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Marine propulsion systems on Warships to AUVs, submarines and Aircraft carriers to revolutionize underwater warfare

Marine transport is the backbone of international trade. As per the data revealed by the International Chamber of Shipping based in United Kingdom, nearly 90% of the total volume of merchandise trade occurs via sea route owing to its low cost compared to other mode of transports such as rail and road.


Marine propulsion systems move ships through the water, ensures a better safety standard for the marine ecosystem and are cost-efficient. Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or engine turning a propeller, or less frequently, in pump-jets, an impeller.


Diesel propulsion system is the most common marine propulsion system used in all types of vessel along with small and recreational boats. Moreover, diesel marine propulsion engine led the overall market, accounting for 70% in 2015. This is attributed to its benefits such as high reliability, economical nature, low maintenance cost, and easy availability of diesel globally. The cons are they are more expensive to build , generate more noise and vibration and are heavier.


Today, 80 percent of the world’s shipping fleet runs on heavy fuel oil, or bunker fuel. However, the combustion of this fuel to provide propulsion and auxiliary power to ships causes between 2% and 3% of global carbon emissions.  The World Bank estimates that a single large shipping vessel, produces as much sulphur as 50 million cars. At around 800 million tonnes per year, the industry as a whole is responsible for approximately 2.2 per cent of all global emissions.


Combustion of bunker fuel also emits sulfur and particulate matter that causes respiratory illness. A 2018 study found that health impacts due to pollution from shipping include 14 million cases of childhood asthma annually and 400,000 premature deaths a year from lung cancer and cardiovascular disease. The industry is looking to alternative propulsion methods like electric, fuel cell and nuclear. This is why the UN is leading a number of projects aimed at significantly cutting emissions and, eventually, phasing them out altogether.


Worldwide goals have been set for emission reductions for the maritime sector. “The IMO is targeting a reduction in the carbon intensity of international shipping by at least 40% by 2030 compared with 2008 levels, and by 70% by 2050. The IMO took this action to support the United Nations Sustainable Development Goal 13, to take urgent action to combat climate change and its impacts.”


A number of exciting options are currently being explored by the industry including battery-powered and hybrid ferries, ships trialing biofuels or hydrogen fuel cells, and wind-assisted propulsion.


The current trend in  Navies is moving to electric hybrid gas turbine propulsion plants, again improving efficiency and reducing the need to refuel, while increasing operational availability and performance. The German Navy’s fourth and final new F125 frigate Rheinland-Pfalz uses a reliable and powerful GE LM2500 gas turbine-based propulsion system. These gas turbines reliably operate the world over in some of the most arduous conditions in temperatures ranging from -40 to 120 degrees F/-40 to 48 degrees C. All four of the new F125 frigates built for the German Navy employ one GE LM2500 gas turbine, two electric motors and four diesel generator-sets in a combined diesel-electric and gas turbine (CODLAG) propulsion arrangement.


Indian  Navy is considering hybrid electric propulsion for a planned future aircraft carrier, most likely in partnership with a US based partner. “Our plan is to build a 65,000 tonner, possibly with electric propulsion and CATOBAR (Catapult Assisted Take off but Arrested Recovery) so that if we have three aircraft carrier, at least two will be operational at any given time,” the Navy chief said at the side-lines of a seminar on warship building by FICCI.


Sources said that the Virginia, US based Huntington Ingalls – the sole designer and builder producer of American aircraft carriers – could be roped in for a consultant for the future Indian warship plan. India and the US have an official Joint Working Group on Aircraft Carrier Technology Cooperation that has been meeting to work on the project.


Navy has also harnessed nuclear power for submarines and aircraft carries.  The nuclear powered submarines  have large endurance or mission times before resupply, limited only by the available food and air purification supplies on board. This eliminated the need for submarines to surface to recharge batteries, significantly improved stealth and performance, and improved the range and speed of aircraft carriers. Surface ships equipped with nuclear propulsion have long refueling intervals and do not need to be accompanied by vulnerable fuel supply tankers. Nuclear reactors producing steam are  also used to propel warships and icebreakers. Nuclear reactors to power commercial vessels has not been adopted by the marine industry.


The Navy and industry are investing in propulsion technologies that offer the potential to improve future naval ship designs. The goals of the current and planned technology development efforts are to improve affordability, power density, efficiency, and satisfy the energy demands of future mission systems. New generations of ship must meet new challenges, particularly in terms of energy efficiency, reliability and environmental impacts.

Propulsion Requirements

Developing ship power and propulsion requirements entails a detailed understanding of the power and energy requirements for each ship concept driven by ship mission and capability requirements. Choice of a suitable powerplant depends on: size of the ship, speed (type of cargo), length, duration of voyage, cost (operational expenses) and fuel. Ships are integrated with one or more than one propulsion engines, depending on their size (gross tonnage).


Like the engine rating for an automobile, ship design power requirements are driven by limiting mission needs. For example, for each ship concept, a determination is made of the maximum power requirements to simultaneously support propulsion and ship service electrical loads with design/construction and service life margins.


Similarly, the energy needs of the ship can be thought of as sizing the “gas tank.” In this case, mission needs (both  propulsion speed/range and electrical energy usage) for sustained periods without refueling drive energy requirements for the fossil fuel variants. For nuclear propulsion options, mission needs are determined for the ship’s service life to size the energy rating of the nuclear reactor.


