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Hydrogen and Ammonia for the Decarbonization of Shipping
Abstract
Maritime transportation is the most efficient transportation type. Despite, maritime transportation is an effective way to transport goods and passengers, fossil fuels are still in use. Ammonia and hydrogen are promising alternative fuels for the complete decarbonization of maritime transportation with their zero-carbon content and they are also suitable fuels for fuel cells. In this study, ammonia and hydrogen were compared by using safety, cost, commercial constraint, sustainability, and environmental impact criteria to find which one is the best possible fuel option for fuel cells in terms of use for the shipping industry.
... The literature studies and applications on machinery systems mainly focus on alternative fuels and prime movers (Inal et al. 2021), carbon capture and storage (Güler and Ergin 2021), waste heat recovery (Akman and Ergin 2019) and emission control systems. Moreover, hull form optimization, trim and ballast optimization, slow steaming and planned and timely maintenance are the available design and operational measures for decarbonization and energy-efficient shipping, respectively (Akman and Ergin 2021). ...
... Moreover, hull form optimization, trim and ballast optimization, slow steaming and planned and timely maintenance are the available design and operational measures for decarbonization and energy-efficient shipping, respectively (Akman and Ergin 2021). In this study, the main and auxiliary engines of in-service 20 Bodrum Gulets with different lengths are analysed and the hull forms of these yachts are modelled for resistance calculations at service and design speeds using the Holtrop-Mennen method (Holtrop and Mennen 1982). The design power requirements (MAN 2013) are determined and the engine load factors are calculated to compare the actual data for the environmental impact evaluation. ...
... where c 1 , c 2 , c 3 , m 1 , m 2 and λ are the coefficients related to the form of the hull (Holtrop and Mennen 1982). F n is the Froude number depending on the velocity and length of the yacht. ...
... Ammonia has many usages, but with around 80% of annual ammonia production accounts for the use as agricultural fertilizers [97]. Ammonia is also an important feedstock for the synthesis of some chemicals such as plastics, synthetic fibers and resins, refrigerants and explosives [98]. Like methanol, it can be used as a synthetic fuel in diesel or internal combustion engines and gas turbines [99] and considered as a chemical storage medium for renewable energy [100]. ...
Renewable power-to-fuel (PtF) is a key technology for the transition towards fossil-free energy systems. The production of carbon neutral synthetic fuels is primarily driven by the need to decouple the energy sector from fossil fuels dependance which are the main source of environmental issues. Hydrogen (H 2) produced from water electrolysis powered by renewable electricity and direct carbon dioxide (CO 2) captured from the flue gas generated by power plants, industry, transportation, and biogas production from anaerobic digestion, are used to convert electricity into carbon-neutral synthetic fuels. These fuels function as effective energy carriers that can be stored, transported, and used in other energy sectors (transport and industry). In addition, the PtF concept is an energy transformation that is capable of providing services for the balancing of the electricity grid thanks to its adaptable operation and long-term storage capacities for renewable energy surplus. As a consequence, it helps to potentially decarbonize the energy sector by reducing the carbon footprint and GHG emissions. This paper gives an overview on recent advances of renewable PtF technology for the e-production of three main hydrogen-based synthetic fuels that could substitute fossil fuels such as power-to-methane (PtCH 4), power-Please cite this article as: Nemmour A et al., Green hydrogen-based E-fuels (E-methane, E-methanol, E-ammonia) to support clean energy transition: A literature review, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2023.03.240 to-methanol (PtCH 3 OH) and power-to-ammonia (PtNH 3). The first objective is to thoroughly define in a clear manner the framework which includes the PtF technologies. Attention is given to green H 2 production by water electrolysis, carbon capture & storage (CCS), CO 2 hydrogenation, Sabatier, and Haber Bosch processes. The second objective is to gather and classify some existing projects which deal with this technology depending on the e-fuel produced (energy input, conversion process, efficiency, fuel produced, and application). Furthermore, the challenges and future prospects of achieving sustainable large-scale PtF applications are discussed.
... The total demand for hydrogen in Europe was estimated at 8.6 Mt in 2020 [66]. The Table 2. Global Warming Potential indicators for the 100-year horizon [65,[76][77][78][79][80][81][82]. ...
To reduce pollution from ships in coastal and international navigation, shipping companies are turning to various technological solutions, mostly based on electrification and the use of alternative fuels with a lower carbon footprint. One of the alternatives to traditional diesel fuel is the use of hydrogen as a fuel or hydrogen fuel cells as a power source. Their application on ships is still in the experimental phase and is limited to smaller ships, which serve as a kind of platform for evaluating the applicability of different technological solutions. However, the use of hydrogen on a large scale as a primary energy source on coastal and ocean-going vessels also requires an infrastructure for the production and safe storage of hydrogen. This paper provides an overview of color-based hydrogen classification as one of the main methods for describing hydrogen types based on currently available production technologies, as well as the principles and safety aspects of hydrogen storage. The advantages and disadvantages of the production technologies with respect to their application in the maritime sector are discussed. Problems and obstacles that must be overcome for the successful use of hydrogen as a fuel on ships are also identified. The issues presented can be used to determine long-term indicators of the global warming potential of using hydrogen as a fuel in the shipping industry and to select an appropriate cost-effective and environmentally sustainable production and storage method in light of the technological capabilities and resources of a particular area.
