Ship speed optimisation in green approach to tidal ports

The objective of this study is the formulation and solution of the optimal green ship approach to a tidal port, from the economic and environmental points of view. The work presented is the first quantitative modeling approach for this problem. In the model presented in this paper , the total cost of ship fuel consumption in the approach of a ship to a tidal port is minimized, which is the sum of the cost of fuel consumption in open sea and of ship waiting cost whilst the ship is waiting for berthing.. The aforesaid cost minimisation is carried out subject to ship draft restrictions in shallow waters due to tidal elevation variation with time. In this manner, not only monetary cost is reduced but also concomitant greenhouse gas emissions reduction is incurred. The model is applied to the real case of a bulker approaching a major tidal port, which is the second import-export port in Brazil and in South America with connecting routes to Europe and Asia. Results obtained by the computational implemenation of the model show that the optimum of zero ship waiting time prior to access to port service occurs when ship travel time coincides with tidal window finish time instant. In this scenario, the total waiting cost is a minimum and is equal to the fuel cost in ship travel from its initial position in open sea to destination port. It is recommended that future research explores other constraints that arise in practice, such as a finite number of tidal port berths and the presence of other ships that need to be serviced at a tidal port.