Steam turbine

Marine steam turbine was developed by Sir Charles Algernon Parsons. It provides Low noise, low weight, low maintenance costs, more space obtained (power /weight ratio raised) but have  higher fuel consumption. Most new-build ships with steam turbines are specialist vessels such as nuclear-powered vessels, and certain merchant vessels (LNG, coal carriers) where cargo can be used as bunker fuel.

Marine Steam Turbine | Kawasaki Heavy Industries

Gas Turbine

In Gas turbines, compressor draws in and compresses atmospheric air which is mixed with fuel injected  in a  combustion system and burned providing power from turbine to the shaft.The gas turbine (GT) is rapidly becoming the standard surface combatant power plant used by navies across the world. The advantages of GTs for warship use include the capability for rapid acceleration and deceleration which is necessary in case of the ship coming under attack. In addition they have low noise, reliability, and power density.  The design of GTs also facilitates the design of unmanned engine rooms, with consequent crew savings.



Gas turbines are commonly used in combination with other types of engine. Most recently, RMS Queen Mary 2 has had gas turbines installed in addition to diesel engines. Because of their poor thermal efficiency at low power (cruising) output, it is common for ships using them to have diesel engines for cruising, with gas turbines reserved for when higher speeds are needed.

Diesel Propulsion

Despite the universal move to GTs, diesel engines are still the primary power source for the majority of the world’s warships. There are many reasons for this: Diesels are durable, require less bunker space and are economical to operate as long as they are not continuously throttled up and down. They can draw on civilian infrastructure both for support personnel and for logistics provisions.


Marine Propulsion


Green propulsion

Big ships, large engines also mean large amount of pollution. Ships produce above 2 per cent of CO2 emissions every year. This is expected to increase to 17 per cent by 2050 as sea travel is and will continue to be the main mode of economic transport. Marine diesel engines burn approximately 60 million barrels of crude oil every year. This represents an annual emission of almost one thousand million tonnes of CO2 equivalents, more than 20 million tonnes of NOx, more than 10 million tonnes of SOx and more than one million tonnes of particulates


Therefore, air pollution and its effect on climate change will worsen unless new alternative fuels or energy efficient measures are widely implemented. One of the future goals of shipbuilding is to reduce the impact of ship emissions to respond to existent and future regulations of the International Maritime Organization (IMO) on greenhouse gas and pollutants emissions.


The 2020 cap on sulphur content is now close enough to be of concern to marine fuel purchasers as well as engineers, with compliance a matter of choosing exhaust gas scrubbing in combination with HFO, or switching to lower sulphur fuel oils including MGO, LNG, methanol, or another alternative.


Meanwhile, IMO’s broader commitment to halve shipping’s CO2 emissions by 2050 looks beyond the reach of even the most energy-efficient combustion engine, whether or not supplemented by carbon capture. Assuming that there are also limits to carbon offsetting, meeting such a target will rely on supplementary or even replacement ship propulsion technologies. Maritime has developed many  environmentally friendly strategies, such as the development of alternative fuels, hybrid propulsion,  energy auditing, engine waste heat recovery,  speed and voyage optimisation, and slow steaming and wind-powered propulsion.


LNG fuel based Propulsion

It is said that LNG fuel is the future of the Shipping industry. LNG fuel helps in reduction of air pollution from ships, and a combination of LNG fuel with diesel oil will lead to efficient engine performance, resulting in fuel saving. The global availability and development of infrastructure makes LNG as bunker oil feasible. Development in liquefied natural gas (LNG) fueled engines are gaining recognition for their low emissions and cost advantages.

Liquefied Natural Gas | Cat | Caterpillar

While LNG is an excellent technology for reducing SOx and NOx emissions, it only reduces CO2 by about 20 per cent over bunker fuel. Stirling engines, which are more efficient, quieter, smoother running producing less harmful emissions than diesel engines, propel a number of small submarines. The Stirling engine has yet to be upscaled for larger surface ships. Analysts predict that the number of LNG-fueled ships will be more than 200 by 2020.


Bloom Energy and Samsung Heavy Industries (SHI), a part of Samsung Group, announced a collaboration in Sep 2019 to design and develop ships powered by Bloom Energy’s solid oxide fuel cell technology. Bloom Energy is the world’s leading provider of stationary fuel cells and SHI is one of the world’s largest shipbuilding companies.


SHI aims to be the first shipbuilder to deliver a large cargo ship for ocean operation powered by fuel cells running on natural gas. Such an innovation will play a key role in helping the company exceed the 50 percent emissions reduction target, compared to 2008 levels, that the International Maritime Organization (IMO) has mandated all shipbuilders should achieve by 2050. The IMO, an arm of the United Nations, is the global standard-setting agency for the safety, security, and environmental performance of international shipping.


Hydrogen propulsion

To reach goals for the shipping industry set by the United Nations, industry leaders say the first net-zero ships must enter the global fleet by 2030. Ships powered by green hydrogen could help meet the target. Made from electrolysis to split water into hydrogen and oxygen using electricity from renewable energy, green hydrogen is emissions-free.


