The Resource Constrained Project Scheduling Problem with a flexible Project Structure (RCPSP-PS) is a generalization of the Resource Constrained Project Scheduling Problem (RCPSP). In the RCPSP, the goal is to determine a minimal makespan schedule subject to precedence and resource constraints. The generalization introduced in the RCPSP-PS is that, instead of executing all activities, only a subset of all activities has to be executed. We present a model that is based on two graphs: one representing precedence relations and one representing the activity selection structure. The latter defines which subset of activities has to be executed. Additionally, we present theoretical properties of this model and give an exact solution method that makes use of these properties by generating cutting planes and setting bounds on variables. Furthermore, three problem properties are introduced to classify problems in the literature. We compare our model to a model from literature on instances that possess a subset of these three problem properties and find a reduction in computing time. Furthermore, by comparing results on instances that possess all problem properties, it is shown that the computing times are decreased and better lower bounds are found by the cutting planes and variable bounds presented in this paper.

@en

Ship pipe route design is often overlooked in the context of the energy transition, although it is a crucial driver for design time and costs. Motivated by this, we propose a mathematical approach for modeling uncertainty in pipe routing with deterministic optimization, stochastic programming, and robust optimization. The uncertainty entails not knowing which type of fuel will be used in the ship's future. All three models are based on state-of-the-art integer linear programming models for the Stochastic Steiner Forest Problem and adjusted to the maritime domain using specific constraints for pipe routing. Our results highlight the importance of accounting for uncertainty in ship pipe routing, demonstrating cost reductions of up to 22% based on experiments with artificial and realistic data. Our methods enable engineers to explore different levels of preparedness for the energy transition with minimal effort during the early design phase.

@en

The integration of methanol power, propulsion and energy systems (PPE) generates uncertainties linked to the selection and sizing of systems, layout design and compliance with strict safety regulations. This paper argues that alternative fuels, such as methanol, should be treated as disruptive innovations, in part due to the uncertainties linked to their implementation. These uncertainties strongly connect to the PPE dimensions and the dependencies among the systems because of integration requirements. Through a model based system engineering inspired approach, the uncertainties are elucidated into relevant inputs for the proposed framework. The authors introduce an uncertainty evaluation framework that uses Monte Carlo simulations to generate the layout design space under uncertainty. The impact of uncertainty on the design is examined through a case study on the layout of a notional engine room. Multiple probability distributions for the PPE dimensions and varied logical architectures – reflecting systems dependencies – are applied to identify patterns in the generated design space. The varied logical architectures influence drastically the dominating solutions of the design space regarding the length. For a 1000-kW notional vessel, under the varied scenarios, the length of the engine room clustered in specific values while the connection costs produced wide value spectrum.@en

The International Maritime Organization aims to achieve full decarbonization by 2050 in response to climate change. This ambitious goal demands well-defined strategies guided by techno-economic assessments. The complexity of global shipping systems makes predicting long-term maritime trade patterns challenging, necessitating scenario-building rather than precise forecasts. Investigating shipping demand scenarios is crucial due to the uncertainty brought by the energy transition and its role as the primary driver of shipping emissions. This paper improves the representation of maritime shipping in Integrated Assessment Models (IAMs) by examining the impacts of climate targets on future shipping demand. A novel econometric model, grounded in advanced gravity theory and integrated with machine-learning algorithms, is proposed to estimate the elasticities of variables in bilateral seaborne trade. By coupling this model with the WITCH IAM, we explore various scenarios, providing deeper insights into trade patterns and their implications. The results show that stricter climate policies and higher carbon taxes reduce GDP due to higher abatement costs, higher fuel prices, and therefore reduced seaborne trade, especially for oil products and containerized cargo. Early adoption of carbon taxes in Europe may shift oil production and consumption patterns, temporarily boosting seaborne trade. Sub-Saharan Africa could experience significant demand growth due to economic and population increases.

