Ship Fuels Research Articles

Decarbonization in Shipping—The Hopes and Doubts on the Way to Hydrogen Use

This article presents the initial processes of changing ship fuels aimed at reducing emissions of carbon dioxide and other greenhouse gases. A significant reduction in GHG emissions is only possible by using carbon-free fuels. The process of reducing CO2 emissions was forced by legal regulations introduced in recent years by the International Maritime Organization and the Parliament of the European Union. The year 2050 was set as the target year for achieving the intended goals, but intermediate goals should be achieved already in 2030 and 2040. This article attempts to analyze the ongoing changes in the fuel market in maritime transport on the way to achieving the threshold of climate neutrality with this form of transport. A number of hopes related to this were indicated but also so were obstacles that may slow down this process. In 2023, there was an increased interest among shipowners in adapting ship engines to burn more ecological ship fuels. However, it is far from our expectations. Meeting the gradually increasing emission limits through imposed regulations was possible in the years 2020–2023 by using dual-fuel engines in which gaseous fuels, mainly LNG and LPG, were used for long periods of operation. The next step is the use of biofuels or synthetic fuels, which, however, will not meet the requirements after 2030. Interest is moving towards the use of ammonia and, ultimately, after 2040, hydrogen. The aim of this article is to analyze the ongoing processes and assess the directions of changes that justify the sense of the actions taken.

Risk Assessment of Ammonia Fueled Ships: Consequences on Human Health of Ammonia Releases from Damaged Fuel Storage Tanks

Risk Assessment of Ammonia Fueled Ships: Consequences on Human Health of Ammonia Releases from Damaged Fuel Storage Tanks

Optimization study of BOG re-liquefaction process for ammonia fueled ship

Optimization study of BOG re-liquefaction process for ammonia fueled ship

Ejector design for compressorless BOG utilization system for a LNG fueled ship

In general LNG fueled ships, boil-off gas (BOG) produced by heat leakage into the storage tank is directly utilized as fuel for engines and generators by transport using compressors, which have many moving parts making the maintenance difficult, and require much power consumption for pressurizing the BOG. This paper proposes a new BOG utilization system with a compressorless configuration adopting an ejector and a static mixer. In this system, the BOG is transported and liquefied by the ejector and the static mixer, respectively, and then temporally stored before fueling. This paper also introduces an innovative optimization for ejector, which is a key component and should sufficiently entrain the BOG with less motive fuel gas. A preliminary thermodynamic analysis was performed to identify the effect of the ejector entrainment ratio on the effectiveness of BOG liquefaction. Considering system configurations, two ejectors depending on the motive pressure were initially designed by applying a theoretical method. A new optimization method with a modification procedure including maximizing the entrainment ratio in relation to key parameters and resizing to satisfy the requirements was applied to the initial ejector designs with validated CFD methodology. After the modification procedure, the entrainment ratios were enhanced up to 101% compared to before. The results showed that the designed ejectors achieved the liquefaction effectiveness of 10.3, which is close to that of a commercial one. Additionally, the performance characteristics for various off-design BOG conditions based on the designed ejector were also investigated.

Dynamic performance simulation of combined gas electric and steam power plants for cruise-ferry ships

This work aims at investigating the feasibility of COmbined Gas Electric and Steam (COGES) plants onboard Liquefied Natural Gas (LNG) fueled ships, by means of a novel, flexible tool. Firstly, the nominal operating conditions of 6 commercially available gas turbines (GTs) as well as their dynamic performance are simulated. Secondly, 6 different integrated COGES-reciprocating engine power plants are assembled and compared in terms of cogeneration efficiency within an optimized repowering study for the cruise-ferry ship GNV La Suprema. The optimization accounts for variable ship speed, season and GT control strategy for an overall number of 264 operating conditions considered. Thirdly, the time-dependent performance of the best COGES plant is assessed under actual navigation conditions for La Suprema. Overall, the results show the great potential of combining COGES plants with reciprocating engines for the marine sector. In particular, in the ship speed range centered around the actual cruise speed for La Suprema (i.e. 22 knots), all the COGES plants are able to cover the propulsion and hotel power demands more efficiently than reciprocating engines, with a 1–5 % benefit on cogeneration efficiency. Overall, a 51 % maximum cogeneration efficiency is found to be provided by COGES plants based on LM2500 and TITAN250 gas turbines.

Optimizing ship speed depending on cargo and wind-sea conditions for sustainable blue growth and climate change mitigation.