... The second approach is the marine alternative fuels. Currently, methanol, biodiesel, ammonia, biogas, hydrogen, and LPG can be accepted as promising marine alternative fuels owing to their energy capacity [25][26][27][28]. Methanol as being the simplest alcohol can be obtained from natural gas, coal, and different agricultural products [29]. ...
Increasing environmental concerns are driving the shipping industry to take strict measures to deal with greenhouse gas emissions. International Maritime Organization drives the industry to find more efficient and environmentally friendly power systems. To mitigate harmful emissions, researches on marine alternative fuels, operational improvements like slow steaming or predictive maintenance, and additional emission abatement technologies are not sufficient. The use of electricity as the main energy vector is one of the ways to improve the shipping propulsion system's efficiency. In this study, power generation technologies, energy storage components , energy management systems, and hybrid propulsion topologies are reviewed. Diesel engines, fuel cells, solar and wind power as renewable energy sources are discussed as power generation units. On the energy storage side, batteries, supercapacitors, and flywheels are presented and described. Three common hybrid propulsion configurations, serial, parallel, and serial-parallel architectures are detailed with their pros and cons by highlighting commonly used energy management systems and optimization methods. Lastly, criteria for hybrid system selection are defined according to eight different ship types and assessed by providing a generic methodological approach. It is shown that electrical components and architectural design should be elaborated according to operational and architectural characteristics for ships. In short term, it is concluded that internal combustion engines are still the major hybridization element with different energy storage systems. New regulations on the mitigation of harmful emissions will accelerate the transition to hybrid power which is an important option for the ultimate zero-carbon shipping goal.
The growth of the global shipping industry has increased the interest in the environmental impact of this sector. The International Maritime Organization adopted the initial Greenhouse Gas strategy for reducing GHG emissions from ships at the 72nd Marine Environment Protection Committee in April 2018. In this study, we carried out a life cycle assessment of nine production pathways of alternative fuels, including LNG, ammonia, methanol, and biofuels, and conducted an economic analysis considering the life cycle carbon pricing of each fuel pathway. Our results indicate that biomass-based FT-diesel, e-methanol, and e-ammonia are the most environmentally friendly, with GHG reductions of 92%, 88.2%, and 86.6%, respectively. However, our net present value analysis of ship life cycle cost considering carbon price indicated that using those fuels would not be cost-effective during the target period of study. Sensitivity analysis was performed by changing the life cycle carbon pricing from the baseline scenario, and we investigated the approximate years for when these alternative fuels will become more cost-effective compared to conventional fossil fuels. Further, to provide practical implications for shipping stakeholders, we analysed the effect of blending the same kinds of fuels with different production pathways.
The selection of main and auxiliary engines is a substantial design phase for powering ships. Considering the economic concerns and environmental measures, high-efficient, low-emission and suitable engines should be selected, installed and operated on onboard ships. In this study, the main and auxiliary engines of active 20 Bodrum Gulets are analysed and the hull forms of these yachts are modelled for resistance and power calculations. Holtrop-Mennen method is used for obtaining the total resistance of the selected yachts, and the design power requirements are compared with those of the actual data for environmental impact evaluation. Finally, the solutions to increase the energy efficiency of yachts are offered from the design perspective. According to the results, it is revealed that most of the yachts have larger engines causing higher fuel consumption and pollutant emissions compared to the design data. Considering the efficient engine operating conditions, the load factors of main engines operated in some yachts are very low or very high causing up to 6% higher fuel consumption compared to the data supplied by the engine manufacturers.KeywordsEnergy efficiencyYacht designBodrum GuletEmissionEnvironmental impact
Maritime transportation has drawn international attention due to the gradual rise and projected growth of Greenhouse Gas (GHG) emissions resulting from fossil fuel consumption. It is alarming that the overall maritime transportation emissions are neither attended to nor mainstreamed under the transportation sector. The actual national inventory of GHG emissions vis-à-vis all types/sizes of maritime vessels is so far not established particularly in developing countries, which clearly indicates the inadequacy of their climate mitigation response. Accurate assessment of GHGs is essential to provide reliable input for climate policy, strategies, and decision-making processes by flag states. Therefore, the establishment of a baseline reference scenario by considering all types/sizes of maritime vessels is crucial to know the actual gravity of the problem, which is still unknown. This entailed the need to explore the actual extent of GHG emissions from the maritime transportation sector. In this context, the present study tried to assess the potential GHG emissions from maritime vessels by undertaking the case of Pakistan and using the top-down approach, which took into account fuel consumption and emission factors for GHGs. It revealed that 2,468,789.21 tonnes of GHGs (CO2e) are being emitted annually from the maritime vessels of Pakistan, which is 4.9% of the overall transport sector emissions of the country. Carbon offset cost of 37, 031, 838.14 US$/annum and approximately 20,020 hectares of mature mangrove forest to remove 2,468,789.21 metric tonnes of CO2e emissions from the atmosphere in a timeline of 1 year are required to become carbon neutral. It is anticipated that this study’s outcome will serve as a baseline reference scenario for national GHG inventory and help in devising climate mitigation responses for maritime vessels by bridging the existing knowledge gap.
