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This paper examines the potential of solar and hydrogen (H 2) energy-based hybrid energy systems for residential applications. The growing need for energy and the demand for sustainable energy sources have led to the development of integrated energy systems that combine renewable energy resources to meet energy needs. This paper overviews recent studies on hybrid energy systems for on-grid and off-grid residential utilizations. It discusses the system configuration and components of hybrid energy systems, including solar panels, electrolyzers, fuel cells (FC), and batteries. It also covers the technical optimization of integrated energy systems, including sizing, control strategies, and economic analysis. The key findings of this review paper indicate that hybrid energy systems can offer dependable and sustainable energy for residential applications. Through numerical analyses, the optimal dimensioning of the system elements and control strategies can significantly enhance the system's performance and lower the cost of energy. This study also highlights the challenges and opportunities for integrating hybrid energy systems within residential applications. Overall, it provides in-depth perspectives on the possibilities inherent in solar and hydrogen energy-based hybrid energy systems for residential applications. The findings can guide future research and the advancement of hybrid energy systems for sustainable energy solutions. • Comprehensive review on solar and hydrogen-based residential applications. • Holistic approach to system configuration, optimization, and economics. • Detailed analysis of interconnected components enhancing system efficiency. • Unique focus on real-world residential applications and scenarios. • Broad applicability across diverse geographical regions. [ABSTRACT FROM AUTHOR]

The single-stack fuel cell system is utilized extensively in several industries. Unfortunately, the main problems are its low efficiency and durability, and unsatisfied reliability, especially in the high-power situation. Due to its significant performance, which includes high output power, durability, and reliability, multi-stack fuel cell systems (MFCS) are becoming more and more attractive. In this study, it is aimed to develope a control algorithm in parallel structure in the Matlab/Simulink software for the efficient use of hydrogen fuel consumption of PEM fuel cells – based boost converter using PI controller with PSO method. Models of both single and parallel connected PEM fuel cells were created in Matlab using mathematical equations in this paper. The analysis made in the study were applied for both models. PEMFCs were connected in parallel and only one DC-DC converter was used for the entire system. According to the load change, the required number of cells are activated due to control algorithm to provide the required power. As a result, the proposed method reduces hydrogen consumption by approximately 5 times under the same load, while optimized parameters reduce output voltage oscillation. • A new control algorithm for parallel connected PEM fuel cell has been successfully implemented. • The suggested method reduces hydrogen consumption by approximately 5 times under the same load. • Using small-capacity fuel cells instead of huge ones minimizes hydrogen consumption. • Optimized parameters decrease the voltage oscillation. [ABSTRACT FROM AUTHOR]

This paper presents a cryogenic turbo-electric hybrid propulsion system (TEHPS) for a 70–80 seat class turboprop regional aircraft, integrating superconducting technology with liquid hydrogen (LH 2) cooling. LH 2 is selected as the cooling medium for the designed cryogenic cooling circuit, and the evaporated hydrogen gas is channeled to a hydrogen fuel cell for electricity generation, making full use of the energy content of the hydrogen. Parametric modeling of critical components is conducted to determine mass, power and heat loss parameters under feasible operating temperature conditions. Four propulsion schemes are conceptualized based on power matching combinations of turbo-engines, hydrogen fuel cell and battery during cruise, descent and landing phases. Performance comparison and analysis of the cryogenic TEHPS for a typical mission profile in 2035 is conducted, considering three projected scenarios – conservative, baseline, and optimistic – derived from existing data. The results show that propulsion Scheme 1, combining turbo-engines, fuel cell and battery for cruise, significantly reduces aviation fuel mass and pollutants emissions, cutting fuel consumption by 34.2%–38.6% at specific power parameters and potentially doubling the cruising range. Propulsion Scheme 3, employing turbo-engines for cruise and a combination of fuel cell and battery for descent and landing, achieves the lowest total mass and highest power-to-weight (PTW). In optimistic scenarios, the PTW ratio reaches 2.40 kW/kg, with baseline and conservative scenarios at 1.81 kW/kg and 1.16 kW/kg respectively, demonstrating significant advancements in propulsion efficiency and sustainability. • Innovative design for a cryogenic turbo-electric hybrid propulsion system. • Developed a cryogenic cooling circuit for efficient hydrogen energy recovery. • Detailed dimensional modeling of critical system components. • Evaluation of performance parameters in different scenarios and propulsion schemes. [ABSTRACT FROM AUTHOR]

The shared energy storage system is recognized as a promising business model for the coordinated operation of integrated energy systems (IES) to improve the utilization of energy storage and the consumption of renewable energy. As the hydrogen energy gradually receives more attention, this paper constructs the structure of a hybrid hydrogen energy storage system shared by an IES alliance in a dynamic pricing mode. A bi-level optimization model for the shared hybrid hydrogen energy storage system (SHHESS) is proposed to optimize the capacity configuration decisions and the pricing strategy jointly. The upper level determines the capacity and dynamic price of SHHESS with maximum profits and the lower level obtains the optimal operation of the IES alliance minimizing the total operation costs. The proposed model is solved by an improved PSO-GA algorithm and CPLEX solver. Finally, numerical tests are conducted in different scenarios. The results show that the hybrid energy storage system improves the daily profits of SHHESS by 70.3% and 5.44%, and reduces the renewable energy curtailment by 80.93% and 48.92% respectively compared to the battery-only and hydrogen-only systems. Additionally, the daily operation cost of the IES alliance is 35.2% lower than the individual operation scenario. The proposed model confirms the feasibility and superiority of the hybrid hydrogen energy storage system in a sharing business mode. • Design an interactive structure of a shared hybrid hydrogen energy storage system. • Propose a bi-level planning optimization framework for shared hybrid hydrogen energy storage. • The dynamic price of energy storage sharing service is optimized. • Determine the optimal operation strategy of the integrated energy system alliance. • Propose a hybrid method combining an improved PSO-GA and CPLEX optimizer. [ABSTRACT FROM AUTHOR]

This paper examines the complex relationship between the role of H 2 , carbon emissions and their impact on global warming and the economy. Despite improvements in energy efficiency, fossil fuel consumption continues to increase. CO 2 from industrial activities at high temperatures, such as cement, iron, steel and glass production, have increased rapidly, resulting in an increase in the concentration of greenhouse gases in the atmosphere. These emissions accelerate climate change, leading to dangerous consequences such as increasing average atmospheric temperature and decreasing agricultural productivity. To combat this, it is advocated to reduce CO 2 emissions by using renewable energy sources such as hydroelectricity, biomass, wind solar energy. Current study also discusses carbon reduction methods, including oxy-fuel combustion capture, pre-combustion capture, and post-combustion capture. Despite their unique advantages and disadvantages, these methods play an important role in reducing CO 2 emissions from power plants. Additionally, the article highlights the importance of H 2 as a cornerstone in the development of synthetic fuels and future energy systems. H 2 from renewable sources holds the potential to use carbon-neutral synthetic liquid fuels and revolutionize transportation. Although traditional H 2 production methods are associated with emissions, sustainable H 2 production techniques can facilitate low-carbon fuel production. The article concludes by highlighting the importance of sustainable energy practices and the role of H 2 in reducing carbon emissions, highlighting research efforts to improve production methods, integrate renewable energy, and develop carbon capture technologies for a sustainable future. • Methods used in synthetic fuel production and sources of hydrogen production. • Carbon capture methods and their comparative discussion. • The importance of hydrogen production in synthetic fuel production and future plan. [ABSTRACT FROM AUTHOR]

