Modern Propulsion Systems: Moving Beyond Diesel

The International Maritime Organization's (IMO) greenhouse gas (GHG) reduction strategy, as outlined in Resolution MEPC.304(72), aims to reduce carbon emissions from shipping by at least 50% by 2050 compared to 2008 levels. With the global fleet accounting for around 2.2% of total GHG emissions, the pressure is on shipowners and operators to explore alternative propulsion systems. One key area of focus is the development of high-capacity battery storage for coastal vessels, with Norway leading the charge: as of 2022, the country has over 70 battery-powered vessels in operation, with a further 100 on order. The Norwegian Maritime Authority's (NMA) introduction of a discount on the annual ship registration fee for vessels with a documented reduction in emissions has been a significant driver of this uptake, with a 23% reduction in emissions from Norway's domestic shipping sector between 2018 and 2020.

The shift towards battery-powered propulsion is also being driven by tightening emissions regulations, particularly in Emission Control Areas (ECAs). As of 2021, the IMO's MARPOL Annex VI regulation 14.4 requires vessels operating in ECAs to use fuel with a sulfur content of no more than 0.1%, or to employ an approved equivalent arrangement, such as a scrubber or liquefied natural gas (LNG) system. However, with the European Union's (EU) proposed FuelEU Maritime regulation set to introduce a 75% reduction in GHG emissions from maritime transport by 2050, the industry is being forced to think beyond traditional fossil fuel-based systems. The use of high-capacity battery storage, either as a primary propulsion source or as part of a hybrid system, is seen as a key component in achieving these ambitious emissions reduction targets.

The engineering challenges associated with developing high-capacity battery storage systems for coastal vessels are significant, with the need for reliable, efficient, and safe operation being paramount. The American Bureau of Shipping (ABS) has developed a series of guidelines and notation requirements for the installation of battery systems on vessels, including the ABS Guide for Battery Power Systems. This guide provides recommendations on the design, testing, and survey of battery systems, as well as the training of crew members in their operation and maintenance. Classification societies such as DNV GL and Lloyd's Register are also working closely with shipowners and operators to develop and implement bespoke battery-powered propulsion systems, with a focus on optimizing energy efficiency and reducing emissions.

Modern Propulsion System Design

The design of modern propulsion systems is becoming increasingly complex, with the need to integrate multiple power sources and systems. The use of hybrid propulsion systems, which combine traditional diesel or gas engines with battery power, is becoming increasingly popular, particularly for coastal vessels with variable operating profiles. A study by the International Council on Clean Transportation (ICCT) found that hybrid propulsion systems can reduce emissions by up to 20% compared to traditional diesel-powered systems, depending on the specific application and operating conditions. The ICCT study also highlighted the importance of optimizing energy management systems (EMS) to maximize the efficiency of hybrid propulsion systems, with the use of advanced EMS capable of reducing fuel consumption by up to 10%.

The development of high-capacity battery storage systems is also being driven by advances in technology, particularly in the area of lithium-ion batteries. The use of lithium-ion batteries, which offer high energy density and long cycle life, is becoming increasingly widespread in the maritime industry, with companies such as Corvus Energy and Akasol leading the charge. The Corvus Orca battery system, for example, has a capacity of up to 6,100 kWh and is designed for use in hybrid and fully electric propulsion systems. The system has been installed on a number of vessels, including the MS Color Hybrid, a 160-meter-long cruise ferry operating in Norway.

The Norwegian classification society, DNV GL, has developed a series of type approval certificates for lithium-ion battery systems, including the Corvus Orca system. These certificates provide assurance that the battery systems meet the required safety and performance standards, and are recognized by regulatory authorities such as the IMO and the EU. The use of type-approved battery systems is seen as a key factor in reducing the risk of battery-related incidents, such as fires and explosions, which have been a major concern for the industry in recent years.

Hybrid Retrofitting and Energy Management

Hybrid retrofitting, which involves the installation of battery power systems on existing vessels, is becoming an increasingly popular option for shipowners and operators looking to reduce emissions and improve efficiency. The process of hybrid retrofitting can be complex, requiring significant modifications to the vessel's propulsion and electrical systems. However, the benefits can be significant, with hybrid retrofitting capable of reducing emissions by up to 20% and fuel consumption by up to 15%, depending on the specific application and operating conditions. The use of advanced energy management systems (EMS) is critical to maximizing the efficiency of hybrid propulsion systems, with the ability to optimize energy usage and reduce waste.

The BIMCO Guidelines for the Selection and Installation of Hybrid Power Systems provide a framework for shipowners and operators to follow when selecting and installing hybrid power systems. The guidelines cover key areas such as system design, installation, and testing, as well as the training of crew members in the operation and maintenance of hybrid systems. The guidelines also highlight the importance of monitoring and evaluating the performance of hybrid systems, with the use of data analytics and other tools to optimize energy efficiency and reduce emissions.

The IMO's Marine Environment Protection Committee (MEPC) has also developed a series of guidelines for the use of hybrid propulsion systems, including the MEPC.1/Circ.881 guidelines for the reduction of GHG emissions from ships. These guidelines provide recommendations on the use of hybrid propulsion systems, as well as other emission-reducing measures such as slow steaming and weather routing. The guidelines also highlight the importance of monitoring and reporting emissions, with the use of data analytics and other tools to track progress and identify areas for improvement.

Implementation and Future Developments

The implementation of high-capacity battery storage systems and hybrid propulsion systems is expected to continue to grow in the coming years, driven by tightening emissions regulations and increasing demand for more efficient and sustainable propulsion solutions. The EU's proposed FuelEU Maritime regulation, for example, is expected to drive significant investment in alternative propulsion technologies, including battery power and hybrid systems. The regulation, which is set to come into force in 2025, will require vessels operating in EU waters to reduce their GHG emissions by 75% by 2050, compared to 2008 levels.

The development of new technologies and innovations is also expected to play a key role in the growth of the hybrid and battery-powered propulsion market. The use of advanced materials and designs, such as solid-state batteries and fuel cells, is expected to improve the efficiency and performance of propulsion systems, while reducing costs and increasing safety. The use of digitalization and data analytics is also expected to play a key role, with the ability to optimize energy usage and reduce waste through the use of advanced EMS and other tools. As the industry continues to evolve and develop, it is likely that we will see significant advancements in the design and implementation of modern propulsion systems, with a focus on reducing emissions and improving efficiency.