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Maritime Blogs

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The Energy Efficiency Design Index - What Does It Mean For Ships

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The EEDI is a tool for controlling CO2 emissions from ships and is primarily applicable to new ships. It was first developed by the IMO in 2003 and draft guidelines on its voluntary implementation were developed in 2009 with input from flag states and other industry bodies. The EEDI is voluntary at present but will possibly become mandatory in 2013.

Regulatory implementation

Once it is mandatory, the EEDI’s regulatory mechanism will allow CO2 to be controlled in much the same way that MARPOL Annex VI has regulated NOx and SOx emissions – through phased reductions in limits.

 

The key regulatory elements are:

Reference line:

The required baseline EEDI for each ship type.

Reduction rate:

The percentage of EEDI reduction relative to the reference line.

Cut-off levels:

At present, smaller size vessels are excluded from EEDI control.

 

In order for a ship to comply, it's attained EEDI must be less than or equal to the required EEDI for the ship type and size.

 

The first stage of implementation will apply to the following ship types above 400 gt:

– bulk carriers

– tankers

– gas carriers

– container ships

– general cargo ships

– refrigerated cargo ships

– combination carriers

Other ship types, such as ro-ro and cruise vessels are being investigated for inclusion in later phases of implementation and turbine, diesel-electric and hybrid propulsion types will initially be excluded.

 

Verification

EEDI verification will require input from the shipyard, shipowner and a recognized organization (RO) in order to achieve certification under the guidelines. Pre-verification will occur at the design stage whereas final verification will be conducted after sea trials and upon commissioning.

EEDI equation can be expressed as following:

 Ship

The Energy Efficiency Design Index (EEDI) is already being adopted on a voluntary basis and will possibly become mandatory from 2013, but how does the EEDI equation apply to your ship, and how can a good rating be achieved?

 

A formula for efficiency

The EEDI is a formula for calculating ships’ specific CO2 emissions (per ton-mile). The equation certainly looks complicated, but it can be divided into four sections, each one applicable to the ship’s machinery or the technologies being used on board.

 

Sections one and two of the formula calculate the CO2 produced by the ship’s propulsion and auxiliary power systems. Section three accounts for any secondary energy usage by machineries such as shaft propulsion motors and generators. And section four subtracts the CO2 saved through innovative energy saving technologies like kites or sails.

The resulting CO2 figure is divided by the ship’s transport work or ‘benefit to society’ (in effect, the ship’s capacity multiplied by its speed) to arrive at the final EEDI.

For each of the four sections, the listing is done of some of the existing and developing technical measures which may be considered in order to achieve a better EEDI, and also highlighted are other general measures which will influence the EEDI overall.

These general measures are not just limited to reducing speed, and indeed speed reduction may not suit to every ship’s need. Other options include simple hydrodynamic (underwater) and aerodynamic (above water) design modifications and the application of advanced coatings

Case study

Dragging the EEDI down

  • Aerodynamic modifications to ship structures can reduce drag, leading to fuel savings and a lower overall EEDI.
  • In 2010, Lloyd’s Register  carried out a study with a London and Greece-based ship owner/operator  to apply this theory to a 95,000 dwt bulk carrier using computational fluid dynamics (CFD). Air flow was modelled to assess wind drag and this included examining the effect of adding fairings and repositioning deckhouse appendages.
  • The findings showed that large reductions in wind drag of up to 20% were possible by attaching well-designed fairings to the ship and altering appendages on the deckhouse and funnel.
  • This equated to an estimated fuel saving of 2.5% when sailing at 14 knots into a 22 knot headwind. Smaller, but still significant, fuel reductions were also estimated for lower wind speeds.
  • Since completion of this work, they have repeated the study on a 59,000 dwt bulk carrier. This achieved a similar fuel consumption reduction, demonstrating the potential for consistent savings when applying the same technique to ‘classic’ bulk carrier designs.

   Air flow around the deckhouse before (left)and after (right) the modifications, showing the achieved wind drag reduction

 

 

He is the best sailor who can steer within fewest points of the wind, and exact a motive power out of the greatest obstacles.

Walter Scott

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