Optimum sizing of energy storage for an electric ferry ship

Each vessel has a different load profile based on its application. Among the vessels, the ones that have electrical propulsion systems with high fluctuations of propulsion demand power incur poor fuel consumption efficiencies due to: a) low loading of the generators and the lower efficiency in lower loads, and b) variations in the output power of the generators. Therefore, it may be economically feasible to install energy storage units in such ships to improve generator efficiencies. Given the load profile of a vessel, this paper formulates a simple but general deterministic dynamic optimization problem to find the optimal loading strategy for the ship generators in the presence of an energy storage unit. It then adds an outer layer to the optimization problem that finds the optimum capacity for the energy storage.