Regional integrated energy systems (RIES) can economically and efficiently use regional renewable energy resources, of which energy storage is an important means to solve the uncertainty of renewable energy output, but traditional electrochemical energy storage is only single electrical energy storage, and the energy efficiency level is low. Hydrogen energy storage has the advantages of large energy storage capacity, long storage time, clean and pollution-free, and can realize the synergistic and efficient utilization of electricity and thermal power. Based on this, this paper proposes a synergistic planning method for an integrated energy system with hydrogen storage taking into account the coupled use of electric-thermal energy, which effectively reduces the system carbon emission and improves the comprehensive energy efficiency level. Firstly, this paper constructs an electric-thermal coupling model of the hydrogen energy storage unit and proposes an optimization strategy for the integrated energy system containing hydrogen storage taking into account the utilization of electricity and thermal power. Secondly, a planning optimization model with the lowest economy and carbon emission and the highest comprehensive energy efficiency was constructed. Third, the CSPO-GE optimization algorithm is proposed for solving the problem, which significantly improves the solution efficiency. Finally, a planning optimization simulation of RIES for a residential community W in northern China verifies the effectiveness of the model and method proposed in this paper. The comparative analysis of the three schemes shows that compared with the integrated energy system with conventional electrochemical energy storage and heat storage tank as the main form of energy storage and the integrated energy system with only hydrogen storage, the integrated energy system with hydrogen storage and heat storage tank can reduce carbon emissions by 43.8% and 7.61%, respectively, and improve the integrated energy efficiency level by 337.14% and 14.44%. • An electrothermal coupled production strategy based on dynamic equilibrium feedback regulation is proposed. • A hydrogen-containing RIES planning and optimization model considering economy-environment-efficiency is constructed. • A multi-objective chaotic particle swarm algorithm (CPSO-GE) based on greedy and elite retention strategies is proposed • The impact of cost variation of hydrogen storage devices on the economics of integrated energy systems is considered. [ABSTRACT FROM AUTHOR]

Considering the escalating global warming and its severe consequences, the exploitation of hydrogen, an eco-friendly energy carrier, is gaining great interest. This paper comprehensively reviews the most common hydrogen production, storage, transportation and utilization processes, while their effectiveness is explored from energy, water, economic and environmental perspectives. Their main characteristics, advantages, shortcomings and challenges are discussed as well. The research reveals that the hydrogen's water footprint, energy consumption, carbon emissions, and cost vary significantly depending on the specific technologies used throughout its life cycle, from production to end use. For instance, fossil fuel-based hydrogen production methods, such as steam methane reforming, offer elevated energy performance and cost-effectiveness, but have a significant carbon footprint. In contrast, water electrolysis is environmentally friendly, but requires more water and has lower energy efficiency. Besides, high-pressure containers are the preferred method for hydrogen storage, while liquid and solid storages are better suited for high-energy-density applications. Regarding hydrogen transportation, pipelines are effective over long distances, whereas tankers are convenient for short distances. Furthermore, fuel cells are more energy, carbon and water efficient when using hydrogen as fuel, but they are generally more expensive than internal combustion engines. [Display omitted] • Hydrogen production, storage, transportation and utilization methods are reviewed. • Their energy efficiency, water use, cost, and environmental impact are explored. • Key recommendations to boost the utilization of hydrogen systems are outlined. • Fossil fuel-based technologies are more energy-efficient and cost-effective. • Renewable-based processes are more environmentally friendly but water-intensive. [ABSTRACT FROM AUTHOR]

Financing, sizing, operating, or upgrading a hydrogen refueling station (HRS) is challenging and may be complex, much more so in today's rapidly changing and growing hydrogen industry. There is a significant information gap regarding experimental hydrogen station activities. A high-level perspective on such data and information may facilitate the transition between present and future HRS operations. To address the need for such high-level perspective, this paper presents a comprehensive data set on the performance of the California State University Los Angeles Hydrogen Research and Fueling Facility, based on multi-year operational data. The analysis of over 4500 refueling events and over 8800 kg of hydrogen dispensed, as well as the operation of the facility electrolyzer and of both storage and refueling compressors from 2016 to 2020, reveals a comprehensive picture of HRS energy performance and the identification of useful key performance indicators. In 2016, the station's energy efficiency was 25%, but in 2017 and the first three quarters of 2018, it dropped to 15%. Station-specific energy consumption increased during these quarters. The 2020 first quarter energy consumption was between 70 and 80 kWh/kg. At this time, the energy efficiency of the station reached 40%. This research is based on an unprecedented and unique dataset of an HRS operating under real-world conditions, with an approach that can be informative for modeling the performance of other stations, providing a dataset that HRS designers, operators, and investors may utilize to make data-driven choices regarding HRS components and their specs and size, as well as operating strategies. • Evaluation of the Energy Performance of an HRS from 2016 to 2020. • Multi-annual Assessment and Breakdown of the Station Energy Expenditure. • Analysis based on 4500 Refueling Events and over 8800 kg of Hydrogen Dispensed. • A new approach to HRS operation is recommended. • Usage of Historical Data Source to Document and Evaluate Station Performance. [ABSTRACT FROM AUTHOR]

The paper presents a critical analysis of a commercial pre-feasibility study for hydrogen generation from sewage sludge generated in a wastewater treatment plant sized Population Equivalent (PE) = 160,000 Three commercial offers based on hydrothermal carbonization, gasification/plasma gasification and gas separation, are analysed and validated in terms of chemical reactions and energy balance. The obtained hydrogen yield equals 10 kg H 2 /Mg sludge for Technology#2 and 5.5 kg H 2 /Mg sludge for Technology#3, while the process efficiency equals 31.4% and 41.2%, respectively. The offer for Technology#1 is inconsistent. The potential market can be built in the transport sector, based on buses (8–12/day) or locomotives (1–2/day) and complemented by passenger cars (16–22/day). Hydrogen surplus can be disposed into the natural gas network at a city gate station, with target concentration <2%. Alternatively, it is possible to install a fuel cell unit for on-site electricity generation of 1780 MWh/a sold to the public grid. • Commercial technologies of hydrogen production from sewage sludge were studied. • Technologies of hydrothermal carbonization and plasma gasification were validated. • 1 of 3 commercial offers was found inconsistent regarding thermodynamics. • Hydrogen yield was found 5.5–10 kg/Mg sludge. • Process energy efficiency was found 31.4%–41.2%. [ABSTRACT FROM AUTHOR]

The transition to a low-carbon energy system can be depicted as a "great reconfiguration" from a socio-technical perspective that carries the risk of impact shifts. Electrification with the objective of achieving rapidly deep decarbonisation must be accompanied by effective efficiency and flexibility measures. Hydrogen can be a preferred option in the decarbonisation process where electrification of end-uses is difficult or impractical as well as for long-term storage in energy infrastructure characterised by a large penetration of renewable energy sources. Notwithstanding the current uncertainties regarding costs, environmental impact and the inherent difficulties of increasing rapidly supply capacity, hydrogen can represent a solution to be used in multi-energy systems with combined heat and power (CHP), in particular in urban energy districts. In fact, while achieving carbon savings with natural gas fuelled CHP is not possible when low grid carbon intensity factors are present, it may still be possible to use it to provide flexibility services and to reduce emissions further with switch from natural gas to hydrogen. In this paper, a commercially established urban district energy scheme located in Southampton (United Kingdom) is analysed with the goal of exploring potential variations in its energy demand. The study proposes the use of scalable data-driven methods and probabilistic simulation to generate seasonal energy demand patterns representing the potential short-term and long-term evolution of the energy district. • Hydrogen role in the transition to low carbon energy systems for urban energy district. • Data-driven urban energy modelling using regression-based approaches. • Probabilistic modelling of energy demand in terms of electricity and fuels. • Climate change impact and energy efficiency measures accounting. • Seasonal variations of energy demand patterns from short-term to long-term scenarios. [ABSTRACT FROM AUTHOR]