The impact of fuel consumption on merchant ships is categorized in both economic and environmental ways in terms of sustainable blue growth. Apart from the economic benefits of reducing fuel consumption, attention should be paid to related environmental concerns with ship fuels. As a result of global regulations and agreements concerning mitigating greenhouse gases on board, such as the International Maritime Organization and Paris Agreement, ships have to take a step to reduce fuel consumption to adopt these regulations. The present study aims to determine optimal speed diversity depending on ships' cargo amounts and wind-sea states to reduce fuel consumption. Within this context, one-year voyage data from two model sister Ro-Ro cargo ships were used, including daily ship speed, daily fuel consumption, ballast water consumption, total ship cargo consumption, sea state, and wind state. The genetic algorithm method was used to determine the optimal diversity rate. In conclusion, after speed optimization, optimum speed result values are calculated between 16.59 and 17.29 knots; thus, approximately 18% of exhaust gas emissions were also reduced.

A methodology for risk assessment of LNG carriers accessing vulnerable port areas

The navigation course of Liquefied Natural Gas (LNG) carriers and fueled ships may cross vulnerable areas where commercial, civil, and industrial assets are present. Despite the effort made by scientific community and authorities, there are no consolidated methodologies addressing the risks arising from the interaction between LNG carriers and fueled ships accessing ports and onshore facilities. This work focuses on the development of a simplified methodology for risk assessment of LNG carriers and fueled ships in port areas able to identify accident scenarios involving the ship course and vulnerable targets. The analysis starts verifying the compliance with respect to the port regulations and the feasibility of the course with respect to the channels. Then, based on standard features of LNG carriers and fueled ships, a set of reference accidental scenarios to be considered during the risk assessment is identified. A specific guidance for the identification of hazards, estimation of frequencies and consequences is provided, finally adopting a customized risk matrix to support decision-making on prevention and mitigation measures. The application of the methodology to a real case study dealing with an important Italian harbor, highlights the capability of the method to support land use planning.

A Study on Monitoring and Supervision of Ship Nitrogen-Oxide Emissions and Fuel-Sulfur-Content Compliance

Regulations for the control of air-pollutant emissions from ships within pollutant emission control areas (ECAs) have been issued for several years, but the lack of practical technologies and fundamental theory in the implementation process remains a challenge. In this study, we designed a model to calculate the nitrogen-oxide-emission intensity of ships and the sulfur content of ship fuels using theoretical deduction from the law of the conservation of mass. The reliability and availability of the derived results were empirically evaluated using measurement data for NOx, SO2, and CO2 in the exhaust gas of a demonstration ship in practice. By examining the model and the measured or registered fuel-oil-consumption rates of ships, a compliance-determination workflow for NOx-emission intensity and fuel-sulfur-content monitoring and supervision in on-voyage ships were proposed. The results showed that the ship fuel’s NOx-emission intensity and sulfur content can be evaluated by monitoring the exhaust-gas composition online and used to assist in maritime monitoring and the supervision of pollutant emissions from ships. It is recommended that uncertainties regarding sulfur content should be considered within 15% during monitoring and supervision. The established model and workflow can assist in maritime monitoring. Meanwhile, all related governments and industry-management departments are advised to actively lead the development of monitoring and supervision technology for ship-air-pollutant control in ECAs, as well as strengthening the quality management of ships’ static data.

Tracking Liquefied Natural Gas Fuelled Ship’s Emissions via Formaldehyde Deposition in Marine Boundary Layer

One of the reasons that anthropogenic greenhouse gas emissions estimation is imprecise is the uncertainty of aerosol impacts on cloud properties. Maritime transportation is slowly changing fuel preferences. With the policy framework changing regulations, the shipping business is going in a direction that emits less sulfur dioxide and black carbon, which are the compounds that cause linear cloud formations known as ship tracks. Aside from their effects on the total radiative forcing of a transportation mean, this phenomenon enables the detection of ships via satellite imagery sensors. The rapidly increasing trend of shifting propulsion of maritime transportation from conventional heavy fuel oil and distillate marine fuels to liquefied natural gas causes enormous hikes in methane emissions. Therefore, oxidation of the volatile organic compound in the marine boundary layer by the hydroxyl radical in the troposphere makes significant deposition of formaldehyde which causes human effects, ecosystem damage, and climate impact. The primary triggering substance among the compounds in the ship plume is methane. This paper discusses methods to assess near real time tracking of anomalies and the deposition of the short lived substance in different seasons in one of the main occurring areas, shipping corridors. The study also employs anomaly map analysis for June and December 2010 and 2020. Several global tracking methods are available with satellites, monitoring experiments, and other satellite tracking tools. Apart from a few areas the results are not indicative since the formaldehyde formations caused by LNG fueled ships are not widespread enough alongside with overall LNG fueled fleet. On the other hand, the analysis and method are promising for the follow-up of the emissions in the future.

