A container ship emitting white smoke, shown from above.

Waste Heat Recovery for EEXI Compliance?

The Energy Efficiency Existing Ship Index (EEXI) comes into force later this year, putting shipowners under increasing pressure to comply with new regulations. With most existing vessels exceeding the emissions thresholds set out in the EEXI, shipowners will need to modify ship designs to reduce emissions in order to continue operating. 

While various technologies could be used to modify existing vessels, waste heat recovery has been cited as a viable method of achieving EEXI compliance (Severn and Hoare, 2021). 

By retrofitting waste heat recovery systems, shipowners can increase the energy efficiency of their vessels, effectively reducing emissions and satisfying the EEXI mandates. So, why is WHR so beneficial in light of EEXI regulations and why are so many shipowners likely to choose this method of energy conservation to meet their environmental obligations? Read on to find out!

What is the EEXI?

Emitting 1,056 million tons of CO2 and 2.89% of global greenhouse gas emissions each year (Fourth IMO GHG Study, 2020), shipping decarbonisation is a top priority for environmentalists, governments and shipping companies.

A table with eight columns and eight rows, showing global voyage and vessel-based shipping emissions.
Global voyage and vessel-based shipping emissions, 2012-2018. Source: Fourth IMO GHG Study, 2020

The IMO’s ambitious Greenhouse Gas Strategy (IMO, 2018) aims to reduce carbon emissions per transport work emissions by at least 40% by 2030 and 70% by 2050, compared to 2008 baseline emissions. To achieve these objectives, various schemes and methodologies have been introduced. For example, the EEDI, introduced in 2013, ensures that all newbuild vessels meet specific emissions targets.

However, ships are typically operational for decades, which means that many vessels built prior to the introduction of the EEDI continue to emit vast amounts of CO2. To accelerate the decarbonization of the shipping industry, the IMO saw fit to address the energy efficiency of existing vessels via the EEXI shipping regulations. 

Approved in 2021 by the IMO's Marine Environment Protection Committee (MEPC 76) via an amendment to the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI, the EEXI shipping regulations come into force in November 2022 and take effect from January 2023. 

Applicable to all oceangoing ships exceeding 400 gross tonnage, the EEXI requirements will have a widespread effect throughout the industry. Indeed, the vast majority of in-service vessels that exceed the 400 gross tonnage application limit will need to be modified to achieve EEXI compliance. 

How are EEXI Calculations Made?

Various factors are taken into account when calculating a vessel’s EEXI value but, in simplistic terms, the requisite EEXI calculation can be expressed as follows:

EEXI Formula. Source: Napa, 2021

The IMO sets out a ‘Required EEXI’ value for various types of ships. Shipowners will be required to submit technical documentation to their respective classification society, so that an International Energy Efficiency (IEE) survey can be completed. The results of the IEE survey will enable an International Energy Efficiency Certificate (IEEC) to be issued for the vessel and this will state the ship’s ‘Attained EEXI value’, based on the EEXI formula set out above. 

A ship’s ‘attained EEXI value’ must meet the ‘required EEXI value’ for its type and, if it fails to do so, shipowners will be expected to increase the vessel’s energy efficiency accordingly. 

When Do EEXI Regulations Come into Force?


The EEXI comes into force in November 2022 and takes effect in January 2023. However, shipowners must act now to achieve compliance before the EEXI applies. As the EEXI is concerned with design efficiency, it is likely that design modifications will be required on in-service vessels. 

Shipowners, operators and charterers will be reluctant to disrupt services and routes to accommodate these modifications, which is why careful planning must take place to enable appropriate adjustments to be made to the ship’s design efficiency before the EEXI regulation deadline passes.

With only a few months left to achieve EEXI compliance, shipowners are under pressure to implement effective emissions-reducing modifications. However, legal compliance isn’t the only driving force prompting shipowners to accelerate their ships’ energy efficiency strategies. 

The expected revision to the IMO’s GHG Strategy in 2023 and uncertainty regarding the real-world implications of the EEXI and the incoming Carbon Intensity Indicator (CII), has left ship operators and charterers hesitant to sign long-term agreements beyond 2023. As a result, freight rate price fluctuations are expected, with shipowners facing potential financial losses (Mattälä, 2021). 

By achieving CII and EEXI compliance as quickly as possible, shipowners can fulfil their incoming legal obligations and reassure operators and charterers that vessels will operate with reduced emissions and maximum efficiency in both the short and long-term. 

Ensuring EEXI Compliance

As emissions are intrinsically linked to a ship’s engine power, reducing the vessel’s speed is arguably one of the most straightforward ways to achieve EEXI compliance. This process, known as ‘slow steaming’, was first introduced by Maersk (JOC, 2010) and has been used throughout the industry for some time. The reduced amount of fuel required to propel the ship at a slower speed reduces emissions and could, therefore, enable vessels to meet EEXI thresholds.

