Search Results (23)

This study investigates the environmental and economic performance of integrating a proton exchange membrane fuel cell, battery systems, and an organic Rankine cycle-based waste heat recovery system for ship electrification. The analysis examines an onboard ammonia decomposition system for hydrogen production and ammonia production pathways. Additionally, the study benchmarks the effectiveness of onboard ammonia decomposition against green hydrogen bunkering scenarios (H₂-BS). The analysis is based on data collected over two years from a bulk carrier provided by Laskaridis Shipping Co., Ltd. The environmental analysis includes well-to-wake emissions calculations. At the same time, economic performance is assessed through levelised cost of energy (LCOE) computations for 2025 and 2040, factoring in different fuel and carbon price scenarios. Consequently, the analysis utilises the Complex Proportional Assessment method to compare configurations featuring various ammonia production pathways across economic cases. The results indicate that green and pink ammonia feedstocks achieve maximum equivalent carbon dioxide reductions in the electrification plant of up to 47.28% and 48.47%, respectively, compared to H₂-BS and 95.56% and 95.66% compared to the base scenario. Ammonia decomposition systems prove more economically viable than H₂-BS due to lower storage and fuel costs, leading to competitive LCOE values that improve under higher carbon pricing scenarios. Full article

The aim of this article is to examine existing technologies for the use of electrical energy and to develop proposals for their improvement on maritime vessels. As a criterion for evaluating the effectiveness of alternative energy sources on ships, factors such as greenhouse gas emissions levels, production and transportation characteristics, onboard storage conditions, and technoeconomic indicators have been proposed. The analysis of fuel types reveals that hydrogen has zero greenhouse gas emissions. However, transportation and storage issues, along with the high investment required for implementation, pose barriers to the widespread use of hydrogen as fuel for maritime vessels. This article demonstrates that solar energy can serve as an alternative to gases and liquid fuels in maritime transport. The technologies and challenges in utilizing solar energy for shipping are analyzed, trends in solar energy for maritime transport are discussed, and future research directions for the use of solar energy in the maritime sector are proposed. The most significant findings include the identification of future research directions in the application of solar energy in the maritime sector, including the adaptation of concentrated solar power (CSP) systems for maritime applications; the development of materials and designs for solar panels specifically tailored to marine conditions; the development of methods for assessing the long-term economic benefits of using solar energy on vessels; and the creation of regulatory frameworks and international standards for the use of solar energy on ships. Furthermore, for hybrid photovoltaic and diesel power systems, promising research directions could include efforts to implement direct torque control systems instead of field-orientated control systems, as well as working on compensating higher harmonics in the phase current spectra of asynchronous motors. Full article

Methanol reforming is considered to be one of the most promising hydrogen production technologies for hydrogen fuel cells. It is expected to solve the problem of hydrogen storage and transportation because of its high hydrogen production rate, low cost, and good safety. However, the strong nonlinearity and slow response of the pressure and temperature subsystems pose challenges to the tracking control of the methanol reforming hydrogen production system. In this paper, two internal model-based temperature and pressure controllers are proposed, in which the temperature is adjusted by controlling the air flow and the pressure is adjusted by controlling the opening of the back-pressure valve. Firstly, a lumped parameter model of the methanol reforming hydrogen production system is constructed using MATLAB/Simulink^® (produced by MathWorks in Natick, Massachusetts, USA). In addition, the transfer function model of the system is obtained by system identification at the equilibrium point, and the internal model controller is further designed. The simulation results show that the control method achieves the robustness of the system, and the temperature and pressure of the reforming reactor can quickly and accurately track the target value when the load changes. Small-load step tests indicate stable tracking of the temperature and pressure for the reforming reactor, without steady-state errors. Under large-temperature step signal testing, the response time for the reforming temperature is about 148 s, while the large-pressure step signal test shows that the response time for the reforming pressure is about 8 s. Compared to the PID controller, the internal model controller exhibits faster response, zero steady-state error, and no overshoot. The results show that the internal model control method has strong robustness and dynamic characteristics. Full article

Leveraging the liquid-phase immiscibility effect and phase diagram calculations, a sequence of alloy powders with varying Fe content was designed and fabricated utilizing the gas atomization method. Microstructural characterizations, employing SEM, EDS, and XRD analyses, revealed the successful formation of an incomplete shell on the surfaces of Al-Bi-Fe powders, obviating the need for Sn doping. This study systematically investigated the microstructure, hydrolysis performance, and hydrolysis process of these alloys in deionized water. Notably, Al-10Bi-7Fe exhibited the highest hydrogen production, reaching 961.0 NmL/g, while Al-10Bi-10Fe demonstrated the peak conversion rate at 92.99%. The hydrolysis activation energy of each Al-Bi-Fe alloy powder was calculated using the Arrhenius equation, indicating that a reduction in activation energy was achieved through Fe doping. Full article

