Design related speed loss and fuel consumption of ships in seaways
Fuel consumption is directly related to ship resistance. The design of ships is usually performed on the basis of powering requirements in calm water without considering actual operating conditions. The effect of the seaway is included using an experience-based allowance on the required power, the so-called sea margin. This practice can lead to either unnecessary excessive power reserves or to underpowered ships that cannot sail against wind and waves in heavy weather. Furthermore, a ship may rarely ever experience calm water conditions it was optimized for. To fulfill requirements of limited carbon emissions and to optimize fuel consumption, ships should be optimized for sea condition in which most of the fuel is consumed. To reliably predict a ship’s fuel consumption in seaways, a velocity prediction program accounting for calm water resistance, wave resistance, wind drag, and propulsion characteristics, we calculated ship speed and engine output in seaways. Using a scatter table based on encountered sea states during worldwide service, we calculated fuel consumption for a post-Panamax containership, a VLCC tanker, and a cruise ship.