This paper considers the problem of determining the optimal vessel fleet to support maintenance operations at an offshore wind farm. We propose a two-stage stochastic programming (SP) model of the problem where the first stage decisions are what vessels to charter. The second stage decisions are how to support maintenance tasks using the chartered vessels from the first stage, given uncertainty in weather conditions and the occurrence of failures. To solve the resulting SP model we perform an ad-hoc Dantzig–Wolfe decomposition where, unlike standard decomposition approaches for SP models, parts of the second stage problem remain in the master problem. The decomposed model is then solved as a matheuristic by apriori generating a subset of the possible extreme points from the Dantzig–Wolfe subproblems. A computational study in three parts is presented. First, we verify the underlying mathematical model by comparing results to leading work from the literature. Then, results from in-sample and out-of-sample stability tests are presented to verify that the matheuristic gives stable results. Finally, we exemplify how the model can help offshore wind farm operators and vessel developers improve their decision making processes.
Maritime shipping is the transmission belt of the global economy. It is also a major contributor to global environmental change through its under-regulated air, water and land impacts. It is puzzling that shipping is a lagging sector as it has a well-established global regulatory body—the International Maritime Organization. Drawing on original empirical evidence and archival data, we introduce a four-factor framework to investigate two main questions: why is shipping lagging in its environmental governance; and what is the potential for the International Maritime Organization to orchestrate emerging private ‘green shipping’ initiatives to achieve better ecological outcomes? Contributing to transnational governance theory, we find that conditions stalling regulatory progress include low environmental issue visibility, poor interest alignment, a broadening scope of environmental issues, and growing regulatory fragmentation and uncertainty. The paper concludes with pragmatic recommendations for the International Maritime Organization to acknowledge the regulatory difficulties and seize the opportunity to orchestrate environmental progress.
The 76th session of the Marine Environment Committee (MEPC 76) of the International Maritime Organization adopted several mandatory measures in June 2021 to reduce carbon emissions from ships. One of the measures is the carbon intensity indicator (CII), which is the carbon emissions per unit transport work for each ship. Several options of CIIs are available and none of them is chosen to be applied yet. We prove that, at least in theory, requiring the attained annual CII of a ship to be less than a reference value, no matter which CII option is applied, may increase its carbon emissions. Therefore, more elaborate models, combined with real data, should be developed to analyze the effectiveness of each CII option and possibly to design a new CII.
With international rules of navigation, the IMO COLREGS, describing the regulatory behaviours of marine vessels relative to each other, correct interpretation of situations is instrumental to the successful navigation at sea. This becomes even more crucial when temporal unattended bridge or fully unmanned navigation is aimed at. Based on a breakdown of COLREG rules, this paper presents a framework for representation of manoeuvering behaviours, that are expected when all vessels obey the rules. Our analysis is based on discrete-event systems theory and the proposed framework consists of sets of finite automata, segregating situation assessment from decision making. A intermediate supervisory layer coordinates the communication of these automata modules. The framework is tested in simulation environment using a realistic scenario.
The paper discusses the use of CFD simulations to analyse the parametric excitation of moored, full scale wave energy converters in six degrees of freedom. We present results of VOF-RANS and VOF-Euler simulations in OpenFOAM!R for two body shapes: (i) a truncated cylinder; and (ii) a cylinder with a smooth hemispherical bottom. Flow characteristics show large differences in smoothness of flow between the hull shapes, where the smoother shape results in a larger heave response. However the increased amplitude makes it unstable and parametric pitch excitation occurs with amplitudes up to 30". The responses in surge, heave and pitch (including the transition to parametric motion) are found to be insensitive to the viscous effects. This is notable as the converters are working in resonance. The effect of viscous damping was visible in the roll motion, where the RANS simulations showed a smaller roll. However, the roll motion was found to be triggered not by wave-body interaction with the incident wave, but by reflections from the side walls. This highlights the importance of controlling the reflections in numerical wave tanks for simulations with WEC motion in six degrees of freedom.
The shipping industry faces huge challenges with regard to improving its environmental performance. The current regulatory approach has not been successful. Public and private actors increasingly rely on partnerships. The literature on partnerships for sustainability has contributed to a better conceptualisation of the subject. However, less is known about the processes and the outcomes of the partnerships as well as interactions between partnerships. This paper aims to improve the understanding of how partnerships contribute to developing cleaner technologies in the Danish shipping industry. Two partnerships have been analysed: Partnership for Cleaner Shipping and the Green Ship of the Future. Participation, scope and division of roles among partners have influenced both partnerships. Furthermore, both partnerships have developed organisational forms that proved to overcome the tensions in traditional partnerships, between open and information-based networking on the one side and closed and development-oriented collaboration on the other side.
As of January 2015, the new maximum limit of fuel sulfur content for ships sailing within emission control areas has been reduced to 0.1%. A critical decision for ship owners in advance of the new limits was the selection of an abatement method that complies with the regulations. Two main options exist: investing in scrubber systems that remove sulfur dioxide emissions from the exhaust and switching to low-sulfur fuel when sailing in regulated waters. The first option would involve significant capital costs, while the latter would lead to operating cost increases because of the higher price of the fuel used. This paper presents a literature review of emissions abatement options and relevant research in the field. A cost–benefit methodology to assess emission reduction investments from ship owners is also presented. A study examined the effects of recent drops in bunker fuel price to the payback period of a potential scrubber investment. The results show that lower prices would significantly delay the payback period of such investments, up to two times in some cases. The case studies present the emissions generation through each option for representative short sea shipping routes. The repercussions of low-sulfur policies on large emission reduction investments including cold ironing are examined, along with implications of slow steaming for their respective payback periods. Recommendations are made for research in anticipation of future regulations and technological improvements.
