Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Review of different propulsion methods for hybrid-electric propulsion ship
Shuo Zang1, Xiao Lang2, Wengang Mao2, Yuanqiao Wen1
1National Engineering Research Center for Water Transport Safety, Wuhan University of Technology.

Wuhan, Hubei, China
Dept. of Mechanics and Maritime Sciences, Chalmers University of Technology.
Gothenburg, Västra Götaland, Sweden2oceans (Jin et al., 2019). Electric propulsion ships are mainly divided
into pure-electric and hybrid-electric propulsion ships. Pure-electric
propulsion ships use a single battery pack as an energy supply, and it isan ideal propulsion method to achieve zero emissions. There aredeficiencies, such as the high price of lithium batteries, poor
compatibility, low energy density, and other issues that have not been
resolved (Nuchturee at al., 2020). Hybrid-electric propulsion ships thus
play an essential role nowadays. It uses multiple energy sources as power,
effectively reducing the limitations of battery packs and improving
power redundancy, which can be used as an alternative propulsion
method before 2030 when battery technology is not mature (Jafarzadehand Schjolberg, 2018). The current hybrid-power systems mainly
include series hybrid-power systems, parallel hybrid-power systems, andseries-parallel hybrid-power systems. The propulsion system of electric
propulsion ships is closely related to the power system. Ships using
electric propulsion provide greater possibilities for propulsion due to theadvantages of saving space and eliminating part of the shafts (Inal et al.,2022). There are three main propulsion methods for electric propulsion
ships: direct shaft propulsion, shaftless rim propulsion, and podpropulsion. The power systems can be integrated with various propulsion
systems onboard, and the matching method has a significant effect on
the propulsion efficiency of the ship.

ABSTRACTThis paper reviews different hybrid-electric propulsion modes, i.e.,series hybrid, parallel hybrid, and series-parallel hybrid. It then focuseson traditional propeller propulsion, shaftless rim propulsion, and podpropulsion. It mainly distinguishes and compares various propulsion
methods, from advantages and disadvantages, power range, to technicalissues, and analyzes the applicable ships and propulsion efficiencies foreach type of propulsion method. Although shaftless rim propulsion andpod propulsion have various key technical challenges, their propulsion
efficiencies are higher than traditional propeller propulsion. And they arepromising to be used in hybrid power ships in the near future.

KEY WORDS: Energy efficiency; electric propulsion; propulsion
methods; hybrid-electric systems.

INTRODUCTION
The IPCC reported that various human activities had caused global
warming of the terrestrial, atmospheric, and marine environments. The
global surface temperatures will continue to rise unless greenhouse gas
emissions are dramatically reduced in the next few decades, otherwise,
global warming in the 21st century will exceed 1.5°C or even 2°C(Preston, 2021; Huy et al., 2017; Gao et al., 2017b). It drives thedevelopment of the energy sector toward zero emissions, and it isessential for energy, shipping, and other industries to carry out rapid andfar-reaching transformations (Park, 2020; Shao et al., 2018). In recentyears, with the development of ships in the direction of high-speed andlarge-scale, the shipping industry’s emissions have become higher andhigher, and the share of global emissions has gradually increased. The
IMO issued an agreement to determine the carbon emissions of theworldwide fleet in 2030, around 40% lower than in 2008 (Wang et al.,2020, 2021c). It is urgent to promote the development of new energy
ships, especially electric propulsion ships.

This paper starts with a review study of the hybrid-electric system andits working modes, advantages, and disadvantages. The principles,characteristics, and power ranges of the three most commonly used
propulsion methods for electric propulsion are then discussed. Finally,
the application, i.e., typical products and power ranges of the three
propulsion methods is studied, and the propulsion efficiency is compared.

DEVELOPMENT OF HYBRID-POWER SYSTEM
When there are still many difficulties in applying pure-electric
propulsion ships, hybrid-power is used as a power solution for electric
propulsion ships in the transition stage. It is environmentally friendly,
reduces pollutants and greenhouse gas emissions, and avoids technicalproblems such as insufficient research on battery packs (Geertsma et al.,Electric propulsion is an ideal clean energy source due to its highefficiency, low emissions, and good adaptability to inland rivers and3727