How to Discretise a Ship’s Voyage when Optimising for High Fractions of Wind Propulsion?

Abstract Environmental impacts of shipping must be rapidly cut to limit the sector’s contribution to the ecological catastrophe. Primary wind propulsion has potential to drastically reduce the industry’s GHG-intensity but requires adjustments to ship operations, in particular with weather routing. Here, a 3D Dynamic Programming route and engine power allocation optimisation program is presented, and metrics are proposed to assess the effect of discretisation on its output. Interrelations between discretisation parameters are investigated analytically and empirically to impose a new condition on the space-time grid and to show that optimal combinations of parameters can yield improved results. A convergent behaviour is identified for space and time resolution of the grid and weather data, as well as search space width. The work demonstrates the importance of careful selection of discretisation parameters by illustrating how poor choices may yield significant error, leading to over- or underestimation of voyage time and energy consumption. Keywords Wind propulsion; Weather routing; Optimisation; Shipping; Discretisation; Energy transition