In this study, the environmental and economic effects of the ammonia-diesel dual-fuel
engine are evaluated by a case study with the real voyage data of a ship. Thirteen scenarios are formed by three different fuel fractions and three different types of ammonia which are classified according to their production routes (brown, blue, and green ammonia). Brown ammonia has worse (137.7%) or slightly lower (3%) CO2 emissions than MDO depending on the feedstock. Blue ammonia complies with the IMO 2030 target with a 42.8% CO2 reduction while green ammonia from solar energy has a similar reduction capacity with blue ammonia, and green ammonia from wind energy provides 79.2% CO2 reduction and complies with the 2050 target. SOX and PM emissions are decreased up to 95% by ammonia usage. NOX emissions are 19.4% lower at 60% ammonia energy fraction than MDO, but it increases 133.1% at 95% ammonia energy fraction. The selective catalytic reduction system is required for high ammonia energy fraction cases. The N2O emission is an important issue during ammonia usage. The fuel expense analyses show that brown ammonia is cheaper and blue ammonia is slightly higher (8.8%e13.9%) than MDO. Green ammonia does not be feasible recently, due to its significantly high price.
The global energy transition has started and the mankind actively looking for new way to replace the fossil fuels based technology. This paradigm change is quite hard to accomplished due the many drawbacks related to a complete rethinking of the engines. So, a solid solution could be represented by the use of oil derived analogue fuels produced using renewable sources known as drop-in fuels. In this field, the thermal conversion of fats has played a main role due the easily conversion in hydrocarbon mixture very close to diesel fraction.
Rapid economic growth, especially in developing countries, directly impacts transport fuel demand, waste generation and greenhouse gas (GHG) emissions. Hence, there is an increasing need to supplement fossil fuel demand with sustainable alternative options while also addressing solid waste and GHG emissions. India generates the highest amount of annual municipal solid waste (MSW) (277 million tonnes out of the global 2.01 billion tonnes); this is estimated to double by 2050. This high MSW generation rate, inadequate management, unscientific landfilling and inefficient disposal practices is a serious concern to health and the environment. The organic fraction of MSW generated in India is estimated to be in the range of 40–60% and contains huge potential fuel value for waste to energy (WtE) options. Owning to the large availability of MSW and its associated environmental and social burdens, MSW for fuel production to support the nations’ sustainability commitments looks attractive, if done scientifically. Considering India as the case study, this chapter reviews the possible routes for converting MSW to useful automobile fuels. Additionally, through life cycle assessment (LCA), this chapter discusses the amount of fossil fuel substitution in the total mobility fuel mix by the MSW derived fuel. LCA evaluation revealed a net 85.03 kg CO2 eq. global warming potential, 0.184 mol H⁺ eq. acidification potential, 7.794 × 10–3 mol of N eq. eutrophication potential and 4.873 CTUh human toxicity potential, respectively, for ethanol production from 1 tonne of organic fraction of MSW. The findings can help assess the MSW utilization in a more scientific way wherein the benefits are assessed in terms of mitigation of GHG and environmental costs averted, in addition to foreign savings through the reduced import of fossil fuels. Few successful pilot projects as case studies will help getting several stakeholders together, which will be essential for taking this waste utilization option to a useful scale.
Carbon emissions are one of the important topics in maritime transportation recently since International Maritime Organization (IMO) implemented stricter regulations. IMO announced Initial Greenhouse Gas (GHG) Strategy in 2018 for decarbonization of maritime transportation. International shipping consumed 300 million tons of high carbon content fossil fuels annually and it is increasing year by year. Maritime transportation constitutes 3.1% of the total global CO2 emissions which depends on the usage of high carbon content fossil fuels. The Initial GHG Strategy aims to reach zero-carbon shipping in the future. One way to achieve this aim is the usage of alternative fuels with zero-carbon content. Ammonia is one of the alternative fuels that can be either used for fuel cells on ships and at marine diesel engines. Ammonia has a carbon-free and sulfur-free structure and it can be combusted by the dual-fuel combustion concept at marine diesel engines as same as other alternative marine fuels. In this chapter, a review study is conducted on ammonia to show its importance for decarbonized maritime transportation. The outcomes of the chapter reveal that although there are some barriers to ammonia as a marine fuel, the existing experience of the maritime industry, supply chains and infrastructures of fertilizer industry, low modification requirement on engines, and achievement of significantly lower CO2 and soot emissions, and almost zero SOX emissions will facilitate the use of ammonia, and it can be one of the options for full decarbonized maritime transportation by 2050.