In this paper, wind resource availability was determined by analyzing the meteorological wind energy potential at the hub height of wind turbines. The wind resource potential was identified in specific geographic locations. Technical factors, such as siting requirements and resource availability, were taken into account in the investigation. The economic potential was calculated for each area of Algeria, considering overall losses. Subsequently, the potential for reducing fossil fuel usage was determined through wind to hydrogen estimation. The main components utilized in this work were a Vestas-90 wind turbine (V90–2.0 MW) and an alkaline electrolyzer. The analysis employed a Geographical Information System (GIS) tool. The results demonstrate Algeria's significant potential for wind to hydrogen production, estimated at 1.093 Gt/year without constraints, and reduced to 1.066 Gt/year when considering constraints. The levelized cost of wind to hydrogen production in Algeria varies between 1.51 and 15.37 US $/kg, depending on the chosen wind turbine. The wind to hydrogen production potential identified has the capacity to replace the entire current fossil fuel consumption in the transportation sector, which amounts to 5.28 Mt H 2 /year. The utilization of wind to hydrogen in the transport sector results in a significant reduction of CO 2 emissions, with a calculated avoidance of 45.69 Mt compared to the use of gasoline and diesel. Hydrogen produced from wind energy resources also could be used to support other sectors, including residential, agricultural, and industry in Algeria. • GIS-Based approach is used to evaluate the potential for wind to hydrogen production in Algeria. • The total wind to hydrogen potential in Algeria, when considering constraints, is estimated at 1.066 Gt/year, covering an area of 730,719 km2. • The levelized cost of wind to hydrogen production in Algeria ranges between 1.51 and 15.37 US $/kg, depending on the selected wind turbine (V90–2.0 MW). • The CO 2 emissions avoided in the transport sector are 45.69 Mt compared if the same amount of gasoline and diesel used. [ABSTRACT FROM AUTHOR]

With rapid industrialization, rising fossil fuel consumption, and environmental concerns, developing clean and green energy is an inescapable option. Hydrogen has emerged as a significant potential energy carrier and a viable future replacement fuel for fossil fuels due to its renewable and pollution-free properties. Previous review papers have significantly contributed to the body of literature on the various technologies for producing hydrogen by revealing key insights into their working principles and conditions, as well as the economic and environmental aspects. In addition, they also highlighted the potential pathways to enable the application of these technologies in the context of carbon neutrality. However, these studies have not broken down the evolutionary patterns and developmental progress of either fossil fuel-based or renewable energy-based technologies used to produce hydrogen. In addition, the currently available literature does not contain the most recent research that focuses on the evolution and life cycle of each technology category from a chronological point of view. The key drivers, countries/regions, and their contributions to the field's development have received little attention. As a result, it is critical to monitor technological advances in hydrogen energy production and investigate the key enablers of these advancements. Against this backdrop, the current study employs patent analysis tools to achieve four primary goals: (1) to track the development trends in the field of hydrogen production from 2000 to 2019; (2) to identify and compare the recent development trends in the last five years according to the feedstock, i.e., fossil fuel, water, and biomass-based technologies; (3) to predict the technology life cycle of the two main groups of hydrogen production technologies (fossil and renewable); (4) to identify and compare the key drivers of hydrogen production technologies from a statistical standpoint. The findings of the study may aid in identifying technical prospects in the field of fossil and renewable-based hydrogen production, and decision-makers may use them as a reference in developing a strategic plan for future technological growth. • Patent review on hydrogen production technologies from 2000 to 2019. • Japan, US, China are the leading countries in the field. • Recent developments are focused on renewable energy-based technologies especially water. • Technology maturity rate of renewable-based technologies is about 57%. • R&D expenditure strongly promotes hydrogen production innovations. [ABSTRACT FROM AUTHOR]

World's energy demand is majorly met by fossil fuels. An increase in the demand for energy and the depletion of fossil fuels leads to look for the alternate source of energy. Hydrogen is one of the most viable alternate sources of alternate energy. This paper presents the performance study of a Compression Ignition engine using a fuel combination of diesel and hydrogen-diesel. The performance parameters have been analyzed with two input factors, load and Compression Ratio and three output responses, Brake Thermal efficiency (BTE), Brake Specific Fuel Consumption (BSFC) and Volumetric efficiency. The experimental results indicate the improvement in BTE, reduction in BSFC and volumetric efficiency. The BTE was improved by 6.38%, BSFC was reduced by 4.87% and Volumetric efficiency got reduced by 1.89% when hydrogen-diesel fuel is used in place of neat diesel. The experiments have been designed with the help of Design Expert® 13.0.5 using Response Surface Method. The experiments are conducted using Optimal (Custom) design. Mathematical relations are developed between the process parameters and the input factors using regression analysis. The optimal solution has been obtained using the desirability approach. The confirmation experiments have been performed on the optimal solution to verify with the experiment results. Results of the confirmation test shows that the developed mathematical are appropriate for the use in CI engine. • Use of Hydrogen (H 2) as alternate fuel in CI engine. • Experimental investigation of CI engine's performance parameters using Diesel and Hydrogen fuels. • Optimization of CI engine's performance parameters using Response Surface Method. • Performance parameters of H 2 fuelled CI Engine increased at higher compression ratio under varying load condition. [ABSTRACT FROM AUTHOR]

To reduce the energy consumption of the hydrogen liquefaction process, a hydrogen liquefaction process based on cascaded mixed refrigerant cycles is proposed in this paper. The two mixed refrigerant cycles are connected in series so that the cooling capacity of refrigerants can be fully utilized. Cascaded processes with different numbers of pre-cooling stages are compared. The processes are optimized using the particle swarm algorithm. And cascaded and non-cascaded processes are compared under the same conditions. The results show that the more the number of pre-cooling stages, the lower the SEC and the higher the exergy efficiency. And the cascaded process has higher energy efficiency than the non-cascaded process. The specific power consumption of the process is 5.664 kWh/kg LH2 , the coefficient of performance is 0.2322, and the exergy efficiency is 52.77%. This research can provide valuable ideas and methods for the improvement of hydrogen liquefaction process design. • A cascaded dual mixed refrigerant hydrogen liquefaction process is put up. • The cascaded process has higher energy efficiency than the non-cascaded process. • The SEC of the process is 5.664 kWh/kg LH2 and the exergy efficiency is 52.77%. • The efficiency of this liquefaction process reaches the highest level currently. [ABSTRACT FROM AUTHOR]

The use of hydrogen energy and the associated technologies is expected to increase in the coming years. The success of hydrogen energy technology (HET) is, however, dependent on public acceptance of the technology. Developing this new industry in a socially responsible way will require an understanding of the psychology factors that may facilitate or impede its public acceptance. This paper reviews 27 quantitative studies that have explored the relationship between psychological factors and HET acceptance. The findings from the review suggest that the perceived effects of the technology (i.e., the perceived benefits, costs and risks), and the associated emotions, are strong drivers of HET acceptance. This paper does, though, highlight some limitations with past research that make it difficult to make strong conclusions about the factors that influence HET acceptance. The review also reveals that few studies have investigated acceptance of different types of HET beyond a couple of applications. The paper ends with a discussion about directions for future research and highlights some practical implications for messaging and policy. • Perceived effects, and associated emotions, are strong predictors of acceptance. • Unclear what context-specific beliefs underpin attitudes towards hydrogen. • Most studies focused on acceptance of hydrogen fuel stations and hydrogen cars. • A dearth of research investigating acceptance of the whole hydrogen value chain. • Identified inconsistencies in the measurement of psychological constructs. [ABSTRACT FROM AUTHOR]

International trade volumes have grown due to acceleration of marine transportation of goods between continents. However, there is a concomitant increase in fossil fuel consumption and adverse environmental impact. This paper presents a new design of marine engines comprising of gas Brayton cycle, solid oxide fuel cell, and two organic Rankine cycles to replace two-stroke internal combustion engines. Hydrogen, methane, dimethyl ether, ethanol, and methanol are potentially selected as green fuels. In addition, liquified natural gas is used for cooling processes. This integrated hybridized marine engine is thermodynamically analyzed using the Aspen Plus software to assess its performance energetically and exergetically. It is found that the engine's total power is boosted by 33% to an average of 15758 kW with average energetic and exergetic efficiencies of 38% and 46%, respectively. The maximum power is fulfilled using all sustainable fuel blends to reach 16087 kW with a maximum carbon emission reduction of 83% and minimum specific fuel consumption. The proposed engine has better performance and less environmental impact, which is a more convenient choice than traditional engines. [Display omitted] • Five alternative fuels are chosen with different concentrations. • Integrated hybrid marine engine produces a total power of 16087 kW by 33% increase. • Engine runs at a 38% energy efficiency and 46% exergetic efficiency. • Alternative fuels can reduce carbon emissions by more than 80%. • New engine fuel consumption is reduced by more than 55%. [ABSTRACT FROM AUTHOR]