@en

Inland water vessels are impacted by climate change in two respects. First of all, they will need to convert to low-impact power propulsion and energy (PPE) systems. Secondly, they will need to deal with the impact of climate change, especially longer periods of very low and high water. This paper reviews the multi facet impacts of climate change on inland waterway vessel performance and problems associated with the choice of alternative power energy and propulsion (PPE) system on the vessel’s performance.@en

The current sea margin estimate applied in early ship design, commonly assumed 15-20% extra installed engine power, is not based on calculations, but has nonetheless become an industry standard. These sea margin estimations, applied in early ship design, are insufficiently accurate. This paper evaluates if a data driven approach is suitable to more accurately predict the sea margin in early ship design. Using operational data this method considers the whole operational profile of the vessel not limited to design or calm water conditions. A case study is performed where a data driven model is trained to make power predictions, subsequently this trained model is used to make calm water predictions. This proof of concept illustrates the potential of proposed method to be utilised for sea margin estimations in early ship design.@en

This paper investigates the factors influencing innovation adoption in ports by conducting a systematic literature review and proposes a comprehensive framework for understanding the process of innovation adoption. The maritime sector is a typical example of a business-to-business market, whereas the information technology industry is an example of a business-to-consumer market. We show that factors for innovation adoption applicable to a business-to-consumer market are also relevant to a business-to-business market. The factors that were found relate to the adopting port’s characteristics and include know-how, organization support, organizational structure, financial capacity, a port’s network embeddedness, and risk-taking. Furthermore, they concern the characteristics of the innovation such as the costs, relative advantage, complexity, compatibility, trialability, and observability. Finally, stakeholder pressures were identified relating to the customer, competitive port, regulatory bodies, and society.

@en

Editorial.@en

With space constraints onshore, strong renewable resources available far offshore and growing green hydrogen demand, far offshore green hydrogen production may be an attractive option. To assess this potential, a mixed integer quadratically constraint programming (MIQCP) optimization model was developed to find the cost per kilogram of far offshore green hydrogen in specific scenarios. The design of the far offshore green hydrogen supply chain was optimized with this model for six high potential scenarios in varying locations and the results were analyzed. It was found that far offshore green hydrogen costs are in the same order of magnitude as the costs of its alternatives. Far offshore green hydrogen may be considered marginally competitive with these alternatives from 2035 onwards in the analyzed scenarios when taking into account the considerable advantages of far offshore production, such as avoidance of scarce land usage in crowded areas and certain geopolitical considerations.@en

The energy transition from fossil fuels to sustainable alternatives makes the design of future-proof ships even more important. In the design phase of a ship, it is uncertain how many and which fuels it will use in the future due to many external factors. In fact, a ship typically sails for decades, increasing the likelihood that it will use different fuels during its lifetime. Pipe route design is expensive and time-consuming, mainly done by hand. Motivated by this, in previous research, we have proposed a mathematical optimization framework for automatic pipe routing under uncertainty of the energy transition. In this paper, we build on the state-of-the-art by implementing design constraints in mathematical models based on discussions with maritime design experts. Additionally, we apply these models to realistic, complex situations of a commercial ship design company. Our experiments show that location-dependent installation costs, which reflect reality, increase the usefulness of stochastic optimization compared to deterministic and robust optimization. Additionally, to prepare for a possible transition to more sustainable fuels, we recommend installing suitable pipes near the engine room upfront to prevent expensive retrofits in the future.@en

Intermodality is regarded as one way of achieving more sustainable transport solutions. To make intermodal transport the preferred solution among shippers, it must be attractive according to the concept of generalized transport costs. An extended model for generalized transport costs is developed which includes elements important for comparing maritime transport solutions in the Artic. This framework forms the basis for a principal discussion on the conditions that make one transport solution preferable to another within the context of maritime logistics. This model is then applied to the context of the Northeast Passage to discuss the necessary requirements for making an intermodal transport solution attractive relative to the current main route from Northeast Asia to Northwest Europe through the Suez Canal. Even though intermodality could be preferable in principle, current solutions cannot compete with either Arctic routes using unimodal solutions with high ice-class vessels or with the Suez route. Due to uncertainty and limited empirical evidence, a sensitivity analysis is conducted, focusing on the variables with the greatest impact on the result. Policymakers and stakeholders can consider the findings to improve transport competitiveness via the Northeast Passage.

