- 1 Intro
- 2 Lithium Battery in Marine
- 3 Lithium Battery in Ship Energy Storage
- 4 Incomplete Technical Regulations
Lithium batteries have revolutionized the marine industry with their exceptional energy storage capabilities and numerous advantages. As the demand for more sustainable and environmentally friendly solutions grows, lithium battery systems have emerged as a powerful alternative to traditional propulsion systems in marine vessels. With their high energy density, long cycle life, and rapid charging capabilities, lithium batteries are paving the way for a new era of clean and efficient marine transportation. In this article, we will delve into the application of lithium batteries in the marine sector, exploring their benefits, challenges, and the transformative impact they are having on the industry.
Lithium Battery in Marine
The most commonly used power system for ships at present is the diesel engine propulsion system. However, diesel engine power systems have many problems. Firstly, diesel engines use heavy oil or non-renewable energy, resulting in significant resource pressure and high operating costs. Secondly, the issues of noise and vibration generated during diesel engine operation are difficult to solve. Thirdly, the emissions of exhaust gases and waste from diesel engines pose extremely serious environmental pollution problems.
With increasing concerns about environmental pollution and resource scarcity, the issue of pollution in the shipping industry has drawn more and more attention. Ships are major emitters, and in recent years, the maritime industry in various countries has taken proactive actions to promote and expand the application of green ship technologies.
Although there are numerous types of new energy sources that the industry focuses on, such as LNG, methanol, LPG, biomass fuels, solar energy, hydrogen, fuel cells, and lithium batteries, only electric ships powered by lithium batteries are truly capable of achieving zero emissions, gradually promoting their use in the shipping industry, and having initial market scale. Pure battery-powered ships are mainly suitable for fixed routes with short distances and convenient charging facilities. For occasions with relatively long routes, diesel-electric hybrid power systems can better balance energy efficiency, emission reduction, and adaptability to voyage distance.
Lithium Battery in Pure Electric Vessels
Compared to traditional propulsion systems, electric propulsion systems have the advantages of good economy, flexible maneuverability, high safety, low vibration, and high reliability. Electric propulsion systems are now widely used in ferries, dredgers, tugs, and large cruise ships. With the rapid development of power electronics technology and the increasing energy crisis, electric propulsion is becoming an unstoppable trend to replace traditional diesel propulsion.
Electric propulsion technology relies on its significant advantages in maneuverability, reliability, operational efficiency, flexible arrangement, economy, and ease of maintenance. It is widely applied in engineering vessels, oil tankers, luxury yachts, and other ships. In a world where sustainable development and low-carbon economy are pursued by countries worldwide, electric propulsion will become the driving force for future green shipping.
In foreign countries, several major ship electric propulsion manufacturers have their own series of electric propulsion products, such as the Azipod propulsion system and the SSP propulsion system, which have been put into practical operation. However, ship electric propulsion has always faced a technical challenge, namely the significant impact of frequent load disturbances on the performance of the propulsion system. On the one hand, the marine environment is complex and variable, and the effects of wind, waves, and currents on the load are unpredictable, resulting in constantly changing disturbances. On the other hand, certain engineering vessels (icebreakers, dredgers, offshore drilling platforms, etc.) not only face environmental disturbances during operations but also experience varying power demands due to changes in operating conditions and other objective factors. This can lead to significant load disturbances. Clearly, these load disturbances can have a huge impact on the ship’s power grid and affect the performance of the propulsion system.
One solution to address this problem is the use of energy storage technology. Energy storage units can improve system stability by instantly absorbing or releasing energy when the power system experiences disturbances, mitigating the effects of disturbances and enhancing system stability. In recent years, high-capacity energy storage technology has rapidly developed, and several major energy storage unit manufacturers are producing their own high-capacity energy storage products for practical operation.
Lithium Battery in Hybrid-powered Vessels
In the past, hybrid propulsion ships typically referred to diesel-electric hybrid propulsion ships. However, as new energy technologies for ships are gradually being promoted, the definition of hybrid propulsion ships has become broader with the application of new energy technologies such as solar power and fuel cells (e.g., LNG) on ships. Hybrid propulsion ships encompass various sources of energy centered around electricity, providing advantages of flexibility and economy in ship operations. To effectively reduce energy consumption and emissions while ensuring the functionality and safety of the ship, it is necessary to manage and utilize the characteristics of different energy sources and coordinate their flow.
In hybrid propulsion ships, lithium batteries serve two main purposes: power supply and energy storage. Lithium batteries can be designed according to the specific requirements of the ship, and they have the following applications:
- Power reserve to prevent power loss on the ship.
- Peak shaving and valley filling: Lithium batteries can provide short-term power supply during peak loads, and they can be charged by the grid during periods of lower loads.
- Compensating for deficiencies in generator characteristics: Sudden additional loads can be transferred to the battery pack, effectively avoiding the risk of power imbalance.
- Direct power supply to the grid: Ships without diesel generators can use the battery system to directly supply power to onboard equipment, while propulsion systems use electric motors for propulsion, achieving “zero emissions” for the ship.
Lithium Battery in Ship Energy Storage
In most cases, the power propulsion system of ships is powered by internal combustion engine-driven generators. Due to the complex and changing marine environment, the load varies. When the load deviates from the optimal load point, the fuel cannot be fully burned, resulting in a significant decrease in fuel efficiency and the generation of a large amount of nitrogen oxides and sulfur oxides, which pollute the environment.