As the main energy consumption terminal and emission source, the engine is expected to achieve zero carbon emission with the help of hydrogen energy. Focusing on the current status and difficult issues of hydrogen engine research, this paper firstly emphasizes the importance of applying hydrogen energy in the future development of engines, secondly reviews and summarizes the development of hydrogen engines in terms of traditional structural inheritance and innovation, and then provides updated ideas for the development route of pure hydrogen fuel and the promotion of hydrogen fuel applications from the perspective of new combined fuels and industrialization challenges. A summary of the classification of hydrogen engine operating strategies is included to point out the prevailing regulation and influencing factors on hydrogen engines and the understanding of the working process. The obstacles to industrialization are related to a broader field, besides the field of scientific research, there are issues of infrastructure development, cost control, and safety standards development. • Different ignition and injection methods and mechanisms of hydrogen engines are investigated. • The inheritances and innovations of the hydrogen engine on the traditional structure are investigated. • Hydrogen engine working strategies are classified into four categories. • Blend fuels and clean alternative fuels other than hydrogen are investigated. • The challenges faced in the industrialization of hydrogen engines are investigated. [ABSTRACT FROM AUTHOR]

Linear hydrogen engine (LHE) is a new technology of hydrogen energy utilization due to its flexible compression ratio coupling with ignition, fuel-air mixing, and combustion to optimize thermal efficiency. Fuel-air mixing in LHE is expected to be promoted by using ignition, which differs with conventional engine. This paper develops a full-cycle model which couples with dynamics, hydrogen-air mixing and combustion to describe the effect of ignition position, meanwhile a loop iterative calculation method is proposed to solve the coupling model for hydrogen-air mixing predication. The results show that ignition position variation can cause the piston trajectory to change significantly, and the higher equivalent speed is obtained in the medium ignition position. Besides, the higher equivalent speed in the injection stage is conducive to the diffusion of hydrogen, but the higher equivalent speed is not conducive to diffusion and mixing in the diffusion stage. More importantly, the equivalence ratio distribution at the ignition position is more uniform for the later ignition position due to the longer mixing stroke, and the mixture uniformity index at the ignition position is inversely proportional to the advance of the ignition position. Therefore, the late ignition is recommended to obtain a uniform hydrogen mixture. [Display omitted] • The effects of variable ignition position on hydrogen mixing and diffusion of LHE was revealed. • Different diffusion characteristics of hydrogen in injection stage and diffusion stage. • There is an equivalent speed peak at the ignition position is 3mm. • A later ignition position can bring a more uniform hydrogen-air mixture to form homogeneous ignition. [ABSTRACT FROM AUTHOR]

Consumers conventionally adopt diesel generation to meet the energy needs where the grid connection is unreliable or unavailable. While electrification has provided these communities a variety of economic and social opportunities, diesel consumption has resulted in adverse costs and environmental pollution. Two technologies available to reduce the expense and emissions of diesel fuel reliance include dual fuel or hybrid diesel applications. The dual-fuel approach involves a supplementary gas fuel charge in support of reduced diesel fuel consumption. Hybrid applications involve the integration of renewable generation to displace diesel fuel consumption. This paper reviews the potential for hybrid dual-fuel applications, identifying engine flexibility as a major integration barrier. In comparing the flexibility of various dual-fuel technologies to operate dynamically, this paper presents a critical review across hydrogen, liquified petroleum gas (LPG), natural gas (NG) and blended hydrogen and NG derivatives. The results identify a range of approaches able to improve engine flexibility and thus reduce the cost and carbon intensity of diesel-fired internal combustion engines. At low load conditions, while NG and LPG exhibit similar performance, the use of hydrogen and hydrogen blends provide improved engine performance and response. Unfortunately, given the current cost of hydrogen fuel, significant commercial barriers exist to the adoption of hydrogen or hydrogen blended fuels. Despite this, this review indicates the potential of hydrogen-NG blends to offer additional flexibility in comparison to alternative dual-fuel technologies. This position is furthered considering near term cost targets associated with the development of a global green hydrogen industry, coupled with its ability to serve as a demand-side management approach within isolated power systems, one of the multiple future research themes. • The potential of dual fuel approach in renewable energy applications was assessed. • Different dual fuel technologies were compared over various conditions. • Dual fuel low load application was discussed to manage the variability of RE sources. • The ability of H 2 , NG and LPG dual fuel approaches operate at low load was compared. • EGR and Fuel Injection were effective methods to improve combustion performance. [ABSTRACT FROM AUTHOR]

Microalgae originating from wastewater has been exhibiting particularly promising results in terms of biohydrogen production and wastewater treatment. This paper aims to review the factors affecting production, pretreatment techniques to improve synthesis, advanced technologies utilized for enhancing biohydrogen production, and techno-economic feasibility evaluation of the processes at a commercial scale. Microalgae possess metabolic components to synthesize biohydrogen using photobiological and fermentative processes but must undergo pretreatment for efficient biohydrogen production. The efficiency of these processes is influenced by factors such as the microalgae species, light intensity, cell density, pH, temperature, substrates, and the type of bioreactors. Moreover, many limitations, such as oxygen sensitivity, altered thylakoid constitution, low photon conversion efficiency, light capture disruption, and the evolution of harmful by-products hinder the sustainability of biohydrogen production processes. High operational and maintenance costs serve as the major bottleneck in the scaling up of the process as an industrial technology. Therefore, future research needs to be directed towards increasing optimization of the processes by reducing energy and resource demand, recycling metabolic wastes and process components, genetically engineered microalgae to adopt more efficient routes, and conducting pilot studies for commercialization. • Wastewater-based microalgae is a potential source of biohydrogen. • Factors affecting the biohydrogen production from microalgal biomass are discussed. • Technologies related to biohydrogen production from microalgae are reviewed. • Key challenges of biohydrogen production process from microalgae are highlighted. [ABSTRACT FROM AUTHOR]

The widespread use of non-renewable energy has caused serious environmental problems such as global warming and the depletion of fossil fuels. Hydrogen, as a well-known carbon-free gaseous fuel, has become the most promising energy carrier for future energy. Hydrogen has an excellent mass-basis calorific value and no carbon atom contained, which makes it to be an attractive fuel for various power devices (like the internal combustion engine, gas turbine, and fuel cell). Nowadays, the production of hydrogen is still predominated by fossil-based techniques, which is considered undesirable due to low conversion efficiency and release of greenhouse gases. It is necessary to find green and sustainable hydrogen production routes with low energy consumption and cost. In this paper, the different hydrogen production technologies via fossil routes or non-fossil routes are reviewed in general, and it is found that bio-hydrogen production has certain environmental advantages and broad prospects compared with other hydrogen production technologies. Then, the characteristics and research status of different bio-hydrogen production technologies are discussed in depth. It is found that each bio-hydrogen production technique has its own advantages, challenges, and applicability. The economic analysis of bio-hydrogen energy is also performed from the aspects of production, storage, and transportation. The results show that bio-hydrogen production technology could be a good possibility way for producing renewable hydrogen, which is of high efficiency and thus competitive over other hydrogen production methods both in economics and environmental benefits. [Display omitted] • Renewable hydrogen production is crucial to achieving the goal of carbon neutrality. • Bio-hydrogen production is of reliable stability, decent efficiency and high generation rate. • Chemical hydrogen storage shows the advantages of high efficiency and low environmental impact. • Promising prospects are expected by incorporating biomass technology into hydrogen utilization. [ABSTRACT FROM AUTHOR]

