Knowledge

All-electric ships, and especially the hybrid ones with diesel generators and batteries, have attracted the attention of maritime industry in the last years due to their less emission and higher efficiency. The variant emission policies in different sailing areas and the impact of physical and environmental phenomena on ships energy consumption are two interesting and serious concepts in the maritime issues. In this paper, an efficient energy management strategy is proposed for a hybrid vessel that can effectively consider the emission policies and apply the impacts of ship resistant, wind direction and sea state on the ships propulsion. In addition, the possibility and impact of charging and discharging the carried electrical vehicles’ batteries by the ship is investigated. All mentioned matters are mathematically formulated and a general model of the system is extracted. The resulted model and real data are utilized for the proposed energy management strategy. A genetic algorithm is used in MATLAB software to obtain the optimal solution for a specific trip of the ship. Simulation results confirm the effectiveness of the proposed energy management method in economical and reliable operation of the ship considering the different emission control policies and weather condition impacts.

This study concerns nitrogen based emissions from a hydrogen enriched ammonia fueled SI engine. These emissions deserve special attention as their formation may differ from conventional HC combustion due to the nitrogen content in the fuel. A range of experiments are conducted with a single cylinder 0.612 l CFR engine with a compression ratio varying from 7 to 15 using a fuel composition of 80 vol% NH3 and 20 vol% H2. Wet exhaust samples are analysed with an FT-IR. Emission measurements reveal that nitric oxide stem from other reaction paths than the dissociation of molecular nitrogen. This causes the NO emissions to peak around 35% rather than 10% excess air, as is typical in HC fueled SI-engines. However the magnitude of NO emissions are comparable to that of measurements conducted with gasoline due to lower flame temperatures. Nitrogen dioxide levels are higher when comparing with gasoline, but has a relatively low share of the total NOx emissions (3–4%). Nitrous oxide is a product of NH2 reacting with NO2 and NH reacting with NO. The magnitude is largely affected by ignition timing due to the temperature development during expansion and the amount of excess air, as increased oxygen availability stimulates the formation of the NH2 radical and the levels of NO2 are higher. Under ideal operating conditions (MBT ignition timing) N2O levels are very low. The dominating contributors to unburned ammonia are chamber crevices as the magnitude of these emissions is greatly affected by the compression ratio. However, levels are lower than required in order to eliminate all NOx emissions with a SCR catalyst.

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.

I this video, Associate Professor Anders Ivarsson (DTU Mechanical Engineering) present the current status of their projects and experimental capabilities in the field of green marine fuels (lignin fuel, ammonia, and dimethyl ether) in their combustion engine laboratory.
The session was developed in collaboration with MARLOG.

Det Blå Danmark har en ambition om at være et internationalt foregangsland for klimavenlig skibsfart. Omstillingen til en mere bæredygtig skibsfart er dog en stor udfordring, der vil kræve betydelige investeringer i både ny teknologi, skibe og energiinfrastruktur og en systemisk tilgang til samarbejde på tværs af sektorer og mulige aftagere af grønne brændstoffer. Med denne rapport præsenterer DTU resultatet af et arbejde i at kortlægge forskningsmulighederne for Grønne Brændstoffer i det Blå Danmark. Arbejdet har afdækket, at der er behov for forskning på tværs af systemer og over hele værdikæden. Kortlægningen er lavet med viden fra DTU forskere samt input fra industrien og brancheorganisationerne.

Rapporten præsenterer en kortlægning af udfordringer forskningsbehov og rammebetingelser, som kan medvirke til at understøtte potentialet for grønne brændstoffer i det Blå Danmark. Kortlægningen er afrundet med anbefalinger til forskningsbehov inden for udvalgte områder samt uddannelse og test- og demonstrationsprojekter. Det er vores håb, at rapporten kan være med til at sikre det Blå Danmark en plads helt fremme i førerfeltet inden for bæredygtig skibsfart i mange år endnu.

