Maritime fleet deployment with speed optimization and voyage separation requirements

A shipping company operates a heterogeneous fleet of ships to service a given number of voyages on a number of trade routes over the planning horizon. Each ship has a predefined speed range within which it can sail. Fuel consumption, and hence fuel cost, significantly depends on the chosen speed. Furthermore, the shipping company makes Contracts of Affreightments with the shippers stating that the voyages on each trade route should be fairly evenly spread. This leads to the maritime fleet deployment problem with speed optimization and voyage separation requirements. We propose two formulations for this problem, i.e. one arc flow and one path flow model. The non-linear relationship for fuel consumption as a function of ship speed is linearized by choosing discrete speed points and linear combinations of these. Computational results show that the path flow model performs better than the arc flow model and that incorporating speed decisions in the fleet deployment gives better solutions and more planning flexibility.acceptedVersio

A Vessel Pickup and Delivery Problem from the Disruption Management in Offshore Supply Vessel Operations

This paper considers a vessel pickup and delivery problem that arises in the case of disruptions in the supply vessel logistics in the offshore oil and gas industry. The problem can be modelled as a multi-vehicle pickup and delivery problem where delivery orders are transported by supply vessels from an onshore supply base (depot) to a set of offshore oil and gas installations, while pickup orders are to be transported from the installations back to the supply base (i.e. backload). We present both an arc-flow and a path-flow formulation for the problem. For the path-flow formulation we also propose an efficient dynamic programming algorithm for generating the paths, which represent feasible vessel voyages. It is shown through a computational study on various realistic test instances provided by a major oil and gas company that the path-flow model is superior with respect to computational performance.acceptedVersio

Can autonomous ships help short-sea shipping become more cost-efficient?

There is a strong political focus on moving cargo transportation from trucks to ships to reduce environmental emissions and road congestion. We study how the introduction of a future generation of autonomous ships can be utilized in maritime transportation systems to become more cost-efficient, and as such contribute in the shift from land to sea. Specifically, we consider a case study for a Norwegian shipping company and solve a combined liner shipping network design and fleet size and mix problem to analyze the economic impact of introducing autonomous ships. The computational study carried out on a problem with 13 ports shows that a cost reduction up to 13% could be obtained compared to a similar network with conventional ships