Full-Voyage Operational Validation of a Load Optimization Strategy for a Dual-Fuel Diesel-Electric LNG Propulsion System

This study presents a full-voyage operational validation of a load optimization strategy applied to a Dual-Fuel Diesel-Electric (DFDE) liquefied natural gas (LNG) propulsion system. The proposed approach was evaluated onboard an LNG carrier equipped with five four-stroke dual-fuel engines. The operational validation was conducted exclusively with the generator engines operating in LNG (gas) mode, while operation on conventional liquid fuels was outside the scope of this study. A complete 26-day voyage cycle, including cargo loading, loaded passage, cargo discharge, and ballast passage, was defined. Representative steady-state operating intervals for each operational mode were analyzed under both conventional Power Management System (PMS) load distribution and optimized load allocation. Real-time manual redistribution of engine loads was performed to validate the proposed load optimization strategy under real operating conditions. The results show consistent fuel savings across all operating modes, with the highest reduction observed during ballast passage (1.51%), followed by loaded passage (0.74%). A voyage-scale analysis reveals cumulative fuel savings exceeding 22 metric tons per operational cycle, equivalent to annual reductions of more than 300 metric tons under typical service conditions. These savings consistently reduce both carbon dioxide (CO2) and nitrogen oxides (NOx) emissions across all operating modes. Ultimately, the proposed load optimization strategy demonstrated stable performance under the investigated steady-state operating conditions and provides a practical approach to improving ship energy efficiency. The results support the potential application of the proposed strategy in existing ship energy management systems, while further validation under long-term and transient operating conditions is recommended.