Optimal design of propulsive system for mini polar cruises is of great significance for improving ship energy efficiency and reducing ship vibration and noise. The present study proposes a hybrid diesel engine/battery/shore power propulsive system and a tri-objective optimization considering annual fuel consumption, lifecycle cost and annual pure electric time is carried out. The results show that 0.27% fuel reduction and 37.48% annual pure electric time are gained by sacrificing 7.85% lifecycle cost compared with the conventional diesel electric propulsive system.
For passenger ships, comfort is an important design index of the propulsive system (Cinquemani and Braghin 2017). In particular, the design requires of propulsive system for mini polar cruises are very different from those of ordinary ships. On one hand, the polar sea conditions are relatively bad, even accompanied by ice floes. In addition, mini polar cruises start and stop frequently, and required power fluctuates drastically. Diesel engines cannot always run in high-efficiency area, which increases fuel consumption and operational costs. On the other hand, the vibration and noise of mini polar cruises will not only reduce the comfort, but also affect creatures underwater and destroy the polar environment (Gardiner 2020, Shijin, Yaqiong et al. 2020). Not only can annual pure electric navigation improve the comfort of the ship, but also reduce the vibration and noise of the ship, reduce the disturbance to creatures underwater, and achieve zero emissions. Therefore, the design of propulsive system for mini polar cruises needs to take into account fuel consumption, operational costs and annual pure electric time.
With the development of shipping industry, environmental pollution and operational costs are increasing year by year (Wang, Yan et al. 2016, Yuan, Wang et al. 2018). To improve ship energy efficiency, the (International Maritime Organization (IMO) 2010) has proposed a number of stringent regulations, including ship energy efficiency management plan (SEEMP) and energy efficiency design index (EEDI). Thus, many approaches (Zhu, Chen et al. 2018, Zhang, Zhang et al. 2019, Nuchturee, Li et al. 2020) to improving ship energy efficiency have been proposed in recent years. Among them, hybrid electric propulsive systems (HEPSs) have attracted more and more attention due to its potential of saving fuel and reducing emission (Yuan, Wang et al. 2020). Since the HEPSs include at least two energy sources, optimal design is beneficial to improve the performance, for example, economy, environmental protection, and comfort. Existing research takes annual fuel consumption, greenhouse gas emissions or lifecycle cost as optimization objectives. In (Yuan, Wang et al. 2018), the solar power generation system was applied to a 5000-vehicle space pure car and truck carrier. Through the analysis of experimental data, they concluded that the HEPS can save 4.02% of fuel and 8.55% of carbon dioxide emission every year. In (Zhu, Chen et al. 2018), taking fuel consumption, greenhouse gas emission, and lifecycle cost as optimization objectives, the optimal design were obtained for the HEPS of an anchor handling tug supply vessel. In (Giap, Lee et al. 2020), the indirect-coupling and direct-coupling configurations of hybrid solid-oxide fuel cell and gas engine propulsive systems were proposed for crude oil tanker. The results showed that direct-coupling configurations can reduce more exergy destruction. In (Wu and Bucknall 2020), aiming at the constraints of power and energy density of fuel cell and lithium-ion battery in HEPS of coastal ships, an overall design method combining outer power multi-objective optimization and inner dynamic programming was proposed. It was verified that this method can reduce at least 65% of lifecycle greenhouse gas emissions.
