Development of an integrated energy efficiency control system for ship power balance and diesel generator fuel consumption optimization

In the maritime industry, high fuel costs cause changes to the vessel´s operating profile regarding the use of Main Engine (M/E) and auxiliary machinery. This results in deviations from the original load balance study and Power Management System (PMS) adjustments that were performed during shop tests, as Diesel Generators (D/Gs) often operate in parallel at low load far from their best efficiency points. In this paper, an integrated process control scheme is proposed in order to improve power balance in the vessel´s air ventilation and central water cooling systems, involving the variable frequency control of Engine Room (E/R) Fans and Cooling Sea Water Pumps (C.S.W P/Ps). Experimental results derived from system retrofit application to a typical 105,000 DWT Aframax tanker vessel verify the effectiveness of the proposed control scheme towards achieving significant energy savings, which are in accordance with the theoretical results obtained from the air and heat balance studies. Power balance improvement leads not only to fuel savings but also to the use of only one D/G while sea going. Power quality measurements show compliance with relevant marine harmonic standards.