Over the recent decades, there has been an increasing focus on energy-efficient operation of vessels. It has become part of the political agenda, where regulation is the main driver, but the maritime industry itself has also been driven towards more energy-efficient operation of the vessels, due to increasing fuel costs. Improving the energy efficiency on board vessels is not only a technical issue - factors such as awareness of the problem, knowledge skills and motivation are also important parameters that must be considered.
The paper shows how training in energy-efficient operation and awareness can affect the energy consumption of vessels. The study is based on navigational, full-mission simulator tests conducted at the International Maritime Academy SIMAC. A full-mission simulator is an image of the world allowing the students to obtain skills through learning-by-doing in a safe environment. Human factors and technical issues were included and the test sessions consisted of a combination of practical simulator exercises and reflection workshops.
The result of the simulator tests showed that a combination of installing technical equipment and raising awareness - making room for reflections-on and in-action - has a positive effect on energy consumption. The participants, on average, saved approximately 10% in fuel.
The wave loads and the resulting motions of floating wave energy converters are traditionally computed using linear radiation–diffraction methods. Yet for certain cases such as survival conditions, phase control and wave energy converters operating in the resonance region, more complete mathematical models such as computational fluid dynamics are preferred and over the last 5 years, computational fluid dynamics has become more frequently used in the wave energy field. However, rigorous estimation of numerical errors, convergence rates and uncertainties associated with computational fluid dynamics simulations have largely been overlooked in the wave energy sector. In this article, we apply formal verification and validation techniques to computational fluid dynamics simulations of a passively controlled point absorber.
The phase control causes the motion response to be highly nonlinear even for almost linear incident waves. First, we show that the computational fluid dynamics simulations have acceptable agreement to experimental data. We then present a verification and validation study focusing on the solution verification covering spatial and temporal discretization, iterative and domain modelling errors. It is shown that the dominating source of errors is, as expected, the spatial discretization, but temporal and iterative errors cannot be neglected. Using hexahedral cells with low aspect ratio and 30 cells per wave height, we obtain results with less than 5% uncertainty in motion response (except for surge) and restraining forces for the buoy without phase control. The amplified nonlinear response due to phase control caused a large increase in numerical uncertainty, illustrating the difficulty to obtain reliable solutions for highly nonlinear responses, and that much denser meshes are required for such cases.
Different port operating policies have the potential to reduce emissions from shipping; however, their efficacy varies for different ports. This article extends existing literature to present a consistent and transferable methodology that examines emissions reduction port policies based on ship-call data. Carbon dioxide (CO2); sulphur dioxide (SO2); nitrogen oxides (NOx); and black carbon (BC) emissions from near-port containership activities are estimated. Two emissions reduction policies are considered for typical container terminals. Participation of all calling vessels with a speed reduction scheme can lead to reductions of 8–20 per cent, 9–40 per cent and 9–17 per cent for CO2, SO2 and NOx, respectively. However, speed reduction policies may increase BC emissions by up to 10 per cent. Provision of Alternative Marine Power (AMP) for all berthing vessels can reduce in-port emissions by 48–70 per cent, 3–60 per cent, 40–60 per cent and 57–70 per cent for CO2, SO2, NOx and BC, respectively. The analysis shows that emissions depend on visiting fleet, berthing durations, baseline operating pattern of calling ships, sulphur reduction policies in force and the emissions intensity of electricity supply. The potential of emissions reduction policies varies considerably across ports making imperative the evaluation and prioritization of such policies based on the unique characteristics of each port and each vessel.
The results of load-varying self-propulsion model-scale experiments in calm water and regular deep-water following regular waves are presented. Open water tests were also performed at different propeller rotational speeds to evaluate the impact of the Reynolds number on the propeller thrust and torque. A model-scale fishing trawler was selected as the case study. Two ship speeds were considered. The open water curves showed a minimal influence of the Reynolds number on the thrust coefficient. However, the torque coefficient decreased with the increase of the Reynolds number. A good linear relationship between the tow force and the propeller thrust was detected in following waves and calm water conditions. The effective wake fraction increased in following waves compared to calm water conditions. The amplitude of the effective wake fraction decreased with the increase of the ship speed. A small influence of the ship motions and wave–particle velocities was reported on the thrust deduction fraction. The hull, relative rotative, propeller, and propulsive efficiency increased compared to calm water. The propulsive characteristics were estimated by considering the wave added resistance and the propulsive coefficients equal to their calm water values. Compared to the propulsive characteristics computed with the propulsive coefficients measured in waves, the propulsive efficiency was underestimated by about 2%–5%.
