To help shipowners, vessel designers, etc to come to terms with the IMO’s Energy Efficiency Design Index (EEDI), DNV, together with the independent privately-owned German Hamburg Ship Model testing facility HSVA, has published ‘DNV Fuel Saving Guideline - for Tankers’.
This is part of a trilogy of guidelines - the other two concern containerships and bulk carriers.
With new designs offering up to 30% higher fuel efficiency, it is expected that charterers will focus more on fuel efficiency in the future, DNV’s business director Jost Bergmann warned.
At the guide’s launch, Bergmann illustrated this point by saying recently MOL had sold a 14-year old VLCC for recycling. Although the reasons for selling the vessel were not known to DNV, Bergmann suggested that with today’s high fuel costs, the vessel might not be as competitive today as when it was designed and built in the mid 1990s.
DNV said that any measure considered for reducing EEDI must affect one or more of the index’s equation’s parameters. For example, the most effective method is to reduce the vessel’s design speed. A 10% reduction in the design speed results in at least a 25% reduction in installed power, giving an EEDI reduction of around 20%.
It is the installed power that reduces the EEDI and not the power demand, the guideline pointed out.
The guide listed some of the possibilities on offer today for reducing EEDI, together with the parameter affected. DNV gave the following examples;
M/e installed power reduction - the hull and propeller efficiency can be improved and/or the speed reduction can be achieved by de-rating the engine.
Lower specific fuel consumption – switch to a more efficient engine/engine control tuning.
Increase the speed without increasing installed power – improved hull and propeller efficiency (ie, fitting Mewis Duct, prop boss cap fin, or other flow devices).
Fuel as an energy source with lower carbon content - eg LNG, biofuel (no guideline in place).
Innovative mechanical energy efficient technology – eg kites (no guideline in place).
Innovative electrical energy efficient technology – eg waste heat recovery.
Increase the capacity – larger vessels.
In addition there will be compensation when using shaft generators and applying ice strengthening. Other correction factors are under development, eg voluntary structural enhancements.
Some of the suggestions, such as kites and solar panels, cannot provide the power needed all the time for the main engine and thus the EEDI will not be reduced. There are no guidelines in place for the use of these measures to reduce EEDI, but they are expected to be developed at a later stage, DNV said.
Propulsion efficiency devices are not expected to reduce the engine power, but will enable the vessel to attain a higher speed, while the use of biofuels is not covered in the current framework, as their cargo content cannot easily be ascertained.
Source: Tanker Operator. 23 March 2012