While hydrogen’s green credentials make it attractive to industrial users, including ship owners and oil majors, it is far less dense than other fuels, meaning more onboard fuel storage capacity is needed. “The big challenge using hydrogen for deep sea shipping is the cargo volume you would lose to have enough hydrogen stored for long voyages, which could be a commercial killer,” Kasper Søgaard, GMF head of research, said. That makes it more feasible, for now, for use in vessels on short voyages.


Japanese firms Kawasaki Heavy Industries, Yanmar Power Technology and Japan Engine Corporation have formed a consortium to jointly develop hydrogen fuelled marine engines for ocean and coastal vessels. The scope of the collaboration will include elementary experiments and analysis on hydrogen combustion, materials and sealing techniques, along with the requirements of the classification society. Additionally, the companies will devise a hydrogen fuel storage and supply system as part of the integrated hydrogen fuel system.


In March, Korea Shipbuilding & Offshore Engineering (KSOE) partnered with Korean Register (KR) to develop the world’s first hydrogen vessel standard. They will work to evaluate the settings for safely handling hydrogen.


Green hydrogen fuel costs around 4-8 times the price of very low sulphur fuel oil, estimates by risk management firm DNV GL find. Other types of hydrogen are cheaper, but that is because they are produced using fossil fuel, which means they are not emissions free. Green hydrogen is expected to fall in price over the next couple of decades as the cost of renewable energy and electrolysers falls.


Fuel Cell Propulsion

Fuel cell propulsion systems use hydrogen as the main fuel component. Electricity is created in the fuel cell without any combustion whatsoever. The process is clean and therefore has been regarded as a very important alternative marine propulsion system. There are various types of propulsion under the fuel cell propulsion head like PEM (Photon-Exchange-Membrane) and the molten-carbonate systems. The fuel cell propulsion utilizes power from a combination of fuel cells, solar cells and battery systems. This helps in reduction of GHG emission to a great extent.

Sandia-led team designs feasible hydrogen fuel-cell coastal research vessel; implications for large hydrogen-fueled vessels - Green Car Congress

Electric motors using electric battery storage have been used for propulsion on submarines and electric boats and have been proposed for energy-efficient propulsion. An all electric ship propulsion concept was adopted for the future USA surface combatant power source. This next evolution or Advanced Electric Power Systems (AEPS) involves the conversion of virtually all shipboard systems to electric power; even the most demanding systems, such as propulsion and catapults aboard aircraft carrier.


ABB and SINTEF Ocean are undertaking groundbreaking research to test the viability of fuel cells as an energy source for main ship propulsion  in commercial and passenger ships. The trials will explore more than the technicalities of scaling-up and optimized fuel cell/battery combinations alone. “SINTEF is contributing the hydrogen supply and infrastructure, while having a test lab gives ABB and SINTEF Ocean the opportunity to increase in-house competence for integration, control and safety of fuel cell technology in marine applications,” says Anders Valland, research manager for maritime energy systems at SINTEF Ocean.


Another key objective will be establishing how to enhance the control of fuel cell plant in combination with energy storage, and how to optimize efficiency, reliability and the lifetime of fuel cell stacks. “We will be seeking the decisive and practical solutions to develop fuel cell technology for main propulsion,” says Kristoffer Dønnestad, R&D engineer, ABB Marine & Ports, Trondheim. “Research will focus not only on fuel flow and fuel handling, but on what a hydrogen ship bunkering infrastructure might look like.”


Using hydrogen as fuel, the proton exchange membrane fuel cells (PEM) separates electrons and protons, with protons passing through and electrons used as electrical output. Hydrogen is converted directly to electricity and heat without combustion. PEM fuel cells operate at a lower temperature, are lighter and more compact than their solid oxide counterparts.


A researcher from Ecole Polytechnique Federale de Lausanne (EPFL) claims to have developed a system based on fuel cells to reduce the carbon footprint and energy consumption of cruise ships. You need to store enough energy on board without taking up too much space,’ says Baldi. ‘Hydrogen fuel cells are not suitable, because storing enough energy to travel long distances would take up a huge amount of space – around one third of the ship’s capacity – which is not realistic for a cruise ship.’


According to Baldi, although they require high temperatures to work and take up to 20 hours to turn on, solid oxide fuel cells (SOFC) are said to be a good fit for ships. Therefore, a use for the surplus energy which results from having them in constant use (which is necessary given the long start-up times), needed to be found. Baldi sought to use a system developed at EPFL to transform unused energy into hydrogen, which is then stored. The resulting fuel cells, customised for ships, could thus generate either electricity to be consumed on board or hydrogen to be stored for later use. According to Baldi, this concept is particularly well suited to cruise ships.


However, despite the environmental benefits, fuel cells cost 10 times as much to produce as a traditional engine. ‘But prices will fall if demand increases,’ argues Baldi. ‘Also, the long-term cost is only 20–30% higher than that of a traditional engine and opting for this cleaner type of fuel will enhance the image of the ships’ operators.’


Bloom Energy and Samsung Heavy Industries Team Up to Build Ships Powered by Solid Oxide Fuel Cells

Bloom Energy and Samsung Heavy Industries (SHI), a part of Samsung Group, today announced a collaboration to design and develop ships powered by Bloom Energy’s solid oxide fuel cell technology. Bloom Energy is the world’s leading provider of stationary fuel cells and SHI is one of the world’s largest shipbuilding companies.


