Developments in Marine Hybrid Propulsion

The shipping sector is becoming increasingly aware of global environmental impact of ships and is forced, by international legislation, to gradually reduce its emissions. International conventions (IMO) and energy efficiency standards set challenges to shipping sector, to ship owners and ship designers, to offer propulsion concepts which will effectively reduce or completely eliminate emission rates and increase energy efficiency with acceptable technological costs and adjustment time. New concepts include environmental friendly fuels in existing propulsion architecture, hybrid propulsion and all-electric propulsion architecture with the possible application of renewable energy sources, which are reviewed in this paper. Each concept has advantages and disadvantages regarding adjustment time, implementation cost and energy storage system capacity. The conclusion of this paper is that the Internal Combustion (IC) engines won't be completely replaced in the shipping sector in middle term, but will be able to use environmental friendly fuels or fuels without global carbon footprint, such as e-ammonia, blue-ammonia and bio-methanol as the most promising carbon-neutral fuels in the decarbonization path.