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Porous polytetrafluoroethylene (PTFE) reinforced sulfonic acid-based proton exchange membranes (PEMs) are widely used for proton exchange membrane fuel cells (PEMFCs) due to their superior mechanical durability compared with pristine/free-standing sulfonic acid-based PEMs. However, the development of advanced porous PTFE reinforced sulfonic acid-based PEMs (PTFE-PEMs) still faces some technical challenges, including poor ionomer filling, poor interface bonding between PTFE skeleton and ionomer, limited chemical durability, inferior performance at low humidity, limited interface combination between PTFE-PEMs and catalyst layers, and unclear effect of the number of PTFE skeleton layers. Extensive research has been implemented to overcome these scientific issues, thus realizing the practical prospects of PTFE-PEMs. Nevertheless, relevant summary about these studies is scarce. On this basis, this paper highlights the technical challenges of PTFE-PEMs and reviews the research advances in solving these scientific issues of PTFE-PEMs. In addition, the challenges and future perspectives of PTFE-PEMs are also discussed. The systematic summary and proposed directions can trigger thoughts and provide ways to reasonably design PTFE-PEMs for PEMFCs in the near future. [Display omitted] • Fundamentals of porous PTFE reinforced SA-PEMs are introduced. • Technical challenges of PTFE-PEMs are summarized. • Research advances in PTFE-PEMs are reviewed. • Challenges and future development on PTFE-PEMs are discussed. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cell (SOFC) is a promising energy conversion technology for accelerating the process of carbon neutrality. This paper develops and validates a 1D mathematical model for a planar SOFC (10 cm × 10 cm) along the fluid flow direction with a less than 0.2% deviation. When the SOFC operates in an adiabatic environment with different inlet gas temperatures (T in) and current density (I avg), the distributions of its key parameters are calculated and analyzed. The results show that the optimal inlet gas temperature for the SOFC working in an adiabatic environment is between 873 K and 973 K when I avg varies from 0.05 A cm−2 to 0.25 A cm−2. The maximum temperature appears at the outlet position and between the outlet and the center point along the flue flow for the co-flow and counter-flow SOFC. Compared with the co-flow pattern, the counter-flow design can benefit the fuel cell power output when T in and I avg are identical, especially with lower T in and higher I avg. The output power of counter-flow SOFC is larger 11.3% than that of the co-flow one at most with the research range in this work. • A 1D model of the SOFC is developed and validated within 0.2% deviation. • Distribution characteristics of the SOFC in the adiabatic environment are analyzed. • The temperature gradient of the fuel cell decreases with the inlet gas temperature. • 11.3% more power can be obtained by adopting counter-flow SOFC in adiabatic. • The optimal inlet gas temperature varies from 873 K to 973 K for the adiabatic SOFC. [ABSTRACT FROM AUTHOR]

The hydrogen pump is an important component in the hydrogen circulation system of fuel cells. Excessive pulsation at the outlet of the pump is challenging when the Roots hydrogen pump is used, which has a negative impact on the operation performance. To reduce the impact of excessive fluctuations in the hydrogen circulation system, a new structure of reflow grooves is proposed in this paper, which connects the different chambers and adjusts the pressure using a diversion method. The internal flow of the two pumps was studied for comparison, using a three-dimensional simulation model established by Computational Fluid Dynamics (CFD) method. Results showed that the reflow grooves reduce the exhaust pressure and mass flow pulsations, which has a positive effect on the pressure stabilization of the hydrogen circulation system and the anode inlet pressure of the fuel cell stack, contributing to the long durability and stability of the fuel cell stack. [Display omitted] • A novel reflow structure is proposed for the Roots hydrogen pump. • The internal flow of the pump is simulated by the dynamic grid method. • The gas pressure variation in one compression in the Roots pump was analysed. • The reductions in flow fluctuations at different rotational speeds are compared. • Pressure fluctuation is supressed at high rotation speed by the reflow structure. [ABSTRACT FROM AUTHOR]

There are complex coupling relationships between flight motion and energy management for hybrid electric fixed wing UAVs with photovoltaic/fuel cell/battery. Aiming at realizing high-energy-efficiency long endurance autonomous flight, this paper proposes a coordinated optimization method of trajectory optimization and energy management for hybrid electric UAVs. Numerical simulation and experiment are carried out. Separated by surplus demand energy except that produced by PV, this method includes an optimal energy flight trajectory optimization layer and an energy management layer. For the former, fuzzy neural network sequential convex optimization (FNNSCP) is proposed to handle the flight trajectory optimization problem for maximizing utilization solar energy. For the latter, an online energy management strategy based on convex quadratic programming MPC (CQPMPC) is proposed to realize the power allocation. Numerical simulation results show that FNNSCP reduced 2% energy requirement compared with Radau pseudo-spectral method (RPM) from flight trajectory optimization level. From energy management level, CQPMPC saves hydrogen consumption by 3.1% and 16.3% compared with nonlinear model predictive control (NMPC) and fuzzy logic state machine (FLSM), respectively. In the experiment, less hydrogen fuel is consumed by proposed method by 5.2% and 15.6% compared with NMPC and FLSM, respectively. Experimental results show that the proposed method has better energy-saving performance and excellent real time performance. It indicates that optimizing flight trajectory and improving energy management efficiency can realize the high-energy-efficiency flight of hybrid electric UAVs. This method is conducive to promoting the application of hydrogen energy in the field of UAVs. [Display omitted] • A coordinated optimization method is proposed for the high-energy-efficiency flight. • Fuzzy neural network adaptive sequential convex optimization method is proposed. • Online energy management strategy with convex quadratic programming MPC is proposed. • The proposed method is verified by simulation and energy management experiment. [ABSTRACT FROM AUTHOR]

Encountering complex traffic conditions such as the dynamic interference of preceding and rear vehicles and gradients, a control strategy that simultaneously considers inter-vehicle cooperative control and energy economy is one of the key technologies, that improves traffic efficiency and exploits the energy-saving potential of platoon vehicles. In this paper, a hierarchical optimization control strategy is proposed for the intelligent fuel cell hybrid electric vehicles (FCHEV) platoon in a network-connected environment. The hierarchical control framework consists of upper speed control and lower power distribution. In the upper layer, the improved particle swarm optimization (PSO) algorithm is applied to calculate the global optimal speed trajectory, and then the model predictive control (MPC) is adopted for global speed trajectory tracking and self-adaptation, which can ensure the ego vehicle tracks the pre-calculated speed trajectory, and can re-plan the vehicle speed under the condition of safety priority when sudden disturbances occur in the foreground. The lower layer utilizes Q-learning (QL) to achieve power distribution between hybrid power sources, reducing the number of fuel cell starts and stops, slowing battery degradation and improving vehicle economy. Simulation results based on complex road conditions show that the proposed controller has good energy economy and tracking performance. Under the condition of the slope, the total platoon cost of the proposed strategy is reduced by 3.99% compared with the constant speed cruise strategy, and under the interference condition, the total platoon consumption cost of the proposed strategy decreased by 6.79% compared with adaptive cruise control (ACC). • A hierarchical strategy of IFCHEV platoon in complex conditions is proposed. • Speed planning is conducted using offline optimization with real-time adjustment. • Online adjustment adopts fixed headway to ensure platoon stability and safety. • Complex working conditions are considered to guarantee strategy adaptability. [ABSTRACT FROM AUTHOR]

The hybrid combination of hydrogen fuel cells (FCs) and batteries has emerged as a promising solution for efficient and eco-friendly power supply in maritime applications. Yet, ensuring high-quality and cost-effective energy supply presents challenges. Addressing these goals requires effective coordination among multiple FC stacks, batteries, and cold-ironing. Although there has been previous work focusing it, the unique maritime load characteristics, variable cruise plans, and diverse fuel cell system architectures introduce additional complexities and therefore worth to be further studied. Motivated by it, a two-layer energy management system (EMS) is presented in this paper to enhance shipping fuel efficiency. The first layer of the EMS, executed offline, optimizes day-ahead power generation plans based on the vessel's next-day cruises. To further enhance the EMS's effectiveness in dynamic real-time situations, the second layer, conducted online, dynamically adjusts power splitting decisions based on the output from the first layer and instantaneous load information. This dual-layer approach optimally exploits the maritime environment and the fuel cell features. The presented method provides valuable utility in the development of control strategies for hybrid powertrains, thereby enabling the optimization of power generation plans and dynamic adjustment of power splitting decisions in response to load variations. Through comprehensive case studies, the effectiveness of the proposed EMS is evaluated, thereby showcasing its ability to improve system performance, enhance fuel efficiency (potential fuel savings of up to 28%), and support sustainable maritime operations. [Display omitted] • Hybrid PEM fuel cell/battery system enables zero-emission shipping. • Two-layer EMS enhances fuel efficiency while satisfying real-time load requirements. • Rotational sequential distribution prevents uneven degradation. • Rotational sequential distribution enhances computational efficiency. [ABSTRACT FROM AUTHOR]

