Energy Savings in Coastal Fisheries: Use of a Serial Battery Hybrid Power System

Abstract

Fuel effectivization and emission reductions have been on the forefront of research for marine power system solutions. The reduction in fuel use was originally motivated by savings on the principal operating cost of vessels. The need to reduce emissions, both CO2 for the global environment and nitrous oxides (NOx) and soot for the local environment, is on the agenda for the maritime industry. The introduction of shore power supply for ships in port and the NOx emission tax and reduction support scheme are examples of this in Norway. Another initiative that is intended to reduce emissions is the development of battery-based propulsion systems with electric power distribution. Unfortunately, the use of an electric power distribution system, with power conversions from a diesel generator and subsequent storage and retrieval from battery banks, will inevitably result in power losses. However, the actual operation of normal diesel-powered ships is seldom optimal, and only larger ocean-crossing vessels may hope to operate their prime mover and support power systems in an optimal fashion for prolonged periods of time. This article presents the application of a serial-diesel-battery hybrid power system installed onboard a Norwegian costal fisheries vessel, where the variation in power demand allows the batteries to replace the traditional diesel power used in fisheries. A power and propulsion system design is presented as well as energy and time use data for the vessel's operation during one calendar year. The simple design of vessels, such as of the example vessels in this article, allows battery hybrid power systems to deliver energy savings due to the low-power demand of the diesel engine operation at idle power used during the operation of the fishing gear. The prime mover is used to supply limited propulsion power, which is mainly hydraulic and electric. The power system for the example vessel is designed as a serial hybrid where the diesel engine is exclusively used to supply electric power to the batteries, which has the added benefit of shielding the diesel engine from load variations on the propeller. The hybrid battery power system is expected to cut operating costs by minimizing fuel consumption during fishing, reducing the use of engine lubricants, diminishing maintenance costs by requiring fewer engine-running hours, and increasing the lifetime of the onboard diesel engine in calendar days due to decreased running time.