Chalk reservoirs, due to their high porosity and very low permeability, represent one of the most interesting cases for engineering studies of carbonates. They exhibit complex fluid-rock interactions because of their reactive surfaces and dense porous medium. The reinjection of produced water is an attractive strategy for managing wastewater flow from oil wells. However, the complex composition of produced water, the reactive nature of carbonate rocks, and their low permeability create challenges related to permeability loss.
This study examines the stages of permeability change during core flooding experiments up to the point of complete clogging. A distinctive feature of this study is the presence of residual oil in the core samples, which simulates real reservoir conditions during produced water reinjection. The presence of residual oil is an additional factor influencing the change in core permeability, but there is no clear consensus in the research community on its impact on permeability during produced water injection.
All experiments were conducted in a core flooding system simulating well conditions in terms of pressure (170 bar) and temperature (70 ◦C). Produced water samples from the Dan field were used to replicate the chemical and thermodynamic processes occurring in a real well. The experiments identified three stages of permeability change: an initial increase in permeability (+12%), a period of pressure stabilization, and a subsequent decrease in permeability (− 8%) due to the formation of inorganic precipitates within the core channels.
The primary objective of the experiments is to investigate the relationship between permeability changes and the stages of reinjection, with a focus on the effects of residual oil. The study focuses on identifying the processes occurring up to the point of complete clogging, considering the impact of residual oil saturation in the chalk core samples. Image analysis using scanning electron microscopy, particle size measurement with a zeta-potential meter, and thermodynamic scale formation modeling with ScaleCERE software were employed to explain these processes.
Three stages of permeability change were identified during the injection of 200 pore volumes of produced water: increased permeability (+12%), pressure stabilization, and decreased permeability (− 8%). The positive influence of residual oil saturation on the filtration and storage properties of the reservoir was established, due to the mobilization of chalk core particles. Additionally, the theory of core channel clogging during the reinjection of formation water by the formation of inorganic precipitates within the channels was confirmed.
Understanding the causes of permeability reduction that occurred during the stage of permeability decrease enables the development of water purification methods specifically targeted at the causes of rock clogging. Predicting the process of injecting a mixture of produced and seawater will help in interpreting the data during disposal operations by injecting formation water into an injection well, and it will allow for the selection of effective measures to mitigate the impact on the reservoir.
Background: Evidence on workplace safety and health promotion interventions shows that the interventions have failed to demonstrate substantial benefits for seafarers. It is therefore important to explore what is the evidence of interventions with empowering elements regarding seafarers’ safety and health. This study aims to examine what is known about health promotion interventions in a maritime setting and whether they include an empowerment perspective. And secondly, what were the effects of these efforts. Methods: We systematically searched PubMed and NLM Gateway (for MEDLINE), Institute of Scientific Information/Web of Science (ISI/WOS), and SCOPUS up to July 2022 by using standard keywords including empowerment in the maritime setting. Data extraction was done by three independent reviewers. The quality of included studies was assessed by using the critical appraisal checklists from Joanna Briggs institute. Results: From 3313 studies initially identified, 10 articles met the inclusion criteria and were included in this review. Interventions covered a wide range of topics such as educational interventions on safety, first aid training, weight management, healthy eating, sexual harassment, alcohol abuse, and cancer prevention training. None of the studies applied a specific theory or definitions of empowerment even though their aim was to increase seafarers’ empowerment in these areas. Conclusion: The studies focused on improving the safety and health status of the seafarers, however, they had no explicit focus on participation and empowerment. Increasing research with an empowerment approach in maritime sector is recommended to enhance the feasibility and success of the programs in this hard-to-reach occupation. Systematic review registration number in PROSPERO: CRD42021260098.
Background: Evidence on workplace safety and health promotion interventions shows that the
interventions have failed to demonstrate substantial benefits for seafarers. It is therefore important to explore what is the evidence of interventions with empowering elements regarding seafarers’ safety and health. This study aims to examine what is known about health promotion interventions in a maritime setting and whether they include an empowerment perspective. And secondly, what were the effects of these efforts. Methods: We systematically searched PubMed and NLM Gateway (for MEDLINE), Institute of Scientific Information/Web of Science (ISI/WOS), and SCOPUS up to July 2022 by using standard keywords including empowerment in the maritime setting. Data extraction was done by three independent reviewers. The quality of included studies was assessed by using the critical appraisal checklists from Joanna Briggs institute. Results: From 3313 studies initially identified, 10 articles met the inclusion criteria and were included in this review. Interventions covered a wide range of topics such as educational interventions on safety, first aid training, weight management, healthy eating, sexual harassment, alcohol abuse, and cancer prevention training. None of the studies applied a specific theory or definitions of empowerment
even though their aim was to increase seafarers’ empowerment in these areas. Conclusion: The studies focused on improving the safety and health status of the seafarers, however, they had no explicit focus on participation and empowerment. Increasing research with an empowerment approach in maritime sector is recommended to enhance the feasibility and
success of the programs in this hard-to-reach occupation.