Method comparison to assess the potential of hydro-generation for wind-assisted ship

Wind propulsion systems (WPS) are emerging technologies to reduce international shipping carbon emission. If the WPS is designed to provide on average the most important part of the propulsion power, then in some situations WPS provides more power than required for propulsion and propeller can be used to generate electricity (hydro-generation). Few studies have been conducted on this technology, especially on the fuel consumption reduction it allows. The objective of this study is to compare different estimation methods for the potential fuel savings allowed by hydro-generation for wind-assisted ships. A case-study diesel-electric ship with KCS (KRISO Container Ship, a benchmark container ship hull form) hydrodynamic characteristics is simulated with three wings sails configurations and three reference speeds. A theoretical approach estimates fuel saving up to 0.046 % on global wind matrix and up to 0.54 % on selected routes. EEDI calculation estimate fuel savings up to 0.83 % in 2018 version and up to 2.26 % in 2021 version. A statistical approach at constant speed estimates fuel savings up to 1.60 %. Speed optimization on Great Circle Route voyages estimates fuel savings up to to 1.75 %. Weather routing estimates fuel savings up to 10.52 %. All of these results tend to demonstrate the relevance of weather routing to estimate full hydro-generation potential fuel savings. It provides the highest estimation and is the closest method to the real use of a wind-assisted ship.