The All-electric ship (AES) concept has revolutionized the maritime sector. Indeed, AES is a promising solution for modern vessels where decreasing emission pollution, suppressing fossil fuel consumption, and making economical operation are its brilliant merits. Fuel cell (FC) technology based on clean hydrogen energy sources can play a significant role in meeting these requirements in the AES platform. Because of the slow transient response of the FC, an energy storage system (ESS) is required to improve AES performance in different operation scenarios. Therefore, optimal sizing of the FC and the ESS and proper design of energy management strategy is a challenging problem. This paper proposes a systematic approach for the optimal design of hybrid FC-ESS of AES power systems. The proposed method is based on an optimization technique to determine the optimal sizing of the FCs and the ESS. Capital investment, fuel consumption, personnel electrical safety, and occupied volume of the AES power system are the main objectives. The FC size, the battery size, the scheduled output power of the FC, and the battery are the decision variables. Genetic Algorithm (GA) is used to solve the optimization problem. To validate the numerical results, the optimization problem is also solved by Mayfly Algorithm (MA) separately. To assess the feasibility of the proposed strategy, the optimal design of hybrid FC-ESS for a vessel is implemented based on the proposed method. The simulation results validate the proposed approach's sufficiency to investigate and optimize the economic, safety, and dimensional aspects of designing the FC ship's IPS. Numerical results are reported for each design aspect. Considering the minor differences of the numerical results obtained by GA and MA, the optimum points are validated by the two techniques. Using the obtained results, various perceptions can be derived from the FC ship's IPS design. For example, the IPS cost in the cases with optimum volume, weight, and safety, has 2.3%, 2.6%, and 7.3% penalties, respectively compared to the case with the minimum cost. • Fuel cell-based electrification of a fishing ship based on practical information. • Systematic approach for optimal power system design of hydrogen-powered ship. • Proposing safety objective function for integrated power system of fuel cell ship. • Fuel cell hybrid IPS optimization based on volume, mass, cost and safety. • Estimation of propulsion power demand based on ship's resistance and speed profile. [ABSTRACT FROM AUTHOR]

Conventional turboshaft engines are high power density movers suffering from low efficiency at part power operation and producing significant emissions. This paper presents a design exploration and feasibility assessment of a hybrid hydrogen-fueled powerplant for Urban Air Mobility (UAM) rotorcraft. A multi-disciplinary approach is devised comprising models for rotorcraft performance, tank and subsystems sizing and engine performance. The respective trade-offs between payload-range and mission level performance are quantified for kerosene-fueled and hybrid hydrogen tilt-rotor variants. The effects of gas turbine scaling and fuel cell pressurization are evaluated for different hybridization degrees. Gas turbine scaling with hybridization (towards the fuel cell) results in up to 21% benefit in energy consumption relative to the non-scaled case with the benefits being more pronounced at high hybridization degrees. Pressurizing the fuel cell has shown significant potential as cell efficiency can increase up to 10% when pressurized to 6 bar which translates to a 6% increase in overall efficiency. The results indicate that current fuel cells (1 kW/kg) combined with current hydrogen tank technology severely limit the payload-range capability of the tilt-rotor. However, for advanced fuel cell technology (2.5 kW/kg) and low ranges, hybrid powerplant show the potential to reduce energy consumption and reduce emissions footprint. • Design space exploration of hybrid hydrogen-fueled powerplant for UAM rotorcraft. • Hybrid-electric rotorcraft compared against the hydrogen-fueled counterpart at different hybridization degrees. • Performance and environmental assessment conducted at payload-range and mission level. • Effects of gas turbine scaling with hybridization and fuel cell pressurization are quantified. • Fuel cell technology level sensitivity analysis is conducted. [ABSTRACT FROM AUTHOR]

This paper focuses on the main chemical, electrochemical, and mechanical degradation mechanisms and poisoning effects that influence the life-time, the performance, and the functionality of PEM (polymer electrolyte membrane) fuel cell stack components reversibly and irreversibly. The underlying causes are explained, possible influencing factors are listed, and the effects of degradation on fuel cell operation and state of health are described. Based on this, further consequences as well as mitigation strategies are presented. The summary gives an overview of the affected causes of voltage decay, the influence of operating conditions, strategies, and events on each specific degradation mechanism, and additionally the influence of initial degradation on any further degradation. [Display omitted] • Main degradation mechanisms and poisoning effects of PEM fuel cells are reviewed. • Influencing factors and consequences of degradation mechanisms are reviewed. • Influence of operating conditions is summarized and evaluated. • Mitigation strategies to minimize degradation are summarized. • Influence of initial degradation on further degradation mechanisms is evaluated. [ABSTRACT FROM AUTHOR]

With the rise of the hydrogen energy industry, countries worldwide have introduced relevant policies to elevate the development of the hydrogen energy industry to the height of national energy strategy, and hydrogen energy will become a significant factor affecting the future industrial structure and national competitiveness. The path of technology evolution can trace the history of technology development and predict the trend of technology development, which can help to grasp the first opportunity of technological innovation and lead the direction of technological development. However, there are fewer studies on technology evolution in hydrogen energy. The existing studies mainly use bibliometrics to mine a single technology, and the studies using text mining suffer from the defect that keywords are difficult to decipher. Given this, this paper conducts research on identifying the technology evolution path in the field of hydrogen energy, adopts text mining methods to mine patent data, and introduces document vectorization and phrase mining algorithms to improve the mining depth while increasing the interpretability of the results. It is found that the hydrogen energy industry is in a period of rapid development; the succession and integration of hydrogen energy technologies are good, and the technological development trend focuses on hydrogen storage materials, hydrogen fuel cell vehicles, and green hydrogen preparation. • Identify the mesh evolution path of hydrogen energy technology using text mining. • Introduce a phrase-mining algorithm to make interpreting the results easier. • Analyze the overall development trend of hydrogen energy technology. • Explore the technological themes and evolution patterns in the field of hydrogen energy. [ABSTRACT FROM AUTHOR]

A model to locate hydrogen refueling stations (HRSs) for hydrogen fuel cells vehicles (HFCVs) or hydrogen internal combustion engines vehicles (HICEVs) is proposed in this paper. The model integrated the flow-capturing location allocation (FCLA) model and stochastic user-equilibrium (SUE) status of network flow. An equilibrium algorithm obviating cannibalization was also presented. We compared the effectiveness between node location and link location determined by FCLA between SUE status and non-equilibrium status of the transportation network taking the city of Anaheim in California in America as an example. The results showed that the capture ratios of node-serving and link-serving are different. For the non-equilibrium case, equilibrium case, and hybrid case, the capture ratios of node-serving are 77.72%, 69.51%, and 60.25%, respectively, while the capture ratios of link-serving are 54.37%, 46.34%, and 31.49%, respectively. This means Node-serving performs better than link-serving in terms of capturing flow, either in equilibrium status or non-equilibrium status. The node locations or link locations obtained by the FCLA method in SUE status should be used for locating HRSs because they are consistent with peoples' route choice behavior and thus can fully capture the expected flow in reality. Practically speaking, link locations are preferable to node locations in locating HRSs because the construction and operation of HRSs on nodes are relatively difficult to implement. • A model of FCLA in SUE status to locate hydrogen refueling stations. • Node-serving and link-serving determined by non-equilibrium flow. • Node-serving and link-serving determined by SUE flow. • Compare the effectiveness between node-serving and link-serving in both cases. [ABSTRACT FROM AUTHOR]

The hybridization of energy storage systems consisting of fuel cells, batteries, and ultracapacitors has tremendous potential in fuel cell hybrid electric vehicles. However, the utilization of ultracapacitors in existing energy management strategies is insufficient, preventing complete exploitation of the energy storage system's benefits. To strengthen the utilization of ultracapacitors, this paper proposes an energy management strategy for fuel cell vehicles with three energy sources, considering the ideal state of charge (SOC) of ultracapacitors. The proposed method disassembles the motor power demand, with the ultracapacitor primarily supplying the acceleration portion. It calculates the ideal SOC of the ultracapacitor, and controlling the actual SOC of the ultracapacitor to match the ideal SOC. Furthermore, a fuzzy logic controller is designed to modify the fuel cell's output power, reducing power fluctuation. Additionally, according to the variation of the SOC of the battery, the fuel cell output power is modified to enhance the overall performance of the composite energy storage system. Simulation and hardware-in-loop results demonstrate that, compared to the adaptive filtering strategy with fuel cell power constraints and dynamic programming strategy, the strategy proposed in this paper reduces operational costs by 14.56 % and 4.99 %, respectively. • An energy management strategy considering ideal SOC in ultracapacitor is proposed. • The ideal SOC of UC is defined, with adjusting based on the average vehicle speed. • A fuzzy logic controller is designed to adjust the limits of the FC output power. • The output power of FC is adjusted according to the changes in the SOC of BAT. • This strategy offers better overall costs compared with the AFS strategy. [ABSTRACT FROM AUTHOR]