This paper presents the application of a multidisciplinary approach for the preliminary design and evaluation of the potential improvements in performance and environmental impact through the utilization of compressed (CGH2) and liquefied (LH2) hydrogen fuel for a civil tilt-rotor modelled after the NASA XV-15. The methodology deployed comprises models for rotorcraft flight dynamics, engine performance, flight path analysis, hydrogen tank and thermal management system sizing. Trade-offs between gravimetric efficiency, energy consumption, fuel burn, CO 2 emissions, and cost are quantified and compared to the kerosene-fuelled rotorcraft. The analysis carried out suggests that for these vehicle scales, gravimetric efficiencies of the order of 13% and 30% can be attained for compressed and liquid hydrogen storage, respectively leading to reduced range capability relative to the baseline tilt-rotor by at least 40%. At mission level, it is shown that the hydrogen-fuelled configurations result in increased energy consumption by at least 12% (LH2) and 5% (CGH2) but at the same time, significantly reduced life-cycle carbon emissions compared to the kerosene counterpart. Although LH2 storage at cryogenic conditions has a higher gravimetric efficiency than CGH2 (at 700 bar), it is shown that for this class of rotorcraft, the latter is more energy efficient when the thermal management system for fuel pressurization and heating prior to combustion is accounted for. [Display omitted] • A civil tilt-rotor is retrofitted for liquid and gaseous hydrogen fuel. • The hydrogen-fuelled rotorcraft are compared against the kerosene-fuelled counterpart. • Performance and environmental assessment is conducted at payload-range and mission level. • Liquid hydrogen offers higher gravimetric densities but its requirement for heating penalizes performance. [ABSTRACT FROM AUTHOR]

Because of the requirement of the utilization of energy resources in a way that is both effective and efficient, solid oxide fuel cells have become a notable preference due to their advantages such as high efficiency and use with different fuels. In addition, the integration of these systems in the production of alternative fuels such as hydrogen and ammonia are important for a sustainable future to combat environmental problems. For this reason, the main intention of this paper is to introduce a new plant combining the different systems that use the solid oxide fuel cell for a cleaner and sustainable future. In the modeled work, a solid oxide fuel cell, a gas turbine, an organic Rankine cycle, a Kalina cycle with ejector, a hydrogen generation and storage process, a wood steaming plant, and an ammonia production system is integrated, to generate useful products. Detailed thermodynamic modeling is performed through energy and exergy methods, to determine the performance of the advised system and subsystem. Moreover, energy efficiency, exergy efficiency, and exergy destruction analyses methods are applied to each sub-plant and the whole system separately. In addition, parametric research is carried out to examine the effects of modifying key parameters on the plant's and subsystems' performance. Looking at the analysis results, the amount of the hydrogen and ammonia generation capacities of this work are 0.0085 kgs−1and 0.2023 kgs−1, respectively. In addition, the modeled power plant produces a power rate of about 20,180 kW. As a result, this proposed study is calculated to have 61.04% energy efficiency, and 57.13% exergy efficiency. • A novel combined plant with SOFC is developed for hydrogen and ammonia generation. • Modeled system is investigated thermodynamically with energy and exergy efficiencies. • Parametric analysis is conducted to determine the how the effect of each parameter on the system's performance. • Overall energy and exergy efficiency of this modeled plant is 61.04% and 57.13%, respectively. [ABSTRACT FROM AUTHOR]

This paper uses the TRNSYS software to investigate the hourly energy generation potential, storage, and consumption via an electrolyzer and a fuel cell in the Canadian city of Saskatoon, which is a region with high solar and wind energy potential. For this purpose, a location with an area of 10,000 m2 was considered, in which the use of solar panels and vertical-axis wind turbines (VAWTs) were simulated. In the simulation, the solar panels were placed at specific distances, and the energy generation capacity, amount of produced hydrogen, and the energy available from the fuel cell were examined hourly and compared to the case with wind turbines placed at standard distances. The results indicated energy generation capacities of 1,966,084 kWh and 75,900 kWh for the solar panels and the wind turbines, respectively, showing the high potential of solar panels compared to wind turbines. Moreover, the fuel cells in the solar and wind systems can produce 733,077 kWh and 22,629 kWh of energy per year, respectively, if they store all of the received energy in the form of hydrogen. Finally, the hourly rates of hydrogen production by the solar and wind systems were reported. • Solar panels and vertical-axis wind turbines are used to produce hydrogen. • TRNSYS is employed to perform the simulations. • Energy generation capacity of solar panels is 1,966,084 kWh. • Energy generation capacity of wind turbines is 75,900 kWh. [ABSTRACT FROM AUTHOR]

The world is experiencing unprecedented development in the clean energy sector in residential and industrial applications. This paper provides a case study assessing different scenarios of greenizing the electrical energy demand in El-Mostakbal city in Egypt. Three scenarios are studied with consideration of a photovoltaic (PV) system integrated with the grid-connected city with different integrated system configurations. The scenarios for the grid-connected city are scenario-I: only PV, scenario-II: PV with batteries for electricity storage along with grid electricity, and scenario-III: PV with hydrogen production, storage, and utilization for covering the electric demand along with grid electricity, these scenarios are assessed technoeconomically, and the results show an optimized case where the electricity demand of the city can be met with 64.3% produced from solar energy, at $71.7 M of the net present cost. • Energy demand is evaluated using different proposed green scenarios that are assessed techno-economically. • Electricity demand of the city can be met with 64.3% produced from solar energy. • The cost of energy generation for scenario-I is found to be $0.0512 per kWh. [ABSTRACT FROM AUTHOR]

Environment-friendly, safe and reliable energy supplies are indispensable to society for sustainable development and high life quality where even though social, environmental, political and economic challenges may play a vital role in their provision. Our continuously growing energy demand is driven by extensive growth in economic development and population and places an ever-increasing burden on fossil fuel utilization that represent a substantial percentage of this increasing energy demand but also creates challenges associated with increased greenhouse gas (GHG) emissions and resource depletion. Such challenges make the global transition obligatory from conventional to renewable energy sources. Hydrogen is emerging as a new energy vector outside its typical role and receiving more recognition globally as a potential fuel pathway, as it offers advantages in use cases and unlike synthetic carbon-based fuels can be truly carbon neutral or even negative on a life cycle basis. This review paper provides critical analysis of the state-of-the-art in blue and green hydrogen production methods using conventional and renewable energy sources, utilization of hydrogen, storage, transportation, distribution and key challenges and opportunities in the commercial deployment of such systems. Some of the key promising renewable energy sources to produce hydrogen, such as solar and wind, are intermittent; hydrogen appears to be the best candidate to be employed for multiple purposes blending the roles of fuel energy carrier and energy storage modality. Furthermore, this study offers a comparative assessment of different non-renewable and renewable hydrogen production systems based on system design, cost, global warming potential (GWP), infrastructure and efficiency. Finally the key challenges and opportunities associated with hydrogen production, storage, transportation and distribution and commercial-scale deployment are addressed. • A detailed review on hydrogen production methods and utilization. • Green, blue and purple hydrogen production methods are described thoroughly. • Hydrogen storage and infrastructure, transportation and distribution are also covered in utilization. • Recent advancements, challenges and opportunities are described in detail. • Comparative assessment is conducted on the basis of system design, cost, storage, GWP, infrastructure and efficiencies. [ABSTRACT FROM AUTHOR]

A typical problem in Northeast China is that a large amount of surplus electricity has arisen owing to the serious photovoltaic power curtailment phenomenon. To effectively utilize the excess photovoltaic power, a hybrid energy system is proposed that uses surplus electricity to produce hydrogen in this paper. It combines solar energy, hydrogen production system, and Combined Cooling Heating and Power (CCHP) system to realize cooling, heating, power, and hydrogen generation. The system supplies energy for three public buildings in Dalian City, Liaoning Province, China, and the system configuration with the lowest unit energy cost (0.0615$/kWh) was obtained via optimization. Two comparison strategies were used to evaluate the hybrid energy system in terms of unit energy cost, annual total cost, fossil energy consumption, and carbon dioxide emissions. Subsequently, the annual total energy supply, typical daily loads, and cost of the optimized system were analyzed. In conclusion, the system is feasible for small area public buildings, and provides a solution to solve the phenomenon of photovoltaic power curtailment. • A novel system implements cooling - heating - power - hydrogen multi-generation. • Hydrogen production of the optimal system is 700 kg per day. • Novel system is superior to existing systems in economy, energy, and environment. • The system conduces to solve the photovoltaic power curtailment phenomenon. [ABSTRACT FROM AUTHOR]

