An efficient hybrid propulsion system for an ice-capable ship

Abstract

The impact of climate change has accelerated melting of ice in the Arctic Sea, which has provided opportunities for commercial shipping between Asia and Europe on the Northern Sea Route (NSR). However, the Arctic environment is vulnerable to ever-growing emissions produced by current Arctic shipping propulsion systems. The aim of this work is to investigate a more effective propulsion system with a robust control strategy to reduce the fuel consumption, and thus the emissions. Diesel electric and hybrid propulsion systems for Arctic shipping have been introduced, with their components modelled mathematically. In terms of methodology, a 3-level control strategy has been developed to ensure DC-grid stability according to the system power demand, whilst at the same time avoiding over-discharging of the battery. The proposed 3-level controlled hybrid propulsion strategy enabled optimisation of the power efficiency, fuel consumption and emissions. System stability has been tested mathematically using the Routh-Hurwitz Criterion. In this light, a simulation model has been generated to test the performance of the hybrid propulsion system with the 3-level control strategy as well as a diesel electric system for ice conditions and open water shipping, as would be encountered on the NSR. As for the key findings, the simulation results indicate the hybrid propulsion system with the proposed 3-level control strategy can offer up to 22.7% fuel savings when compared with a DC diesel electric system over a typical operating cycle in ice and achieved a 43.1% fuel reduction over a particular variable-speed voyage in open water. In addition. a laboratory-scale experiments have been conducted to validate the simulation of the propulsion configurations. The results of the laboratory-scale experiments indicate that the 3-level controlled hybrid propulsion system contributes a 5.35% fuel saving over a fixedspeed diesel electric system with acceptable stability, which further justified the use of hybrid propulsion as a more environmentally friendly propulsion system for future icecapable ships in the NSR.