruising operations.?
In order to prevent damage to the shafting from vibrations causing excessive strains, a barred speed range imposed by the vibrations in the shafting must be traversed rapidly enough. Therefore, a battery system installed with a shaft generator is considered a beneficial solution to be used to boost the acceleration of the shafting.?It has also been recommended that using batteries in conjunction with a shaft generator could guarantee enough power for navigation in adverse weather. It is worth noting that operation in adverse weather lasts for extended periods, requiring a substantial battery capacity, in contrast to the short crossing of the barred speed range.?
Despite the several benefits of installing battery systems onboard ships, there are some technological barriers like the availability of shore power infrastructure for charging batteries and the design consideration of battery system compartment.?
As the adoption of battery-powered and hybrid vessels grows, the need for robust charging infrastructure in ports becomes increasingly critical. This infrastructure is essential to support the charging requirements of various maritime vessels, from short-route ferries to larger container ships and tankers. Installing reliable, efficient charging systems at ports not only enables vessels to maintain optimal operations but also facilitates the maritime industry’s shift toward greener and more sustainable energy solutions [4].
The development of port-side charging infrastructure faces unique challenges, including the need for high-capacity power supply, compatibility with different vessel types, and the ability to handle frequent, rapid charging cycles [4]. Additionally, ports must consider space constraints, electrical grid upgrades, and energy storage solutions to meet demand during peak times. By investing in and advancing port charging infrastructure, the maritime industry can effectively support the transition to electric and hybrid vessels, ultimately reducing emissions, improving energy efficiency, and promoting a cleaner, more sustainable future for global shipping.
The ports are rapidly putting shore power projects into place in an attempt to meet environmental requirements and remain ahead of the global decarbonization game. An overview of shore power infrastructure that?exists and is?under construction is displayed in Figure 2.?
In order to ensure safe operation and serviceability, battery system compartments must adhere to the specifications set out by classification societies and battery system providers. The main idea behind current installations is the combination of several cells to create a battery module. Then, a number of these modules are joined in series to create a battery pack to achieve the desired voltage of the vessel’s power demand. A battery string would then be created by joining several packs in parallel. The pack is connected and disconnected from the string via a battery junction box (BJB), which also has safety components such as?contactors, fuses, and current sensors.?
The battery management system (BMS) is a critical component in any battery system. The BMS regulates the charging and discharging of individual cells, protects the battery from overloading, and checks the level of charge, system voltage, and other parameters.
To achieve the required capacity for a marine system, strings can also be joined in parallel. These strings are subsequently placed in a distinct room onboard that has enough space to accommodate the various modules. Therefore, the resulting energy density of this arrangement is lower than the reported density of the?battery rack from the battery system vendor. Figure 3 shows the required architecture of the?battery system compartment onboard the?ship following the recommendation from classification societies [5].
The thermal management system aims to extend battery life and prevent thermal runaway, a major concern associated with battery operation. It's critical to keep the battery rack cool throughout regular use, particularly when charging and discharging. To guarantee uniform cell aging and avoid differences in self-discharge rates and capacity among the individual cells, the management system must maintain an even temperature distribution across the system. Active cooling, which can be accomplished via air conditioning systems, can provide the ideal operating temperature.?The air-conditioning system just requires connectivity with the electrical grid. Moreover, filters can help limit exposure to salt in the air. Air-cooled systems have cheaper component costs, which is a significant advantage compared to liquid-cooled systems.?
The total area required to house the batteries onboard a ship should be increased by taking into account the required space for the ancillary systems (such as ventilation and firefighting apparatus) and the required access space to the rather closely spaced battery racks. Furthermore, classification societies' current standards [6] for ships that run entirely on batteries call for redundancy in the battery room layout, which duplicates auxiliary systems and empty areas to facilitate access to battery racks.
Battery systems represent a transformative advancement in maritime technology, offering cleaner, and more efficient alternatives to conventional fuel-powered systems. The benefits of reduced emissions, fuel savings, and quieter operations are compelling for a range of maritime applications, from short-distance ferries to larger ocean-going vessels. While challenges remain—such as the need for further advancements in battery capacity, safety, compartment design and charging infrastructure—the momentum toward electrification in maritime applications is undeniable. With ongoing innovation and investment, battery systems are poised to play a central role in shaping a sustainable and resilient future for the maritime industry.
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