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The scope of this paper is to examine proposed e-fuels (e-hydrogen, e-ammonia, e-methanol) as alternative maritime fuels. A techno-economic analysis is conducted considering the current energy demand of the shipping sector, the solutions for decarbonisation that are based on e-fuels, and the projections and scenarios regarding the energy mix towards 2050, to meet the IMO targets. According to the current preliminary study, apart from the barriers related to technological maturity levels, applicability and safety, there are barriers related to (a) the Well-to-Wake characteristics of e-H2, e-NH3, and e-CH3OH, (b) the existing infrastructure that utilises Renewable Energy Sources and the current and projected percentage of RES in the global energy mix, and (c) the availability of resources required for the development of the infrastructure to support e-fuels’ utilisation. Estimated fuel prices in 2050 that include production and distribution costs, indicate that alternative fuels are expected to be uncompetitive. Though they become relatively competitive when carbon-price is added to production and distribution costs of fossil fuels, the Well-to-Wake Analysis of biofuels and e-fuels proves that a significant RES rump-up is required, which further requires huge capital investment costs and raw materials. Ultimately, a re-prioritisation is proposed targeting decarbonisation of “easier-to-abate” sectors before decarbonising “hard-to-abate” sectors such as shipping and aviation.

This review paper examines the applicability of biogas and biomethane as potential maritime fuels and examines issues of these fuels from a supply chain perspective (from production to end use). The objectives are to identify: (1) the latest research, development, and innovation activities; (2) issues and key barriers related to the technology readiness to bring biogas/biomethane to market; and (3) commercialisation issues, including cost parity with natural gas (the main competitor). A survey of the literature was carried out based on research articles and grey literature. The PESTEL and SWOT analyses identified opportunities for these fuels due to the relevant regulations (e.g., Fit for 55; the recent inclusion of the Mediterranean Sea as a SECA and PM control area; MPEC 79), market-based measures, and environmental, social, and governance strategies. The potential of biomass feedstock is estimated to have a substantial value that can satisfy the energy needs of the maritime industry. However, production costs of biomethane are high; estimated to be 2–4 times higher compared to natural gas. The market is moving in the direction of alternative drop-in fuels, including liquefied and compressed biomethane (LBM and CBM) and biogas. In terms of potential market penetration, LBM can be used as a marine drop-in fuel for the existing fleet that already combust LNG and LPG due to similar handling. Currently, these vessels are LNG and LPG tankers. However, in newly built vessels, LBM can be also supplied to container ships, vehicle carriers, and bulk carriers (about 20% of newly built vessels). Provided that compressed natural gas infrastructure exists, CBM can be exploited in vessels with low energy needs and low space requirements and shore-side electrification, because investments in retrofits are lower compared to constructing new infrastructure. [ABSTRACT FROM AUTHOR]

Hydrogen, as a maritime fuel, is one of the solutions that will assist the shipping sector in addressing the challenges regarding decarbonization, taking into consideration the targets set for 2030 and 2050. The extensive utilization of hydrogen requires massive production of green hydrogen and the development of proper infrastructure to support a sustainable supply chain. An alternative solution is based on the on-board production of hydrogen, where production units are installed on-board the vessel. Along these lines, the HYMAR project aims to test the utilization of a hydrogen production unit for on-board use. The article deals with the use of hydrogen as a fuel for internal combustion engines, taking into consideration reports from literature and the preliminary results of the HYMAR project, focusing on the environmental impact and the reduction in emissions. Experimental investigation on a marine auxiliary engine for power generation, under the HYMAR project, leads to promising results regarding the environmental footprint of the internal combustion engine when hydrogen is added in the fuel mix with increasing percentages. [ABSTRACT FROM AUTHOR]

The recent inclusion of shipping in the Fit for 55 legislation package will have large knock-on effects on the industry and consequently on end consumers. The present paper presents an innovative top-down methodology, the MSF455 model, which estimates the new vessel Operational Expenditure (OPEX) as per the provisions of the Fit for 55 package and various scenarios based on carbon tax, penalty allowances, maritime fuel tax and effect. The methodology is presented and tested against six scenarios that are based on Det Norske Veritas's (DNV) fuel maritime projections. The model illustrates that the distinction between intra-EU and extra-EU penalty allowance creates a large disparity and thus reduction in the competitiveness of goods (produced and transported). [ABSTRACT FROM AUTHOR]

Hydrogen supplementation in diesel Compression Ignition (CI) engines is gaining more attention, since it is considered as a feasible solution to tackle the challenges that are related to the emission regulations that will be applied in the forthcoming years. Such a solution is very attractive because it requires only limited modifications to the existing technology of internal combustion CI engines. To this end, numerous work on the investigation of an engine's performance and the effects of emissions when hydrogen is supplied in the engine's cylinders has been completed by researchers. However, contradictory results were found among these studies regarding the efficiency of the engine and the emission characteristics achieved compared to the diesel-only operation. The different conclusions might be attributed to the different characteristics and technology level of the engines that were utilized, as well as on the chosen operational parameters. This paper aims to present an overview of the experimental studies that have examined the effects of hydrogen addition in CI four-stroke diesel engines, reporting the characteristics of the utilized engines, the quantities of hydrogen tested, the method of hydrogen induction used, as well as the operational conditions tested, in order to help interested researchers to easily identify relevant and appropriate studies to perform comparisons or validations by repeating certain cases. The presented data do not include any results or conclusions from these studies. Furthermore, an experimental configuration along with the appropriate modifications on a heavy-duty auxiliary generator-set engine that was recently developed by the authors for the purposes of the HYMAR project is presented. [ABSTRACT FROM AUTHOR]

