This Energy Efficiency Technologies Information Portal* provides users access to energy efficiency technology information in a user-friendly format and highlights the wide spectrum of ways to potentially reduce ship fuel consumption. It builds on the work undertaken by the Ad Hoc Expert Working Group on Facilitation of Transfer of Technology for Ships (TT-EG) and supports implementation of resolution MEPC.229(65) on Promotion of technical cooperation and transfer of technology relating to the improvement of energy efficiency of ships.
Relevant information about energy efficiency measures can be found under each technology group as appropriate.
This information comprises a description of the measure, the typical associated costs, expected savings and links to more information related to the measure. All suggested energy efficiency measures are known technologies that have been applied with varying degrees of success for different vessel types. The savings potential and associated costs for each measure depends on the type of the vessel and the operation of the vessel. The savings potential and costs are therefore indicated with a range. Some measures are only applicable to some vessel types, and this is also indicated in the description of the measure.
Machinery: This technology group includes measures that improve the energy efficiency of main and auxiliary engines. These include measures such as auxiliary systems optimization, optimizing heat exchangers, waste heat recovery systems, electronic auto-tuning, batteries, and other solutions.
Propulsion and hull improvements: Technologies in this group focus on improving the hydrodynamic performance of the vessel. This includes solutions that reduce the resistance of the vessel and/or also improve the propulsive efficiency of the vessel. Examples include measures such as propeller polishing, hull cleaning, PIDs (Propulsion Improving Devices), air lubrication and more.
Energy consumers: Consumers are equipment or devices that use energy when operated. Technologies in this group focus on minimizing the energy consumption by improving the device or optimizing the utilization of the device. Examples of measures in this group are frequency controllers, cargo handling systems, low energy lighting and more.
Energy recovery: Technologies in this group focus on capturing energy from the surroundings of the vessel and using or transforming this to useful energy for the vessel. This involves measures such as application of kites, fixed sails or wings, Flettner rotors, or solar panels.
Technical solutions for optimizing the operation: Technologies in this group focus on improving the operation of the vessel more than improving the vessel itself. The list of suggested measures includes both technologies and suggestions for best practice (without direct application of a technology). Measures in this group include trim and draft optimization, speed management, autopilot adjustment and use, combinator optimizing, and others.
Improving the energy efficiency of vessels means lower fuel consumption and reduced CO2 emissions. With this concept in mind, IMO adopted the Energy Efficiency Design Index (EEDI) – the first industry-wide global regulation of CO2 emissions.
The EEDI establishes the energy efficiency requirements of individual vessels in terms of CO2 emissions per capacity-mile, i.e. grams CO2 per tonne-mile. The EEDI for a given vessel is calculated by a mathematical formula which takes into account the vessel’s theoretical energy consumption based on the engines installed, measures to improve efficiency, and the vessel’s size and capacity. The lower the calculated EEDI for a vessel, the more energy efficient the vessel is deemed to be. The regulation mandates that the calculated EEDI for a given vessel should be below a required level. The limitations will gradually become stricter towards 2025. Calculation of the EEDI is mandatory for new ships over 400 gross tonnes of the following types and keel-laid dates:
Ships with conventional propulsion contracted after 1 January 2013 or delivered after 1 July 2015:
Ships with conventional propulsion contracted after 1 September 2015 or delivered after 1 July 2019:
Ships with non-conventional propulsion machinery contracted after 1 September 2015 or delivered after 1 July 2019:
Although EEDI applies to ships above 400 GT, the starting size threshold is usually much larger and varies by ship type. Each ship type defined above has its own specific EEDI reference line and required EEDI, thus considering the differences in design between ship types.
Ships which are not propelled by mechanical means, platforms including FPSOs, and FSUs and drilling rigs (regardless of propulsion), as well as category A ships as defined in the Polar Code are exempt from the EEDI requirements.
The formula for calculating the EEDI is shown in more detail below:
The top line of the EEDI formula can be divided into four key parts:
The bottom line of EEDI formula consists of capacity and reference speed Vref, which represent the transport work capacity of the vessel.
For more detailed information related to these parameters, please refer to Resolution MEPC.245(66) 2014 Guidelines on the Method of Calculation of the Attained Energy Efficiency Design Index (EEDI) for New Ships.
For new ships the EEDI is an important driver aimed at promoting the use of more energy efficient equipment. By improving the energy efficiency of the vessel, fuel consumption and the EEDI can be reduced. A wide range of different measures and technologies are available in this portal.
IMO requirements concerning the Energy Efficiency Existing Ship Index (EEXI) were adopted at 76th Marine Environment Protection Committee (MEPC 76) held in June 2021. A similar calculation methodology applies as its predecessor, the EEDI, however EEXI specifically targets existing vessels instead of new vessels, though the ship types and size thresholds remain the same as EEDI.
Ships to which the regulation applies are required to calculate the EEXI value of each individual ship, called attained EEXI. This figure must be equal to or less than a given threshold value, the required EEXI. If the attained EEXI is larger than the required EEXI, the ship must implement measures to ensure compliance. Typical actions would be to install shaft/engine power limitation, retrofitting energy saving devices, etc. Compliance with EEXI regulations is similar as EEDI, only required once for the entire vessel lifetime targeting design parameters. A certified EEXI technical file will need to be in place for vessels that are satisfying the Required EEXI by the first annual, intermediate or renewal survey after 1 January 2023.
The required EEXI value is determined by the ship type, the capacity and principle of propulsion and is the maximum acceptable attained EEXI value.
The Carbon Intensity Indicator (CII) was adopted at the 76th Marine Environment Protection Committee (MEPC 76) held in June 2021 as one of IMO’s short-term GHG reduction measures for existing ships. The CII rating scheme is a regulation addressing the operational efficiency of a ship. The index provides the amount of CO2 emitted by each vessel per annual transport work, as shown in the equation below.
The CO2 emissions are determined based on verified IMO DCS data which is required for all ships above 5,000 GT. The ship capacity is for most vessel types given as the deadweight in tonnes. This would provide the “Average Efficiency Ratio” (AER). For passenger vessels, vehicle carriers and RORO ships are gross tonnage used as the capacity measure, providing the “cgDist” value. Both AER and cgDist are considered as CII values, only with different applicability dependent on ship type. Sailed distance is always given in nautical miles.
Opposed to EEDI/EEXI, CII is an operational parameter where the actual CO2 emissions are reported. Therefore, any measure which will reduce the physical CO2 emissions will be directly beneficial for the vessel’s CII rating.
The calculated annual CII value is set against a reference value, then the distance between the obtained CII and the reference value determines which “rating” a ship is assigned (A, B, C, D, or E). The reference values are differentiated by ship type and size. They are based on 2019 values which was the first full calendar year for which ships have reported IMO DCS data. The rating thresholds will become increasingly stringent towards 2030, as indicated in table below.
Table 1. Yearly reduction factors CII
Each ship needs to achieve rating C or better. If a vessel obtains rating D for 3 consecutive years or rating E, the vessel needs to implement an approval corrective action plan as part of SEEMP to achieve rating C or better. Pending this, an annual Statement of Compliance is issued. In addition, companies should be prepared for strengthened corrective actions and/or a need for enhancement of the enforcement mechanism.
This Energy Efficiency Technologies Information Portal was developed in cooperation with DNV GL.
This webpage serves as an Information Portal for Energy Efficiency Technologies for Ships. IMO does not make any warranties or representations as to the accuracy or completeness of the information provided. View our disclaimer
