Design wave and wind environment for minimum power requirements of vessels in the southern North Sea

Energy efficiency regulations like EEDI lead to reductions in installed vessel power, which should not be at the expense of operability and safety in waves. When evaluating the consequences of reduced power, a design environment has to be selected – this first step is the focus of the present paper. The influence of common assumptions about environmental conditions in the southern North Sea on the wave drift forces experienced by a typical vessel was evaluated. For this purpose, hindcast environmental databases were compared to measurements and both were used to calculate added resistance. It was concluded that the use of common databases may lead to conservative results. Neglecting swell components in the waves seems to have a relatively small effect on the predicted forces. A typical spectral shape like JONSWAP yields a fair estimate of added resistance. Specifically for typical general purpose ships in the southern part of the North Sea, critical wave conditions were identified for evaluation of the minimum power requirements.