Energy storage technology is one of the solutions to this problem. By using energy storage units to store excess energy during light load conditions, the impact of this energy on the power grid can be prevented. During system overload, the energy storage unit releases energy to meet the load demand. Energy storage technology has been well applied in the electric vehicle industry. The development of high-capacity energy storage technology makes it possible to apply energy storage units to ship power propulsion systems, and using energy storage units to overcome the impact of power fluctuations on ship power propulsion systems will be a new direction for the future development of ship propulsion technology.
Energy storage systems can enhance the power boost capability of steam turbines, improve the speed control level of steam turbines, improve power grid quality, and achieve smooth power output, thereby increasing the stability and reliability of the system. At the same time, energy storage systems can also store excess energy, which improves the economy of ship operations to some extent. In addition, due to the harsh environment and long-term distance from land, the timeliness of emergency rescue for ships is poor, so there is a high demand for ensuring a safe power system. As the most reliable energy source of the power system, energy storage systems serve as the last line of defense for protecting ship safety.
According to the classification of energy storage carriers, energy storage methods are mainly divided into three types: electrochemical energy storage, physical energy storage, and electromagnetic energy storage. Electrochemical energy storage mainly includes battery energy storage and supercapacitor energy storage; physical energy storage mainly includes pumped storage, compressed air energy storage, and flywheel energy storage; electromagnetic energy storage mainly includes superconductor energy storage.
Among various energy storage methods, pumped storage and compressed air energy storage cannot meet the requirements of ships due to their slow response speed. Superconductor energy storage has low energy density, high cost, and low technological maturity, so its reliability and economy are not high, making it unsuitable for ship applications. The main energy storage methods used in ships are battery energy storage, supercapacitor energy storage, and flywheel energy storage. Supercapacitor energy storage and flywheel energy storage have the characteristics of fast response and high power density. Comparatively, supercapacitor energy storage has higher power density but lower energy density, very short discharge time, and higher cost.
In battery energy storage, lead-acid batteries and lithium batteries are widely used batteries. Both types of batteries have the advantages of high rated power and long discharge time. Comparatively, lead-acid battery technology is more mature, has lower cost, and higher safety, but its energy density is much lower than that of lithium batteries, and it has poor environmental performance. Lithium batteries have superior battery characteristics, but their technological maturity is not high, heat dissipation issues are severe, and they lack sufficient safety. As power sources, lithium batteries can be classified into several types based on the cathode materials, including ternary lithium, lithium manganese oxide, lithium iron phosphate, and lithium titanium oxide. Currently, the mainstream applications are ternary lithium batteries and lithium iron phosphate batteries. Ternary lithium batteries have the highest energy density, but due to safety reasons, more funds need to be invested in the battery management system, which limits the application of ternary lithium batteries in domestic ships to some extent. Lithium iron phosphate battery technology is quite mature, and it is widely used in onshore transportation, solar and wind power generation and storage, electric tools, and other fields. Large-scale production has also brought battery prices down to a reasonable level. Considering the actual situation of domestic ships and the battery industry, lithium iron phosphate batteries are developing rapidly in the field of ships.
Incomplete Technical Regulations
Battery-powered vessels are one of the most innovative types of ships internationally, and their electrification characteristics provide a foundation for the development of next-generation intelligent ships. The design and construction of these vessels are not simply replacements for power systems; they require innovative design and construction concepts. It poses significant challenges for design and construction departments. The equipment, operation requirements, crew skills, operational environment, accident prevention and handling, and other aspects of ship systems and functions are more complex compared to conventional powered vessels. Classification societies and maritime authorities are still in the early stages of research, and related research and design systems are not yet perfect.
First, ship standards have not been established.
The performance standards for lithium batteries vary depending on different application areas. Currently, the performance standards for maritime lithium batteries refer to relevant standards for electric vehicles, but basic general performance and testing standards have not yet been formed. Considering that the energy storage capacity of marine lithium batteries is tens or even hundreds of times that of automotive lithium batteries, and marine products operate in harsher working environments with higher safety requirements, the use of IEC and national electric vehicle standards as references for maritime testing standards has certain limitations and inapplicability. The construction and improvement of maritime standards are urgent problems that need to be addressed.
Second, inspection regulations are incomplete.
Although relevant maritime bureaus have compiled technical specifications for inland power vessels, the maritime lithium battery industry currently lacks the capability to supply long-distance, high-power vessels. Therefore, the formulation of regulations for coastal battery-powered vessels is still in the initial stages.
Third, further research is needed for the application of lithium batteries in ship propulsion.
Battery-powered vessels can generally be classified into two types based on their energy sources: pure battery-powered vessels and hybrid-powered vessels. Due to the limited number of actual battery-powered vessels, there is still a lack of research and accumulated experience regarding the safety and power compatibility of these systems. The advantages and disadvantages of these two technological paths still need to be verified through actual operation, which requires data accumulation. The drawbacks of pure battery-powered propulsion, such as poor safety, low energy density, and high initial investment costs, are the main obstacles to its large-scale application in the maritime field. As a high-capacity energy storage component, power batteries themselves have risks of fire and explosion. There is a risk of battery failure and control system failure during vessel navigation, a risk of safety return due to malfunctions or special weather conditions during vessel maneuvering, and a risk of accidents during ship-shore charging operations.