SHI aims to be the first shipbuilder to deliver a large cargo ship for ocean operation powered by fuel cells running on natural gas. Such an innovation will play a key role in helping the company exceed the 50 percent emissions reduction target, compared to 2008 levels, that the International Maritime Organization (IMO) has mandated all shipbuilders should achieve by 2050. The IMO, an arm of the United Nations, is the global standard-setting agency for the safety, security, and environmental performance of international shipping.


In contrast to bunker fuel combustion, Bloom Energy solid oxide fuel cells generate electric power through an electrochemical reaction, without combustion, that virtually eliminates particulate emissions, NOx, and SOx – an important consideration for the shipping industry.


Bloom Energy Servers use natural gas, biogas or hydrogen as fuel. Bloom Energy and SHI envision onboard fuel cells being powered by natural gas, converted from liquefied natural gas (LNG), which is already commonly transported by marine shipping worldwide.


The modularity of Bloom Energy Servers makes them well suited to the space constraints of ships. Unlike large, multi-megawatt generating combustion engines, Bloom Energy Servers can be deployed in increments as small as 200 kilowatts, enabling power sources to be distributed throughout a ship to optimize space utilization. SHI envisions Bloom Energy Servers displacing existing power generation sets, and therefore requiring no additional space, or even reducing the total space required for power generation.


Electric propulsion

Over the last five years, a series of technical advances have turned electric propulsion from a technical backwater into perhaps the predominant form of warship powertrain for the next decade. The modern revival of this system was led by the British, who adopted a combined dieselelectric/ gas turbine (CODLAG) drive system for their Type 23 frigates.

Electric Propulsion Systems - Wärtsilä

The electric propulsion system consists of a prime mover which may be of two types:  Diesel driven or  Turbine or steam driven both generate mechanical energy and drive generators. The propeller shaft of the ship is connected to large motors, which can be D.C or A.C driven and are known as propulsion motors. Power for propulsion motor is supplied by the ship’s generator and prime mover assembly. Both the systems produce less pollution as compared to conventional marine propulsion system, which involves burning of heavy oil.

Electrical Propulsion System in Ships

Instead of driving the ship’s propellers directly, diesel engines turn electric generators, which in turn power electric motors that drive the propellers. This arrangement enables diesels to be placed away from the shafts and propellers in sound-insulated compartments. Because the engines are not directly coupled to the shafts, their vibration does not pass along the shaft and thus does not get transmitted to the water as sound. An advantage of the system is that it eliminates the need for gears between the engines and the shaft. By doing so, removes a production bottleneck. The result is an almost silent propulsion system.

ABB icebreaking propulsion to power fleet of LNG carriers

ABB has secured a contract from Daewoo Shipbuilding & Marine Engineering, valued in excess of US$300 million, to deliver a comprehensive power and propulsion package for six new specialised vessels that will transport LNG along the Northern Sea Route. Each of the six new-build vessels will feature a trio of the largest and most powerful ABB Azipod® propulsion units ever supplied for ships operating in ice. Together, the giant 17 MW Azipod units will provide a total power of 51 MW (68 400 HP), enabling the vessels to navigate safely through ice up to 2.1 m thick. In similar conditions and without ABB’s technology, comparable ships would require icebreaker assistance.


ABB’s Azipod propulsion system  propulsion system, where the electric drive motor is located in a submerged pod outside the ship hull, can rotate 360° to boost manoeuvrability, which is particularly crucial for vessels operating in ice. The new LNG carriers will be classed to ARC7 – the highest ice class rating for merchant vessels.


The order follows the successful delivery of ABB’s leading-edge technology for the 15-ship series servicing the Yamal LNG project – one of the largest orders ever for ABB Marine & Ports, completed in 2019. “We are proud to see our technology to be once again chosen for demanding operations in the Arctic,” said Juha Koskela, Division President, ABB Marine & Ports. “We are committed to supporting the growing Arctic maritime industries with our unparalleled technology that has over the years proven to enable safe, sustainable operations and ensures year-round transportation of cargoes across the Northern Sea Route.” Upon delivery starting from 2023, the six vessels will service Arctic LNG 2 – one of the largest industrial projects in the Arctic – and will each have the capacity to transport 170 000 m3 of LNG.


Hybrid diesel-electric propulsion

The biggest problem is that diesel engines operate efficiently only over a narrow range of speeds. Outside this speed range, fuel economy is poor and exhaust emissions increase. With direct-drive propulsion, the speed of the diesel engine must at all times match the speed of the vessel. This means that when, for example, the vessel is moving slowly – as is invariably the case in harbors and ports – the engine is constrained to run inefficiently.


One solution that has delivered valuable benefits is diesel-electric propulsion. With this form of propulsion, the vessel’s diesel engine or engines are used to drive a generator to produce electricity. This electricity is used to power electric motors, and it is these motors that drive the propellers. There is another vital element in the system, however, and that’s an AC drive that sits between the generators and the propulsion motors.