Global warming and, correspondingly, reducing CO2 emissions is one of the most challenging tasks the world faces today. The maritime industry contributed to 2.89% of the global anthropogenic CO2 emissions. To decrease this share, the International Maritime Organization (IMO) defined, among others, the goal to reduce the carbon intensity of international shipping by 40% until 2030. In this context, the short-term measures recently adopted, in the form of a technical standard (Energy Efficiency Existing Ship Index, EEXI) and a rating scheme based on an operational indicator (Carbon Intensity Indicator, CII), mark a crucial step to achieving the mentioned goal. In addition, the EU Commission has recently introduced the FuelEU Maritime Initiative limiting the annual greenhouse gas (GHG) intensity of a ship’s energy use incorporating a reduction occurring in a five-year rhythm between 2025 and 2050. The paper investigates the practical options availed to existing containerships of different sizes and technological vintages for meeting the specific EEXI, CII, and GHG intensity reduction requirements imposed by the regulations. The investigation will be based on the actual technical and operational profiles of six sample ships and will consider a set of possible compliance options including, but not limited to, engine power limitation, waste heat recovery system, variable frequency drives, and virtual arrival. The data used originates from noon reports of existing containerships provided by a European industry leader. The ship-specific CO2 emission reduction potentials required for the impact assessment result from either literature or actual data-based calculations. Financial data is used for investigating the economic impact of the reduction requirements. Conclusions drawn include an operational advantage that pre-EEDI ships enjoy when applying engine power limitation (EPL) for EEXI compliance, the occurrence of payback periods exceeding ship lifetimes, and an estimate of the effect that onshore power supply can have on complying with the FuelEU Maritime Initiative.

In a premixed dual-fuel (DF) methane-diesel engine, the ignition of the lean premixed methane/air mixture starts with the assistance of a pilot diesel injection. Auto-ignition of pilot fuel is important as it triggers the subsequent combustion processes. A delay in the auto-ignition process may lead to misfiring, incomplete combustion, and thus higher greenhouse emissions due to methane slip. Hence, a better understanding of the auto-ignition process for the pilot fuel can help to improve the overall engine performance, combustion efficiency, and to lower exhaust emission levels. In the present study, large eddy simulation (LES) is used to investigate the auto-ignition process of micro-pilot diesel in premixed DF combustion in a constant volume combustion chamber (CVCC). The entire DF combustion processes including methane gas injection, methane/air mixing, pilot diesel injection, and ignition are simulated. The numerical model is validated against experimental data. The present numerical model is able to capture the ignition delay time (IDT) within a maximum relative difference of 7% to the measurements. A higher relative difference of 38% is obtained when methane gas injection and mixing are omitted in the simulation and the methane/air is assumed homogeneous. This demonstrates the importance of inhomogeneity pockets. To study the effects of temperature and methane inhomogeneities separately, different idealized inhomogeneities in temperature and methane distribution are considered inside the CVCC. The inhomogeneity in the temperature is observed to have a more profound influence on the IDT than the methane inhomogeneity. The inhomogeneity pockets of temperature advance the first-stage ignition and, subsequently, the second-stage ignition. A sensitivity analysis on the effect of inhomogeneity wavelength reveals that the larger wavelengths enhance the combustion due to the presence of pilot diesel jets in the desirable regions for a longer time duration.

Several replacement fuel to today’s fossil based ship propulsion fuels have been addressed in MarEfuel. Key ones are; pyrolysis oil (blend in fuel), methanol and ammonia. These were singled out among many possible fuels from a preliminary analysis that indicated that they could play a key role in fulfilling the emission targets set politically and by the sector in the most cost effective manner. In the following they shall be treated in turn in some detail. Costs of several “blue” fuels have also been assessed. The projected costs are used in other parts of the MarEfuel project (e.g. for assessing the total cost of ownership).

This report is a background report to the MarE-Fuel project financed by the Maritime Fund and the Lauritzen Fund. Partners of the project has been DTU, Anker Invest, Mærsk Line, Copenhagen Economics, OMT and DFDS. In the report, potential decarbonization roadmaps or pathways for the maritime industry are presented, as well as the methodology of deriving them. Different future fuels and their emissions are highlighted. In addition, biomass availability plays an essential role in climate mitigation efforts towards net-zero by 2050, and thus we examined different biomass availability scenarios alongside greenhouse-gas emissions cap scenarios. The assumptions related to the underlying emissions can be found in the first chapter of the report. Besides the underlying emissions for a decarbonized maritime industry, the ship stock and the underlying transport demand play an essential role for a future decarbonized maritime industry. In the second chapter of the report, we address this issue by explaining how ship stock and shipping demand have been incorporated into the model. Finally, we present the optimization ship stock model developed to generate roadmap scenarios. We show the objective function and the underlying constraints of the model. The results of this work are presented and discussed. We also show some sensitivity analysis, which will shed light on the relevant parameters for the futureof the maritime industry. Our main findings can be found in the end of the report.