Smart decarbonisation: Top 8 ways that ferry operators can do it profitably

From flexible engines and electrification to hybridisation and future fuels, take a look at the top 8 ways that ferry operators can decarbonise profitably.

The ferry industry is leading shipping's drive to decarbonise. There are plenty of opportunities open to this diverse sector to reach its goals. From flexible engine and propulsion technologies to electrification, hybridisation and future fuels, we take a look at the top eight.

Driven by pressure from the passengers and businesses it serves and increasingly strict global and local regulations, the ferry industry is among the first to target zero-carbon operations. Its diversity, encompassing everything from small commuter vessels to large RoRo and RoPax ships, means there is no one-size-fits-all solution to decarbonising this sector.

Many ferry companies operate with slim profit margins, and demanding schedules are part and parcel of their daily reality. New technologies to improve vessel efficiency and cut emissions need to be introduced with an eye on minimal service disruption and maximum return on investment.

Download white paper: The Route to Profitable Decarbonisation – insights and practical guidance for the ferry segment

From bow to stern and everything in between, let’s take a look at what’s on offer to help ferries of all shapes and sizes decarbonise.


1 – Fuel-flexible engines

Once the sole power source for ferries, engines are increasingly accompanied by electrical sources either onboard or at port. This will not change in the foreseeable future for all but the smallest vessels and those operating short routes. However, operators will increasingly choose engines that are able to burn low-carbon fuels and which can operate in at least partially electrified setups.

An example is a hybrid setup between mechanically driven main engines combined with diesel or gas-electric machinery, all supported by batteries. This type of setup:

  • reduces fuel consumption and emissions
  • allows the ship to operate on one type of engine
  • ensures the engines always run at optimal load
  • future-proofs the machinery
  • reduces the installed power requirement
  • reduces engine-room size, maximising passenger and cargo space, and therefore earning potential
  • makes it possible to integrate batteries, a shore power connection and renewable power sources like wind and solar.

The ferry engines of the future will need to be capable of using multiple fuels, and increasing hybridisation will place further demands on integration. And with future fuels likely to be more expensive than conventional fuels, fuel efficiency is key to making them a viable option for ferries.

Even though engine demands are changing, it is still crucial to look for engines that provide:

  • efficiency
  • power density
  • ease of maintenance.


2 – Efficient waterjets

For high-speed ferries, reducing speed to comply with regulations like CII is not an option. This makes efficient and fuel-flexible propulsion even more critical. When correctly specified and paired with the right engine, they offer unbeatable efficiency above 25–30 knots compared to other propulsion methods.

Waterjets need to generate as much thrust as possible from the input power available and have robust mechanical integrity. They should:

  • offer good manoeuvrability and fast acceleration response
  • be as light as possible to save on payload
  • be easily maintainable as part of normal ship docking intervals.

Partnering with a single OEM that can offer the whole package will mean an optimised drivetrain in terms of performance, fuel consumption and OPEX. It also reduces risk by minimising complexity in terms of both vessel design and ongoing maintainability.


3 – Optimised thrusters

Thrusters are critical for ferries of all types and sizes, providing the power for safe, accurate manoeuvring, especially when in port. Thrusters must be carefully integrated with your vessel’s propulsion and engine control systems. This means taking care in the early design stages to identify the optimal number of thrusters and the correct thrust and power output for your application. Doing so will helping to optimise CAPEX and operational efficiency.

Calling in hydrodynamic expertise is a huge benefit because it will help you to optimise the design of the entrances on tunnel thrusters. This:

  • minimises resistance during ferry transit
  • maximises thruster performance
  • keeps noise and vibration to a minimum, improving passenger comfort.

The key to optimising thruster energy efficiency, and therefore reducing emissions, is to take a holistic view when specifying them. It is important to avoid simply specifying thrusters in terms of the required power output, as this ignores the following critical factors:

  • thruster design
  • hull design
  • your vessel’s operational profile.


4 – Low and zero-carbon future fuels

Adopting future fuels is a must if the ferry industry is to hit its decarbonisation targets. The challenge is that, for many future fuels, the infrastructure and availability are still maturing. By opting for flexible, multi-fuel engine technology you gain the flexibility to take the first steps towards decarbonisation with a transition fuel such as LNG. You can then progress through drop-in and fuel-blend strategies towards renewable zero-carbon fuels.

Let’s look at the future-fuel menu currently on offer for the ferry industry.

  • LNG – Immediately cuts carbon, SOx and NOx emissions and provides an established and viable route towards more sustainable operations. LNG-fuelled marine engines have been deployed on a broad range of passenger vessels.
  • Methanol – One of the best options to meet current and future emissions targets. Readily available and widely transported by sea, with storage and handling facilities at most major ports. Low environmental risk as it degrades rapidly in water. Can be stored in similar tanks to diesel. Engine platforms under development.
  • Ammonia – Produces no CO2 emissions when used in engines and shows excellent potential as a viable marine fuel. First commercial engine platforms under development and due for launch within the next few years.
  • Hydrogen – Today’s dual-fuel engine technologies can use fuel blends comprising LNG and up to 25% hydrogen.