The severe slugging flow is always challenging in oil & gas production, especially for the current offshore based production. The slugging flow can cause a lot of potential problems, such as those relevant to production safety, fatigue as well as capability. As one typical phenomenon in multi-phase flow dynamics, the slug can be avoided or eliminated by proper facility design and control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key operational parameters with severe slugging flows. These correlations are reflected through an obtained stable surface in the parameter space, which is a natural extension of the bifurcation plot. The maximal production opportunity without compromising the stability is also studied. Relevant studies have already showed that the capability, performance and efficiency of anti-slug control can be dramatically improved if these stable surfaces can be experimentally determined beforehand.
Formålet med denne anden version af dette notat er stadig at få de vigtigste fakta om atomkraft i Danmark på bordet. I første version af notatet lagde vi op til en åben debat og inviterede til kommentarer og input. Dem har vi modtaget mange af. Det vil vi gerne takke for. Vi har brugt de mange kommentarer til at rette, forbedre, tilføje og uddybe, hvorfor vi nu kan fremlægge anden forbedrede og udbyggede udgave af notatet. Vi er selvfølgelig stadig åbne for at modtage kommentarer og inputs frem mod en version 3.
Nogle af de væsentligste ændringer i forhold til version 1 er:
Der er blevet spurgt til detaljerne i vores analyser og modelberegninger, da det for mange kan være svært at forstå, hvordan en fremtidig elforsyning baseret på vedvarende energi kan være stabil. Derfor har vi uddybet modelberegninger fra version 1 af notatet i to appendikser og tilføjet nye modelberegninger, som uddyber analyserne i forhold til det danske energisystems rolle i Europa. Desuden har vi tilføjet et helt afsnit om stabilitet, som forklarer, hvordan stabilitet og forsyningssikkerhed sikres i et vedvarende energisystem såvel som i et atomkraftsystem.
Der har været kritik af vores valg af eksempler på atomkraftværker, når vi har identificeret anlægsomkostninger og byggetider. Derfor har vi tilføjet flere til listen og uddybet diskussionen af hvilke omkostninger og byggetider, der er
relevante og aktuelle i en dansk sammenhæng. Et særskilt kritikpunkt har været valg af ’kapacitetsfaktor’. Kapacitetsfaktoren udtrykker, hvor meget et værk producerer igennem en periode sammenlignet med, hvor meget det maksimalt vil kunne producere, hvis det kørte ved fuld belastning (fuldlast) i hele perioden. Ved en kapacitetsfaktor på 100% vil værket køre fuldlast i hele perioden og ikke have ’udetider’, hvor værket ikke kan benyttes f.eks. ved direkte nedbrud, vedligehold eller regulering af driften for at følge behovsprofiler. Vi er her blevet kritiseret for at vælge 75% for atomkraftværker, og i stedet er der blevet peget på 85% som mere retvisende. Vi er også blevet kritiseret for ikke at indregne en eventuel udnyttelse af overskudsvarmen fra et atomkraftværk til fjernvarme, og der er blevet spurgt til, om vi har alle omkostninger til elnettet med. Som svar på disse kritikpunkter har vi foretaget flere beregninger med forskellige kapacitetsfaktorer for atomkraftværker samt analyser med og uden fjernvarmeudnyttelse. Hermed kan man klart se betydningen af disse valg af forudsætninger.
Kilden for vores valg af 75% er Det Internationale Energiagenturs World Energy Outlook, hvor de forudser, at atomkraft i 2050 i det Europæiske energisystem vil have en kapacitetsfaktor mellem 70% og 80%. 85% er teknisk muligt, men vælges typisk når atomkraft ikke indgår i sammenhæng med et energisystem med vedvarende energi.
For at styrke gyldigheden af vores beregninger har vi desuden tilføjet nye analyser af Danmark i en Europæisk sammenhæng, hvor vores beregningsmodeller både optimerer på investeringer i produktionskapacitet og på transmissionsledninger.
Disse ekstraanalyser ændrer dog ikke på den centrale hovedkonklusion: At et dansk energisystem med atomkraft er dyrere end et med vind og sol, og at atomkraft tager længere tid at opføre end vind- og solanlæg.
Endelig har der blandt nogle været en forvirring om, hvem vi er, og hvad vores faglighed er i forhold til atomkraftdebatten sammenlignet med forskere, som har en mere specialiseret baggrund i kernefysik eller lignende. Vi er en bred sammensætning af ingeniører, fysikere og økonomer. Vores fælles faglighed er koncentreret om energisystemanalyse, og vores forskningsområde er at analysere, hvordan vi på energiområdet bedst og billigst kan gennemføre den grønne omstilling og hurtigst muligt opnå et CO2-neutralt samfund. Vi er således ikke kun specialister i en enkelt teknologi. Vi er først og fremmest specialister i, hvordan teknologierne spiller sammen, så vi kan finde de bedste løsninger og
optimere det samlede energisystem.