Recently, the integration of various energy resources, including renewable generation and combined heat and power (CHP) units in microgrids, has created the opportunity of off-grid operation with a suitable range of reliability. This paper presents an optimization model to schedule an islanded MG with various resources, including CHP, photovoltaic (PV), and boiler, as the primary energy provision sources besides electric battery storage, thermal storage and hydrogen energy system (HES). The HES has the power-to-hydrogen (P2H) and hydrogen-to-power (H2P) modes, which increases the flexibility of the scheduling. The uncertainty management is the most essential task in the CHP-based MGs scheduling problem, since the power and heat productions are interrelated and can result in economic losses without enough deliberations. Hence, this paper proposes the robust optimization approach (ROA) to cope with the uncertainties associated with the PV production and electric and heat load demands. The robust counterparts are applied to the deterministic problem to create a tractable adjustable robust framework. The problem is structured as a mixed-integer linear programming (MILP) handled by the General Algebraic Modeling System (GAMS) using CPLEX solver. The results verified the effectiveness of the proposed robust counterparts in managing the associated risk. The results illustrated a conscious scheduling strategy under robust conditions. However, the more preserved decisions are taken, the higher operational cost is realized. In this regard, the increment of robustness level from the lowest value (deterministic condition) to the highest value (conservatism condition) increased the operation cost by about 43.29%. • Risk-constrained optimal scheduling of a multi-energy microgrid (MEMG) is studied. • The MEMG contains combined heat and power, solar system and hydrogen energy storage. • Electrical and thermal storage units considered for flexible operation of the MEMG. • Robust counterparts manage uncertainties of generation and loads simultaneously. • The solutions obtained for different values of robustness level. [ABSTRACT FROM AUTHOR]

The paper presents a technical, economic and environmental analyses of a chamber furnace used to heat the charge before forging. The energy efficiency of the furnace before the modernization was 18%, after the modernization it was 31% (partial modernization due to large financial outlays). Other variants were also analysed: complete modernization, the variant of furnace modernization with 30% hydrogen content in the gas and the variant with 100% hydrogen as fuel. The analyses showed that with the current gas price (0.025 EUR/kWh) and the price of emission allowances (nearly 60 EUR/MgCO 2) and 100 cycles/year, the difference in Net Present Value (NPV) before base variant and partial modernization is around 900,000 EUR and before base variant and full modernization is 1,200,000 EUR. The introduction of the gas and 30% of hydrogen co-combustion option versus the base scenario option for 150 cycles per year results in a NPV difference of at least 2 million EUR. The option of 100% hydrogen as a fuel is the most advantageous from the point of view of reducing CO 2 emissions - it is largely influenced by the rising prices of CO 2 emission allowances. • Effects of the modernization of a chamber furnace. • Net Present Value and CO 2 emission reductions during the lifetime of a chamber furnace are calculated. • The study provides maps to compare the economic efficiency (natural gas, hydrogen, and mix). [ABSTRACT FROM AUTHOR]

In this paper, the energy, exergy, economic, environmental, steady-state, and process performance modeling/analysis of hybrid renewable energy (RE) based multigeneration system is presented. Beyond the design/performance analysis of an innovative hybrid RE system, this study is novel as it proposes a new methodology for determining the overall process energy and exergy efficiency of multigeneration systems. This novel method integrates EnergPLAN simulation program with EES and Matlab. It considers both the steady-state and the process performance of the modeled system on hourly timesteps in order to determine the overall efficiencies. Based on the proposed new method, it is observed that the overall process thermodynamic efficiencies of a hybrid renewable energy-based multigeneration system are different from its steady-state efficiencies. The overall energy and exergy efficiencies reduce from 81.01% and 52.52% (in steady-state condition) to 58.6% and 39.33% (when considering a one-year process performance). The integration of the hot water production with the multigeneration system enhanced the overall thermodynamic efficiencies in steady-state conditions. The Kalina system produces a total work output of 1171 kW with a thermal and exergy efficiency of 12.23% and 52% respectively while the wind turbine system produces 1297 kW of electricity in steady-state condition and it has the same thermal/exergy efficiency (72%). The economic analysis showed that the Levelized cost of electricity (LCOE) of the geothermal energy-based Kalina system is 0.0103 $/kWh. The greenhouse gas emission reduction analysis showed that the proposed system will save between 1,411,480 kg/yr and 3,518,760 kg/yr of greenhouse gases from being emitted into the atmosphere yearly. The multigeneration system designed in this study will produce electricity, hydrogen, hot water, cooling effect, and freshwater. Also, battery electric vehicle charging is integrated with process performance analysis of the multigeneration system. [Display omitted] • A novel methodology for multigeneration systems' steady-state and process performance evaluation. • Modeling and analysis of a geothermal-wind hybrid comprehensive energy systems. • The overall energy and exergy efficiencies are 81.01% and 52.52% in steady-state condition. • Also, the overall energy/exergy efficiencies are 58.6% and 39.33% based on a one-year process performance. [ABSTRACT FROM AUTHOR]

This paper studies the Solid Oxide Electrolyzer Cell as a promising system in the sustainable development for the hydrogen economy and energy systems as a robust system. The Solid Oxide Electrolyzer Cell converts the steam and carbon-dioxide directly to functional fuels through consumption of the additional electrical power of green power sources or off-peak network powers. The present paper evaluates the static efficiency of the SOEC under four various gas mixtures. Modeling of this system is performed using Elman neural network (ENN) and modified particle swarm optimization (MPSO) algorithm. The MPSO algorithm is utilized to determine the optimal values for ENN adjustable parameters. It's known from the empirical results that the steam and carbon-dioxide concentrations can affect the SOEC efficiency. The operational potential and volume share of the hydrogen, carbon dioxide and steam are considered as the system inputs, and efficiency (current) is remarked as its output. The correlation factors of the achieved model are greater than 0.999, and its MSE (mean squared error) is lower than 0.017. It reveals that the forecasted values are almost equal to the empirical data. Subsequently, the efficiency of the SOEC is studied using the achieved model of the MPSO-based ENN in various feedstock concentrations. Thus, this dataset that is used for ENN model can be desirable for different applications of fast-modeling in a standalone group. It as well can be useful for cost, computing-time, and computing burden reduction in a model construction in the efficiency analyzing and system-level designing processes. • The static model of a SOEC is identified in this paper. • Elman neural network is applied in this paper as a novel method in the modeling process. • MPSO algorithm is used to increase the accuracy of the obtained model. • Static efficiency of the SOEC is evaluated for various gas mixtures. • The obtained results demonstrated the high precision of the proposed model. [ABSTRACT FROM AUTHOR]

In a hydrogen station that operates with direct fueling through the use of a 700 bar boost compressor, the outlet hydrogen temperature can significantly increase, stressing the chiller system. This paper evaluates improvements that can be made to the auxiliary cooling system integrated with the compressor. Both theoretical modeling and experiments were performed at Cal State LA Hydrogen Research and Fueling Facility. The findings suggest that adjusting the auxiliary closed-loop cooling system from 15 °C to 10 °C reduced the station energy consumption and decreased the demand on the station chiller that needed to provide −20 °C hydrogen at the hose. The overall energy consumption for a single fueling reduced by between 2.86 and 9.43% for the set of experiments conducted. After the temperature of the closed-loop cooling system was reduced by 5 °C, the boost compressor outlet temperature dropped from 46-50 °C–40 °C and consequently at the hose the hydrogen temperature declined by 3 °C. Results were scaled up with a forecast on the number of daily refueling events. With a low number of daily fuelings, the proposed set-up showed a minor influence on the overall station energy consumption. However, the benefits were more pronounced for a connector station with sales at 180 kg/day, where the energy efficiency improved by between 1.4 and 5.5%, and even more so for a higher capacity station at 360 kg/day, where the improvement was between 2.9 and 8%. [Display omitted] • Hydrogen Station with two booster compressors and a hydrogen chiller. • Water process chiller tuning-up and new-set-up. • Hydrogen Refueling Process Energy Reduction. • Results scaled up by forecasting the number of fueling events. • Pilot, Connector, and Main Stations Evaluation. [ABSTRACT FROM AUTHOR]

