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The top 4 ways to comply with EEXI without slowing down your vessels

Want to comply with EEXI regulation without reducing your sailing speed? Here are the top four ways to improve energy efficiency and reduce emissions.


How can you comply with the Energy Efficiency Existing Ship Index (EEXI) and improve the Carbon Intensity Indicator rating (CII) of your vessels without reducing sailing speeds? Here are the top four ways to comply by improving the energy efficiency of your vessels and reducing emissions in the process.

To comply with EEXI regulation and CII, you have two main options. The first is simple: slow down your ship, for example by adopting engine power limitation (EPL) or shaft power limitation (ShaPoLi).

The second option, which this article concentrates on, is to make your vessel more efficient by reducing the amount of energy needed to propel it through the water. Better efficiency means you burn less fuel and reduce your emissions but – crucially – it allows you to maintain market speeds and competitiveness.

The EEXI regulation and CII have been in force since the start of 2023. Both aim to reduce the carbon intensity of international shipping. EEXI defines a minimum energy efficiency level for existing vessels, while CII gives vessels an annual rating on a scale of A to E, with A being the least carbon intensive. Take a look at the Wärtsilä website to learn more about decarbonisation and net zero for the shipping industry.


Four ways to make your vessel more efficient

There are four main ways you can improve energy efficiency and reduce emissions without slowing down your ships:

  • Install energy saving technologies
  • Install shaft generator systems
  • Adopt hybrid systems
  • Use alternative fuels

Let’s take a closer look at each of these approaches.


1 - Energy saving technologies

Energy saving technologies (ESTs) directly impact your vessel’s propulsion efficiency, for example by reducing hull resistance and improving propeller thrust. They are a popular choice among vessel operators across a variety of sectors because, in the right combinations, they can reduce emissions by as much as 28%. You can choose from a wide variety of proven technologies, including:

  • Rotor sails – harness wind power to provide additional propulsion
  • Wärtsilä’s EnergoProFin propeller cap – reduces energy losses around and behind the propeller
  • Wärtsilä’s EnergoFlow pre-swirl stator – reduces power losses in the propeller slipstream
  • Wärtsilä’s EnergoPac integrated propeller and rudder design – optimises propulsion
  • GATE RUDDER™ by Wärtsilä – replaces rudder drag with a thrust-generating arrangement

Learn more about how these different energy saving technologies work.

How exactly can different combinations of energy saving technologies help you comply with CII? You will find all the information you need in this article: Unsure about CII compliance? Here’s how energy saving technologies can help. The article also includes real-world examples of the percentage savings you can expect for bulkers and container ships.

For even more insights into how proven, readily available energy saving technologies can ensure you comply with CII, watch our 60-minute webinar: How to improve your CII rating with energy saving technologies.


2 - Shaft generator systems

Shaft generator systems have been around for decades. They can supply all the electricity your ship needs while sailing by using the main engine, instead of the auxiliary gensets, to generate it. Modern converter technologies and software make it possible to generate electricity across a wide engine rpm range. Because of their positive impact on a vessel’s Energy Efficiency Design Index (EEDI – the corresponding index to EEXI for newbuilds) shaft generator systems are now standard onboard most newbuilds.

A shaft generator system can improve your ship’s energy efficiency by 3–5% and cut your fuel bill and overall operating costs. If you operate a bulker or tanker, the system can pay itself back in just five years. The more days your ship sails, the quicker the payback time. If you’ve already installed some ESTs, shaft generators are often seen as the next-best technical option to comply with EEXI while reducing OPEX and positively impacting your ship’s CII rating. Wärtsilä has installed shaft generator systems on more than 550 vessels sailing today.


3 - Hybrid systems

A hybrid system typically combines a battery energy storage system and a conventional engine. To get the most from hybrid technology you need a dedicated energy management system (EMS) to optimise the interaction of the different power sources and protect the battery by directly controlling the converter that determines the charge and discharge rate. A standard power management system (PMS) won’t do the job.

A hybrid system on a vessel can help you cut fuel consumption, and therefore emissions, by 15–25% compared to diesel-fuelled propulsion. You also benefit from less wear and tear on auxiliary gensets because they can be powered down when the battery kicks in, so maintenance costs are lower too.

When your ship is running on battery power it also generates less noise and vibration, so it is quieter and more comfortable for passengers and crew. And if shoreside power is on offer at the ports you visit, the electricity already comes from up to 50% renewable sources.

If your hybrid system is intended to be an integral part of a ‘free power-source technology’ installation such as photovoltaic (PV) cells, you can expect an EEXI impact of 4% and a vastly superior return on investment.


4 - Alternative fuels

New, cleaner alternative fuels have a critical role to play in helping the maritime industry to decarbonise. There are currently several options on the table, including:

  • LNG, which instantly and drastically reduces CO2, NOx, SOx and particulate emissions
  • Methanol, which can be carbon neutral when made using hydrogen from renewable electricity and recaptured carbon
  • Ammonia, which emits no CO2 when combusted and can be carbon free when it’s made using renewable energy
  • Biofuels, which are produced from renewable biomass like vegetable oils, animal waste and crop residues.

Curious about how these future fuels can help you comply with EEXI and CII regulations, save money, and hit your decarbonisation targets? Head over to future fuels in shipping to learn more.


How well-maintained and optimised engines can help with EEXI and CII compliance

It’s easy to forget that well-planned and executed maintenance alone can offer some big efficiency gains, giving your EEXI and CII compliance efforts a big boost without needing to sail your ships at slower speeds.

Every single component has a part to play; for example, exchanging a filter or cleaning an air cooler at the right time can help to cut fuel consumption. Data collection and expert analysis can help you identify the best time to carry out these tasks.

For some helpful tips on how good maintenance practices can benefit your business, read our Insights article: Want to cut costs and extend CII compliance? The top 4 ways good maintenance practices can help.

A trusted partner and a lifecycle service agreement can help you find the small efficiency gains that really add up – depending on your ship type, installed equipment and operating profile you could improve efficiency by as much as 20%. If you want to learn how to transform your emissions reduction strategy with marginal gains, our Insights article is a must read: One simple secret that will make your emissions reduction strategy look awesome. The article includes details of the four levels of support you can choose from with a Wärtsilä Lifecycle Agreement, all of which are based on solid, actionable data. 

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Could slowing down be an option for you?

It is believed that most shipowners will try to comply with EEXI by adopting either engine power limitation (EPL) or shaft power limitation (ShaPoLi). Power limitation means reducing a vessel’s maximum sailing speed, and it’s a quick and easy method of complying with EEXI because the main propulsion power is the biggest factor influencing the EEXI calculation formula.

Speed reduction might be a valid option if your ships have high installed power and a high design speed. Slowing down your ship with power limitation can ensure EEXI compliance on a tight schedule. To learn more, watch our webinar about how engine power limitation can help you with EEXI compliance.

Want to know how energy saving technologies can keep your ship productive and competitive for longer? Download our white paper: How to ensure a good CII rating while staying competitive

Written by
Charlie Bass

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