The high demand for natural gas (NG) worldwide has led to an increase in the size of the LNG carrier fleet. However, the heat losses from this type of ship’s engines are not properly managed, nor is the excess boil-off gas (BOG) effectively utilised when generation exceeds the ship’s power demand, resulting in significant energy losses dissipated into the environment. This article suggests storing the lost energy into green H₂ for subsequent use. This work compares three different electrolysis technologies: solid oxide (SOEC), proton exchange membrane (PEME), and alkaline (AE). The energy required by the electrolysis processes is supplied by both the LNG’s excess BOG and engine waste heat through an organic Rankine cycle (ORC). The results show that the SOEC consumes (743.53 kW) less energy while producing more gH₂ (21.94 kg/h) compared to PEME (796.25 kW, 13.96 kg/h) and AE (797.69 kW, 10.74 kg/h). In addition, both the overall system and SOEC stack efficiencies are greater than those of PEME and AE, respectively. Although the investment cost required for AE (with and without H₂ compression consideration) is cheaper than SOEC and PEME in both scenarios, the cost of the H₂ produced by the SOEC is cheaper by more than 2 USD/kgH₂ compared to both other technologies. Full article

The reaction of water with Al-based alloys presents a promising alternative for on-board hydrogen production. This method, free from carbon emissions, has the advantage of addressing issues related to hydrogen storage and logistics. Al-Sn-Fe alloys are potential candidates for this application. However, the current literature lacks an in-depth understanding of the role of microstructural evolution in the hydrogen generation performance of these alloys. The present work investigates the influence of the microstructural length scale on the hydrogen production behavior of an Al-9Sn-1Fe (wt.) alloy. Directionally solidified samples with different microstructural length scales were subjected to hydrogen evolution tests in a 1 M NaOH solution. The results revealed that the microstructure of the studied alloy comprised α-Al-phase dendrites with a plate-like morphology along with the presence of Sn-rich particles and Al₁₃Fe₄ intermetallic compounds (IMCs) in the interdendritic areas. In addition, the microstructural refinement induced a 56.25% rise in hydrogen production rate, increasing from 0.16 to 0.25 mL g^–1 s^–1, without affecting the hydrogen yield, which stayed around 88%. The corrosion process was observed to be stimulated by Sn-rich particles and Al₁₃Fe₄ IMCs at their interfaces with the α-Al phase, positively impacting the hydrogen production rate. An experimental equation based on the Hall–Petch relationship and multiple linear regression (MLR) is proposed to associate the hydrogen production rate with dendritic arm spacings. Full article

We are currently seeing how new marine fuels are being introduced, such as Liquefied Natural Gas (LNG), Liquefied Petroleum Gas (LPG), hydrogen, ammonia, methanol, batteries, etc., for the propulsion of the world fleet with the aim of complying with the increasing IMO emissions regulations. The frenetic effort made by shipping companies to decarbonize maritime transport must be followed by an unstoppable adaptation of ports from the historical supply of only fuel and diesel to covering the demands of new fuels, ensuring their renewable origin; onshore power supply (OPS); or even the storage of captured CO₂. This article compiles the current environmental regulations applied to maritime transport to provide an analysis of the current situation and a link between vessels’ requirements to comply with such regulations and port environmental infrastructure. This work demonstrates that technological development is growing faster onboard vessels than at ports. It is demonstrated that except for the case of LNG, the theoretical shipping fuel world demand of each type of alternative fuel cannot be absorbed by current world production, where we found big gaps between supply and demand of up to 96.9%. This work concludes that to speed up this process, ports will need European aid as well as private investment. It is proposed that for the next steps, the port system needs to provide the required infrastructure to vessels on time, which inevitably means improvements in competitiveness and governance to promote the blue economy and the concept of smart ports, attracting main international shipping lines with a complete decarbonization hub on their routes by taking advantage of the geostrategic role of the Iberian ports. At the same time, the port governance model must be more flexible in the decision-making process, anticipating changes in maritime regulations with the challenge of coordinating public and private interests, serving as a link, once again, between ship and society. Full article