Rolls-Royce introduces new MTU hybrid propulsion systems for ships – Rolls-Royce

This AC drive allows the speed of the propulsion motors to be controlled all the way from zero up to their maximum rated operating speed, without any need for change in the running speed of the diesel engines driving the generators. As a result, the diesel engines can always run at a speed where they operate efficiently, and their emissions are minimized.


Further the  diesel-electric system can be  hybridized by adding  energy storage to the system in the form of batteries and gain even greater benefits.  This is because the AC drive used to control the propulsion motors has three key elements. The first of these converts the AC power from the generator to DC, and the second – the DC link – provides a small amount of energy storage, usually in the form of a capacitor. This is provided principally to help handle peaks in demand from the third stage, the inverter, which converts the DC power back to AC at the frequency needed to drive the motor at the required speed.


In essence, all that’s needed to add large-scale energy storage to this arrangement is to replace the capacitor in the DC link by batteries of suitable capacity. The system then works in this way: when the ship’s generators are running, they provide a supply not only to the propulsion motors but also to the batteries, charging them. When the generators are not running, the inverter stage of the AC drive can draw power from the batteries to operate the electric propulsion motors.


This arrangement has the immediate benefit that, particularly when the vessel is maneuvering at low speed, which is typically the case when it is in a harbor, the diesel engines don’t need to run at all. Propulsion power can be provided solely from the batteries. Not only does this save fuel, it also means that there are no environmentally damaging emissions and that noise levels are low, which is a significant benefit for vessels close to the shore.


And, as a further benefit, provision can be made, at comparatively little extra cost, for charging the batteries from a shore supply when the vessel is in port. As well as being cost-effective, especially when off-peak tariffs are available, this is an attractively “green” arrangement, as on-shore power from the utility grid is increasingly derived from wind energy and other renewable resources.


However,  it is necessary to make provision for battery management and for handling the very high short-circuit currents that the batteries can deliver under fault conditions. Many practical systems also include a grid converter. This essentially delivers power to the ship’s grid at constant frequency even if the input frequency from the generators changes, as it will if the speed of the diesel engines fluctuates. In ocean-going vessels, the grid converter has the added benefit of allowing the ship’s systems to draw power from the shore supply irrespective of whether the port happens to be in a part of the world with 50 Hz supplies or 60 Hz supplies.


Rolls-Royce Unveils Autonomous Naval Vessel Featuring Electric Propulsion

(Rolls-Royce) has announced plans for an autonomous, single role, naval vessel that will feature electric propulsion. “Rolls-Royce is seeing interest from major navies in autonomous, rather than remote controlled, ships. Such ships offer a way to deliver increased operational capability, reduce the risk to crew and cut both operating and build costs,” said Benjamin Thorp, Rolls-Royce, General Manager Naval Electrics, Automation and Control.



“Over the next 10 years or so, Rolls-Royce expects to see the introduction of medium sized unmanned platforms, particularly in leading navies, as the concept of mixed manned and unmanned fleets develops. With our experience and capabilities we expect to lead the field.”


The initial design features a full electric propulsion system and features two Rolls-Royce MTU 4000 Series gensets to provide approximately 4MW electrical power to a 1.5MW propulsion drive. “An alternative to diesel engines could be small gas turbines, further improving the system’s reliability and reducing onboard maintenance,” explained Rolls-Royce.


“To reduce fuel consumption and extend operational range an additional 3000 kWh of energy storage will facilitate efficient low speed loiter operations and the vessel will also be fitted with photovoltaic solar panels to generate power when the vessel is on standby.” The company notes that, with an absence of crew, autonomous vessels increases the need for reliable power and propulsion systems. In response, Rolls-Royce says the vessel will utilise a suite of autonomous support tools, including Energy Management, Equipment Health Monitoring, and predictive and remote maintenance to ensure vessel availability.


Magneto Hydrodynamic Propulsion for Ocean Vehicles

Magnetohydrodynamic drive or MHD accelerator is a method for propelling vehicles using only electric and magnetic fields with no moving parts, accelerating an electrically conductive propellant (liquid or gas) with magnetohydrodynamics. The fluid is directed to the rear and as a reaction, the vehicle accelerates forward.

Cognitive Diet: Magnetohydrodynamic Propulsion

The working principle involves the acceleration of an electrically conductive fluid (which can be a liquid or an ionized gas called a plasma) by the Lorentz force, resulting from the cross product of an electric current (motion of charge carriers accelerated by an electric field applied between two electrodes) with a perpendicular magnetic field. The Lorentz force accelerates all charged particles (positive and negative species) in the same direction whatever their sign, and the whole fluid is dragged through collisions. As a reaction, the vehicle is put in motion in the opposite direction.


The concept of Magneto-Hydrodynamic (MHD) propulsion can be used to implement a propeller-less propulsion system for marine vehicles. Electrodes are lined up along the walls of the duct which act as the source of the electric field. Seawater acts as the conducting medium for the current when it passes through the duct. This medium is then subjected to a strong magnetic field within the duct, thereby producing an axial force, i.e., an axial thrust. Propulsion systems based on MHD require virtually no mechanical components, therefore a good application would be to design a propulsor which produces very little noise for small underwater vehicles.