Shipping is the most energy-efficient way for the transportation of goods and it has a substantial role in the global economy. The vast majority of the ships are addicted to fossil fuels as an energy source due to economic advantages, strong bunkering nets, and well-experienced operations of marine diesel engines. However, environmental concerns drive the industry to take precautions on the ship-sourced greenhouse gas emissions, and the International Maritime Organization (IMO), the ruler of the maritime industry, is bringing strict rules to regulate the emissions under The International Convention for the Prevention of Pollution from Ships—Annex VI (MARPOL). On the way of decarbonization and emission-free shipping, marine alternative fuels may draw a framework for the future of the maritime industry. In this perspective, hydrogen is a promising alternative for maritime transportation with its carbon-free structure. Furthermore, green hydrogen is one of the electrofuels for maritime transportation to solve the issue to achieve full decarbonization. The use of hydrogen for ships is still under investigation at the level of research projects. Therefore, elaboration of the feasibility from different points of view for the commercial fleet is necessary to enlighten the future of the industry. This chapter includes information about the status of maritime transportation, recent international maritime emission rules and regulations, and hydrogen compliance with the International Code of Safety for Ships Using Gas or Other Low-flashpoint Fuels (IGF Code). Furthermore, hydrogen production technologies, onboard hydrogen storage methods, hydrogen combustion concepts on marine diesel engines, and fuel cells are reviewed. Lastly, the conclusion section comprises the chapter discussion.
The high environmental impacts of transport mean that there is an increasing interest in utilising low-carbon alternative energy carriers and powertrains within the sector. While electricity has been mooted as the energy carrier of choice for passenger vehicles, as the mass and range of the vehicle increases, electrification becomes more difficult. This paper reviews the shipping, aviation and haulage sectors, and a range of low-carbon energy carriers (electricity, biofuels, hydrogen, and electrofuels) that can be used to decarbonise them. Energy carriers were assessed based on their energy density, specific energy, cost, lifecycle greenhouse gas emissions, and land-use. In terms of haulage, current battery electric vehicles may be technically feasible, however the specific energy of current battery technology reduces the payload capacity and range when compared to diesel. To alleviate these issues, biomethane represents a mature technology with potential co-benefits, while hydrogen is close to competitiveness but requires significant infrastructure. Energy density issues preclude the use of batteries in shipping which requires energy dense liquids or compressed gaseous fuels that allow for retrofits/current hull designs, with methanol being particularly appropriate here. Future shipping may be achieved with ammonia or hydrogen, but hull design will need to be changed significantly. Regulations and aircraft design mean that commercial aviation is dependent on drop-in jet fuels for the foreseeable future, with power-to-liquid fuels being deemed the most suitable option due to the scales required. Fuel costs and a lack of refuelling infrastructure were identified as key barriers facing the uptake of alternatives, with policy and financial incentives required to encourage the uptake of low-carbon fuels.
Since sea transportation is one of the sources of air pollution and greenhouse gas emissions, so restrictive regulations are entering into force by the International Maritime Organisation to cope with the ship sourced emissions. Alternative energy generating systems are one of the key concepts and fuel cells can be one of the solutions for the future of the shipping industry by their fewer hazardous emissions compared to diesel engines. In this perspective, a Liquefied Natural Gas using molten carbonate fuel cell is evaluated instead of a conventional marine diesel engine for a chemical tanker ship. As a case study, the real navigation data for a tanker is gathered from the shipping company for the 27 voyages in 2018. Emissions are calculated respecting fuel types (marine diesel oil and heavy fuel oil) and designated Emission Control Areas for both diesel engine and fuel cell systems. The results show that more than 99% reduction in SOx, PM, and NOx emissions and a 33% reduction in CO2 emissions can be reached by the fuel cell system. At last, fuel cells seem very promising technologies especially for limited powered vessels under 5 MW for propulsion to use as main engines by complying with current and new coming emission limitations on the way of emission free shipping.
