Reducing Cost and Environmental Impacts through Hybrid Power Options

Power solutions for seagoing vessels have typically been designed to enable operation at maximum economic speeds based on hydrodynamic considerations, and to ensure that vessels have the necessary power to be seaworthy and maneuverable in heavy weather and in high sea states. Historically, fuel costs have been low compared to fixed and other variable costs, but more recently, rising fuel prices and environmental concerns have made it more attractive to reduce fuel consumption through lower steaming speeds. Since speed reduction drastically reduces power requirements, it has become common to operate at 15 to 50% of the installed power in calm to moderate sea conditions. When engines operate at low power, fuel consumption per kWh produced power increases slightly, while the emissions of exhaust gases increase rapidly due to incomplete combustion. This study investigates flexible hybrid power solutions, i.e. power take out (PTO), power take in (PTI) and batteries in combination with internal combustion engines. The focus is on the full operational range from being idle at berth to the peak power needed in critical situations in high sea states. Our results indicate that hybrid solutions are cost-competitive with traditional engine setups. They also reduce the environmental impact, including greenhouse gas emissions and cost effectively satisfies IMO’s energy efficiency requirements (EEDI).