Effective recovery of hydrogen from refinery off-gas and coke oven gas, in which hydrogen and methane are key components, is increasingly important for the development of hydrogen energy. In this paper, we introduced a new energy efficient process for hydrogen purification from CH 4 /H 2 mixture. Firstly, we conducted a phase equilibrium experimental study for CH 4 /H 2 in zeolitic imidazolate framework-8 (ZIF-8)/glycol–water slurry. The simple absorption and desorption configuration is adopted for the continuous separation of CH 4 /H 2 using ZIF-8/glycol–water slurry. The multi-stage pseudo-absorption modeling approach was introduced for the modeling and simulation of the absorption–adsorption and desorption columns via using multiple flash modules in Aspen Plus. The binary interaction parameters in the thermodynamic model were fitted by experimental data within an acceptable error (4.93%). The operating conditions (i.e., the number of theoretical stages, feed stage, flash pressure, and desorption pressure) were determined to increase H 2 concentration in product and H 2 recovery ratio. The energy performance of the process was also evaluated. Given the feed gas contains 50 mol% H 2 , the gas–slurry volume ratio of 43.27 is required to produce 95 mol% H 2 with a high recovery of 97.94%. The total energy consumption per unit volume of product is 0.06254 kW·h/Nm3. Results indicate that the hybrid absorption-adsorption process is a promising energy efficient technique to separate CH 4 /H 2 in the future. [Display omitted] • ZIF-8/glycol–water slurry was experimentally effective for the separation of CH 4 /H 2. • Use multi-stage pseudo-absorption model to simulate absorption–adsorption column. • Total energy consumption per unit volume of product is only 0.06254 kW·h/Nm3. • New process can produce hydrogen of 95 mol% with high hydrogen recovery of 97.94%. [ABSTRACT FROM AUTHOR]

Ammonia represents one of the most promising potential solutions as energy vector and hydrogen carrier, having a higher potential to transport energy than hydrogen itself in a pressurized form. Furthermore, solid oxide fuel cells (SOFCs) can directly be fed with ammonia, thus allowing for immediate electrical power and heat generation. This paper deals with the analysis of the dynamic behavior of commercial SOFCs when fueled with ammonia. Several measurements at different temperatures have been performed and performances are compared with hydrogen and a stoichiometrically equivalent mixture of H 2 and N 2 (3:1 M ratio). Higher temperature led to smaller drops in voltage for both fuels, thus providing higher efficiencies. Ammonia resulted slightly more performant (48% at 760 °C) than hydrogen (45% at 760 °C), in short stack tests. Moreover, different ammonia-to-air ratios have been investigated and the stack area-specific resistance has been studied in detail by comparing numerical modeling predictions and experimental values. [Display omitted] • Ammonia efficiently feeds solid oxide fuel cells for combined generation. • Higher efficiencies are obtained with ammonia rather than with hydrogen. • Area-specific resistance for ammonia is larger than for hydrogen. [ABSTRACT FROM AUTHOR]

This paper discusses the current development strategy, technology and industrialization of China's hydrogen energy industry in the transportation field, summarizes the characteristics and development experience, and makes a comparative study with the situation of some developed countries. The results show that the current development of hydrogen energy has formed a broad consensus in China and is becoming the overall development of China's national level consciousness. However, China's hydrogen energy industry is still facing problems such as high cost of comprehensive utilization, imperfect standards and regulations for hydrogen energy utilization, obvious tendency of industrial blind development and structural overcapacity risk. Therefore, some policy suggestions were proposed for the future development, such as strengthening top-level design, strengthening pilot demonstration, promoting the development of the whole hydrogen industry chain, and reducing the cost of hydrogen and fuel cell vehicles in the field of transportation. [Display omitted] • The development of hydrogen energy industry has become China's national consensus. • China has formed three major industrial clusters of hydrogen and fuel cells. • China's hydrogen industry is facing the risk of overcapacity. • China should strengthen the top-level design of hydrogen development strategy. [ABSTRACT FROM AUTHOR]

This paper studies the potentials of green hydrogen production from hydropower energy and its application in electricity regeneration and replacement of petroleum products from the transportation sector in Nepal. The potential surplus hydroelectric energy, and hydrogen production potential from the surplus energy considering different scenarios, is forecasted for the study period (2022–2030). The results showed that hydrogen production potential ranges from 63,072 tons to 3,153,360 tons with the utilization of surplus energy at 20% and 100% respectively, in 2030. The economic analysis of hydrogen from hydropower projects that electricity is valued based on per kg of hydrogen when the surplus electricity is provided at feasible lower price values compared to the US $1.17. This study concludes that hydrogen production from spilled hydro energy and its use in the transportation sector and independent electricity generation is a niche opportunity to lead the country towards sustainable energy solutions and an economy running on hydrogen. • Methodological study for quantification of excess hydropower and hydrogen production. • Cost projections scenarios from green hydrogen from surplus hydropower electricity. • Identification of role of green hydrogen in multiple end-use areas of developing nation. • Potential replacement of conventional fuel with hydrogen in transportation sector. [ABSTRACT FROM AUTHOR]

Numerous studies explored the possibility and effective strategies for supplementing hydrogen along with fossil or biofuels on internal combustion engines. Hydrogen is also being employed for formulating fuels such as hydrogen compressed natural gas in the gaseous form and hydrogenated biofuels in the liquid form. The present study evaluates (i) hydrogen usage on the fuel formulation and (ii) investigates the engine operation of an automotive turbocharged diesel engine operated with karanja biodiesel blended diesel (B20) as a reference fuel. Existing literature outlines that biodiesel blends possess lower energy content and emit higher nitric oxide (NO) emission than fossil diesel. The present research paper partially hydrogenates karanja biodiesel using an autoclave reactor with a palladium catalyst to increase the saturation levels and mitigate the biodiesel-NO penalty. Besides, the drop in energy release of B20 is compensated through the provision of hydrogen induction along the intake manifold. The hydrogen flow rates to the turbocharged engine are maintained at a fixed energy share of 10%. Both biodiesel and hydrogenated biodiesel were blended on a volume basis (20%) with fossil diesel (80%) and are designated as B20 and HB20, respectively. The test results reveal that HB20 effectively mitigates the biodiesel-NO penalty with a maximum reduction of 29.8% compared to B20. Further, hydrogen induction yielded a significant improvement (23.7%) in fuel consumption with HB20 relative to B20 without hydrogen addition. The compounding effect of hydrogen usage on the engine operation and fuel formulation exhibited a better performance and emission trade-off at mid load conditions. • The synergy of hydrogen use on fuel formulation and engine operation is examined. • Partial hydrogenation yields lower NO emission with biodiesel operation. • Hydrogen induction promotes an improvement in fuel consumption with B20 blend. • The compounding effect of hydrogen exhibits a better smoke–NO–BSFC trade-off. [ABSTRACT FROM AUTHOR]

This paper presents a case study focusing on fourteen most used energy alternatives in Brazil, possible to feed large scale hydrogen production plants for the automotive sector. The evaluations are made using a Decision Making Support Method, MACBETH - Measuring Attractiveness by a Categorical Based Evaluation Technique, with the computational code M-MACBETH 3.2.0, using criteria that include economic and financial, technological, environmental and social aspects. The selected criteria that were used in the assessment, for each of the energy alternatives are capital to be invested in a plant, leveled cost of electric energy produced, CO 2 emissions, mortality rate due to the technology use and energy efficiency of technology. The main results obtained showed that photovoltaics off grid electric energy is the most attractive alternative, followed by the photovoltaic on grid alternative, for an eventual automotive hydrogen program in Brazil. • Multicriteria method was used in this study. • Economic, financial, technological and environmental aspects were considered. • Several criteria were considered including emissions and mortality rate. • Photovoltaics off grid was considered the most attractive energy alternative. [ABSTRACT FROM AUTHOR]