The paper focuses on the analysis of innovative energy systems onboard ships with the aim to evaluate, in a preliminary stage, which can be the most promising solution depending on the considered application. For this purpose, the dedicated tool HELM developed by the authors’ research group is employed. The tool uses maps reporting the main indicators (weight, volume, costs and emissions) for each component in relation to the installed power and the operational hours required (given by the user as an input), then it compares the results providing the best solution depending on the considered application. The maps have been built from a database developed throughout a wide analysis of the available market solutions in terms of energy generation devices (i.e. fuel cells, internal combustion engines), fuels (hydrogen, natural gas, diesel, methanol) and related storage technologies. The main strong point of HELM resides in its flexibility: it can be used for different typologies and sizes of ships (e.g. ferry boat, cruises, yachts); moreover, the database can be easily updated with more technologies. In this work, the focus is particularly on hydrogen application with PEM Fuel Cells and the use of innovative fuels (methanol, ammonia) in Internal Combustion Engines. Analysing different applications, it will be highlighted how the specific characteristics and priorities of the application affect the results of the best solutions. Furthermore, considering the regulation roadmap for the next years in the maritime context, promising technologies are highlighted also for future scenarios.
Maritime transportation is the major transportation type in the world and almost all of the ships have consumed conventional fossil fuels which result in shipboard emissions. International Maritime Organization (IMO) has implemented stringent emission rules and regulations to control and mitigate shipboard emissions. Besides, IMO has a decarbonisation strategy in maritime transportation. To cope with the stringent emission regulations and reach to the IMO Greenhouse Gas (GHG) Strategy targets, the ships have to be equipped with emission mitigation systems or have to use alternative fuels. Ammonia is one of the promising alternative fuels for maritime transportation recently. It is a carbon-free and sulphur-free alternative fuel that complies with IMO CO 2 regulations, IMO GHG Strategy, and IMO Sulphur Cap. This study focuses on a short review of ammonia as an alternative fuel for maritime transportation. The important ammonia properties were mentioned, previous ammonia studies on diesel engines were explained, and a discussion about ammonia as a marine alternative fuel was done in the study. Although the ammonia combustion has issues of high NO X emission, N 2 O emission, and ammonia slip, these issues are eliminated by optimum combustion strategies and after-treatment systems, and ammonia has a future in maritime transportation.
On 13 April 2018, the International Maritime Organization (IMO) published an initial strategy on reduction of greenhouse gas (GHG) emissions from ships. The ambitious vision of this strategy is to reduce the total annual GHG emissions from international shipping by at least 50% by 2050 compared to 2008. One of the solutions to achieve this vision is to operate vessels on alternative marine fuels that generate less or no GHG emissions, like liquefied natural gas (LNG), hydrogen, ammonia, methanol, ethanol, biofuel, synthetic fuel, electricity (produced by battery), and so on.
The challenge is that each alternative fuel has its own characteristic on various aspects. For instance, some alternative fuels may generate no GHG emission but can have higher risk than conventional marine fuel. Other alternative fuels may generate no GHG emission with relatively low risk, but the capital and/or operational expenditure can be significantly higher than other fuels.
The main objective of this paper is to explore the properties of selected alternative marine fuels and to emphasize the necessity of integrated evaluation of them. It is concluded that the alternative marine fuels need to be comprehensively evaluated with respect to environmental impact, risk to human, and business value.
To reach the International Maritime Organization, IMO, vision of a 50% greenhouse gas (GHG) emission reduction by 2050, there is a need for action. Good decision support is needed for decisions on fuel and energy conversion systems due to the complexity. This paper aims to get an overview of the criteria types included in present assessments of future marine fuels, to evaluate these and to highlight the most important criteria. This is done using a literature review of selected scientific articles and reports and the authors’ own insights from assessing marine fuels. There are different views regarding the goal of fuel change, what fuel names to use as well as regarding the criteria to assess, which therefore vary in the literature. Quite a few articles and reports include a comparison of several alternative fuels. To promote a transition to fuels with significant GHG reduction potential, it is crucial to apply a life cycle perspective and to assess fuel options in a multicriteria perspective. The recommended minimum set of criteria to consider when evaluating future marine fuels differ somewhat between fuels that can be used in existing ships and fuels that can be used in new types of propulsion systems.
The shipping industry is becoming increasingly aware of its environmental responsibilities in the long-term. In 2018, the International Maritime Organization (IMO) pledged to reduce greenhouse gas (GHG) emissions by at least 50% by the year 2050 as compared with a baseline value from 2008. Ammonia has been regarded as one of the potential carbon-free fuels for ships based on these environmental issues. In this paper, we propose four propulsion systems for a 2500 Twenty-foot Equivalent Unit (TEU) container feeder ship. All of the proposed systems are fueled by ammonia; however, different power systems are used: main engine, generators, polymer electrolyte membrane fuel cell (PEMFC), and solid oxide fuel cell (SOFC). Further, these systems are compared to the conventional main engine propulsion system that is fueled by heavy fuel oil, with a focus on the economic and environmental perspectives. By comparing the conventional and proposed systems, it is shown that ammonia can be a carbon-free fuel for ships. Moreover, among the proposed systems, the SOFC power system is the most eco-friendly alternative (up to 92.1%), even though it requires a high lifecycle cost than the others. Although this study has some limitations and assumptions, the results indicate a meaningful approach toward solving GHG problems in the maritime industry.