Few large-scale working prototypes have been built, as marine MHD propulsion remains impractical due to its low efficiency, limited by the low electrical conductivity of seawater. Increasing current density is limited by Joule heating and water electrolysis in the vicinity of electrodes, and increasing the magnetic field strength is limited by the cost, size and weight (as well as technological limitations) of electromagnets and the power available to feed them


Solar Propulsion

Solar propulsion for ships was utilised for the first time in the year 2008. Solar propulsion benefits include a high reduction in the poisonous carbon dioxide emissions. Solar propulsions are capable of generating a capacitance as high as 40 kilowatts (kW)


Water-Jet Propulsion

Water-jet propulsion has been used since the year 1954. The most important advantage of water-jet propulsion is that it does not cause noise pollution and offers a high speed to the vessels. In contrast the water-jet propulsion as a ship propulsion system is costlier to maintain which can cause problems to the user.

Pump it up! Bigger and better uses for water-jet technology | E&T Magazine

Wind propulsion emerged as an alternative to those systems which emit huge quantities of CO2 gases in the marine atmosphere. However, the usage of wind turbine marine propulsion has not started extensively in large commercial ships because of a requirement of constant windiness. Two wind propulsion systems for ships that have become lately are- kite propulsion and sail propulsion for merchant ships.

Biodiesel Fuel Propulsion

Biodiesel propulsion has been deemed as a potential marine propulsion system for the future. Currently tests are being carried out to find out about the viability of this propulsion system which is expected to be in full operation by the year 2017.


Biodiesels have been considered as a potential substitute for conventional marine fuels. Large and exhaustive research has been undertaken that focuses the combustion and engine performance on broad biodiesel types and blend configurations and injection characteristics, mainly for inshore applications. In contrast, the use of biodiesel in shipping or fishing alike presents more challenging conditions than land-based uses due to its higher density and viscosity compared with distillate fuel oils and long-term storages in humid environments, which could lead to stability problems.

Instruction to marine propulsion systems

These challenges have hampered the progress of biodiesel use in shipping. Likewise, other difficulties include biodiesel’s feedstock costs dependence and higher production, the incompatibility with some plastic and metallic materials for fuel feeding systems, low temperature fluidity and the high quantity of biomass feedstock required to cope with a representative fleet.


One of the solutions for shipping is to use mineral origin alternative oils, such as recycled waste oils. Waste oils are abundant residues with the production of 24 million metric tonnes a year. The recovery of valuable energy content coproducts, such as waste plastics, waste cooking oils, or waste lube oils may represent an important feedstock for energy conversion plants. Recent study  found that the alternative fuel burns rapidly but with a delay at the end of combustion, which should be expected for this type of fuel. Additionally, the energy efficiency of the diesel engine is comparable to the distillate fuel commonly used by the fishing fleet; however, due to its higher heating value, the alternative fuel presents lower fuel consumption. Hence, waste oil-based alternative fuel oils are acceptable for use in marine diesel engines operated on-board a ship under real conditions and meet the rules applicable to marine environments for burning fuel oils.


Nuclear Propulsion

Naval vessels incorporate the usage of nuclear maritime propulsion. Using the nuclear fission process, nuclear propulsion is a highly complex system consisting of water reactors and other equipments to fuel the vessel. The nuclear reactors in the ships are also used to generate electricity for the ship. Several merchant ships are also being planned to be constructed with this propulsion system.

Nuclear Ship Propulsion: Is it the Future of the Shipping Industry?

Naval reactors use high burn-up fuels such as uranium-zirconium, uranium-aluminum  and metal ceramic fuels in contrast to land based reactors which use uranium di oxide UO2. These two factors provide the naval vessels, theoretically infinite range and mission time. For these two considerations, it is recognized that a nuclear reactor is the ideal engine for naval propulsion.


Until recently, American, British, and Russian nuclear submarines have used steam produced by the onboard nuclear power plant for propulsion; the steam would drive a turbo-gear unit, rotating the propeller. At the same time, French and Chinese nuclear submarines have used the principle of electric propulsion. The nuclear power plant set in motion turbines which are not connected to propellers, and which pump all their power into electric generators. The current from these generators, in turn, sets propulsion systems in motion.” Military analyst Vasily Kashin  noted, the latter setup means decreased noise, but at the cost of a drop in maximum speed. Furthermore, “a great deal also depends on the quality of the installation itself, and other factors.


China’s new submarine engine is poised to revolutionize underwater warfare

In a recent interview with China Central Television, Rear Admiral Ma Weiming, a leading Chinese naval engineer, showed a component of a new Integrated Electrical Propulsion System (IEPS) for naval warships in a laboratory. He said the system, which turns all the engine’s output into electricity, and a rim-driven pump-jet had been fitted to the People’s Liberation Army Navy’s newest nuclear submarines.  IEPS turns all the output of the ship’s engine into electricity, unlike traditional propulsion designs, which convert engine and reactor output into mechanical action to turn the propeller shaft.


The high electrical output can be used to power motors for the propellers or potentially high-energy weapons. Additionally, IEPS has far fewer moving parts, making them quieter, and thus ideal for use on submarines. When coupled with quieter reactors like the Type 095’s reported natural circulation reactor, the rim-driven pumpjet and IEPS can drastically reduce the acoustic signature of any SSN.


