Abstract
The main engine of tugboats is designed for high-power propulsion relative to hull size, but most of its operation is at low loads. In order to improve the performance of such ships, we came to the conclusion that a composite system was needed and developed a hybrid propulsion system. This system consists of an engine and a propulsion system using a motor and lithium ion batteries and it has achieved the fuel consumption and CO2 emissions reduction goal of 20% in comparison with conventional tugboats. The lithium ion batteries can be charged by the power generator, as well as by plugging in to electric power on land (shore power). On March 2013, Japan’s first hybrid tugboat was put into service.