There is a need for alternative marine fuels in order to reduce the environmental and climate impacts of shipping, in the short and long term. This study assesses the prospects for seven alternative fuels for the shipping sector in 2030, including biofuels, by applying a multi-criteria decision analysis approach that is based on the estimated fuel performance and on input from a panel of maritime stakeholders and by considering, explicitly, the influence of stakeholder preferences. Seven alternative marine fuels—liquefied natural gas (LNG), liquefied biogas (LBG), methanol from natural gas, renewable methanol, hydrogen for fuel cells produced from (i) natural gas or (ii) electrolysis based on renewable electricity, and hydrotreated vegetable oil (HVO)—and heavy fuel oil (HFO) as benchmark are included and ranked by ten performance criteria and their relative importance. The criteria cover economic, environmental, technical, and social aspects. Stakeholder group preferences (i.e., the relative importance groups assign to the criteria) influence the ranking of these options. For ship-owners, fuel producers, and engine manufacturers, economic criteria, in particular the fuel price, are the most important. These groups rank LNG and HFO the highest, followed by fossil methanol, and then various biofuels (LBG, renewable methanol, and HVO). Meanwhile, representatives from Swedish government authorities prioritize environmental criteria, specifically GHG emissions, and social criteria, specifically the potential to meet regulations, ranking renewable hydrogen the highest, followed by renewable methanol, and then HVO. Policy initiatives are needed to promote the introduction of renewable marine fuels.
The paper explores “green ammonia” as a potential fuel to decarbonise international shipping. It can be synthesised from renewable electricity, water and air.
In this paper applicability of eleven hydrogen production methods for shipboard use is investigated. Various criterions including safety, applicability to ships, feedstock need, maturity, reliability, efficiency, and hydrogen production cost of the systems are used for evaluation. Alkaline electrolysis and polymer electrolyte membrane electrolysis gets the highest evaluation points with 25. Polymer electrolyte membrane electrolysis has electrolyser material, low capacity, and hydrogen production continuity problems, for this reason it is not commercial for now. As a result alkaline electrolysis is the most applicable method for shipboard hydrogen production with its maturity and reliability.
Within the context of achieving low carbon shipping by 2050, high hopes are placed on alternative marine fuels in addition to a large number of technological and operational measures. A technological review has been carried out in this paper to determine the most promising alternative marine fuels considering the simultaneous reduction of sulphur oxides, nitrogen oxides and carbon dioxide emissions as well as sustainability. Firstly, potential alternative marine fuel options have been summarized based on a review of published literature. Then, key physicochemical properties, feedstocks, production processes, transportation and storage factors, and end uses of zero carbon or carbon-neutral fuels have been analysed. Finally, a qualitative ranking of the potential of different marine fuel options is presented based on a multi-dimensional decision-making framework. It was found that zero carbon synthetic fuels including hydrogen and ammonia accompanied by clean production could play a vital role in domestic and short sea shipping, though current costs and infrastructure are not commercially feasible. Methanol (fossil/renewable) appears likely to be the most promising alternative fuel for global shipping instead of other carbon-neutral biofuels such as renewable natural gas, bioethanol, biogenic dimethyl ether and biodiesels, which may be feasible for domestic and short sea shipping depending on local practices. It should be highlighted that marine fuel substitution is a prolonged process. Accordingly, consensus-building and action-adopting in the maritime community as early as possible is important to anchor expectations and achieve the goals of clean maritime transportation.
Ammonia and hydrogen carry great potential as carbon-free fuels with promising applications in energy systems. Hydrogen, in particular, has been generating massive expectations as a carbon-free economy enabler, but issues related to storage, distribution, and infrastructure deployment are delaying its full implementation. Ammonia, on the other hand, stands as a highly efficient energy vector delivering high energy density and an established and flexible infrastructure capable of mitigating hydrogen’s key drawbacks. This mature infrastructure together with the possibility of producing ammonia through renewable energy sources triggered an exploring route to the transition of ammonia as the next sustainable fuel solution for power generation. In this regard, the transportation sector as one of the main culprits for carbon emissions can benefit from ammonia-powered internal combustion engines. However, the use of pure ammonia as fuel still presents important constraints leading researchers to develop strategies such as dual-fuel concepts or novel combustion approaches. Therefore, this review covers these issues by delving into the underpinning mechanisms required for developing pure ammonia combustion in internal combustion engines. To do so, fundamentals, technical, environmental, and economic aspects associated with the use of ammonia as a transportation fuel are broadly addressed. While the emphasis is given to pure ammonia and ammonia fuel blends operation, NOx emissions control, current challenges related to the detailed and accurate understanding of the ammonia chemistry, and the lack of high-fidelity numerical models are also deeply discussed on their role into aiding the commercial deployment of this technology.