@en

Shipowners need to prepare for low-emission fuel alternatives to meet the IMO 2050 goals. This is a complex problem due to conflicting objectives and a high degree of uncertainty. To help navigate this problem, this paper investigates how methods that take uncertainty into account, like robust optimization and stochastic optimization, could be used to address uncertainty while taking into account multiple objectives. Robust optimization incorporates uncertainty using a scalable measure of conservativeness, while stochastic programming adds an expected value to the objective function that represents uncertain scenarios. The methods are compared by applying them to the same dataset for a Supramax bulk carrier and taking fuel prices and market-based measures as uncertain factors. It is found that both offer important insights into the impact of uncertainty, which is an improvement when compared to deterministic optimization, that does not take uncertainty into account. From a practical standpoint, both methods show that methanol and LNG ships allow a cheap but large reduction in emissions through the use of biofuels. More importantly, even though there are limitations due to the parameter range assumptions, ignoring uncertainty with respect to future fuels is worse as a starting point for discussions.@en

As climate change continues to pose a significant threat to our planet, international maritime shipping plays a crucial role in mitigation efforts. Recognizing the urgency, the International Maritime Organization (IMO) has revised its targets, now aiming for full decarbonization by 2050. However, there is no established pathway to get to the target. To achieve this, there is a need for models depicting possible futures of the maritime sector, and finding feasible pathways. This research aims to find the most suitable way to develop models to find pathways toward decarbonization targets. This involves evaluating existing ranges and scenarios to understand current estimations and their underlying assumptions and assessing the most suitable modeling methods based on defined criteria. Considering the context, the most suitable models for this objective should perform on a global scale. They should include dynamics between shipping demand & supply as well as the derived fuel demand and supply and emissions; integrate the sector with other parts of the economy; incorporate various technologies into the framework; and span multiple scenarios. The study has two main parts. First, existing scenarios on the future of maritime shipping are analyzed to identify current estimations and assumptions impacting these estimations. Second, various modeling frameworks are assessed against the defined criteria to identify the most suitable modeling structure for achieving the decarbonization targets. Many projections do not meet the IMO’s updated targets, highlighting the need for a paradigm shift in setting targets and finding feasible pathways rather than focusing solely on individual measures. Integrated Assessment Models (IAMs) have been identified as suitable for such projections and policy analysis, although international shipping is often underrepresented in current models. Future research should combine the insights of sectoral models in integrated frameworks such as IAMs to develop integrated strategies to investigate pathways to achieve zero-emission targets. The ultimate goal is to understand how to effectively reduce the sector’s emissions and achieve more environmentally friendly international maritime shipping.

@en

In the fiercely competitive shipbuilding industry, precise cost estimates must be considered as they serve as a critical input for determining market prices effectively and ensuring a small profit for the shipyard. In Western Europe, where most projects are Engineering-To-Order (ETO), cost estimations are extra challenging, due to lack of similarity between projects. On top of this, cost estimations are becoming increasingly difficult in a market confronted by mounting challenges related to safety regulations, cost-effectiveness, and the pressing need to address energy conservation and environmental protection. New technologies introduce changes in nearly all aspects of shipbuilding design and construction. This article conducts a literature review, to present the state-of-the-art methods for estimating man-hours, explicitly focusing on man-hours for shipyard production, excluding overhead costs and challenges the suitability of existing systems for ETO and especially for the changes caused to ships by the energy transition. An indication is given of the practicality of each method as outlined in the literature. A solution direction, incorporating the construction process, is proposed to improve cost estimations for ETO projects in pre-contract phase.