The global energy sector is currently undergoing a fundamental transformation as it shifts away from fossil fuels towards renewable energy sources. Green hydrogen is one of the most promising energy carriers of the future in the worldwide effort to reduce the carbon footprint of energy systems. The advancement and uptake of green hydrogen technologies depend on various technological, environmental, and economic factors. In this paper, a comprehensive review of recent studies in green hydrogen energy systems (GHES) is conducted, highlighting technoeconomic aspects from the component to the technology and broader system level. Firstly, the technological principles and recent progress of different green hydrogen generation, storage, and utilization technologies are summarized. Subsequently, an in-depth analysis of various technoeconomic modeling and experimental activities focused on integrated GHES is undertaken. By examining applications in the stationary and transport sectors, this review paper offers an assessment of the current state-of-the-art in terms of development and integration options. The technical challenges, key factors, and future research directions of green hydrogen technologies and systems are outlined, demonstrating that an effective, intelligent, and innovative integration of GHES with other technologies will encourage a more efficient use of resources and enhanced energy system flexibility, resilience, and energy security. • Characteristics, components and configurations of green hydrogen systems are presented. • Technoeconomic studies are collected in tabulated form and exhaustively analyzed. • State-of-the-art applications in stationary and transport sectors are discussed. • A critical review is provided to assess green hydrogen economic viability potential. • Challenges and prospects are evaluated, and future research directions are suggested. [ABSTRACT FROM AUTHOR]

Limitations in current fuel cell technology lead to instability in output voltage for hydrogen fuel cells, particularly under the influence of temperature variations and fuel flow fluctuations, thereby affecting the normal operation of hydrogen-powered vehicles. Improving the motor drive control system and optimizing energy management are crucial for enhancing overall vehicle performance. To improve dynamic response speed while suppressing harmonics, this paper proposes a predictive control strategy for high-speed permanent magnet synchronous motors with LCL filter in hydrogen fuel cell electric vehicles. The proposed control strategy suppresses high-frequency current harmonics by sampling only the current on the motor side, enabling fast predictive control of the high-order system motor-side current. Additionally, to mitigate the issue of unstable torque output of the electric motor at low fuel levels, this paper proposes a new composite predictive torque trajectory control strategy based on the previous control strategy. This strategy ensures rapid and accurate tracking of motor output torque, particularly during decreases in fuel cell output voltage. Experimental results validate the feasibility and effectiveness of the proposed control strategies in this paper. • Torque stability control of hydrogen electric vehicle under low fuel state. • Predictive current direct control for LCL-equipped high-speed PMSM drive based on single-sensor. • A composite predictive current trajectory control strategy balancing small steady-state error and fast dynamic response. [ABSTRACT FROM AUTHOR]

Purging offers a straightforward and cost-effective means of eliminating inert gases that accumulate in high-temperature proton exchange membrane fuel cells (HT-PEMFC) operating in dead-end anode (DEA) mode. Nevertheless, earlier studies primarily concentrated on inert gases, overlooking the significant challenge posed by the strong adsorption of CO within HT-PEMFC, complicating the use of inert gas methods for CO purification. This paper presents an analytical model that was validated experimentally. Leveraging this model, the paper analyzes the crucial parameter of CO concentration within the anode and deduces theoretical extreme values. Subsequently, it proposes purging strategies tailored to different operational conditions. The findings indicate that the minimum CO concentration within HT-PEMFC is influenced by current, feed gas flow rate, and feed gas CO concentration. Additionally, the maximum CO concentration is affected by the off-duration of the purge valve in addition to these factors. Specifically, under the operating condition of 473.15 K, adopting a CO concentration threshold purge strategy is recommended, whereas under the operating condition of 448.15 K, voltage drop and CO concentration threshold purge strategies should be respectively implemented above and below the cutoff line based on the current. This research contributes to mitigating the issue of CO accumulation in DEA mode. • A CO purging model was built in published literature. • The maximum and minimum values of CO molar concentration in CO purge were derived. • Purging strategies for different temperatures and current densities are proposed. • The maximum CO mole fraction that can be purified is increased to 3 %. [ABSTRACT FROM AUTHOR]

The diffusion on large scale of the hydrogen-fueled technologies could be a strategy for boosting the expected decarbonisation of the civil sector. However, there are still a lot of unanswered questions about the real feasibility and the problems of the integration in a pre-existing building-plants system. Despite some conflicting opinions, the research about the application of the hydrogen system in the building sector must continue to make the technology more attractive and easily available at low cost. Therefore, first of all, the paper analyses advantages and issues through a broad overview. The main limits of the available studies regard both the approach and the technology integration. Indeed, there are few data about in-field performance analysis since the simulative/numerical investigations are usually based on in-lab prototypes. The most diffused systems referred to integrated energy solutions with proton exchange membrane fuel cell technology and in any case the integration in very low energy buildings such as the nearly zero energy (nZEB) ones is not discussed. Then basing on the discussed research gap, the paper focuses on the set-up of a new installation of micro-combined cooling, heating and power unit based on solid oxide fuel cell technology fueled by green hydrogen. The complexity in the design of the integration with other innovative plant configurations is discussed considering as real case study a nZEB in Mediterranean climate. Preliminarily experimental results show that the combination of fuel cell and photovoltaic system could bring to positive energy with surplus energy, during autumn season, of about 23.8 kWh. Moreover, it is also proposed the validation of a dynamic numerical model developed by means of TRNSYS (Transient System Simulation Tool) that will be used for further sensitivity analysis. [ABSTRACT FROM AUTHOR]

Developing a fast diagnostic technology for membranes and accurately predicting the lifetime of membranes that can effectively reduce the manufacturing cost and overcome the technical barriers of proton exchange membrane fuel cell (PEMFC) lifetime. This paper focuses on developing an ex-situ accelerated chemical degradation method and investigating the impact of chemical degradation on membrane structure and fuel cell performance. The results show that voltage drop and hydrogen permeation current can detect the state online and predict the remaining lifetime of membrane electrode assembly (MEA). The aging rate is faster by three orders of magnitude than that of the published results by the established aging way. This study provides an additional decision for evaluating performance degradation and fuel cell system optimization, which could potentially lead to further improvements in the efficiency and durability of PEMFC systems. • The paper has developed an ex-situ accelerated chemical degradation method. • Voltage drop and hydrogen permeation current can predict the lifetime of the MEA. • The aging rate is three orders of magnitude faster than that of the published results. [ABSTRACT FROM AUTHOR]

The objective of this paper is to optimize the energy consumption and performance of fuel cell electric bicycles (FCEBs) under specific key input parameters. The paper applied an integrated method that includes an artificial neural network (ANN) and genetic algorithm (GA) to forecast and identify an optimal performance and energy consumption of FCEBs. The simulation model of FCEBs is established and simulated in MATLAB-Simulink environment to generate 1000 data points, that are used for training, validating, testing artificial neural network, the ANN architecture containing five input neurons, two hidden neurons and two output neurons, respectively. Furthermore, the GA is integrated to find the maximum performance and energy consumption once the ANN has exactly been trained. The study found that the FCEB configuration can achieve an effective performance at 30.3 km/h with required power of 210.4 W under speed level_5, radius of wheel 0.39 m, frontal area 0.423 m2, slope grade 0%. In order to validate and verify the simulated results, the experimental approach method was conducted in the same condition. The experimental results fit well with the simulated results in the same initial input parameters. • A method integrating the artificial neural network with genetic algorithm is applied. • The consumed power and fuel cell voltage are optimized by combining artificial neural network and genetic algorithm (ANN-GA). • The effective performance area of fuel cell electric bicycle under various a structure and operating parameters is identified. • Deep-learning results reflect major physical mechanism of fuel cell electric bicycle operation. [ABSTRACT FROM AUTHOR]