In the present study, energy and exergy analyses of a simple supercritical, a split supercritical and a cascade supercritical CO2 cycle are conducted. The bottoming cycles are coupled with the main two-stroke diesel engine of a 6800 TEU container ship. An economic analysis is carried out to calculate the total capital cost of these installations. The functional parameters of these cycles are optimized to minimize the electricity production cost (EPC) using a genetic algorithm. Exergo-economic and exergo-environmental analyses are conducted to calculate the cost of the exergetic streams and various exergo-environmental parameters. A parametric analysis is performed for the optimum bottoming cycle to investigate the impact of ambient conditions on the energetic, exergetic, exergo-economic and exergo-environmental key performance indicators. The theoretical results of the integrated analysis showed that the installation and operation of a waste heat recovery optimized split supercritical CO2 cycle in a 6800 TEU container ship can generate almost 2 MW of additional electric power with a thermal efficiency of 14%, leading to high fuel and CO2 emission savings from auxiliary diesel generators and contributing to economically viable shipping decarbonization. [ABSTRACT FROM AUTHOR]

In the present work, the contemporary exhaust gas treatment systems (EGTS) used for SOx, PM, and NOx emission mitigation from shipping are reviewed. Specifically, after-treatment technologies such as wet scrubbers with seawater and freshwater solution with NaOH, hybrid wet scrubbers, wet scrubbers integrated in exhaust gas recirculation (EGR) installations, dry scrubbers, inert gas wet scrubbers and selective catalytic reduction (SCR) systems are analyzed. The operational principles and the construction specifications, the performance characteristics and the investment and operation of the reviewed shipping EGTS are thoroughly elaborated. The SCR technology is comparatively evaluated with alternative techniques such as LNG, internal engine modifications (IEM), direct water injection (DWI) and humid air motor (HAM) to assess the individual NOx emission reduction potential of each technology. Detailed real data for the time several cargo vessels spent in shipyards for seawater scrubber installation, and actual data for the purchase cost and the installation cost of seawater scrubbers in shipyards are demonstrated. From the examination of the constructional, operational, environmental and economic parameters of the examined EGTS, it can be concluded that the most effective SOx emission abatement system is the closed-loop wet scrubbers with NaOH solution which can practically eliminate ship SOx emissions, whereas the most effective NOx emission mitigation system is the SCR which cannot only offer compliance of a vessel with the IMO Tier III limits but can also practically eliminate ship NOx emissions. [ABSTRACT FROM AUTHOR]

This review paper examines the key barriers to using green ammonia as an alternative fuel in maritime industry. A literature survey is performed based on research articles and grey literature, with the aim of discussing the technoeconomic problems with and benefits of ammonia and the relevant technologies. The limitations of ammonia as a maritime fuel and its supply chain, the expected percentage demand by 2030 and 2050, its economic performance compared to other shipping fuels such as hydrogen, and the current regulations that may impact ammonia as a maritime fuel are discussed. There are several key barriers to ammonia's wide adoption: (1) High production costs, due to the high capital costs associated with ammonia's supply chain; (2) availability, specifically the limited geographical locations available for ammonia bunkering; (3) the challenge of ramping up current ammonia production; and (4) the development of ammonia-specific regulations addressing issues such as toxicity, safety, and storage. The general challenges involved with blue ammonia are the large energy penalty and associated operational costs, and a lack of technical expertise on its use. Regardless of the origin, for ammonia to be truly zero-carbon its whole lifecycle must be considered—a key challenge that will aid in the debate about whether ammonia holds promise as a zero-carbon maritime fuel. [ABSTRACT FROM AUTHOR]

This review paper examines the possible pathways and possible technologies available that will help the shipping sector achieve the International Maritime Organization's (IMO) deep decarbonization targets by 2050. There has been increased interest from important stakeholders regarding deep decarbonization, evidenced by market surveys conducted by Shell and Deloitte. However, deep decarbonization will require financial incentives and policies at an international and regional level given the maritime sector's ~3% contribution to green house gas (GHG) emissions. The review paper, based on research articles and grey literature, discusses technoeconomic problems and/or benefits for technologies that will help the shipping sector achieve the IMO's targets. The review presents a discussion on the recent literature regarding alternative fuels (nuclear, hydrogen, ammonia, methanol), renewable energy sources (biofuels, wind, solar), the maturity of technologies (fuel cells, internal combustion engines) as well as technical and operational strategies to reduce fuel consumption for new and existing ships (slow steaming, cleaning and coating, waste heat recovery, hull and propeller design). The IMO's 2050 targets will be achieved via radical technology shift together with the aid of social pressure, financial incentives, regulatory and legislative reforms at the local, regional and international level. [ABSTRACT FROM AUTHOR]

A thermo-economic analysis of a regenerative dual-loop organic Rankine cycle (ORC) is conducted, which will be coupled with the main diesel engines of a general support vessel. An energy and exergy analysis of the regenerative dual-loop ORC is conducted. The energy and exergy analysis results of the regenerative dual-loop ORC are compared with pertinent results for a simple dual-loop ORC without regeneration. A mission analysis that was based on a vessel speed profile with the proposed ORC was conducted. A heat transfer analysis was performed for dimensioning the heat exchangers of both ORC loops. Finally, an economic analysis is conducted to calculate the total capital cost and the payback period of the proposed ORC. The results showed that the proposed ORC is thermodynamically superior in both energetic and exergetic terms compared to the simple dual-loop ORC. The total fuel cost saving is 337,493 Euros, the total CO2 emission saving is 1,153,416.4 kg, and the SO2 emission saving is 36,044.3 kg. The total capital cost of the proposed ORC is 2,546,000 Euros. Finally, the installation of the proposed ORC in the examined vessel is economically feasible because it results in a reasonable payback period, which is less than nine years. [ABSTRACT FROM AUTHOR]