Decarbonization of the maritime transportation fuels is a primary objective of the shipping industry. Ammonia is an attractive option because of its relatively low greenhouse gas (GHG) emissions, high energy density, competitive cost, and ubiquitous infrastructure for manufacturing, storage, and distribution. The environmental benefits are enhanced when the manufacture of ammonia is assisted by renewable energy and feedstocks. This paper evaluates the potential usage of ammonia, especially renewable ammonia, as a maritime transportation fuel. The assessment covers manufacturing approaches, energy and feedstock sources, economics, and environmental impact based on well-to-tank and tank-to-propeller bases.
Comparison is also made with conventional fuels that are currently used in the shipping industry. Finally, the paper discusses future directions and impact of technological advances on the potential use of renewable ammonia as a transportation fuel.
This contribution delivers the perspectives of ammonia for a clean energy future and examines the potential, achievements, and associated challenges of ammonia for power generation, with a particular focus on ammonia fuelled solid oxide fuel cells (SOFCs). Ammonia, with characteristics of zero-carbon and a high hydrogen content has been increasingly recognised as a clean fuel. The well-established facilities for ammonia production and infrastructures worldwide for storage and transport provide ammonia with indispensable advantages, underpinning its role in enabling a clean energy future. Ammonia can be decomposed into hydrogen and nitrogen free of carbon emission using an appropriate catalyst. Ni-based catalysts are more preferred candidates alternative to Ru-based catalysts with respect to cost and sources. A rational design of catalyst in terms of preparation method, support and promoter is needed to carve out a catalyst that is commercially reliable and affordable. A milestone has been recently achieved using a Ni-based catalyst with long-term stability up to 1000 h. Ammonia also shows promising potentials for clean electricity generation via SOFCs, exhibiting cell performance comparable to that of the hydrogen fuelled counterparts. However, the cell stability is compromised owing to anode degradation, which is primarily attributed to the formation of nickel nitride incurring microstructural deformations in the anode. Feeding SOFCs with pre-decomposed ammonia is then identified to effectively mitigate the nitridation reactions between ammonia and nickel. In such a manner, only a gas mixture consisted of H2 and N2 is fed into the SOFCs, eliminating the reactions of ammonia and the anode.
Ammonia is considered a key energy carrier with potential applications for low carbon energy storage, transportation and power generation. This carbon-free molecule offers several advantages, including high energy density and a well-established production and distribution infrastructure that have been optimized for over a century. In this perspective, we analyze the potential roles of ammonia as an energy carrier, and summarize research areas requiring further development for the implementation of ammonia as a building block in the global low-carbon energy landscape. Ammonia technologies are reviewed with an emphasis on current limitations and recent advances. Focus is placed on available technologies for ammonia synthesis, decomposition into COx-free hydrogen and direct use of ammonia for power generation and transportation.
The maritime industry leading organization International Maritime Organization (IMO) is bringing more and more restrictive and effective rules on reducing greenhouse gas and air polluting emissions since the significant portion of the greenhouse gas emissions in the world are caused by commercial vessels. Therefore, an alternative energy source is seeking by maritime industry and fuel cells can play a major role in converting such energy sources into electrical energy. The aim of this study is to compare commercial fuel cell types that can be used in merchant ships and a maximum of 5 MW main engine power is considered due to the limited power output of fuel cells. The environmental and economical performances of fuel cell types were compared and criterions’ weightings were found according to expert points using the analytic hierarchy process. A final comparison table is formed giving evaluation points for each fuel cell type and weighting for each criterion depending on their importance in the maritime industry. Fuel cells are ranked by eight different criteria and according to experts, safety is the most important criterion and then followed by emissions, efficiency, cost, lifetime, power output, fuel type, and size, respectively. Among seven different fuel cell types; proton exchange membrane, alkaline, phosphoric acid, diesel oil using molten carbonate, liquefied natural gas using molten carbonate, diesel oil using solid oxide and liquefied natural gas using solid oxide fuel cells, the first three places are formed by diesel oil using molten carbonate fuel cell, proton exchange membrane fuel cell and diesel oil using solid oxide fuel cell which are received 4.053, 4.044 and 3.969 respectively from the total point 5.000. As a result, diesel oil using molten carbonate fuel cell, which takes place with a slight margin from proton exchange membrane fuel cell, has been found as the most suitable fuel cell type for ships. This study highlights that despite strict emission regulations, as a fuel, diesel oil is still a strong fuel option for ships with different energy conversion units like fuel cells.