By opting for flexible, multi-fuel engine technology you gain the flexibility to take the first steps towards decarbonisation with a transition fuel such as LNG.

Retrofitting engines and fuel systems to use low-carbon fuels keeps vessels compliant for longer and offers immediate reductions in greenhouse gas emissions. Engaging a single partner rather than multiple vendors to integrate and supply systems and components will make installation and ongoing maintenance simpler and more effective.


5 – Clean power with electrification

Hybrid and fully electric operations are both making inroads in the ferry industry. At the larger end of the scale hybridisation is becoming the norm for newbuild RoPax vessels. Almost all newbuilds today include hybrid propulsion, and some installations include battery power capacities as large as 5–10 MWh. At the smaller end, fully electric ferries are a common sight in countries like Norway.

Designing a hybrid ferry is not as simple as dropping a battery into your existing design. You need to consider the whole propulsion train setup and understand how to manage the complex interactions between power producers and consumers. This is where expert help from a knowledgeable partner really pays off.

A hybrid solution enables fuel savings by optimising propulsion efficiency – something that will become even more relevant as more expensive low and zero-carbon fuels come into play. With a hybrid solution you:

  • can operate with zero emissions for short periods, for example when manoeuvring in port
  • benefit from instant full power from the battery with no ramp-up, for better manoeuvrability and safety
  • have instant reserve power in case of emergency, with no need to wait for a second engine to ramp up.

RoPax ferries operating on longer routes and at constant speeds can use a power take-off/power take-in solution with a shaft generator. This provides electrical power for onboard systems, reducing fuel consumption and helping the engines to run close to their optimal design point.


6 – Smart power management

The core of a hybrid system is not the engine or even the battery, but the energy management system (EMS). With an intelligent EMS you can optimise energy flows under different operational modes between the different power producers for maximum efficiency. This means you get the right amount of power from the right source at the right time. If your hybrid system is well-designed, your vessel’s engines should run at a stable, optimal load and waves and other external forces should not create peaks.

A hybrid solution enables fuel savings by optimising propulsion efficiency – something that will become even more relevant as more expensive low and zero-carbon fuels come into play.


7 – Efficiency measures

If you want to make big, immediate gains in energy efficiency and fuel savings, energy saving technologies and power limitation are a cost-effective and relatively easy way to do so. But choosing the right combination of solutions is critical. Power limitation might help you comply with EEXI, but with strict schedules to stick to it might not be an option. Plus, in the later stages of CII you might need to add other measures to remain compliant.

Let’s look at the options on the table.

  • A new propeller design that considers the full-scale interaction between the propeller and hull can help optimise performance and efficiency while minimising noise and vibration.
  • An integrated propeller and rudder design ­can reduce fuel consumption and emissions without compromising manoeuvrability or comfort.
  • A thrust-generating rudder arrangement can improve your vessel’s manoeuvring capabilities, reduce noise and vibration, and substantially reduce fuel consumption.
  • Air lubrication cuts fuel consumption and associated GHG emissions by reducing hull resistance using a carpet of microbubbles on the full flat bottom of your ferry’s hull.
  • Rotor sails can reduce fuel consumption and emissions by providing auxiliary propulsive power.


8 – Lifecycle agreements and decarbonisation services

Well-maintained engines and other onboard equipment are the starting point for fuel efficiency. The best way to achieve this is with a comprehensive, tailored service agreement. This will help cut fuel consumption and emissions by ensuring that your vessel’s engines run as efficiently as possible throughout its lifecycle.

More advanced agreements can include dynamic maintenance planning, where maintenance is scheduled and performed based on the actual condition of the engine and main components rather than on a fixed schedule based on running hours. This can extend the time between overhauls, increasing uptime and reducing costs while giving you the flexibility to perform major maintenance with minimum disturbance to your operations. You should look for a provider who can tailored the scope of your agreement according to your needs.

To help you get your decarbonisation strategy right first time, there’s Wärtsilä Decarbonisation Services. The service can help you identify the right decarbonisation path for your ferry business with a simple three-step approach:

  1. Analysis of your current fleet
  2. Modelling and data analysis
  3. Selecting the right solutions


One size does not fit all

With dramatically different ship sizes, configurations and operating profiles, the ferry segment requires a wide variety of approaches to decarbonisation. The challenge lies in selecting and employing the right solutions and technologies efficiently, economically and at the right time. 

Want to know how your ferry operations can set course for net zero? Get insight and practical guidance in our white paper: The Route to Profitable Decarbonisation

Written by
Charlie Bass

Related solutions