Energy management and D/G fuel consumption optimization in the power system of marine vessels through VFD-based process flow control

Nowadays marine vessels operate their Main Engine (M/E) at low speeds to minimize fuel consumption. This practice leads to significant load balance variation in vessel´s autonomous power system compared to sea trials, frequently requiring an additional Diesel Generator (D/G) to work in parallel at low load to satisfy the limits set by power management system. To improve D/G operating profile and Specific Fuel Oil Consumption (SFOC), a data-driven control topology is proposed, involving speed adjustment of motors related to engine room ventilation and central cooling water processes that exhibit varying flow requirements according to ship´s operating profile. A power saving margin that allows use of only one D/G at sea-going is created, optimizing D/G fuel consumption for M/E slow steaming operation. The proposed system is applied as retrofit installation in a typical tanker vessel´s power system, where experimental results are compared to the previous operating condition to show the impact of D/G optimized operation on fuel consumption. A method is proposed to calculate economic and environmental benefits depending on type of fuel used, D/G SFOC and vessel´s trading pattern. Results show that vessel´s power system annual energy consumption and D/G fuel consumption are significantly reduced by 18.3% and 20.3% respectively.