Large ships are more utilized than ever before to facilitate transporting heavy goods and oils overseas. However, they rely on fossil fuels and cause severe environmental impacts. Utilizing alternative fuels and implementing new engine designs are considered promising methods to reduce greenhouse gas emissions and improve engine performance. This paper compares three developed, hybridized marine engines operated using five fuel blends of hydrogen, methanol, dimethyl ether, ethanol, and methane. In addition, the paper presents a multi-objective particle swarm optimization to increase the engine power and its exergetic efficiency and reduce the cost and environmental impact. A marine engine (SRC-GT-SOFC) containing a steam Rankine cycle, a gas turbine, and a solid oxide fuel cell is considered to weigh less and perform better. It is found that the optimized SRC-GT-SOFC engine power is increased by about 10 %, corresponding to 16269 kW with an increased exergetic efficiency of 70.6 %, respectively. Its specific fuel and product exergetic costs are found to be 12 $/GJ and 15.67 $/GJ, and its specific fuel and product environmental impacts are 7.4 Pt/GJ and 9.3 Pt/GJ, respectively. This results in a significant reduction in the relative cost difference and the relative environmental impact difference of the optimized SRC-GT-SOFC of 30 % and 25.4 %, respectively. • Three hybridized marine engines are compared and optimized to raise performance. • Optimized SRC-GT-SOFC engine has 16.3 MW power and 70.6 % exergetic efficiency. • Specific exergetic cost reduced to 12 $/GJ for fuel and 16 $/GJ for product. • Specific exergetic environmental impact for fuel and product becomes 7.4 and 9.3 Pt/GJ. • New operation conditions of SRC-GT-SOFC have low price and environmental impact. [ABSTRACT FROM AUTHOR]

• Oxygen transfer in CL is important to design CL and manage fuel cell. • Review oxygen transfer mechanism and resistance in Pt/C/polymer, porous aqueous CL. • Several mass transfer pathways for oxygen in mesoporous CL are proposed. • Oxygen solution via interface is main factor affecting its transfer. • Dynamic oxygen transfer mechanisms in aqueous CL needs further study. Oxygen transfer in catalyst layer (CL) is an important issue affecting the oxidation–reduction reaction (ORR) and the output voltage of fuel cells, which is significant for guiding high-performance catalyst and CL design, and steady fuel cell operation for avoiding water flooding and degradation. Apart from the research on catalyst with low- and zero- loading platinum, high oxygen-transfer CL is another hot spot, the result of which will be beneficial to both proton exchange membrane (PEM) fuel cell and its inverse water electrolysis. In this paper, oxygen transfer is systematically reviewed involving oxygen transfer mechanism, model description, oxygen transfer resistance characterization, model solution method, and finally the oxygen transfer investigation in water-filled CL. For the transfer mechanism, in two scales that the studies are consecutively reviewed, which are Pt/C-ionomer agglomerate and porous CL. Among three main transfer paths, different factors influencing oxygen transfer are also clarified. At the point of fuel cell application, the oxygen transfer resistance and impedance, structure modeling and solution for oxygen transfer model, especially the oxygen transfer in water-involved CL are reviewed as well. Some view points on future research are proposed. Firstly, direct experimental validating oxygen transfer mechanism in agglomerate, CL, and water-involved CL should be given more attention. Secondly, the oxygen transfer and water content under transient conditions in CL still need to be closely monitored in terms of oxygen transfer resistance via mathematical methods that combining the basic transfer mechanism and proper structural establishment, where the traditional low-frequency impedance affecting oxygen transfer at large water amount needs more investigations. This paper is of great significance for the forward design of CL as well as fuel cell operation management. [ABSTRACT FROM AUTHOR]

Abstract: Pulse electrodeposition of Pt nanocluster catalysts on graphene oxide (GO)-carbon paper composite electrode for proton exchange membrane fuel cells has been investigated. The primary particle size was found to be 100–300nm for the urchin-like cluster that was composed of a number of secondary grains. Experimental results show that the GO sheets decorated with the Pt clusters displays low-equivalent series resistance (~2.60Ω) and high-power density (~1.3kWg−1 at 60°C). Hence, such a catalyst electrode, consisting of the GO sheets and the metallic Pt clusters, is proved to have several advantages such as good dispersion of catalysts and high catalytic activity. [Copyright &y& Elsevier]

Abstract: To evaluate a suitable electrode material for the efficient green energy generation of a bio-fuel cell, carbonaceous based carbon cloth, carbon paper, and carbon felt electrodes were investigated under different mediators. The larger surface area, low resistance, and open network of interwoven fibers of the carbon felt electrode facilitated higher electron transfer from the microbial organisms to the electrode surface than that of other carbonaceous electrodes. Carbon paper electrode exhibited lower fuel cell performances due to its lower roughness and high tortuous nature. The green power generation experiments were also carried out under different mediators such as 2-hydroxy-l,4-naphthoquinone and thionin. The electrons mitigation and power generation was augmented by 2-hydroxy-l,4-naphthoquinone than thionin due to its high solubility, stability, and minimal adsorption characteristic to the electrodes. By the combined efforts of extended electrons generation and transportation, bio-fuel cell performances were extended and endorsed its doable applications in bio-fuel cells. [Copyright &y& Elsevier]

This paper investigates the economics of a fuel cell bus fleet powered by hydrogen produced from electricity generated by a wind park in Austria. The main research question is to simultaneously identify the most economical hydrogen generation business model for the electric utility owning wind power plants and to evaluate the economics of operating a fuel cell bus fleet, with the core objective to minimize the total costs of the overall fuel supply (hydrogen production) and use (bus and operation) system. For that, three possible operation modes of the electrolyzer have been identified and the resulting hydrogen production costs calculated. Furthermore, an in-depth economic analysis of the fuel cell buses as well as the electrolyzer technology has been conducted. Results show that investment costs are the largest cost factor for both technologies. Thus, continuous hydrogen production with the smallest possible electrolyzer is the economically most favorable option. In such an operation mode (power grid), the costs of production per kg/H 2 were the lowest. However, this means that the electrolyzer cannot be solely operated with electricity from the wind park, but is also dependent on the electricity mix from the grid. For fuel cell buses, the future cost development will depend very much on the respective policies and funding programs for the market uptake, as to date, the total cost of use for the fuel cell bus is more than two times higher than the diesel bus. The major final conclusion of this paper is that to make fuel cell electric busses competitive in the next years today severe policy interferences, such as subsidies for these busses as well as electrolyzers and bans for fossil energy, along with investments in the setup of a hydrogen infrastructure, are necessary. Cost analysis of a fuel cell electric bus and three hydrogen production operation models. [Display omitted] • Economic analysis of fuel cell buses and green hydrogen production. • Identification of the most suitable electrolyzer operation model. • Investment costs are still the largest cost component. • Technological learning and policy funding schemes may decrease the costs. [ABSTRACT FROM AUTHOR]

The severe reduction in the available fossil fuel resources highlights the need to make more use of renewable energy resources (RER), such as solar photovoltaic (PV) modules, wind turbines, hydro-turbines, etc. Hydrogen (H 2) may be seen as a possible alternative fuel which can be produced from renewable energy, as mentioned and a promising contender in the energy storage domain. A hydrogen electrolyser harnesses the energy produced by the RER, in order to produce H 2 , which could be stored in its current form to be used at a later stage to generate electrical energy, by means of a fuel cell. In this paper, an optimal switching control of a solid polymer electrolyte membrane water electrolyser (PEMWE) water heating system is presented, in which actual historic exogenous data obtained from a weather station in the considered area is used as inputs for the established model. The main aim of this paper was to develop an optimal control model, which maximizes the removal of the undesired heat from the PEMWE and transferring it to the hot water storage tank (HWST), whilst ensuring sufficient hydrogen is being produced. Simulations of the optimal switching control of a PEMWE water heating system was conducted successfully with the SCIP (Solving Constrained Integer Programs) solver in the optimization toolbox in MATLAB. The optimal switching control model yields a daily energy consumption of 49.85 kWh by the PEMWE compared to an energy consumption of 48.86 kWh by the standard PEMWE system (baseline). The optimal switching control model resulted in 2.51 kg of hydrogen compared to 2.56 kg which is produced by the standard PEMWE system. Moreover, the optimal control model recovered 1.03 kWh of heat successfully which is transferred to the HWST. The optimal control model development and implementation for a PEMWE to maximize the thermal energy recovery from the PEMWE to the HWST whilst ensuring stable H 2 production are presented as one of the main contributions to the study. Secondly, by recovering the generated heat from the PEMWE, the time period for the membrane to degrade to a thickness of 50% could be prolonged by 0.68 years, after which the membrane degradation occurs non-linearly. • An optimal switching control model of a PEM Electrolyser water heating system is developed. • The model is used to maximize the heat recovery to the domestic hot water storage tank. • Simulation is performed using SCIP solver in MATLAB software. • Result shows that using the model, heat can be effectively recovered from the PEM and used for water heating. • The lifespan of the Electrolyser's membrane could be prolonged, as an added benefit from heat recovery. [ABSTRACT FROM AUTHOR]

