Concept development of a fossil free operated cargo ship

Abstract

The reduction of air pollution caused by shipping is of increasing interest. IMO has implemented regulations regarding the contents of sulfides and nitrates in fossil fuels, and also established a long-term proposal to reduce the GHG emissions. The shipping industry has started a process of transition towards cleaner fuels. This thesis takes one step further by studying the feasibility of a ship concept operating 100% free of fossil fuels, using renewable energy accessible at sea, with all the difficulties in its predictability. The main objective is to develop a simulation tool that can be used to predict the feasibility of a concept ship with a renewable hybrid power system, in each moment of a journey. The thesis starts with an exhaustive study of technologies and renewable systems available in the market. The most promising renewable propulsion systems and electric energy generators are numerically defined to be implemented in the simulation. A hybrid system is found to be the best choice, with Flettner rotors, a wind propulsion system that generates thrust with a relatively low requirement of energy, as well as photovoltaic solar panels and wind turbine generators for electric production. Finally, numerical methods are integrated into a simulation model that evaluates all renewable technologies. Simulations are performed for three different routes: from Rotterdam to Houston, Rio de Janeiro to Gothenburg and Los Angeles to Shanghai. The journeys are defined according to real weather conditions data. The results from the analysis give relevant information about the ship journey (time and speed) and the energy balance of the systems. Results show that in regions with high-intensity winds, the ship speed is high, but the renewable generators onboard cannot supply sufficient energy for the Flettner rotors. On the other hand, for low wind speeds, the ship velocity is small with a surplus of energy generation. The thesis demonstrates the functionality of the concept on some of the routes, with a high dependency on the weather conditions. It opens the way for future studies to keep the relationship between energy consumption and energy production in balance.