Shipowners and operators must find ways to increase energy-efficiency to achieve EEXI compliance. Source: Ian Taylor via Unsplash

However, slow steaming is not necessarily easy or advantageous. When travelling at slower speeds, ships take longer to arrive at their destination, which may leave customers or passengers dissatisfied. Additionally, some types of slow steaming require engine modifications, which will need to be carried out in advance of the incoming EEXI for vessels to remain operational.

Despite the widespread use of slow steaming throughout the industry, many marine engineers remain frustrated by the additional processes that reducing the ship’s speed entails. When the main engine is operating outside of its optimal range, as it is when slow steaming, additional checks are required to ensure that damage is not occurring (Marine Insight, 2012). 

Risks associated with slow steaming include:

  • Loss of efficiency in turbochargers
  • Over-lubrication of cylinder liners
  • Increased deposits due to reduced air flow production by turbochargers
  • Compromised injector performance due to increased carbon deposits
  • Fouling of the exhaust gas economizer
  • Improper combustion caused by a reduction in scavenge air pressure
  • Reduced peak compression pressure
  • Improper fuel atomization
  • Compromised piston ring pack efficiency
  • Increased risk of scavenge fires
  • Reduced economizer efficiency and increased use of oil-fired boiler
  • Increased risk of component failure due to thermal stresses

It is evident, therefore, that slow steaming is not a universally favourable method of achieving EEXI compliance. While some shipowners may see this as a viable way to reduce emissions and support the decarbonization of the shipping industry, many more are seeking alternative solutions that bring fewer risks and bigger rewards.

As the EEXI is a technical measure, modifications to ship’s design can enable existing vessels to meet the requirements of the new design index. By retrofitting equipment designed to increase the ship’s energy efficiency, shipowners can implement effective measures and reduce emissions in accordance with the EEXI regulations, without reducing the ship’s speed.

While various maritime technologies exist, one type of energy-saving tech that should not be overlooked in seeking to satisfy EEXI requirements is waste heat recovery. 

Achieving EEXI Compliance with Waste Heat Recovery

By using waste heat from the vessel to produce clean electricity, shipowners can reduce the vessel’s fuel consumption and, therefore, decrease its CO2 emissions. Already in use on a number of oceangoing vessels, this proven energy-saving technology presents a viable way to reduce global fleet emissions and increase sustainability in the shipping industry.

But why is waste heat recovery technology such an attractive prospect for shipowners in respect of the incoming EEXI regulations?

First and foremost, all vessels produce waste heat and, therefore, have access to requisite input needed to generate clean electricity. In addition to this, the capability of Climeon’s HeatPower System to generate clean electricity from low temperature waste heat enables vessels to produce clean energy from a wider range of sources and at potentially higher volumes.

However, it is the practical and financial benefits associated with waste heat recovery that are also attracting shipowners to this method of emissions reduction ahead of the EEXI regulations coming into force.

For example, Climeon’s HeatPower modules take up a relatively small amount of space in the ship’s engine room, which ensures they can be accommodated on the vast majority of vessels. In conjunction, our modular approach enables shipowners to increase the use of waste heat recovery (and CO2 savings) in line with their needs.

Two men installing a white Climeon HeatPower module.
HeatPower installation in progress

Furthermore, the ability to conduct maintenance and optimise performance remotely ensures maximum fuel savings and emissions reduction without the need for an excessive number of on-board inspections or on-board work. Benefiting both operators and charterers, as well as shipowners, the ability to generate immediate energy savings with little disruption and minimal maintenance and monitor outputs 24/7/365 will enable vessels to meet EEXI requirements efficiently and effectively.

Of course, waste heat recovery’s proven application within the maritime industry will only serve to boost the confidence of shipowners, operators and charterers too. Already in use on a number of vessels, such as Viking Grace and Viking Glory, shipowners have access to verifiable data and case studies to determine how effective the technology can be on their own vessels.

While shipowners will need to invest in waste heat recovery technology to reap its benefits, the payback period, combined with the fuel savings available, make waste heat recovery a viable, and even fiscally alluring, prospect, particularly at a time when shipowners are compelled to undertake some form of modification to existing vessels to achieve EEXI compliance.

Using Waste Heat Recovery Tech to Comply with EEXI Regulations

The shipping industry continues to be a major source of greenhouse gas emissions, which is why the IMO has introduced a variety of regulations designed to reduce emissions. As existing ships are set to be under a greater level of environmental scrutiny, time is running out for shipowners to modify their vessels before the EEXI requirements come into force.

With proven performance, retrofit modifications and environmental and financial benefits, it’s easy to see why many shipowners view waste heat recovery as a preferable method of EEXI compliance. To learn more about Climeon’s proprietary waste heat recovery systems, get in touch with our maritime team today.