Hybrid green energy system, consisting of photovoltaic (PV), fuel cell and battery, receives wide attention because of its autonomy, flexibility and promising potential in accelerating the development of carbon neutrality in the field of power generation. However, the efficient power dispatching of the hybrid energy system is challenging due to the inevitable uncertainties of the solar energy. To this end, stochastic dynamic programming (SDP) is used in this paper to find the optimal solution to minimize the total fuel consumption during a 72-hour operating cycle, with constraints on the magnitude and rate of the fuel cell and battery operation, in which the stochastic characteristics of the solar power are described by Markov chain. The influence of sampling time and number of states on the solar prediction accuracy is discussed. For comparison, the traditional rule-based algorithm and dynamic programming (DP) algorithms are also utilized to describe and solve the power distribution problem, corresponding to different decision results in terms of how to distribute the energy flow for each time period. Numerical optimization results within the 72-hour period demonstrate that, the SDP has a 20.61% economy and 66.34% battery SOC improvement than that of rule-based algorithm, and in most uncertain cases, the SDP produces superior economic performance than those of both the rule-based algorithm and DP, benefited from the inclusion of the solar power probabilities into the optimization framework. The results of this paper lay a solid foundation for the efficient energy management of the hydrogen and solar hybrid energy system. The stochastic dynamic programming is used in this paper to deal with the uncertainties in solar energy and find the optimal energy scheduling of a hybrid fuel cell/PV/battery system. Numerical optimization results demonstrate that, in most uncertain cases, stochastic dynamic programming produces superior economic performance than those of both the rule-based and dynamic programming algorithm. The results lay a solid foundation for the efficient energy management of the hydrogen and solar hybrid energy system. [Display omitted] [ABSTRACT FROM AUTHOR]

• A grid-connected solar PV-based multigeneration energy system is presented. • Economic, energy, environmental assessment for the proposed system is carried out. • Single objective/multi-objective optimization scenarios are analyzed and compared. • Sensitivity analysis is conducted to point out the effect on system performances. Solar photovoltaic-based multigeneration energy systems (SPVMES) which can use the excess energy of photovoltaic (PV) systems for heating and hydrogen production to improve the self-consumption of solar PV, have gained wide attention as a promising solution for clean and efficient production. To reliably meet diverse energy demands, gird system is integrated into a SPVMES as a backup energy source. In this paper, a grid-connected SPVMES is established to meet the electricity, heating and hydrogen loads, including PV, electrolysis, solid oxide fuel cell, electric heater for small-scale centralized heating and energy storage devices for electricity, heating and hydrogen storage, respectively. The emphasis to focus on when designing and dispatching the SPVMES lies in system performance evaluation. The innovation of this paper is to design and dispatch such a grid-connected SPVMES in a preliminary design stage through economic, energy and environmental assessment by considering cost of energy (COE), energy rate (ER) and renewable fraction (RF). Simultaneously, to explore which single objective/multi-objective optimization has better performance in comprehensive system evaluation, four different scenarios named COE optimization, RF optimization, ER optimization and multi-objective optimization are analyzed and compared. The specific application processes of component sizing and system dispatching with different optimization objectives are presented in detail. The results show that the proposed system has the COE of 0.0343$ in COE optimization scenario, the ER of 0.9128 in ER optimization scenario and the RF of 0.8811 in RF optimization scenario, which shows its significant potential in economic, energy efficiency and environmental performance. By comprehensively scoring the four optimization scenarios, it can be found that the multi-objective optimization scenario has better performance in system performance evaluation compared to the other three single objective optimization scenarios. Additionally, the multi-objective optimization could balance the tradeoff of COE, RF and ER and compromise the results of the single objective optimization scenarios. Potentially, sensitivity analysis is conducted to point out the effect of discharging depth of battery, PV subsidy, linear increasement of loads and seasonality effect on system performances. [ABSTRACT FROM AUTHOR]

Road transportation is a significant source of CO 2 emissions and energy demand. Consequently, initiatives are being promoted to decrease the sector's emissions and comply with the Paris agreement. This article synthesizes the available information about heavy-duty fuel cell trucks as their deployment needs to be considered a complementary solution to decreasing CO 2 emissions alongside battery electric vehicles. A thorough evaluation of 95 relevant documents determines that the main research topics in the past ten years converge on public policies, hydrogen supply chain, environmental impact, drivetrain technology, fuel cell, and storage tank applications. The identified research gaps relate to expanding collaboration between institutions and governments in developing joint green macro policies focused on hydrogen heavy-duty trucks, scarce research about hydrogen production energy sources, low interest in documenting hydrogen pilot projects, and minimal involvement of logistic companies, which need to plan their diesel freight's conversion as soon as possible. [Display omitted] • A review of 95 papers about hydrogen fuel cell heavy-duty trucks is presented. • A bibliometric analysis shows a 270% growth in published papers from 2019 to 2021. • Six popular topics emerge as leading research areas. • The trendiest topics are environment, hydrogen supply chain, and trucks' drivetrains. • Main research gaps relate to private involvement and government collaboration. [ABSTRACT FROM AUTHOR]

HydSL hydrogenase from Thiocapsa bogorovii BBS (formerly Thiocapsa roseopersicina BBS) is NiFe hydrogenase belonging to 1e subgroup. Recently it was shown that C-terminal domain of HydS subunit is important for hydrogenase docking to transmembrane protein Isp1 for electron transfer (https://doi.org/10.1016/j.bbabio.2021.148492.) It is suggested that this C-domain is a hydrophobic transmembrane alpha helix located near distal FeS claster. Using this peculiarity, a simple method for oriented HydSL hydrogenase immobilization on a hydrophobic carbon electrode is developed. The method is based on the incubation of the hydrogenase with carbon paper Freudenberg H24C3 or Vulcan nanoparticles in the solution of MOPS buffer and isopropanol alcohol with ratio 1/2 (v/v) with slow (15 h) evaporation of the solution in humidified atmosphere. The developed electrodes were applied to the fuel cell with Pt catalyst as the oxygen electrode and produced 2 mW cm−2 power with current at this power more than 6 mA cm−2. Furthermore, the fuel cell was stable after 49 days of incubation under the air atmosphere with periodic measurements with some power and current increase. [Display omitted] • HydSL hydrogenase from Thiocapsa bogorovii has hydrophobic C-terminus near the distal FeS claster. • A simple method for oriented immobilization of HydSL hydrogenase of on hydrophobic carbon electrodes was developed. • FC with hydrogenase electrode and Pt oxygen electrode showed power ∼2 mW cm−2 at currents above 6 mA cm−2. • The FC with hydrogen electrode was stable for 49 days. [ABSTRACT FROM AUTHOR]

On the road towards greener aviation, hybrid-electric propulsion systems have emerged as a viable solution. In this paper, a system based on hydrogen fuel cells is proposed and evaluated in a laboratory setting with its future integration in a propulsive system in mind and main focus on the ability to lessen the power demand on the opposing side of the bench. The setup consists in a parallel architecture with two power sources: a hydrogen fuel cell and a battery. First, the performance of the fuel cell and its capability to provide power to one of the motors are analyzed. Then, the entire parallel hybrid system is evaluated. Although the experimental setup was shown to be sub-optimal, the results demonstrated the ability of this greener alternative to reduce power demand on the opposing side of the parallel configuration, with a reduction of up to 40.3% in the highest load scenario, and maximum power output on the fuel cell of 257.8 W. The stack performance was also concluded to be very dependent on the operating temperature. [Display omitted] • A parallel hybrid architecture using batteries and fuel cells was tested. • Splitting power from one side to the other may lessen fuel requirements. • The fuel cell performance was found to depend greatly on the testing conditions. [ABSTRACT FROM AUTHOR]