In this paper, we describe pathways for the Danish maritime cargo sector to achiev CO2e (equivalent) neutrality by 2050 in compliance with the Paris Agreement. In the approach of our model, we not only include national greenhouse gas emissions, but also suggest a method for assigning greenhouse gas emissions from international shipping to countries. Our modelling results indicate either that strong regulatory carbon budgets or a carbon price of at most 350–450 €2016/t CO2e would be necessary to induce this urgently needed transition. This would double today's average cargo transport costs, while increasing average import values by only 6–8%. Regarding fuel technologies, hydrogen, methanol and ammonia are the most suitable from a socio-economic cost perspective, though, due to the high cost uncertainties, there is no clear winner. Liquefied natural gas as an alternative intermediate solution would only have a short window of opportunity, due to methane leakage causing high greenhouse gas emissions as well as high fuel and technology costs. In so far as this gaseous fuel is based on renewable sources it can play a role, but only if methane leakage is drastically reduced. At present battery storage is only an option for short ranges.
Ammonia (NH 3 ) is an excellent hydrogen (H2) carrier that is easy to bulk manufacture, handle, transport, and use. NH 3 is itself combustible and could potentially become a clean transport fuel for direct use in internal combustion engines (ICEs). This technical review examines the current state of knowledge of NH 3 as a fuel in ICEs on its own or in mixtures with other fuels. A particular case of interest is to partially dissociate NH 3 in situ to produce an NH 3 /H2 mixture before injection into the engine cylinders. A key element of the present innovation, the presence of H2 is expected to allow easy control and enhanced performance of NH 3 combustion. The key thermochemical properties of NH 3 are collected and compared to those of conventional and alternative fuels. The basic combustion characteristics and properties of NH 3 and its mixtures with H2 are summarized, providing a theoretical basis for evaluating NH 3 combustion in ICEs. The combustion chemistry and kinetics of NH 3 combustion and mechanisms of NOx formation and destruction are also discussed. The potential applications of NH 3 in conventional ICEs and advanced homogenous charge compression ignition (HCCI) engines are analyzed.
Ammonia synthesized using hydrogen from renewable sources, offers a vast potential for the storage as well as transportation of renewable energy from regions with high intensity to regions lean in renewable sources. Ammonia can be used as an energy vector for an emission-less energy cycle in a variety of ways. Ammonia at the point of end use can be converted to hydrogen for fuel cell vehicles or alternatively utilised directly in solid oxide fuel cells, in an internal combustion engine or a gas turbine. One ton of ammonia production requires 9-15 MWh of energy. However, its conversion back to useful form or direct utilisation can lead to substantial energy losses. In this paper, we present an overview of the current processes and technologies for ammonia synthesis and its utilisation as an energy carrier. We have performed an estimation of the round-trip efficiency of different routes for ammonia utilisation at the point of end use along with some sensitivity analysis and we discuss the outcomes resulting from the best and worst case scenarios.
The use of alternative energy sources instead of HFO has been recognized as a promising way for reducing emissions from shipping and promoting the development of green shipping. However, it is usually difficult for the decision-making to select the best choice among multiple alternative marine fuels. In order to address this, a complete criteria system for sustainability assessment of alternative marine fuels was firstly established, and a fuzzy group multi-criteria decision making method has been developed to rank the alternative marine fuels by combining fuzzy logarithmic least squares and fuzzy TOPSIS (Technique for Order Performance by Similarity to Ideal Solution). Fuzzy logarithmic least squares method has been employed to determine the weights of the criteria for sustainability assessment, and fuzzy TOPSIS was employed to determine the sustainability order of the alternatives. An illustrative case with three alternative marine fuels including methanol, LNG and hydrogen has been studied by the proposed method, and hydrogen has been recognized as the most sustainable scenario, follows by LNG, and methanol in the descending order. The results show that the proposed method is feasible for prioritizing the alternative marine fuels; it also has the ability to help the decision-makers to select the most sustainable option among multiple marine fuels.
The selection of alternative energy sources for shipping can effectively mitigate the problems of high energy consumption and severe environmental problems caused by shipping. However, it is usually difficult for decision makers to select the most sustainable alternative energy source for shipping among multiple alternatives due to the complexity of considering different aspects of performances and the lack of information. This study developed a novel multi-criteria decision-making method that combines Dempster-Shafer theory and a trapezoidal fuzzy analytic hierarchy process for alternative energy source selection under incomplete information conditions. According to the developed method, nuclear power has been recognized as the most sustainable alternative energy source for shipping, followed by liquefied natural gas (LNG) and wind power, and sensitivity analysis reveals that the weights of the criteria have significant on the sustainability sequence of the three alternative energy sources for shipping. The developed method can be popularized for selecting the most sustainable alternative energy source despite incomplete information.
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