@en

This research addresses the importance of sustainability in shipping beyond fuel selection, stressing the need for responsible material usage in vessel construction and maintenance. Transitioning to a circular economy is crucial for sustainable waste management in the industry, yet current ship design neglects circularity considerations, prioritising functionality and cost. The research evaluates frameworks such as the butterfly diagram, Cradle-to-Cradle, 10R, and ReSOLVE to integrate circularity into ship design. Combining the 10R framework with the Material Circularity Indicator method, this study offers practical insights for circularity in ship design. Challenges include integrating these methods into standard design processes, which are mitigated by fusing 10R strategies with systems engineering. A case study on wheelhouse redesign demonstrates the effects of this approach, highlighting the importance of supplier collaboration for circularity enhancement.@en

Within the maritime transport sector, data and information have the potential to change the way we work for the betterness. Increasingly shipping companies are generating, storing and reporting data, on their position, their engines, their products and their emissions. As a result, data is sometimes referred to as the new gold and people often protect it in the same way. However, unlike gold, data has actually more value when it is shared and used in collaboration with others. [...]@en

The ongoing technological development of methanol energy converters (EC) towards decarbonization means that their dimensions and performance characteristics will be continually updated during the lifecycle of vessels currently designed. These advancements influence the ease of EC integration within the general arrangement of the vessel. The decision to switch from an internal combustion engine to a fuel cell or a hybrid configuration depends both (1) the technology adoption costs (i.e. CAPEX, OPEX) of the EC and (2)
on the effect of EC on the actual engine room layout. The state-of-the-art literature has typically addressed these two challenges separately. This study proposes a design method to bridge these two fields by combining the use of (1) Markov decision processes to assess uncertain future methanol EC developments during the vessel lifecycle and (2) a generative probabilistic layout algorithm to quantify the risks associated with the EC systems layout integration. The case study identifies the drivers behind the EC technology choice during the lifecycle of a notional yacht vessel.@en

Accurate cost estimates are essential for staying in business in a competitive shipbuilding industry. With new technologies and the energy transition creating an ever-changing landscape, traditional cost estimation methods based on product specifications can no longer keep pace. The need for improvement especially arises for Engineering-To-Order projects, considering that the profit margins are narrow. The use of process information in the estimation process could increase the reliability and flexibility of these estimations. This article presents a concept that utilizes graph theory to include process information in the cost estimations applied to steel buildings. This concept is specifically suited for the early stages of Engineering-To-Order projects.@en

Many fuels are currently considered for reducing the emissions in shipping; Methanol, LNG, Ammonia, Nuclear, Biodiesel, etc. However, Bio-ethanol is not considered at all.This research looked into all aspects of ethanol in a comparison with its most closely related alternative methanol. Using a similar approach as found in earlier comparisons. Though updating the data as well as the application ot vessels relevant for the Dutch ship owners. This research identified that 2nd generation bio-ethanol would in price be close to 2nd generation bio-methanol, but with several technical advantages. Furthermore the bio-ethanol production capacity is far larger than that of any of the other alternative fuels for shipping and with the ongoing electrification of cars, this capacity will most likely be looking for a new market in the future, putting pressure on the price. Hence the report calls for further investigations and reconsiderations of bio-ethanol as a marine fuel. @en

Piping systems are common in many architectures and designing such systems is often a complex task. Design automation of piping systems is therefore a universal research subject. Nonetheless, these piping systems are often still designed by hand as a result of their complexity. Consequently, costs associated with piping design are high, especially for large-scale architectures like ships and chemical plants. The goal of automatic pipe routing is to reduce the design time and associated costs of a piping system by automating the routing of these pipes. This survey provides an overview of the current state of automatic pipe routing literature to assist researchers and practitioners to further the study of automatic pipe routing. This is done by pinpointing and explaining the most important obstacles that stand in the way of making a full-scale automatic pipe routing method. The barriers that are analyzed are related to both model representation and optimization complexity. Finally, a synthesis table of research papers on automatic pipe routing is provided based on the handling of the aforementioned barriers and other general features of automatic pipe routing methodology. The survey concludes by discussing directions for further research.

@en