This paper reports the performance of a molten carbonate fuel cell (MCFC) fed directly with liquid fuels referenced against results with hydrogen fuel in experiments conducted by the research team. Alcohols have greater energy density than pure hydrogen in normal conditions and, if presented as biofuels, the MCFC can be deemed a renewable energy source. For evaluation purposes various alcohols occurring in standard conditions in the liquid state were used for electricity generation in the MCFC: methanol, ethanol, propanol, butanol and glycerol. Since these alcohols can be subjected to steam reforming when mixed with water in specific ratios, they can be delivered directly in the liquid state to the fuel cell, where hydrogen is released and used to produce electricity and heat. The alcohols were mixed with water in ratios of 1:2, 1:3, 1:4. The results were compared to the MCFC fed with pure hydrogen as a fuel. In terms of power referenced to hydrogen (100%), the maximums achieved were 78% for butanol, 80% for glycerol, 83% for propanol, 86% for ethanol and 93% for methanol in comparison to the same amount of hydrogen delivered to the fuel cell in ideal steam reforming situation. Threats such as carbon deposition on the fuel cell surface were also evaluated. • MCFC fed directly with various mixtures of alcohols and water have been studied. • The steam reforming of mixtures of alcohols and water generates energy. • Temperature and anode material provide the necessary conditions for steam reforming. • Maximum power compared to hydrogen fuel for various fuels ranges between 78 and 93%. • Carbon deposition in the anode channel of commercial units can be a problem. [ABSTRACT FROM AUTHOR]

To balance the hydrogen consumption of fuel cell vehicle (FCV), the durability of the fuel cell (FC), and the life of the power battery (PB) to further reduce the whole lifecycle costs of FCV. A multi-objective reinforcement learning-based (MORL-based) energy management strategy (EMS) is proposed in this research. First, the composition mechanism of the FCV lifecycle costs is analyzed, and the equivalent hydrogen consumption model, FC durability degradation model, and PB life decay model are established; Then, a three-dimensional reward function is constructed by integrating the objectives of equivalent hydrogen consumption, FC durability degradation, and PB life decay. And the penalty terms coupled with the decay factors are introduced into the reward function to satisfy the mutual constraint characteristics between the PB and the FC system to ensure the stability of the MORL-based EMS; In addition, the prioritized experience replay technology is introduced into the MORL-based EMS to improve the learning efficiency and convergence of traditional deep Q network (DQN) algorithm; After that, the evaluation and target network of the embedded dueling network are introduced to solve the multi-objective overestimation problem encountered in the training process by generalizing the behavior learning in the presence of similar value behaviors; Finally, the performance of MORL-based EMS and DQN-based EMS is compared by numerical simulation under various driving cycles. The results show that the MORL-based EMS proposed in this paper has better convergence ability, adaptability, and lower lifecycle costs than the DQN-based EMS. In addition, the lifecycle costs of the MORL-based EMS can achieve a 99.2% control effect of the dynamic programming-based EMS. • The prioritized dueling double deep Q network-based EMS is proposed for an FCV. • Three objectives are considered in the PD3QN-based EMS. • Considering the battery life decay, EMS can better reduce the life cycle costs. • The PD3QN-based EMS can achieve a 99.2% control effect of DP-based EMS. • The PD3QN-based EMS can achieve good convergence ability and adaptability. [ABSTRACT FROM AUTHOR]

This article presents an overview of existing fuel cell technologies with a focus on their microgrid applications with and without heat and power coupled cycles. The cogeneration aspects of FCs in microgrid environment are also highlighted in this article. The paper also focuses on providing a detailed idea about the pros and cons of different types of FCs. A brief idea about the working process and construction of the PEMFC is also included in this article. This article mostly emphasizes the control and management issues which are encountered during the operation of a PEMFC. Different control strategies as well as robust control techniques used for the efficient management of PEMFC are also included in this article. The article articulates different type of control strategies to tackle deficiency of fuel (hydrogen and oxygen) in proton exchange membrane fuel cell (PEMFC) systems. [Display omitted] • Comparative studies of all FCs are presented and their properties are discussed briefly. • It also reviews the FCs which can operate in hybrid cycles with their respective efficiency. • The FCs implementation in microgrid topology, their faults and classifications are studied. • A brief study on Control techniques to prevent hydrogen and oxygen deficiency in PEMFCs is presented. [ABSTRACT FROM AUTHOR]

In this paper, we focus on addressing the air supply problem for fuel cells. The air supply system faces a challenge: operating at maximum load consumes a significant amount of power, while insufficient air can lead to oxygen starvation problems in fuel cells. An important metric, the oxygen excess ratio, indicates whether the fuel cell is receiving the appropriate amount of air. Unfortunately, directly measuring this ratio is generally impractical. To overcome this limitation, we propose a fixed-time observer that reconstructs the oxygen excess ratio within a short predetermined period. By utilizing this reconstructed index, we introduce a cascaded double-loop controller. Specifically, both the external and internal loops are regulated using a modified prescribed time control strategy. This approach enables the regulation of the oxygen excess ratio to the optimal value within a prescribed short time. The advantages of our proposed method are validated through hardware in-loop experiments, showcasing its superiority over conventional finite-time control techniques. • The controller ensures the oxygen excess ratio is regulated in a prescribed time. • The oxygen excess ratio is unmeasurable, so we estimate it by a Fixed-time observer. • A comparison with finite-time control is presented in a hardware-in-loop experiment. • The proposed method shows robustness against disturbance and parameter uncertainties. [ABSTRACT FROM AUTHOR]

The start-stop performance of gas foil bearings (GFBs)-rotor system directly affects the operation range and energy consumption of the air compressor for hydrogen fuel cell vehicles which has the inherent characteristic of frequent start and stop. In this paper, the effects of three factors including cooling gas flow, cooling gas pressure, and cooling gas type on the start-stop performance of the GFBs-rotor system are experimentally investigated for the first time. Based on the start-stop response analysis, the take-off speed of 6576 rpm and power consumption of 0.61 kW for the optimum GFBs-rotor system are obtained. The performance of the proposed system for the centrifugal air compressor is compared with the commercial products. The comparison shows that the lowest speed can be decreased by 34.2% while the operating range is expanded by 8.6%, which can in turn improve the performance of the centrifugal air compressors in hydrogen fuel cell vehicles. [Display omitted] • Effects of cooling gas on the start-stop performance were considered. • Start-stop response of the GFBs-rotor system in start-stop processes was studied. • Optimal operating parameters of the GFBs-rotor system were proposed. • Optimal system with minimum takeoff speed and power consumed was identified. • Verification of the optimum GFBs-rotor system was carried out. [ABSTRACT FROM AUTHOR]

Recently, to reach zero emission levels, some new energy systems based on fuel cells have been developed. This paper presents a review of investigations of these systems by thermodynamics performance, mainly, energy and exergy analysis. With energy analysis, the performance of an energy conversion system cannot be effectively and accurately evaluated. But exergy analysis complements and reinforces energy analysis. Using exergy analysis in relation to the degree of irreversibility in each section is a quality method and can be useful in fuel cell analysis. Analysis based on the first and second laws of thermodynamics seems useful in most cases and here reviews for low-temperature and high-temperature fuel cells are given. As a result, regardless of the type of the FC-system and its application, there is always a need of thermo-economic analysis to investigate the effect of various parameters on the system performance, such as different fuel sources, different operating conditions, different subsystems and energy sources to combine with the fuel cell. [Display omitted] • Thermodynamic performance by energy and exergy analysis of different fuel cell systems is reviewed. • New hybrid systems of fuel cells (i.e., PEMFCs, DMFCs, MCFCs, or SOFCs), subsystems and energy sources are analyzed. • Applications of FC-systems in cogeneration (i.e., CHP, CCP, CCHP), residential, industrial, etc. are described thoroughly. • Parametric analysis of FC-systems with different fuels is included. • Comparative assessment is conducted based on system design, infrastructure, and efficiencies. [ABSTRACT FROM AUTHOR]

In this paper a dynamic membrane electrode assembly water transport model, based on the Finite Volume Method, is presented. The purpose of this paper is to provide an accessible and reproductible model capable of real time simulation. To this aim, a detailed explanation is provided regarding the equations and methods used to compute the physical-based fuel cell model. Additionally, the model is purposely developed using basic code (on Matlab™), to not be limited to a single programming language. Two phase water transport through multi-gaseous porous media (electrodes), interfacial transport, as well as diffusion, convection, and electro-osmosis within the polymer are considered. The main novelty relies in the restructuring of all equations into a single implicit system, which can iteratively be resolved through LU decomposition. This computationally efficient method allows the model to be capable of real-time simulation, by displaying the membrane water content profile evolution on a 3D figure. For nominal PEMFC operating conditions, a dry membrane reaches 35% of its final water concentration value after 2 s, and fully converges after 20 s. The final water content profile displays an 18% gradient (9 and 11 molecules per sulfonic acid sites on the anode and cathode sides, respectively). To calibrate and validate this model, mass transfer (flowmeter) and electrical (ohmmeter) methods have been applied. • Dynamic membrane electrode assembly water transport model, based on finite difference method. • Water transport equations and resolution process detailed, to aim for model reproducibility. • Restructuring of water transport equations into implicit equation system. • Iterative equation system resolution through LU decomposition, allowing for real time simulation. • 3-dimensional figures of Nafion™ hydration profile, to study its behavior. [ABSTRACT FROM AUTHOR]

