Design of electric pod propulsion concepts for use in displacement crafts

Electric solutions for powering recreational boats are becoming increasingly popular as environmental awareness grows worldwide and the experience of silent boating is made possible. The greatest problem with electric boats is the short range due to the limited energy density of the batteries. While most of the energy is lost due to the resistance of the boat's hull, conventional propulsion systems with mechanical gears and rudders also contribute to energy loss by several percent. In order to maximise the efficiency and thus the operating range/endurance of such displacement vessels, new types of propulsion systems are being investigated by marine propulsion suppliers. In this thesis, various aspects of pod propulsion systems for displacement vessels are investigated. A method is presented to estimate the added resistance of the pod body and the strut based on recommended procedures from ITTC and resistance coefficients from Hoerner. The cooling performance of the system is investigated using a method that considers an approximated convective heat transfer from the pod shell to the seawater. A concept of a steerable pod is presented using the determined dimensions of a 50 kW electric motor by thesis colleague Akbar Bagaskara. The general arrangement, attachment to an example hull and load bearing capacity of the structure are considered. An optimized propeller is selected based on OpenProp calculations from the Wageningen-B series and the estimated bearing life is calculated. The pod is a standalone electrical drive unit, therefore it is subjected to galvanic corrosion, the possibilities of cathodic protection are considered. A comparison is made between electric pod and L-drive systems and it is concluded that pods are more advantageous in terms of space requirements, cooling, maintenance and overall efficiency at low speeds. Estimated construction costs increase mainly due to the need for a purpose-built electric motor