Kjetil Fagerholt

Optimized selection of vessel air emission controls—moving beyond cost-efficiency

Shipping currently has an unexploited potential for improved energy efficiency and reduced emissions to air. Many existing air emission controls have been proved to be cost-efficient but are still not commonly installed on board vessels. This paper discusses the so-called ‘energy paradox’ in maritime transportation, presenting barriers to overcome and criteria to consider when selecting cost-efficient air emission controls. Current approaches typically select available controls based on their cost-effectiveness. While this is an important aid in the decision-making process, and, in relative terms, easy to quantify, it is not a sufficient criterion to capture the true preferences of the decision-maker. We present in this paper a multi-criteria optimization model for the selection of air emission controls. This decision framework can also incorporate subjective and qualitative factors, and is applied to the shipping company Grieg Shipping. A survey among internal Grieg Shipping stakeholders identifies the important criteria to consider, their relative importance, and the scoring of the controls. This empirical data is used as parameters in the model and the model is then applied on a vessel of the Grieg Shipping fleet. The results show that nonfinancial factors play an important role in the selection of air emission controls in shipping.

Vessel routing with pickups and deliveries

This paper presents a new routing problem, the Vessel Routing Problem with Selective Pickups and Deliveries (VRPSPD), an extension of existing pickup and delivery problems that arises in the planning of logistics operations in the offshore oil and gas industry. The VRPSPD is a single-vessel model that can lead to significant economic improvements to the current planning scheme without having a very large impact on the operations. In addition, we formulate a Multi-Vessel Routing Problem with Pickups and Deliveries (mVRPPD) that leads to even larger economical gains, but also entails more important changes in the current planning and operations. To quantify and justify the benefits of the VRPSPD and mVRPPD, an industry case based on real data was constructed and solved for 300 days. The VRPSPD is solvable with a commercial solver for most real-size instances. However, for the mVRPPD on the largest instances, it was necessary to develop a state-of-the-art adaptive large neighborhood heuristic search to reduce computational time. HighlightsA practical vessel routing problem applied to the supply of offshore oil platforms.Single-vessel model with multiple and selective pickups and delivery orders.Multi-vessel model for joint vessel planning and improved utilization.Improves overall fleet utilization without complicating current planning procedure.

The Static Bicycle Repositioning Problem - Literature Survey and New Formulation

This paper considers the static bicycle repositioning problem (SBRP), which deals with optimally re-balancing bike sharing systems (BSS) overnight, i.e. using service vehicles to move bikes from (nearly) full stations to (nearly) empty stations. An exhaustive literature survey comparing existing models is presented, and a new and improved mathematical formulation for the SBRP is proposed. The model is tested on a number of instances generated based on data from a real BSS.

A traveling salesman problem with pickups and deliveries and stochastic travel times: An application from chemical shipping

Abstract This paper introduces a single-ship routing problem with stochastic travel times that is faced by a chemical shipping company in the Port of Houston. We take into explicit consideration the uncertain waiting times associated with the terminals inside the port, and the resulting inefficient transits caused by severe congestion. We show that the problem can be modeled as a stochastic Traveling Salesman Problem with Pickups and Deliveries (TSPPD), in which the goal is to find the route within the port with maximized probability that its total length does not exceed a threshold. We show that it is important to properly address the inefficient transits, and that including uncertainty in the travel times can have an impact in the choice of optimal route inside a port. We further show that the layout of the relevant terminals as well as their distances to the anchorage are important drivers of such impact. We conclude with the suggestion that one can use the proposed model and method to find a set of alternative routes, followed by a re-evaluation process since our method encompasses an approximation that underestimates the variation of the route completion time.

2D-Packing with an Application to Stowage in Roll-On Roll-Off Liner Shipping

Roll-on/Roll-off (RoRo) ships represent the primary source for transporting vehicles and other types of rolling material over long distances. In this paper we focus on operational decisions related to stowage of cargoes for a RoRo ship voyage visiting a given set of loading and unloading ports. By focusing on stowage on one deck on board the ship, this can be viewed as a special version of a 2-dimensional packing problem with a number of additional considerations, such as one wants to place vehicles that belong to the same shipment close to each other to ease the loading and unloading. Another important aspect of this problem is shifting, which means temporarily moving some vehicles to make an entry/exit route for the vehicles that are to be loaded/unloaded at the given port. We present several versions of a new mixed integer programming (MIP) formulation for the problem. Computational results show that the model provides good solutions on small sized problem instances.

A New Formulation for the Combined Maritime Fleet Deployment and Inventory Management Problem

This paper addresses the fleet deployment problem and in particular the treatment of inventory in the maritime case. A new model based on time-continuous formulation for the combined maritime fleet deployment and inventory management problem in Roll-on Roll-off shipping is presented. Tests based on realistic data from the Ro-Ro business show that the model yields good solutions to the combined problem within reasonable time.

A Shortest Path Heuristic for Evaluating the Quality of Stowage Plans in Roll-On Roll-Off Liner Shipping

Roll-on Roll-off shipping companies transport rolling cargo, such as cars, trucks and large construction machines. When sailing, this type of cargo must be attached to the deck using chains, to prevent damaging the cargo. For each voyage including multiple port calls where the cargo is loaded/unloaded, an important decision is to decide where to place each vehicle (or unit), such that the time used on shifting is minimized. Shifting means temporarily moving some vehicles to make an entry/exit route for the vehicles that are to be loaded/unloaded at a given port. As the vehicles are securely fastened to the deck, shifting is a time-consuming procedure. We present the stowage plan evaluation problem which is to determine the optimal vehicles to shift at each port call, such that the time spent on shifting is minimized. Given a set of alternative stowage plans for a voyage, the results from the stowage plan evaluation problems are used to determine the best among these stowage plans. We present a shortest path based heuristic for solving the problem. Computational results show that the solution method is a powerful tool for comparing stowage plans, due to its fast computing times and high success rate, i.e. its ability to determine the better of two stowage plans.

Base location and helicopter fleet composition in the oil industry

ABSTRACT The daily transportation of employees with helicopters to and from the oil platforms is an important and difficult logistical operation in the offshore oil industry. This paper presents a model for the problem of selecting the optimal helicopter fleet composition and deciding which land bases to allocate the helicopters to as well as deciding whether opening additional hubs for refuelling is required. To capture the operational aspects of the operations, the routing of the helicopters is included as an element of the model. In this paper, we show why including routing is important to ensure a good fleet composition and helicopter allocation. The problem is denoted the base location and fleet composition problem (BLFCP) and a model based on a priori generation of flights is proposed. The test cases are based on estimates of the expansion into new oil-producing sectors outside the Brazilian coast as well as test cases based on the Norwegian expansion into the Arctic. In addition, different approaches for strengthening the formulation or otherwise improving the solution procedure are proposed. These include dynamically added constraints, symmetry breaking constraints, integer rounding cuts and various heuristic approaches to reduce the number of variables and constraints in the problem. The solution procedure proves efficient for realistically sized problems.

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.