A Study on the Enhanced Process of Elaborate Heat Source Model Parameters for Flux Core Arc Welding of 9% Nickel Steel for Cryogenic Storage Tank

Various regulations are being devised and implemented to prevent the environmental pollution that is threatening mankind. The International Maritime Organization has strengthened regulations on sulfur, a notorious pollutant, to prevent sea pollution. In addition, the production of LNG fueled ships is increasing. Among various metals, 9% nickel steel is widely used in the shipbuilding industry because it is advantageous in terms of material strength and cryogenic impact toughness. Various studies are being carried out to predict and prevent its distortion, caused by welding, in the design. To predict welding distortion during flux core arc welding, this study found a way to refine the parameters constituting the Goldak welding heat source. The optimal heat source parameters were derived by using BOP experiments, cross-sectional analysis, finite element analysis and global optimization algorithm. When re-analyzed and verified based on the values, an error of up to 6.3% was found between simulation results and experimental values. The process was improved by clarifying the objective function and reducing the range of candidate welding efficiencies during global optimization and the process efficiency was also improved by reducing analysis time with a simplified model. Therefore, it is thought that this study can contribute to the productivity improvement of LNG storage containers, helping engineers apply it immediately in the industrial field.

Thermodynamic analysis and assessment of novel ORC- DEC integrated PEMFC system for liquid hydrogen fueled ship application

Proton-exchange membrane fuel cell (PEMFC) and liquid hydrogen are gaining attention as a power generation system and alternative fuel of ship. This study proposes a novel PEMFC system, integrated with the organic Rankine cycle–direct expansion cycle (ORC-DEC), which exploits cold exergy from liquid hydrogen and low temperature waste heat generated by the PEMFC for application in a liquid hydrogen fueled ship. A thermodynamic model of each subsystem was established and analyzed from the economic, energy, and exergy viewpoints. Moreover, parametric analysis was performed to identify the effects of certain key parameters, such as the working fluid in the ORC, pressure exerted by the fuel pump, cooling water temperature of the PEMFC, and the stack current density on the system performance. The results showed that the proposed system could generate 221 kW of additional power. The overall system achieved an exergy and energy efficiency of 43.52 and 40.45%, respectively. The PEMFC system had the largest exergy destruction, followed by the cryogenic heat exchanger. Propane showed the best performance among the several investigated ORC working fluids and the system performance improved with the increase in the cooling water temperature of the PEMFC. The economic analysis showed that the average payback time of ORC-DEC was 11.2 years and the average net present value (NPV) was $295,268 at liquid hydrogen costing $3 to $7, showing the potential viability of the system.

Top level design and evaluation of advanced low/zero carbon fuel ships power technology

The greenhouse effect has always been a problem troubling various country, many fields have made corresponding technological improvements and regulations, and the shipping industry is no exception. In the shipping field, governments are actively looking for viable low-carbon/zero-carbon alternative fuels to reduce their dependence on traditional fossil fuels. This paper discusses the challenges and opportunities of replacing fuel oil with clean energies. Firstly, the alternative fuels that have been proposed frequently and widely in recent years are summarized, and their sources, adaptive power systems, and relationships among fuels are systematically summarized. Secondly, when evaluating the advantages and future development trends of each energy, the environmental, economic and safety factors are digitally quantified. Results show that the analysis focuses on the efficiency and economics of carbon reduction. Hydrogen, ammonia and nuclear energy show advantages in environmental quantification factors, while LNG, biofuels and alcohols show benefits in economic quantification factors considering calorific value and fuel price, and LNG and alcohols received high scores in safety assessment. Finally, the study predicts the evolution and development trend of ship fuels in the future, and evaluates the most suitable energy for ship development in different periods.

