Shipboard measurement continues to challenge ship owners and their operators. With the focus on the environment and an effort to reduce green house gases (GHG), which goes beyond achieving fuel economy, there are many approaches that can be classified as small, incremental improvements. Of course these improvements achieve fuel economy, but more importantly they reduce GHG. Most of these approaches are cost-beneficial but challenging to validate in practice. Ships operate on the interface of 2 mediums, water and air, and as a consequence face many variables that can disrupt precise measurements to mask the gains from small, but discreet improvements.

Efforts to validate benefits continue to improve with better measurement tools and data processing. However, as every ship designer knows the general rule of thumb is to allow a 15% sea margin when sizing a propulsion plant to address those uncontrollable forces of wind, waves, current, and degradation of hull and propeller surfaces. With such a large amount of margin it is difficult, if not impossible, to demonstrate small, incremental improvements without a major effort utilizing a scientifically designed approach.

For large ocean-going ships even the main propulsion engines are tested outside the ship not only to demonstrate performance, but also to validate fuel consumption efficiency. However, for most small, incremental improvements validation can only take place on full-size ships in service. Even the hydrodynamic performance of the ship: hull, propeller, and rudder, are evaluated during new building sea trials even though computerized design and model testing were done to set their form.

So what needs to be done to satisfy the skepticism of the majority of ship owners and operators about gains from small, incremental improvements?

First, the concept of stipulated savings needs to be given consideration. If the design engineering is scientifically solid and is then validated in model testing then at least a level of skeptical optimism should be given to the expected level of improvement. Being at a consciousness level of "Trust but Verify" is helpful when one is operating in a continuous improvement mode.

Second, serious weighting needs to be given to these stipulated savings if it is expected that the gains will be always available over the life of the ship. For example, a 3 % improvement would allow a sea margin to be reduced to 12%, or for existing ships GHG could be reduced 3%. Such an approach is necessary when retrofitting existing ships, primarily because many actions are taken at dry docking that make measurement not possible for any one action. How many ship owners actually validate gains solely from propeller polishing?

Third, coordinated long-term planning by both ship owner, as buyer, and ship builder, as seller, to develop a sea trial program that affords a practicable effort is necessary to validate the achievement of these small, incremental savings. This level of cooperation seems to be rarely achieved, especially after specification creation and contract signing.

Fourth, when a series of sister-ships are being constructed, a scientific-logic approach would be to implement the improvements on half the fleet at first. This would permit sea trial comparison and also operational comparative data over several ship years of service. If the success of small, incremental improvements is acceptably demonstrated then installation on the outstanding portion of the fleet could be accomplished at the next availability.

Fifth, and last, the ship owner and operator have an overall moral responsibility to reduce the environmental impact of their operation on the planet. IMO is making an effort to address this global challenge, but formulas that encourage building bigger ships and slowing them down have many practical limitations. Ship design efforts should include all cost-beneficial solutions and selection of approaches should be economically tiered on a basis of fuel cost savings per capital investment, which generally would result in small incremental approaches being first on the list to be implemented.

Ship Propulsion Solutions is willing and ready to work with ship owners and operators who are motivated in meeting the environmental challenge and as a result reduce their operating costs by installing cost-beneficial energy saving devices.

Robert Walsh, President
Ship Propulsion Solutions, LLC
P.O. Box 910148
Lexington, KY 40591-0148 USA
T: +1-859-533-8848
F: +1-859-296-4299
E: contact@shippropulsionsolutions.com
Web Site: www.shippropulsionsolutions.com