To accurately assess the overall energy efficiency of cruise ships and propose optimization strategies, it is necessary to establish calculation formulas for evaluating the energy efficiency of various onboard systems, combined with actual ship data analysis to reveal the characteristics of energy consumption distribution. This paper first constructs a typical model of the energy-consuming systems on a cruise ship, including the propulsion system, electrical system, and thermal system. Then, based on the first law of thermodynamics, corresponding calculation formulas and methods for the energy consumption, work output, and energy loss of each system are established. A comprehensive voyage calculation and analysis for a medium-sized luxury cruise ship is conducted. The analysis of the results reveals that the energy consumption of equipment and systems related to passenger services accounts for a high proportion, approximately 50% of the ship's total energy consumption. This finding shows a significant discrepancy from the simplified approach used in the International Maritime Organization (IMO)'s Energy Efficiency Design Index (EEDI) calculation for luxury cruise ships, where the auxiliary engine power is treated as a fixed percentage (about 5%) of the main engine power. The results of this study provide a methodological foundation for assessing the overall energy efficiency of cruise ships, lay the groundwork for proposing future revisions to the IMO's energy efficiency assessment methodology for cruise ships, and offer insights for optimizing the energy efficiency design of new cruise ships and retrofitting existing ones.

The icebreaker needs to adjust the ship's longitudinal attitude to accomplish icebreaking during missions. To accomplish the rapid longitudinal adjustment of the ship, a multi-medium method is adopted to complete the ballast/deballast process for the fore and aft tanks. The ballast process is based on a hybrid method using ballast pumps and gravity flooding, while the deballast process is based on a hybrid method using ballast pumps and air compressors. For the ship's ballast/deballast system, a network model for the longitudinal attitude adjustment is established based on the designed multi-medium ballast/deballast method, considering both the fore and aft tanks. Simulation analysis shows that compared with the pure ballast pumps, the multi-medium method increases the ballast process speed by 4% and the deballast process speed by 25.6%. The multi-medium ballast/deballast method can greatly shorten the time required for rapid longitudinal attitude adjustment for icebreakers, thereby enhancing their operation flexibility.