Transient performance study of high pressure fuel gas supply system for LNG fueled ships

The transient performance of the fuel system is a critical issue for the operation of liquefied natural gas (LNG) fueled ships. In this paper, experiments and simulations of a high pressure fuel gas supply system (HP-FGSS) were conducted to investigate the system transient responses during load variations and environmental disturbances. A prototype of the HP-FGSS was tested at different running loads from 0% to 110% in combination with a MAN high pressure two-stroke dual fuel engine. A dynamic model of the HP-FGSS was developed and validated by the test data. The effects of the operating parameters and equipment sizes on the system performances were simulated and analyzed. The results show that during the load variations from 75% to 100% the fuel gas pressure fluctuation is nearly 10 bar and lasts for 5 min. The HP-FGSS control system has a high robustness to the LNG composition, but the pressure overshoot increases as the methane content decreases. The LNG composition will also affect the steady state value of the gas temperature. The buffer tank volume has a significant impact on the pressure response. The pressure disturbance in the LNG tank induced by violent sloshing will be transmitted to the suction port of the high pressure pump, causing a cavitation risk.

Environmental Life-Cycle Assessment of Eco-Friendly Alternative Ship Fuels (MGO, LNG, and Hydrogen) for 170 GT Nearshore Ferry

With increasing concerns about environmental pollution, the shipping industry has been considering various fuels as alternative power sources. This paper presents a study of the holistic environmental impacts of eco-friendly alternative ship fuels of marine gas oil (MGO), liquefied natural gas (LNG), and hydrogen across each of their life cycles, from their production to the operation of the ship. The environmental impacts of the fuels were estimated by life-cycle assessment (LCA) analysis in the categories of well-to-tank, tank-to-wake, and well-to-wake phases. The LCA analysis was targeted for a 170 gross tonnage (GT) nearshore ferry operating in the ROK, which was conceptually designed in the study to be equipped with the hydrogen fuel cell propulsion system. The environmental impact performance was presented with comparisons for the terms of global warming potential (GWP), acidification potential (AP), photochemical ozone creation potential (POCP), eutrophication potential (EP), and particulate matter (PM). The results showed that the hydrogen showed the highest GWP level during its life cycle due to the large amount of emissions in the hydrogen generation process through the steam methane reforming (SMR) method. The paper concludes with suggestions of an alternative fuel for the nearshore ferry and its production method based on the results of the study.

Optimal site selection for the remote-monitoring sulfur content of ship fuels in ports

The remote monitoring method based on air-quality monitoring sensors is a common way to monitor the FSC (fuel sulfur content) of oils for ships. Considering the influences of geographical environments, atmospheric conditions, regional ship traffic flow, emission characteristics of ships, and height of monitoring sensors on the monitor station chosen, a new method was proposed to optimize the site selection for monitoring the FSC of fuel oils used by ships in waters of the port. SO2 numeric simulation and observation from sensors were integrated to estimate the FSCs. The proposed method was utilized to recommend the sites of the fixed sniffing monitoring stations in Yantian port, Shenzhen, China from June and July 2018. The results showed that the experimental stations could monitor FSCs, and the relative difference between the estimated and actual FSCs of ships was 16.34%. The proposed method for recommending sites of FSC monitoring sensors contributed to intelligently supervising air pollutants emitted from ships and fuel oils of ships in the emission control areas of China.

Advanced design and analysis of BOG treatment process in LNG fueled ship combined with cold energy utilization from LNG gasification

The use of re-gasified liquefied natural gas (LNG) and boil-off gas (BOG) as a fuel in LNG fueled ships generally results in a waste of cold energy. Meanwhile, when the ship is docked, BOG should be re-liquefied to minimize the LNG loss using external energy. To efficiently utilize wasted cold energy, a novel BOG treatment concept combined with air liquefaction is proposed and a new process for recovering cold energy of BOG and fueled LNG is designed and analyzed in this paper. The system is divided into three sections: the BOG and LNG regasification into the fuel gas supply system (FGSS), liquid air energy storage and liquid air energy release. The proposed system is analyzed in three ways: energy analysis by the first law of thermodynamics, heat exchanging analysis by the heat flow, and exergy analysis by the second law of thermodynamics. The energy efficiency of the BOG and LNG gasification into the FGSS, air storage and air release sections are 34.2%, 93.4%, and 52.3%, respectively. The overall heat exchange efficiency is 42.28% and the exergy efficiency is 30.4%. The economic analysis of the system is investigated on the lifecycle of 20 years. This study not only combines the BOG treatment process and the FGSS of the LNG ship but also reduces the energy consumption of the system onboard.

