Analysis techniques for evaluating the fuel savings associated with wind assistance

Before steam and diesel engines, all cargo merchant ships were propelled by wind power. The arrival of cheap, high-density energy sources such as coal and oil and the economic benefits of the service speed and reliability that this enabled removed wind as a form of propulsion for much of the 20th century. However, higher prices for these energy commodities and environmental regulation, has led some to speculate that wind could return once again as a source of at least some share of a modern merchant ship’s propulsion energy requirement. A number of proposals for the technology that could enable this exist (e.g. soft-sails, wingsails and flettners), all share in common difficulties in their fair assessment, both relative to each other and relative to a conventionally powered ship. A moderately sized rig can supply anywhere between 0-100% of a merchant ship’s propulsion requirements, but this varies as a function of wind speed and direction, which in turn could vary several times a day over the course of multiple-day voyage. The weather, its variability and the specifics of a ship’s route are therefore all key components that render simpler ‘generic’ energy savings assessments meaningless. Furthermore, whilst conventional ships might sail a shortest distance route that avoids extreme weather, a wind-assisted ship might undertake more extreme variation in route and speed over the course of the voyage to maximize benefit obtained from the wind, and this in turn therefore needs to be taken into account in a fair comparison. This paper describes an analysis process that can be applied to any ship design and wind-assistance technology, to fairly evaluate the performance over a range of conditions, and then simulate the performance on a specific voyage using historical records of metocean parameters. The process is applied to an example design to illustrate the method.

Analysis techniques for evaluating the fuel savings associated with wind assistance.

Smith, T.W.P., Newton, P., Winn, G., Grech La Rosa, A. (2013).