The most critical development in conventional underwater applications in recent years is to use hydrogen energy systems, including Air Independent Propulsion (AIP) systems. Proton Exchange Membrane (PEM) fuel cell-powered AIP systems increase interest worldwide. They offer many advantages such as longer endurance time without going to the surface for 2–3 weeks or without snorkeling with an average speed, perfectly silent operation, environmentally friendly process, high efficiency, and low thermal dissipation underwater. PEM fuel cells require a continuous source of hydrogen and oxygen as reactants to sustain a chemical reaction to produce electrical energy. Hydrogen storage is the critical challenge regarding the quality of supplied hydrogen, system weight, and volume. This paper reviewed hydrogen/oxygen storage preferences coupled with PEM Fuel Cell applications in the literature for unmanned underwater vehicles. Since underwater vehicles have different volume and weight requirements, no single hydrogen storage technique is the best for all underwater applications. • Hydrogen is the preferred fuel for underwater vehicles. • Underwater vehicles use hydrogen energy systems having Air Independent Propulsion (AIP) systems. • This paper review H 2 /O 2 storage preferences coupled with PEM Fuel Cell applications for unmanned underwater vehicles. • Compressed, and metal hydride-based H 2 storages are suitable for small to medium submarines. [ABSTRACT FROM AUTHOR]

This study deals with the manufacturing of catalyst-coated membranes (CCMs) for newcomers in the field of coating. Although there are many studies on electrode ink composition for improving the performance of proton-exchange membrane fuel cells (PEMFCs), there are few papers dealing with electrode coating itself. Usually, it is a know-how that often remains secret and constitutes the added value of scientific teams or the business of industrialists. In this paper, we identify and clarify the role of key parameters to improve coating quality and also to correlate coating quality with fuel cell performance via polarization curves and electrochemical active surface area measurements. We found that the coating configurations can affect the performance of lab-made CCMs in PEMFCs. After the repeatability of the performance obtained by our coating method has been proved, we show that: (i) edge effects, due to mask shadowing - cannot be neglected when the active surface area is low, (ii) a heterogeneous thickness electrode produces performance lower than a homogeneous thickness electrode, and (iii) the origin and storage of platinum on carbon powders are a very important source of variability in the obtained results. [Display omitted] • The coating thickness and its profile depend on the type of Pt/C powder. • The coating configuration pattern affects the performance in PEMFC. • The thickness of the mask affects the homogeneity of the coating. • The type and storage of Pt/C are a source of variability in the obtained results. [ABSTRACT FROM AUTHOR]

The number of working points and response speed are two essential characteristics of proton exchange membrane fuel cell (PEMFC). The improper setting of the number of working points and response speed may reduce the life of PEMFC and increase the hydrogen consumption of the vehicle. This paper explores the impact of the response speed as well as the working points of the PEMFC on the hydrogen consumption in the real-system level. In this paper a dynamic model of the PEMFC system is established and verified by experiments. The model is able to reflect the dynamic response process of PEMFC under a series different number of working points and different response speed. Based on the proposed model, the influence of working points and the response speed of PEMFC on the hydrogen consumption in the vehicle under different driving cycles is analyzed and summarized, for the first time, in the open literature. The results highlight that the hydrogen consumption will decreases in both cases that with the increase of working point number and increase of response speed. However, the reduction range of hydrogen consumption trends to smaller and may reach to an optimal level considering the trade-off between the hydrogen saving and the other costs, for example the control cost. Also, with a more complex driving cycle, the working points and response speed have a greater the impact on the hydrogen consumption in the vehicle applications. • A dynamic response model of PEMFC considering working points number and response speed is established. • PEMFC dynamic response model is developed and enhanced by experiments. • Discover the influence of working points number and response speeds of PEMFC on hydrogen consumption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different efficient energy conversions of ammonia are comprehensively reviewed. • Existing work on theoretical and experimental aspects of ammonia hybrid systems for hybrid vehicles is summarized. • The possibility of ammonia hybrid systems for automotive use is recognized. • The future research direction of ammonia new energy hybrid vehicles is pointed out. Ammonia is recognized as a promising and environmentally friendly energy source. This paper provides a comprehensive overview of emerging ammonia hybrid power systems and a detailed examination of the potential applications of this technology in automotive scenarios. Firstly, it summarizes three important ammonia energy conversion technologies in hybrids: ammonia internal combustion engine (A-ICE), direct ammonia fuel cell (DAFC), and ammonia decomposition, analyzing the technical characteristics and future development trends of each. Subsequently, this paper further discusses the architectural features of the new energy hybrid powertrain, highlighting the potential for a highly efficient hybrid powertrain based on the combination of the aforementioned powerplants. Currently, modeling optimization plays a crucial role in advancing research on the architecture of ammonia hybrid powertrains. The paper presents a comprehensive review of current research on energy management strategies (EMS) for hybrid vehicles. It discusses the key elements of model building, optimization objectives, and method selection in detail. Furthermore, the direction of these key elements in ammonia hybrid systems is also indicated. [ABSTRACT FROM AUTHOR]

During the driving of the fuel cell vehicles, temperature fluctuations occur in the Proton Exchange Membrane Fuel Cell (PEMFC), whose output efficiency decreases and hydrogen consumption increases. Rule-based (RB) and proportional-integral-derivative (PID) controllers can roughly suppress the temperature fluctuation, but they cannot perform multi-objective optimization, which cannot reduce hydrogen consumption at the same time. To solve this problem, in the first step of this paper, the hydrogen consumption factor and the temperature fluctuation factor in the operating temperature control are introduced to design the DDQN controller. In the second step of this paper, the DDQN controller is trained offline and verified under simulation conditions. The simulation results show that compared with the RB controller and PID controller, the average temperature fluctuation of the DDQN controller is reduced by 27.27 % and 28.50 %, and the hydrogen consumption is saved by 1.78 % and 2.58 %, respectively. The research in this paper is innovative in that it reduces the hydrogen consumption of PEMFC and improves the driving range of fuel cell vehicles from a specific point of view. • Design a DDQN controller to achieve intelligent real-time control of the operating temperature of PEMFC. • It can effectively reduce temperature fluctuations of PEMFC under complex operating conditions. • Simultaneously considering controlling temperature fluctuations and reducing hydrogen consumption. [ABSTRACT FROM AUTHOR]

This paper proposes an extended interconnection and damping assignment passivity-based control technique to control the pressure dynamics in the fuel delivery subsystem of proton exchange membrane fuel cells. The fuel cell stack is a distributed parameter model which can be modeled by partial differential equations. In this paper, the segmentation concept is used to approximate the partial differential equations model by ordinary differential equations model. Therefore, each segment is having multiple ordinary differential equations to obtain the lump-sum model of the segments. Subsequently, a generalized multi-input multi-output lumped parameters model is developed in port-Hamiltonian framework based on mass balance to minimize the modeling error. The modeling errors arise due to the difference between spatially distributed pressures in the segments, and also due to the difference between the actual stack pressure and the measured output pressure of the anode. The segments interconnection feasibility is ensured by maintaining passivity of each segment. With consideration of re-circulation and bleeding of the anode in the modeling, an extended energy-shaping and output tracking state-feedback controller is proposed to control the spatially distributed pressure dynamics in the anode. Furthermore, a sliding mode observer of high order is designed to estimate the unmeasurable pressures with known disturbances. Performance recovery of output feedback control is accomplished with explicit stability analysis. The effectiveness of the proposed control approach is validated by the simulation results. [ABSTRACT FROM AUTHOR]

We investigate a novel gas diffusion layer/catalyst/membrane assembly based on low-cost carbon xerogels replacing the expensive plasma-pyrolyzed carbon black microporous layer (MPL). The tri-layer structure (carbon paper/carbon xerogel/carbon black) of the gas diffusion layer (GDL) was tailored to enhance the bi-phase (gas–liquid) flow dynamics. GDL synthesis was performed by immersing carbon paper in a resorcinol-formaldehyde-graphene oxide precursor solution, followed by thermal treatment. The end product is a carbon xerogel structure with incorporated graphene layers that counter the additional overpotential losses due to conductivity and mass-transfer limitations. MPL structure and porosity were controlled by performing xerogel crosslinking in a centrifugal field at different G-Forces, resulting in a highly conductive material with structural properties tailored to the application of interest. [ABSTRACT FROM AUTHOR]

