Highly reliable situation awareness is a main driver to enhance safety via autonomous technology in the marine industry. Groundings, ship collisions and collisions with bridges illustrate the need for enhanced safety. Authority for a computer to suggest actions or to take command, would be able to avoid some accidents where human misjudgement was a core reason. Autonomous situation awareness need be conducted with extreme confidence to let a computer algorithm take command. The anticipation of how a situation can develop is by far the most difficult step in situation awareness, and anticipation is the subject of this article. The IMO International Regulations for Preventing Collisions
at Sea (COLREGS), describe the regulatory behaviours of marine vessels relative to each other, and correct interpretation of situations is instrumental to safe navigation. Based on a breakdown of COLREGS rules, this article presents a framework to represent manoeuvring behaviours that are expected when all vessels obey the rules. The article shows how nested finite automata can segregate situation assessment from decision making and provide a testable and repeatable algorithm. The suggested method makes it possible to anticipate own ship and other vessels’ manoeuvring in a multi-vessel scenario. The framework is validated using scenarios from a full-mission simulator.
The International Maritime Organization (IMO) has recently adopted short-term measures introducing technical standards for existing ships and a labeling system reflecting their operational carbon intensity. This paper investigates the relevant techno-economic implications from a shipowner's perspective and estimates the effect of six compliance options on six sample containerships. The study applies a new evidence-based bottom-up approach, and the results show that compliance, when possible, is not straightforward and costly. Engine power limitation is the most cost-effective option, but low power limits can lead to substantially increased sailing times (up to 793.92 h/year), which can be prohibitive. The option favors older ships with oversized engines as its effectiveness is mainly determined by the main engine load profile. In general, the effectiveness of the measures is not without limits, particularly concerning older ships and those that have already installed several options. Solutions such as market-based measures and alternative fuels, classed by IMO as medium- and long-term measures, must be considered soon.
Offshore grids can play key roles in the transition of energy systems toward sustainability. Although they require extensive infrastructure investments, they allow for the exploitation of additional resources and may be important in providing for part of the increasing electricity demands driven by sector coupling. This paper quantifies the socioeconomic value of offshore grids and identifies their major drivers, performing energy system optimization in a model application of the northern–central European energy system and the North Sea offshore grid towards 2050. The increasing wake loss with the sizes of hub-connected wind farms is integrated in the modeling. We find that without sector coupling no offshore grid may develop, and that the higher the level of sector coupling, the higher the value of offshore grids. Therefore, it can be strongly stated that offshore grid infrastructure development should not be discussed as a separate political topic, but seen in connection to sector coupling.
Offshore energy hubs connect large amounts of offshore wind to a hub from where the generation can be transmitted to onshore, potentially linking to multiple surrounding countries. The benefits of such hubs, and the related meshed offshore grid to connect them, have been investigated in the North Sea. The system-wide impacts of offshore energy hubs in the Baltic Sea are less studied; however, the region is seeing increased interest in offshore wind development. This paper uses detailed offshore wind generation simulations and energy system optimisation to investigate the cost-effectiveness of offshore energy hubs in the Baltic Sea in different scenarios towards 2050. The results show that the largest deployment of offshore energy hubs occurs when the energy system is highly electrified. The strongest development of the offshore energy hubs occurs in the southern part of the Baltic Sea.
With the current revolution in Shipping 4.0, a tremendous amount of data is accumulated during vessel operations.
Data quality (DQ) is becoming more and more important for the further digitalization and effective decision-making
in shipping industry. In this study, a practical DQ assessment method for raw data in vessel operations is proposed.
In this method, specific data categories and data dimensions are developed based on engineering practice and existing
literature. Concrete validation rules are then formed, which can be used to properly divide raw datasets. Afterwards,
a scoring method is used for the assessment of the data quality. Three levels, namely good, warning and alarm,
are adopted to reflect the final data quality. The root causes of bad data quality could be revealed once the internal
dependency among rules has been built, which will facilitate the further improvement of DQ in practice. A case study
based on the datasets from a Danish shipping company is conducted, where the DQ variation is monitored, assessed
and compared. The results indicate that the proposed method is effective to help shipping industry improve the quality
of raw data in practice. This innovation research can facilitate shipping industry to set a solid foundation at the early
stage of their digitalization journeys.
Methanol, as one of the significant green fuel candidates for the combustion engines, can be produced from Power to X and biomass production. However, compression ignition (CI) of pure methanol in a combustion engine is impractical due to its low cetane rating. The strategy has gained little attention in the past, but is possible if the methanol is premixed with a fuel additive (ignition improver). In order to optimize and understand additivated methanol combustion, a phenomenological spray/packet combustion model is developed in this work. The model is used to calibrate an Arrhenius-type ignition delay equation for CI engine using additivated methanol, and the resulting calibrated ignition delay parameter is 2.14. The procedure involves to compare the modeled and experimental combustion rate profiles that are derived from a small marine CI engine by burning methanol with 3.5 % and up to 7.5 % kg/kg fuel additive. The present work finds that the phenomenological diesel combustion model methodology can be used with good accuracy, to simulate combustion rate profiles of additivated methanol in a CI engine. The model is, furthermore, able to indicate intermediate variables such as burning packet speeds, air mass, droplet mass, air/fuel equivalence ratio, and burning packet temperature for different packets of combustion.