New hypotheses for reusing platforms reaching their end-of-life have been investigated in several works, discussing the potential conversions of these infrastructures from recreational tourism to fish farming. In this perspective paper, we discuss the conversion options that could be of interest in the context of the current energy transition, with reference to the off-shore Italian scenario. The study was developed in support of the development of a national strategy aimed at favoring a circular economy and the reuse of existing infrastructure for the implementation of the energy transition. Thus, the investigated options include the onboard production of renewable energy, hydrogen production from seawater through electrolyzers, CO₂ capture and valorization, and platform reuse for underground fluid storage in depleted reservoirs once produced through platforms. Case histories are developed with reference to a typical, fictitious platform in the Adriatic Sea, Italy, to provide an engineering-based approach to these different conversion options. The coupling of the platform with the underground storage to set the optimal operational conditions is managed through the forecast of the reservoir performance, with advanced numerical models able to simulate the complexity of the phenomena occurring in the presence of coupled hydrodynamic, geomechanical, geochemical, thermal, and biological processes. The results of our study are very encouraging, because they reveal that no technical, environmental, or safety issues prevent the conversion of offshore platforms into valuable infrastructure, contributing to achieving the energy transition targets, as long as the selection of the conversion option to deploy is designed taking into account the system specificity and including the depleted reservoir to which it is connected when relevant. Socio-economic issues were not investigated, as they were out of the scope of the project. Full article

Ultra-fast satellite clock bias (SCB) products play an important role in real-time precise point positioning. Considering the low accuracy of ultra-fast SCB, which is unable to meet the requirements of precise point position, in this paper, we propose a sparrow search algorithm to optimize the extreme learning machine (SSA-ELM) algorithm in order to improve the performance of SCB prediction in the Beidou satellite navigation system (BDS). By using the sparrow search algorithm’s strong global search and fast convergence ability, we further improve the prediction accuracy of SCB of the extreme learning machine. This study uses ultra-fast SCB data from the international GNSS monitoring assessment system (iGMAS) to perform experiments. First, the second difference method is used to evaluate the accuracy and stability of the used data, demonstrating that the accuracy between observed data (ISUO) and predicted data (ISUP) of the ultra-fast clock (ISU) products is optimal. Moreover, the accuracy and stability of the new rubidium (Rb-II) clock and hydrogen (PHM) clock onboard BDS-3 are superior to those of BDS-2, and the choice of different reference clocks affects the accuracy of SCB. Then, SSA-ELM, quadratic polynomial (QP), and a grey model (GM) are used for SCB prediction, and the results are compared with ISUP data. The results show that when predicting 3 and 6 h based on 12 h of SCB data, the SSA-ELM model improves the prediction model by ~60.42%, 5.46%, and 57.59% and 72.27%, 44.65%, and 62.96% as compared with the ISUP, QP, and GM models, respectively. When predicting 6 h based on 12 h of SCB data, the SSA-ELM model improves the prediction model by ~53.16% and 52.09% and by 40.66% and 46.38% compared to the QP and GM models, respectively. Finally, multiday data are used for 6 h SCB prediction. The results show that the SSA-ELM model improves the prediction model by more than 25% compared to the ISUP, QP, and GM models. In addition, the prediction accuracy of the BDS-3 satellite is better than that of the BDS-2 satellite. Full article

Road transport is one of the most energy-consuming and greenhouse gas (GHG) emitting sectors. Progressive decarbonisation of electricity generation could support the ambitious target of road vehicle climate neutrality in two different ways: direct electrification with onboard electrochemical storage or a change of energy vector with e-fuels. The most promising, state-of-the-art electrochemical storages for road transport have been analysed considering current and future technologies (the most promising ones) whose use is assumed to occur within the next 10–15 years. Different e-fuels (e-hydrogen, e-methanol, e-diesel, e-ammonia, E-DME, and e-methane) and their production pathways have been reviewed and compared in terms of energy density, synthesis efficiency, and technology readiness level. A final energetic comparison between electrochemical storages and e-fuels has been carried out considering different powertrain architectures, highlighting the huge difference in efficiency for these competing solutions. E-fuels require 3–5 times more input energy and cause 3–5 times higher equivalent vehicle CO₂ emissions if the electricity is not entirely decarbonised. Full article

Long-haul heavy-duty vehicles, including trucks and coaches, contribute to a substantial portion of the modern-day European carbon footprint and pose a major challenge in emissions reduction due to their energy-intensive usage. Depending on the hydrogen fuel source, the use of fuel cell electric vehicles (FCEV) for long-haul applications has shown significant potential in reducing road freight CO${}_2$ emissions until the possible maturity of future long-distance battery-electric mobility. Fuel cell heavy-duty (HD) propulsion presents some specific characteristics, advantages and operating constraints, along with the notable possibility of gains in powertrain efficiency and usability through improved system design and intelligent onboard energy and thermal management. This paper provides an overview of the FCEV powertrain topology suited for long-haul HD applications, their operating limitations, cooling requirements, waste heat recovery techniques, state-of-the-art in powertrain control, energy and thermal management strategies and over-the-air route data based predictive powertrain management including V2X connectivity. A case study simulation analysis of an HD 40-tonne FCEV truck is also presented, focusing on the comparison of powertrain losses and energy expenditures in different subsystems while running on VECTO Regional delivery and Longhaul cycles. The importance of hydrogen fuel production pathways, onboard storage approaches, refuelling and safety standards, and fleet management is also discussed. Through a comprehensive review of the H${}_2$ fuel cell powertrain technology, intelligent energy management, thermal management requirements and strategies, and challenges in hydrogen production, storage and refuelling, this article aims at helping stakeholders in the promotion and integration of H${}_2$ FCEV technology towards road freight decarbonisation. Full article