PLAN is fitting its newest nuclear attack submarines with a “shaftless” rim-driven pumpjet, a revolutionary and silent propulsion system, stated Chinese naval engineer, Rear Admiral Ma Weimin in the interview. The system is  likely to be used on the first Type 095 nuclear attack submarine (SSN), which is under construction.The Type 095 SSN will likely have VLS cells for launching a wide range of cruise missiles, pumpjet propulsion, and improved quieting technology. US and UK are also developing rim drive pumpjets, whose Columbia and Dreadnought nuclear ballistic missile submarine (SSBN) have the option for rim-drive pumpjets, but will not enter service until 2030.


Rim-Driven Thruster is a novel type of propulsion unit that has a ring-shaped electrical motor inside the pumpjet shroud, which turns the vane rotor (a vane rotor has the fan blades attached to a rotating band built on a cylinder interior, as opposed to a propeller shaft) inside the pumpjet cavity to create thrust.


The blades of the rim-driven thruster are mounted on a ring which constitutes the rotor of an electric motor. It is surrounded by the stator which is also ring-shaped and creates the necessary torque. Rotor and stator are water tight and the whole unit operates submerged.


The largest advantage of this building principle is its minimal noise emissions and the low space requirement. It enables relatively simple integration in many applications. Since the rotor is driven directly by the electro-magnetic forces, no shaft and no gearbox is needed. Sealing of moving parts is not necessary, rotor and stator can be sealed hermetically. Since the blades are mounted to the rotor ring, there is no tip gap. This, together with the gearbox removes prominent sources of noise. Rim-driven thrusters are therefore characterized by an extremely low level of noise emissions.


Previous submarine pumpjets are “shrouded propellers,” which consist of a tubular nozzle covering the propeller. By removing the shaft of the propeller, the reduction in the number of moving parts decreases the noise made by the pumpjet, as well as saving hull space. Civilian manufacturers also claim that rim driven pumpjets are easier to maintain, and have less cavitation (bubbles that form during propeller movement), making them even more quiet. While the system would be on China’s attack submarine, Chinese SSBNs could also use the rim-drive pumpjet to enhance their stealth and survivability—and, by extension, the credibility of China’s second strike nuclear capability.


Ultimately, the commentator noted that “if China really achieves a sharp increase in the stealthiness of its nuclear subs, it will close the main gap in its military potential – the weakness of its submarine and anti-submarine forces. If Chinese nuclear subs reach silent operation indicators comparable to Western and Russian subs, it will make sense to rapidly increase the size of its submarine fleet. The fact that such a build-up is being prepared is evidenced by the expansion of the Bohai Shipyard [in Huludao, northeast China] in recent years. According to various sources, it is now possible to build 5-6 nuclear subs at the shipyard simultaneously.”


Finally, Kashin explained that the latter development will allow for a rapid growth of the naval component of China’s strategic nuclear forces, and alterations in the ratio of nuclear weapons deployed on the ground versus at sea. “It can be assumed that the construction of the prospective large nuclear-powered Type 096 submarines has been timed with the completion of development and testing of the IEPS system, and will now develop at considerable speed.”


Market growth

The marine propulsion engine market size is expected to increase by USD 1.34 billion from 2021 to 2025, registering a CAGR of over 3.87%, according to the latest research report from Technavio.


The key factors driving the growth of the marine engine market include growth in international marine freight transport, growth in maritime tourism, and increasing adoption of smart engines for situational awareness and safety.


Other factors that include prominently rising global population, rapid industrialization particularly in the Asia Pacific region, and liberalization of economies have significantly spurred the rate of trade activities between countries across the globe. The aforementioned factors are likely to further propel international trade at a rapid rate during the forthcoming years. Hence, the demand for cargo ships and containers that are required for international as well as regional transportation of raw materials and goods are likely to rise during the forecast timeframe. Further, the rising need for fuel-efficient and dependent ships are anticipated to prosper the market growth for marine propulsion engines in the upcoming years.


The marine propulsion engine market is expected to witness robust growth during the forecast period owing to various ongoing government investments in shipbuilding industry and inland waterways. Marine Propulsion Engine Industry is gaining a substantial traction on the grounds of powering the world’s largest ships that transport cargo across the globe. Over the years, there has been a tremendous increase in the international trade through marine transportation due to its cost-effectiveness. Consequently, there is a high demand for fuel efficient ships, which will propel marine propulsion engine market. Basically, marine propulsion refers to the mechanism that produces the required thrust for driving the marine objects.


Increase in production & sales of ships globally and rise in international seaborne trade drive the market growth. In addition, increase in demand for resources such as crude oil, coal, steel, and iron from developing countries fuels the market growth. However, stringent environmental rules & regulations and large capital investment required to set up new manufacturing facilities hamper the market growth. Irrespective of these challenges, rise in usage of inland waterways and advancement in technology, such as new alternative fuel propulsion engine, are expected to provide various opportunities for new products and boost the market growth.


According to report “Global Marine Hybrid Propulsion Industry,” the market is expected to reach 5 Billion by 2027, growing at a CAGR of 6.8% over the analysis period 2020-2027. Diesel-electric, one of the segments analyzed in the report, is projected to grow at a 7.3% CAGR to reach US$2.8 Billion by the end of the analysis period.After an early analysis of the business implications of the pandemic and its induced economic crisis, growth in the Parallel segment is readjusted to a revised 6.5% CAGR for the next 7-year period. This segment currently accounts for a 28.9% share of the global Marine Hybrid Propulsion market.


