Calculating ships' real emissions of pollutants and greenhouse gases: Towards zero uncertainties

The energy output and emissions from maritime transport have increased considerably over the last two decades. Countries in Europe, North America and Asia use different methodologies to calculate these important variables; two of the main methods used are known as the Ship Traffic Emission Assessment Model (STEAM) and the Ship Traffic, Energy and Environmental Model (STEEM). Furthermore, the International Maritime Organization has recently required additional parameters to be included in the calculation, but the procedure for calculating these is not defined. In this paper, a model named SENEM (Ship's ENergy Efficiency Model) is proposed to calculate the power delivered in real time by the main engine taking into account all the equations required for defining and calculating all these parameters together with the efficiency of both the shaft and propulsion system. This model has been tested and validated on board four Ro-Pax ships operating across the Strait of Gibraltar - three vessels powered by waterjet and the fourth by propeller. The results show differences of up to 40% compared with other models.