This paper deals with two speed optimization problems for ships that sail in and out of Emission Control Areas (ECAs) with strict limits on sulfur emissions. For ships crossing in and out of ECAs, such as deep-sea vessels, one of the common options for complying with these limits is to burn heavy fuel oil (HFO) outside the ECA and switch to low-sulfur fuel such as marine gas oil (MGO) inside the ECA. As the prices of these two fuels are generally very different, so may be the speeds that the ship will sail at outside and inside the ECA. The first optimization problem examined by the paper considers an extension of the model of Ronen (1982) in which ship speeds both inside and outside the ECA are optimized. The second problem is called the ECA refraction problem, due to its conceptual similarity with the refraction problem when light travels across two different media, and also involves optimizing the point at which the ship crosses the ECA boundary. In both cases the objective of the problem is to maximize daily profit. In addition to mathematical formulations, examples and sensitivity analyses are presented for both problems.
The power to regulate on-board protection of merchant vessels lies with the flag state. However, the national models of regulation are not developed in a unilateral vacuum. In fact, the whole concept of flag state jurisdiction and legislative power has to be understood and exercised on the national level in close relation with the general regime of the international law of the sea. The aim of the article is therefore two-fold: first, it aims to provide a background for the country reports in this special issue by giving a brief insight into the problem of piracy in the twenty-first century and the international approaches towards this problem. Here the article also provides an insight into the legal background by presenting the concept of piracy in the law of the sea and connected law enforcement powers. Thus, this part of the article provides the overall context in which the discussions concerning on-board protection and the development of national regulations have occurred. Second, the article analyses the issue of on-board protection from the perspective of the legal framework in international law, as well as relevant international soft-law instruments, influencing the development on the national level. On-board protection of vessels as such is not regulated in the international law; however, international law provides a form of general legal setting, in which flags states navigate. Thus, this article aims to draw a picture of the international context in which flags states develop their specific legal approach.
Accurate estimation of the roll damping of a ship is important for reliable prediction of roll motions. In particular, characterization and prediction of parametric roll incidence and other events associated with large roll angles require detailed knowledge about the damping terms. In the present paper, an approach to identify the stability parameters, i.e. linear and nonlinear roll damping coefficients in conjunction with the natural roll frequency, based on onboard response measurements is proposed. The method starts by estimating the encountered wave profile using wave-induced response measurements other than roll, e.g., heave, pitch, and sway motions. The estimated wave profile is then fed into a physic-based nonlinear roll estimator, and then the stability parameters that best reproduce the measured roll motion are identified by optimization. In turn, in-situ identification can be achieved while simultaneously collecting the response measurements. A numerical investigation using synthetic response measurements is made first, then follows an experimental investigation using a scaled model ship. Good results have been obtained in both long-crested and short-crested irregular waves.
Slugging flow in offshore oil & gas multi-phase transportation pipelines cause big challenges as the flow regime induces flow and pressure oscillations in the multi-phase pipelines. The negative impacts of the most severe slugs are significant and thus the elimination of slugging flow in the pipelines is a highly investigated topic. To eliminate the slug in an online manner real-time slug detection methods are often required. Traditionally topside pressure transmitters upstream of a 3-phase separator have been used as the controlled variable. In this paper Electrical Resistivity Tomography (ERT) has been examined as an alternative to the traditional pressure transmitters. A lab-scaled testing facility has been constructed in order to obtain test data from an ERT transmitter with 12 probes. Different flow regimes have been generated by a pump and a compressor where 2-phase flow can be tested. Based on the results, the study concludes that the ERT is able to detect the slug very well when the oil and water are well mixed. Furthermore, the traditional pressure transmitters have the limitation that pressure variations can be caused by other operating conditions than slug, such as change in the back pressure from control valves. The biggest limitation using ERT is the lack of ability to distinguish between gas and oil, and thus the ERT can only be used as an effective slug detect measurement when the oil-to-water ratio is low.
Massive investments in offshore wind power generate significant challenges on how this electricity will be integrated into the incumbent energy systems. In this context, green hydrogen produced by offshore wind emerges as a promising solution to remove barriers towards a carbon-free economy in Europe and beyond. Motivated by the recent developments in Denmark with the decision to construct the world's first artificial Offshore Energy Hub, this paper investigates how the lowest cost for green hydrogen can be achieved. A model proposing an integrated design of the hydrogen and offshore electric power infrastructure, determining the levelised costs of both hydrogen and electricity, is proposed. The economic feasibility of hydrogen production from Offshore Wind Power Hubs is evaluated considering the combination of different electrolyser placements, technologies and modes of operations. The results show that costs down to 2.4 EUR per kg can be achieved for green hydrogen production offshore, competitive with the hydrogen costs currently produced by natural gas. Moreover, a reduction of up to 13 pct. of the cost of wind electricity is registered when an electrolyser is installed offshore shaving the peak loads.