Offshore pipelines and structures require regular marine growth removal and inspection to ensure structural integrity. These operations are typically carried out by Remotely Operated Vehicles (ROVs) and demand reliable and accurate feedback signals for operating the ROVs efficiently under harsh offshore conditions. This study investigates and quantifies how sensor delays impact the expected control performance without the need for defining the control parameters. Input-output (IO) controllability analysis of the open-loop system is applied to find the lower bound of the H-infinity peaks of the unspecified optimal closed-loop systems. The performance analyses have shown that near-structure operations, such as pipeline inspection or cleaning, in which small error tolerances are required, have a small threshold for the time delays. The IO controllability analysis indicates that off-structure navigation allow substantial larger time delays. Especially heading is vulnerable to time delay; however, fast-responding sensors usually measure this motion. Lastly, a sensor comparison is presented where available sensors are evaluated for each ROV motion’s respective sensor-induced time delays. It is concluded that even though off-structure navigation have larger time delay tolerance the corresponding sensors also introduce substantially larger time delays.
This paper studies the Quay Crane Scheduling Problem (QCSP). The QCSP determines how a number of quay cranes should be scheduled in order to service a vessel with minimum makespan. Previous work considers the QCSP to be a combinatorially hard problem. For that reason, the focus has been on developing efficient heuristics. Our study shows, however, that the QCSP is tractable in the realistic setting, where quay cranes can share the workload of bays. We introduce a novel linear time algorithm that solves the QCSP and prove its correctness.
I Danmark har vi en god og lang tradition for en åben demokratisk debat om vores fremtidige energiforsyning.
Gennem årene har vi udviklet et godt fælles grundlag for, at en sådan debat er baseret på fakta om, hvad de enkelte teknologier kan i dag, samt en konsensus om fremtidige forventninger. Teknologikataloget, som løbende opdateres af Energistyrelsen og Energinet i en dialog med relevant faglig ekspertise, udgør en fælles ramme for denne forståelse.
I den senere tid har der været en debat om, hvorvidt atomkraft kan og bør være en del af den grønne omstilling af Danmarks energiforsyning eller ej. Debatten har indeholdt mange modsatrettede udsagn om blandt andet økonomien i atomkraft og dens evne til at være en del af det samlede fremtidige elsystem.
Det er forståeligt, at en sådan debat opstår i lyset af de nuværende klima- og energiforsyningsudfordringer, men det er en fordel for debatten, at den bliver så faktabaseret som muligt. Målet med vores notat er at bidrage til dette.
Vi har fundet frem, hvad vi kunne af relevante fakta om nyligt etablerede atomkraftværker i Europa samt forventninger til atomkraft i fremtiden baseret på data fra det Internationale Energiagentur. Disse fakta omhandler anlægsomkostninger, levetider, driftsomkostninger og byggetider.
På baggrund af en sådan viden samt tilsvarende data om eksisterende vedvarende energianlæg i Danmark i kombination med Teknologikatalogets forventninger til fremtiden har vi foretaget en direkte sammenligning af omkostningerne ved at producere el fra henholdsvis vind, sol og atomkraft.
Det er imidlertid svært direkte at sammenligne sol, vind og atomkraft. Atomkraft er kendetegnet ved kontinuert produktion i modsætning til den fluktuerende produktion fra vind og sol. Der er en umiddelbar relativ fordel ved kontinuert elproduktion. Men atomkraften har også nogle ulemper, hvad angår radioaktivt affald og sikkerhed. Den fluktuerende produktion fra vind og sol afføder et behov for kapacitet til at balancere systemet, når der ikke er forsyning fra vind og sol. Det kan fx være transmissionsnetskapacitet til at balancere over geografiske afstande, kapacitet i form af gasturbiner, der kan køre på grøn gas fra nettet i sådanne perioder og det kan være behov for kapacitet i form af elektrolyse til brintproduktion, så brinten produceres, når der er mest el i systemet.
For at kvantificere den økonomiske betydning af dette behov for ekstra kapacitet har vi foretaget energisystemanalyser og regnet på et fremtidigt dansk energisystem henholdsvis med og uden atomkraft. På den måde kan vi vurdere, hvordan atomkraft vil kunne påvirke det samlede energisystem og dets omkostninger.
Vi ser gerne en åben debat om de data, som vi fremlægger her. Derfor kalder vi også dette skrift for ’første version’, og er der noget, som skal korrigeres eller suppleres, så gør vi gerne det i en eventuelt revideret version.
Under alle omstændigheder håber vi, at notatet bidrager til at gøre debatten mere faktabaseret og transparent. Det er der brug for.
Recent times have seen a great interest on environmental issues and efficient, sustainable systems. This interest has required the employment of advanced composites for a myriad of industrial machines and innovative equipments. Among these applications, Flywheel Energy Storage Systems – FESS – represent a group of machines that are being re-invented through this process. Modeling composite flywheels has proven to be a complex task, which current Finite Element models fail to fulfill in a number of design contexts. This demand to model complex composite geometries and systems induced the proposition of new methods, aiming to capture the various physical effects existing in the problem. In the present contribution, the authors consider that it is viable to model the dynamic behavior of a Flywheel Energy Storage System via an adapted Carrera Unified Formulation, both in terms of accuracy and computational cost, for practical applications. The present work presents and explores a Carrera Unified Formulation model with extended capabilities dedicated to rotordynamics applications. The differences from standard Finite Elements models are presented, evidencing advantages and drawbacks of the proposed methodology over more traditional approaches. A case study is then presented, modeled, and the results are compared with those stemming from established formulations.