An under-expanded hydrogen jet from high-pressure equipment or storage tank is a potential incident scenario. Experiments demonstrated that the delayed ignition of a highly turbulent under-expanded hydrogen jet generates a blast wave able to harm people and damage property. There is a need for engineering tools to predict the pressure effects during such incidents to define hazard distances. The similitude analysis is applied to build a correlation using available experimental data. The dimensionless blast wave overpressure generated by delayed ignition and the follow-up deflagration or detonation of hydrogen jets at an any location from the jet, $∆P_{exp}/P_0$, is correlated to the original dimensionless parameter composed of the product of the dimensionless ratio of storage pressure to atmospheric pressure, $P_s/P_0$, and the ratio of the jet release nozzle diameter to the distance from the centre of location of the fast-burning near-stoichiometric mixture on the jet axis (30% of hydrogen in the air by volume) to the location of a target (personnel or property), $d/R_w$. The correlation is built using the analysis of 78 experiments regarding this phenomenon in the wide range of hydrogen storage pressure of 0.5–65.0 MPa and release diameter of 0.5–52.5 mm. The correlation is applicable to hydrogen free jets at ambient and cryogenic temperatures. It is found that the generated blast wave decays inversely proportional to the square of the distance from the fast-burning portion of the jet. The correlation is used to calculate the hazard distances by harm thresholds for five typical hydrogen applications. It is observed that in the case of a vehicle with onboard storage tank at pressure 70 MPa, the “no-harm” distance for humans reduces from 10.5 m to 2.6 m when a thermally activated pressure relief device (TPRD) diameter decreases from 2 mm to a diameter of 0.5 mm. Full article

Methanol steam reforming (MSR) is a promising technology for on-board hydrogen production in fuel cell applications. Although traditional Cu-based catalysts demonstrate high catalytic activity and selectivity towards CO₂ relative to CO, which is produced via methanol decomposition, they suffer from poor thermal stability and rapid coke formation. Nickel phosphides have been widely investigated in recent years for many different catalytic reactions owing to their remarkable activity and selectivity, as well as their low cost. In this work, we present a mechanistic study of methanol decomposition and MSR pathways on Ni₂P using density functional theory (DFT) calculations. DFT-predicted enthalpic barriers indicate that MSR may compete with methanol decomposition on Ni₂P, in contrast to other transition metals (e.g., Pt, Pd, and Co) which primarily decompose methanol into CO. The formaldehyde intermediate (CH₂O*) can react with co-adsorbed hydroxyl (OH*) from water dissociation to produce H₂COOH* which then undergoes subsequent dehydrogenation steps to produce CO₂ via H₂COOH*→ HCOOH* → HCOO* → CO₂. We also examined the conversion of CO into CO₂ via the water–gas shift (WGS) reaction, but we ruled out this pathway because it exhibits high activation barriers on Ni₂P. These findings suggest that Ni₂P is a promising new catalyst for MSR. Full article

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. Full article

The European Green Deal aims to transform the EU into a modern, resource-efficient, and competitive economy. The REPowerEU plan launched in May 2022 as part of the Green Deal reveals the willingness of several countries to become energy independent and tackle the climate crisis. Therefore, the decarbonization of different sectors such as maritime shipping is crucial and may be achieved through sustainable energy. Hydrogen is potentially clean and renewable and might be chosen as fuel to power ships and boats. Hydrogen technologies (e.g., fuel cells for propulsion) have already been implemented on board ships in the last 20 years, mainly during demonstration projects. Pressurized tanks filled with gaseous hydrogen were installed on most of these vessels. However, this type of storage would require enormous volumes for large long-range ships with high energy demands. One of the best options is to store this fuel in the cryogenic liquid phase. This paper initially introduces the hydrogen color codes and the carbon footprints of the different production techniques to effectively estimate the environmental impact when employing hydrogen technologies in any application. Afterward, a review of the implementation of liquid hydrogen (LH₂) in the transportation sector including aerospace and aviation industries, automotive, and railways is provided. Then, the focus is placed on the maritime sector. The aim is to highlight the challenges for the adoption of LH₂ technologies on board ships. Different aspects were investigated in this study, from LH₂ bunkering, onboard utilization, regulations, codes and standards, and safety. Finally, this study offers a broad overview of the bottlenecks that might hamper the adoption of LH₂ technologies in the maritime sector and discusses potential solutions. Full article