LNG AND FUEL CELLS IN MERCHANT SHIPS: ENVIRONMENTAL AND ECONOMIC CONSIDERATIONS

Today, most of the merchant vessels use Heavy Fuel Oil (HFO) for propulsion, that are cost effective but produce significant amounts of pollutants. With the recent rules, imposed by the International Maritime Organization (IMO), which set strict limits for nitrogen and sulphur oxides, the use of Liquefied Natural Gas (LNG) as fuel seems to be an interesting alternative to expensive and bulky exhaust gases after-treatment equipment or fuel with low sulphur content. Furthermore, if LNG is used as fuel for ships, new propulsion technologies could be considered. Among them growing attention has been made for marine applications of fuel cells and several demonstration studies have been carried out. Fuel cells are associated to different operating advantages such as very low emissions and high efficiency at partial load. In particular, when considering an LNG feed ship, they allow using the low pressure Boil Off Gas (BOG) produced during the trip. In order to identify what types and sizes of vessels that mostly benefit from the use of natural gas a statistical analysis of the world's maritime traffic has been carried out, analyzing the time spent by each vessel in the ECA areas and its route. Furthermore, a comparative economic analysis has been carried out in order to quantify the payback period of the LNG solutions respect to the adoption of traditional fuels. Results show that the types of ships that spend most of their time in ECA areas are tankers, bulk carriers, RoRo and passenger ships. The economic analysis shows that the payback period is about three years, thus demonstrating the validity of this fuel in maritime field. The literature analysis of marine applications of fuel cells shows that different projects demonstrated the feasibility of using FC on board and a large market is expected in ships where LNG is used as propulsion fuel.