A comparison among innovative hybrid propulsion systems to reduce the environmental impact of a small passenger ship

Fossil fuels contribute to GHG emissions into the atmosphere. The need to solve this critical global problem has driven the search for alternative energy options to pave the way towards a more sustainable future. This paper analyzes the environmental and economic performance of a small cruise ship operating in the North Atlantic Ocean. The paper compares natural gas-electric and hybrid propulsive configurations, considering LNG and E-LNG produced using renewable electricity. The carbon footprint analysis is based on equivalent CO2 emissions according to a Well-to-Wake approach and includes emissions of the on-shore power for battery charging. A novel index for the energetic classification of ships is proposed, considering their equivalent CO2 emissions using a Well-to-Wake approach. The hybrid propulsive systems show a fair fuel-saving potential, ranging from 3.5% to 5.3%. The E-LNG-powered propulsion is three times more expensive than LNG, while GHG emissions produced using E-LNG are 4.5 to 6 times lower. The battery pack is a major cost item in hybrid systems. Moreover, GHG evaluation through the novel index penalizes hybrid propulsion systems compared to traditional carbon dioxide emission assessment since the former includes ground connection used for battery charging.