Det er vores vurdering, at det netop er den faglighed og de forskningskompetencer, der er brug for, når konsekvenserne af at investere i atomkraft i Danmark skal sammenlignes med ikke at gøre det. Når trafikforhold skal udvikles og optimeres, er det også trafikforskerens kompetence, der efterspørges, og ikke ekspertise i f.eks. forbrændingsmotorteknologien.
Samlet set er rapporten inddelt i fire kapitler, der fokuserer på forskellige pointer. I kapitel 1 sammenlignes omkostningerne ved at producere en enhed (MWh) el fra henholdsvis atomkraft, sol og vind uafhængigt af resten af energisystemet;
Kapitel 2 har et fokus på de samme teknologier, men hvor de er i drift i energisystemet, og dermed kan betydningen af forskelle i produktionsmønstre fra vedvarende energi og atomkraft kvantificeres. Kapitel 3 fokuserer på den del af energisystemanalyserne, der omhandler forsyningssikkerhed og stabilitet. I kapitel 4 diskuterer vi bygge- og planlægningstider på atomkraft.
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.
The energy system needs a range of forecast types for its operation in addition to the narrow wind power forecast that has been the focus of considerable recent attention. Therefore, the group behind the former IEA Wind Task 36 Forecasting for Wind Energy has initiated a new IEA Wind Task with a much broader perspective, which includes prospective interaction with other IEA Technology Collaboration Programmes such as the ones for PV, hydropower, system integration, hydrogen etc. In the new IEA Wind Task 51 (entitled "Foreacsting for the Weather Drive Energy System") the existing Work Packages (WPs) are complemented by work streams in a matrix structure. The Task is divided in three WPs according to the stakeholders: WP1 is mainly aimed at meteorologists, providing the weather forecast basis for the power forecasts. In WP2, the forecast service vendors are the main stakeholders, while the end users populate WP3. The new Task 51 started in January 2022. Planned activities include 4 workshops. The first will focus on the state of the art in forecasting for the energy system plus related research issues and be held during September 2022 in Dublin. The other three workshops will be held later during the 4-year Task period and address (1) seasonal forecasting with emphasis on Dunkelflaute, storage and hydro, (2) minute-scale forecasting, and (3) extreme power system events. The issues and conclusions of each of the workshops will be documented by a published paper. Additionally, the Recommended Practice on Forecast Solution Selection will be updated to reflect the broader perspective.
As the emission legislation becomes further constraining, all manufacturers started to fulfill the future regulations about the prime movers in the market. Lean-burn gas engines operating under marine applications are also obligated to enhance the performance with a low emission level. Lean-burn gas engines are expressed as a cleaner source of power in steady loading than diesel engines, while in transient conditions of sea state, the unsteadiness compels the engine to respond differently than in the steady-state. This response leads to higher fuel consumption and an increase in emission formation. In order to improve the stability of the engine in transient conditions, this study presents a concept implementing a hybrid configuration in the propulsion system. An engine model is developed and validated in a range of load and speed by comparing it with the available measured data. The imposed torque into the developed engine model is smoothed out by implementing the hybrid concept, and its influence on emission reduction is discussed. It is shown that with the hybrid propulsion system, the NOX reduces up to 40% because of the maximum load reduction. Moreover, eliminating the low load operation by a Power Take In during incomplete propeller immersion, the methane slip declines significantly due to combustion efficiency enhancement.
Hydrogen can be key in the energy system transition. We investigate the role of offshore hydrogen generation in a future integrated energy system. By performing energy system optimisation in a model application of the Northern-central European energy system and the North Sea offshore grid towards 2050, we find that offshore hydrogen generation may likely only play a limited role, and that offshore wind energy has higher value when sent to shore in the form of electricity. Forcing all hydrogen generation offshore would lead to increased energy system costs. Under the assumed scenario conditions, which result in deep decarbonisatiton of the energy system towards 2050, hydrogen generation – both onshore and offshore – follows solar PV generation patterns. Combined with hydrogen storage, this is the most cost-effective solution to satisfy future hydrogen demand. Overall, we find that the role of future offshore hydrogen generation should not simply be derived from minimising costs for the offshore sub-system, but by also considering the economic value that such generation would create for the whole integrated energy system. We find as a no-regret option to enable and promote the integration of offshore wind in onshore energy markets via electrical connections.