Benchmarking the energy efficiency of ships is not a straightforward task, mainly due to the diversity of operations. Although driving cycles have been used for decades in evaluating the performance of road vehicles, these do not exist in formal policy-making for maritime transport. This work builds on a previously proposed methodology. It uses noon reports of 327 vessels for 2019 to construct operational cycles for seven size classes of container ships using the main engine power as the main parameter. Concerning the main engine emissions, the resulting cycles reduce variation in the carbon intensity indicator values by more than 30% while maintaining an average accuracy of 97.7% in absolute emissions. These figures show that the concept can improve operational carbon intensity indicators in terms of robustness and their technical counterparts in optimizing ship design. The paper also proposes further work required for benchmarking applications in policy-making.
Operational cycles for maritime transportation is a new concept to improve the assessment of ships’ energy efficiency and offer benchmarking options among similar ship types and sizes. This work extends previous research to consolidate the methodology, bring more comprehensiveness, and provide a more holistic assessment of these operational cycles. The cycles are designed from noon reports from a fleet of around 300 container ships divided into eight size groups. The comparison between cycles derived from speed and draft with those based on main engine power identifies that the cycles based on speed and draft are more accurate and allow for estimating the Energy Efficiency Operational Index but require more data. The main-engine-power cycles are more effective in benchmarking through the Annual Efficiency Ratio. These cycles reduce the inherent variability of the carbon intensity indicator and present good opportunities as a benchmarking tool for strengthening the regulatory framework of international shipping.
The dynamic characteristics of ship structures are becoming more important as the flexibility of modern ships increases, for example, to predict reliable design life. This requires an accurate dynamic model of the structure, which, because of complex vibration environment and complex boundary conditions, can only be validated by measurements. In the present paper the use of operational modal analysis (OMA) for dynamic characterization of a ship structure based on experimental data, from a full-scale measurement of a 210-m long Ro-Lo ship during sea trial, is presented. The measurements contain three different data sets obtained under different operating conditions of the ship: 10 knots cruising speed, 18 knots cruising speed, and at anchor. Natural frequencies, modal damping ratios, and mode shapes have been successfully estimated for the first 10 global modes. Damping ratios for the current ship were found within the range 0.9%-1.9% and natural frequencies were found to range from 0.8 to 4.1 Hz for the first 10 global modes of the ship at design speed (18 knots). The three different operating conditions showed, in addition, a speed dependency of the natural frequencies and damping ratios. The natural frequencies were found to be lower for the 18-knots condition compared with the two other conditions, most significantly for the vertical bending modes. Also, for the vertical bending modes, the damping ratios increased by 28%-288% when the speed increased from 10 to 18 knots. Other modes were not found to have the same strong speed dependency.
Why should we look to the past to understand privacy and the ways we can protect it? Privacy, as a contemporary concept, already seems to be challenging to define and regulate enough. With the ever-speeding technological developments we face today, it is hard to catch up with all the different ways in which our privacy can be breached. In the case of the maritime context, the complexity increases. Issues of jurisdiction, as well as the maritime control of the mobility of goods, information, and people, make tackling ‘privacy at sea’ a difficult task. Regulating forces, such as the European Maritime Safety Agency, need to be clear on their security measures, which must include a balance between surveillance for safety and personal data protection on the one hand and general privacy for people in vessels on the other.1 Looking back to history could, therefore, appear counterproductive, adding intricacies to an already convoluted issue. However, shifting perspectives to understand the historical roots of how such issues developed and to pay heed to what people continuously try to protect when advocating for privacy helps us break those dichotomies that make the balance between public safety and privacy harder to reach.
This scientific study aims to compare the significance of onboard positioning of two different classes of wind propulsion systems for retrofit installations to maximize fuel and emissions savings. The study focuses on comparing the performance a low lift-to-drag ratio wind propulsion system, the Rotor Sail, and a high lift-to-drag ratio one, the DynaRig, installed at different places on a real 84000 DWT bulk carrier ship to identify the most efficient placement of these two distinct systems to achieve maximum fuel efficiency. The investigation involves a comprehensive analysis of available deck spaces, and performance prediction program modeling is employed to estimate potential fuel savings for a typical route followed by the vessel. The results show that placing the WPS far forward, close to the hydrodynamic centre of lateral resistance, results in overall higher savings. Both WPS classes see a penalty when placed far from the hydrodynamic centre of lateral resistance, reducing their overall savings potential. However, Rotor Sails are more adversely affected due to their enhanced side force generation per unit thrust. Consequently, the placement of Rotor Sails becomes crucial, especially under upwind conditions, while DynaRigs prove more versatile for installations in the aft. This research provides valuable insights into enhancing the ship's energy efficiency and reducing its environmental impact in the maritime industry.