Retrofitting towards a greener marine shipping future: Reassembling ship fuels and liquefied natural gas in Norway

The reduction of greenhouse gas emissions has entered regulatory agendas in shipping. In Norway, a debate has been ongoing for over a decade about whether liquefied natural gas (LNG) ship fuel enables or impedes the transition to a greener future for shipping. This paper explores the assembling of ship fuel before and after the introduction of a controversial carbon tax on LNG. It reconstructs how changes in the regulatory apparatus prompted the reworking of natural gas into a ship fuel, yet later slowed down the development of LNG in a strategy to promote alternative zero-emission fuels such as hydrogen. Following ship fuel as socio-materiality in motion, we find that fossil fuels are reworked into new modes of application as part of transition policies. Natural gas continues to be enacted as an “enabler of transition” in the context of shipping, given that current government policies work to support the production of hydrogen from natural gas and carbon capture and storage (CCS). New modes of accounting for emissions reassemble existing fossil fuel materiality by means of CCS and fossil-based zero-emission fuels. We examine retrofit as a particular kind of reassembling and as a prism for studying the politics of fuel and the relation between transitions and existing infrastructures.

Conceptual design and assessment of a novel energy management system for LNG fueled ships with air separation

Medium and large ships always need to carry many different types of gas cylinders. Limited by the hull, their gas storage is small, restricting the ship's ocean voyage time. It is the most effective solution to use the air separation device and cabin air to prepare various purified gases on site. However, the traditional cryogenic air separation system has large energy consumption and low efficiency, which is not suitable for shipboard use. Therefore, this paper innovatively proposes the air separation systems for the cold energy utilization of onboard LNG-powered ships. According to the characteristics of ship engine power and pressure ratio change of LNG fuel supply system, LNG energy management systems (LNGEMSs) with high and low pressure matching cold energy utilization air separation unit processes are proposed and compared. The exergetic analysis model of the design was established using pinch point analysis, energy balance methods, and energy efficiency indexes. The applicability conclusion was determined through actual onshore process verification, comparison, and exergy analysis. The cryogenic air separation system on LNG fueled ships can adopt a different pressures heat exchange network solution to make full use of LNG cold energy to improve energy efficiency. The LNG cold exergy efficiency of the LNGEMSs can reach 83.2%, and the unit liquid product energy consumption is only 0.225 kWh·Nm−1. Due to the additional means of energy conversion and utilization, the ship design and operating indexes with the new system meet or exceed the current regulations and the current technical level. Additional oxygen obtained by air separation can further improve the combustion efficiency of marine gas turbines, which brings good prospects for marine air separation technology.

Modeling, simulation and analysis of tank thermodynamic behaviors during no-vent LNG bunkering operations

The bunkering process is an important issue of the operation of liquefied natural gas (LNG) fueled ships. In this paper, an analytical model was developed to predict and investigate the thermodynamic behaviors of marine LNG fuel tanks during no-vent bunkering operations. The complex heat and mass transfer phenomena inside the cryogenic tanks were considered and modeled. A spray droplet model was developed to quantitatively evaluate the vapor condensation and cooling effect in the tank during top spray filling. The validity of the model was confirmed by the measured data on a Norwegian car ferry. The results show that the vapor condensation and cooling at the droplet-vapor interface dominate the top spray filling process, while the vapor compression dominates the bottom filling process. The impact of vapor condensation on the tank pressure during top spray filling is around 2.6 times as large as the vapor cooling. Furthermore, parametric study reveals that the bunkering performance is very sensitive to the LNG supply temperature and droplet diameter.

Demand Forecasting for Liquified Natural Gas Bunkering by Country and Region Using Meta-Analysis and Artificial Intelligence

Ship exhaust emission is the main cause of coastal air pollution, leading to premature death from cardiovascular cancer and lung cancer. In light of public health and climate change concerns, the International Maritime Organization (IMO) and several governments are reinforcing policies to use clean ship fuels. In January 2020, the IMO reduced the acceptable sulfur content in ship fuel to 0.5% m/m (mass/mass) for sustainability. The use of liquified natural gas (LNG) as a ship fuel is currently the most likely measure to meet this regulation, and LNG bunkering infrastructure investment and network planning are underway worldwide. Therefore, the aim of this study is to predict the LNG bunkering demand for investment and planning. So far, however, there has been little quantitative analysis of LNG bunkering demand prediction. In this study, first, the global LNG bunkering demand was predicted using meta-regression analysis. Global demand for LNG bunkering is forecast to increase from 16.6 million tons in 2025 to 53.2 million tons in 2040. Second, LNG bunkering prediction by country and region was performed through analogy and artificial intelligence methods. The information and insights gained from this study may facilitate policy implementation and investments.