Findings on PEMFC designs grew tremendously in the past decade. Commercially, PEMFCs are usually configured in a stack to achieve higher electrochemical output. However, the two-phase fluid transport in a multiple-cell stack raises the complexity of reactant diffusion towards the porous electrodes than a single-cell stack as the higher current generation naturally increases water and heat production. Ensuring optimum hydration with even thermal distribution is critical in maintaining the MEA durability and overall electrochemical performance. Therefore, this review paper provides a comprehensive discussion of how the inconsistencies in water and thermal distribution impact the electrochemical reactiveness within the cell and electrode layers of a multiple-cell PEMFC stack. Targeting the bipolar plate design is not only essential for uniform fluid distribution but it can also be used to maximise the contact surface area to achieve a greater reactant consumption rate. Hence, the effect of varying manifold, flow field and distribution zone designs towardthe fluid and reaction dynamics per cell of a multiple-cell stack were discussed based on available literature. Although the difference in water and heat saturation between single- and multiple-cell stacks could be highlighted clearly in this paper, more research is needed particularly for novel bipolar plate designs. This would be essential knowledge in generating an optimal bipolar plate design that can enhance the durability and performance of PEMFC stacks. • Water and temperature dispersal in multiple-cell PEMFC stacks differ from single-cell units. • Cell dehydration causes higher performance loss in fuel cells compared to flooding. • The fluid dynamics and electrochemical responses across a single-cell stack differ from a multiple-cell stack. [ABSTRACT FROM AUTHOR]

Abstract New multi-metallic materials have been synthesized to be used as active anodes in direct alcohol fuel cells. However, the separate steps of synthesis, characterization and preparation of the catalyst layer prior to their use are costly and time-consuming. Here, we propose a sustainable new method to in situ decorate catalysts with ad-atoms in flow-through porous electrode configuration. The ad-atoms are electrodeposited in a microfluidic fuel cell by driving the metallic precursor through the electrode under applied potential while blank electrolyte feeds the other half-cell porous electrode. Pt/C-modified carbon paper is decorated with Fe, which is subsequently used as an anode during operating the cell as a microfluidic direct glycerol fuel cell. The ultralow mass of Fe is calculated by integrating the reduction charge, in which the high residence time under controlled flow conditions increases the amount of Fe on Pt/C. The decoration can also be controlled by changing the concentration of the precursor, which is limited by the availability of Pt active sites. The power density of the obtained cell in flow-through porous electrode configuration is enhanced by 36% using the Fe-decorated anode, reaching ∼54 mW cm−2 at ∼0.7 V under mixed media conditions. Hence, the proposed method provides an effective means to modify, analyze and use bimetallic anodes at the same instrument and can be applied post-fabrication in any fuel cell or other flow cells with porous electrodes. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Hydrogen fueling stations (HFSs) with onsite hydrogen production systems, which are usually composed of electrolyzers, hydrogen storage tanks and fuel cells, not only supply hydrogen for hydrogen-powered vehicles but also serve as a dispatchable technology that can bid in electricity markets. Except participating in energy market, joining in reserve market can compensate the cost in energy market and increase the total revenue of HFS. This paper proposes a multi-stage stochastic programming model to find the optimal offering strategy of the HFS in energy, reserve markets taking into account a series of uncertainties: day-ahead price, secondary reserve price, system imbalance price and hydrogen demand. Nonanticipativity constraints are employed to guarantee the decisions are made according to the realized uncertainty information up to the present stage. Compared with traditional stochastic programming model, the proposed model adequately considers the sequential bidding decisions with the gradual revealing of the uncertainty over time. Numerical experiments based on one case study indicate that the participation of reserve market greatly increase the revenue of HFS. In addition, the proposed multi-stage stochastic programming model is effective in characterizing the sequential decision. • This paper proposes a multi-stage stochastic programming model. • To find the optimal offering strategy of the HFS in energy, reserve markets. • A series of uncertainties such as day-ahead price, and hydrogen demand are considered. • Nonanticipativity constraints are employed to guarantee the sequential decisions. [ABSTRACT FROM AUTHOR]

System risks caused by volatility spillover would possibly threaten the stability of financial markets. Effective control of volatility spillover is conducive to prevent of financial system risks. Therefore, this paper studies volatility spillover in the main renewable energy markets from 2010 to 2019 and analyzes how risks spread in hope of finding effective management to reduce financial system risks. For this purpose, this paper identifies the volatility spillover effect from a multidimensional perspective by using the BEKK model and reveals the risk spread path by using the multidimensional analysis method. Further, the risk spread relationships among the renewable energy markets are comprehensively analyzed. The main findings of the paper are: (1) The volatility spillover in the renewable energy markets tends to exist in the high dimensions. (2) In the renewable energy market system, the volatility spillover relationships involving multiple markets are more complicated than those between two markets. (3) The fuel cell energy market and solar energy markets occupy a significant position in the path of risk spread which should be paid more attention by policymakers to prevent financial system risks. [ABSTRACT FROM AUTHOR]

Nowadays, different types of dispatchable and non-dispatchable distributed energy resource (DER) units, combined heat and power (CHP) plants as well as heat only units are integrated into a micro-grid (MG) platform. These facilities can help MG operators to satisfy the required electricity and heat demands of controllable and non-controllable loads even with no power exchange between the external main grid and the MG. This paper introduces a network constrained optimal operation model based on an integrated active-reactive and heat powers scheduling in MG for both grid-connected and isolated modes. The DERs like fuel cell (FC) units, diesel generators (DGs) and micro turbines (MTs) are motivated to take part in providing reactive power to the MG based on a reactive power payment function. Meanwhile, the dependency of produced heat and active power by CHP units through feasible operating region as well as the dependency of produced active and reactive powers by DER units through capability curves are taken into account in the optimal economic dispatch of the MGs. The main goal of this paper is to find the optimal economic dispatch of active and reactive powers as well as heat energy for DER and CHP based micro-grids in which network constraints such as AC power flow limitations are taken into consideration. The proposed model is examined on a 33-bus test MG for grid-connected and isolated modes and the simulation results are presented to investigate and analyze the different features of the proposed method. [ABSTRACT FROM AUTHOR]

An effective online fault diagnosis system is of great significance to improve the reliability of fuel cell vehicles. In this paper, a fault diagnosis model for proton exchange membrane fuel cells is proposed. Firstly, the tests of electrochemical impedance spectroscopy under different fault types (flooding, drying, air starvation) and fault degrees (minor, moderate, severe) are carried out, and each polarization loss of the fuel cell is denoted by an equivalent circuit model (ECM). Then, the parameters of the ECM are identified by the proposed random mutation differential evolution algorithm. Furthermore, the parameters identified under different fault conditions are used to train and test a probabilistic neural network-based fault diagnosis model. The fault diagnosis model achieves diagnosis accuracies of 100% for the fault type and 96.67% for the fault degree. By setting operating conditions with different fault degrees, the fault diagnosis model proposed in this paper can realize the fault type and fault degree diagnosis, effectively avoiding the misjudgment of fault types, and is effective for improving the reliability of the fuel cell system. [Display omitted] • A RMDE algorithm is proposed to realize the impedance parameter identification. • A fault diagnosis model based on the probabilistic neural network is developed. • The diagnosis accuracies for fault type and fault degree reach 100% and 96.67%. [ABSTRACT FROM AUTHOR]

This paper presents computational and experimental studies of a vanadium microfluidic fuel cell using a novel configuration of multi-layer flow-through porous carbon paper electrodes. A priori modeling and simulation revealed that these porous substrates operated with non-uniform reaction rate and the reaction rate distribution is highly sensitive to the flow rate condition. Comparable cell performance was witnessed for electrodes partly modified in the high reaction rate region and electrodes modified in all parts. Therefore, multi-layer stacking of single-layer electrodes was proposed and implemented to facilitate selection of appropriate materials to accommodate the requirements of the different layers of the electrodes. Here, the electrode materials studied were pristine carbon paper and electrochemically superior platinum coated carbon paper. The results stemmed from modeling and experiments consistently revealed that the highest peak power densities were obtained in the case with electrode modification in the high reaction rate region. This study highlights the significance of the multi-layer electrode configuration associated with the balance between performance and cost of this energy system. Moreover, the multi-layer electrode configuration offers flexibility in terms of changing layer arrangement to cope with the operating condition leading to superior cell performance. [ABSTRACT FROM AUTHOR]