Geographical Analysis

Geographically, the market is spread  across North America, Europe, Asia-Pacific, and LAMEA. China, the world second largest economy, is forecast to reach an estimated market size of US$1.1 Billion in the year 2027 trailing a CAGR of 10.6% through 2027. Among the other noteworthy geographic markets are Japan and Canada, each forecast to grow at 3.8% and 6.2% respectively over the 2020-2027 period. Within Europe, Germany is forecast to grow at approximately 4.5% CAGR while Rest of European market (as defined in the study) will reach US$1.1 Billion by the year 2027.


AsiaPacific is the most lucrative marine propulsion engine market, owing to increase in shipbuilding industries in China & South Korea and growth in number of joint ventures with international brands. Japan, China, and South Korea that have emerged as a manufacturing powerhouse within past few years as their economy is largely dependent on the external trade.


Asia Pacific marine propulsion engine market accounted for more than 50% of the overall share in 2015, with a revenue generation of more than USD 4.5 billion. China and South Korea are the prominent revenue contributors. These countries have been investing heavily in regional marine propulsion engine market, thereby augmenting APAC market share. Moreover, favorable government initiatives for the development of solar & wind energy powered products in the region will also drive the market demand.


Moreover, China is the world’s largest exporting nation and thus requires large number of commercial ships that in turn positively impact the market for marine propulsion engines in the country. Apart from surge in trade activities, countries across the globe are beefing up their naval security by increasing the number of ocean border visits to combat the ocean piracy. As the Asian navies are focusing towards strengthening their defense capabilities, the market for marine propulsion engines expected to gain prominent boost.


Moreover, rise in seaborne trade of crude oil mostly from Middle East countries to AsiaPacific is another factor that drives the AsiaPacific marine propulsion engine market.


On the contrary, North America exhibits slow growth in the global marine propulsion engines market during the forecast time period because of increasing adoption of renewable energy. The government of USA has imposed stringent laws on emission in order to curb the rate of rising pollution. Hence, the usage of renewable energy is being promoted in the region by offering attractive incentives and benefits; however, renewable energy powered propulsion engines are only used as auxiliary engines and not as primary engines. Thus, the marine propulsion engines market in North America anticipated to be hindered by the shifting trend towards renewable energies.



Market Segments

The market segmentation is based on power source, ship types, and geography. The power source segment is divided into diesel, gas turbine, natural gas, and others (steam turbine, renewable energy, hybrid, and fuel cell). By ship types, the market is categorized into cargo & container, tanker, bulk carrier, offshore vessel, passenger ship, and others (tugs & service ships).


Serial Segment Corners a 22.9% Share in 2020. In the global Serial segment, USA, Canada, Japan, China and Europe will drive the 5.7% CAGR estimated for this segment. These regional markets accounting for a combined market size of US$603.5 Million in the year 2020 will reach a projected size of US$887.4 Million by the close of the analysis period. China will remain among the fastest growing in this cluster of regional markets. Led by countries such as Australia, India, and South Korea, the market in Asia-Pacific is forecast to reach US$772.6 Million by the year 2027, while Latin America will expand at a 7.4% CAGR through the analysis period. We bring years of research experience to this 6th edition of our report. The 276-page report presents concise insights into how the pandemic has impacted production and the buy side for 2020 and 2021. A short-term phased recovery by key geography is also addressed.


Rising proximity of wind and solar energy as auxiliary power sources will lead this segment to register a CAGR of 5.9% over the period of 2016-2024, having had a contribution of 3.5% of overall marine propulsion engines market stake in 2015. Apart from this, diesel, steam turbine, gas turbine, fuel cell, and natural gas are the noticeable product segments of marine propulsion engine market. The gas turbines product segment is witnessing lucrative gains, owing to its the high-speed sprint operation mode. Such turbines are in great demand in the military & naval sector, thus, boosting the growth prospects of marine propulsion engine industry.


With the depletion of conventional and shale gas reserves, liquefied natural gas is emerging as an efficient source of fuel in marine propulsion engine industry. Growing adoption of liquefied natural gas as a propulsion medium in the United States has significantly boosted the revenue share of marine propulsion engine market in the region. Furthermore, steam turbines are becoming a sustainable option for the alternative fuel source and are anticipated to offer tremendous business scope due to their utilization in coal carriers.


Key players

Some of the key players in the global marine propulsion engines market are BP Shipping, Yamaha, Aegean, Caterpillar, Cummins, Chevron, Hydraulic Marine Systems, Hyundai Heavy Industries Co., Ltd., Exxon Mobil Corp. (XOM), Hydrosta BV, Ingeteam, Idemitsu, MAN Diesel & Turbo, Lukoil, MAN Diesel & Turbo, Masson Marine, Petronas, Mercury Marine, Niigata Power Systems Co., Ltd., Shell, Total, Sinopec, SCANA, Rolls Royce, Volvo Penta, Siemens, and YANMAR Co., Ltd., Yamaha, Wartsila among others.






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