Developing underground coal gasification (UCG)-based hydrogen production (UCG-H 2) is expected to alleviate hydrogen supply and demand contradiction, but its energy consumption and environmental impact need to be clarified. In this paper, comparative study of energy consumption and greenhouse gas (GHG) emissions between UCG-H 2 and typical surface coal gasification (SCG)-based hydrogen production (SCG-H 2) is carried out using life cycle assessment method. Result shows energy consumption of UCG-H 2 is only 61.2% of that of SCG-H 2 , which is 1,327,261 and 2,170,263 MJ respectively, reflecting its obvious energy saving advantage. 80% capture rate can achieve an appropriate balance between energy consumption and emissions. Under this capture rate, emissions of UCG-H 2 and SCG-H 2 are roughly equivalent, which are 207,582 and 197,419 kg CO 2 -eq respectively. Scenario analysis indicates energy consumption in hydrogen industry can reduce by 38.8% when hydrogen production is substituted by UCG with CCS to fully meet demand of 21 Mt in 2030. • Consumption and emissions of UCG-H 2 and SCG-H 2 are first compared using LCA method. • Energy consumption of UCG-H 2 is only 61.2% of that of SCG-H 2. • Implementing CCS reduces GHG emissions of UCG-H 2 to be roughly equivalent to SCG-H 2. • 80% capture rate can achieve a balance between energy consumption and emissions. • Applying UCG-H 2 can reduce energy consumption by 38.8% in selected scenario. [ABSTRACT FROM AUTHOR]

In recent years, there has been considerable interest in the development of zero-emissions, sustainable energy systems utilising the potential of hydrogen energy technologies. However, the improper long-term economic assessment of costs and consequences of such hydrogen-based renewable energy systems has hindered the transition to the so-called hydrogen economy in many cases. One of the main reasons for this is the inefficiency of the optimization techniques employed to estimate the whole-life costs of such systems. Owing to the highly nonlinear and non-convex nature of the life-cycle cost optimization problems of sustainable energy systems using hydrogen as an energy carrier, meta-heuristic optimization techniques must be utilised to solve them. To this end, using a specifically developed artificial intelligence-based micro-grid capacity planning method, this paper examines the performances of twenty meta-heuristics in solving the optimal design problems of three conceptualised hydrogen-based micro-grids, as test-case systems. Accordingly, the obtained numeric simulation results using MATLAB indicate that some of the newly introduced meta-heuristics can play a key role in facilitating the successful, cost-effective development and implementation of hydrogen supply chain models. Notably, the moth-flame optimization algorithm is found capable of reducing the life-cycle costs of micro-grids by up to 6.5% as compared to the dragonfly algorithm. Image 1 • A metaheuristic-driven model is proposed to optimally design H 2 -based microgrids. • An energy management strategy is used to facilitate the uptake of fuel cell vehicles. • The performances of twenty metaheuristics are studied in terms of solution quality. • The moth-flame optimizer outperforms the well-respected algorithms in this area. • Levelized costs of electricity and H 2 are found to be well below the present rates. [ABSTRACT FROM AUTHOR]

Decentralization of electrical power generation using rooftop solar units is projected to develop to not only mitigate power losses along transmission and distribution lines, but to control greenhouse gases emissions. Due to intermittency of solar energy, traditional batteries are used to store energy. However, batteries have several drawbacks such as limited lifespan, low storage capacity, uncontrolled discharge when not connected to a load and limited number of charge/discharge cycles. In this paper, the feasibility of using hydrogen as a battery is analyzed where hydrogen is produced by the extra diurnal generated electricity by a rooftop household solar power generation unit and utilized in a fuel cell system to generate the required electrical power at night. In the proposed design, two rooftop concentrated photovoltaic thermal (CPVT) systems coupled with an organic Rankine cycle (ORC) are used to generate electricity during 9.5 h per day and the extra power is utilized in an electrolyzer to produce hydrogen. Various working fluids (Isobutane, R134a, R245fa and R123) are used in the ORC system to analyze the maximum feasible power generation by this section. Under the operating conditions, the generated power by ORC as well as its efficiency are evaluated for various working fluids and the most efficient working fluid is selected. The required power for the compressor in the hydrogen storage process is calculated and the number of electrolyzer cells required for the hydrogen production system is determined. The results indicate that the hybrid CPVT-ORC system produces 2.378 kW of electricity at 160 suns. Supplying 65% of the produced electricity to an electrolyzer, 0.2606 kg of hydrogen is produced and stored for nightly use in a fuel cell system. This amount of hydrogen can generate the required electrical power at night while the efficiency of electrolyzer is more than 70%. • The feasibility of using hydrogen as a battery in a rooftop household solar power generation unit is investigated. • The generated power by hybrid CPVT-ORC system is converted to hydrogen by an electrolysis system to store power. • By coupling ORC to the CPVT system, the diurnal hydrogen production increases up to 30%. [ABSTRACT FROM AUTHOR]

Hydrogen generation from water electrolysis is attempted to be one of the replacement of sources as a clean fuel with high energy density. However, its application is limited by the high overpotential of oxygen evolution reaction (OER). Herein, hydrogen fuel is obtained from waste water by replacing OER with aniline electrochemical polymerization. Compared to the OER, the potential of aniline electro-polymerization greatly decreases 1240 mV at the current density of 30 mA cm−2 even using carbon paper electrode. Moreover, the Faradaic efficiency of hydrogen production is close to 100%. The as-prepared polyaniline demonstrates good performance as electrochemical capitative materials. This work provides efficient and lower energy consumed access to co-generate hydrogen and polyaniline in a convenient step by starting from the toxic and environmental-unfriendly wastewater. Taking use of co-electrolysis of low oxidation potential of waste water containing aniline to produce hydrogen and polyaniline in highly efficient energy. Image 1 • The potential of water electrolysis decreases 1150 mV. • Providing an efficient and low energy consumed access to generate hydrogen. • As-prepared polyaniline demonstrates good capacitive performance. [ABSTRACT FROM AUTHOR]

This paper focuses on the potential replacement of expansion valves in the fuelling process of hydrogen vehicle by use of ejectors. The main advantage of the ejectors is to exploit the kinetic energy of a high-pressure primary flow to entrain a lower pressure secondary flow resulting in an improved and efficient fuelling process. First, a one-dimensional thermodynamic model was developed to characterise the ejector's performances such as its entrainment ratio and compression ratio. Then, the ejector's components efficiencies of the one-dimensional model were extracted from CFD simulations with the use of a genetic algorithm. Three regression models were compared to express the efficiencies as a function of the boundary conditions (pressure inlets) and the ejector's geometry (aspect ratio). Finally, the one-dimensional model was used to optimize the performance of the ejector for fuelling of hydrogen vehicles by using a simple transient simulation model of the vehicle tank. The new ejector fuelling procedure was compared with the traditional use of expansion valves. The results show that a reduction of the high-pressure hydrogen demand is possible using the optimized ejector, leading to reduced energy consumption, as well as fuelling time. • Replacement of expansion valves by ejectors in hydrogen fuelling stations. • 1-D thermodynamic model of an ejector with variable efficiencies, fitted with CFD. • Simple transient model of a fuelling station using an ejector. • Decrease of 9% (0.23 kg) of high-pressure hydrogen demand; higher fuelling efficiency. [ABSTRACT FROM AUTHOR]

The majority of energy being used is obtained from fossil fuels, which are not renewable resources and require a longer time to recharge or return to its original capacity. Energy from fossil fuels is cheaper but it faces some challenges compared to renewable energy resources. Thus, one of the most potential candidates to fulfil the energy requirements are renewable resources and the most environmentally friendly fuel is Hydrogen. Hydrogen is a clean and efficient energy carrier and a hydrogen-based economy is now widely regarded as a potential solution for the future of energy security and sustainability. Hydrogen energy became the most significant energy as the current demand gradually starts to increase. It is an important key solution to tackle the global temperature rise. The key important factor of hydrogen production is the hydrogen economy. Hydrogen production technologies are commercially available, while some of these technologies are still under development. Therefore, the global interest in minimising the effects of greenhouse gases as well as other pollutant gases also increases. In order to investigate hydrogen implementation as a fuel or energy carrier, easily obtained broad-spectrum knowledge on a variety of processes is involved as well as their advantages, disadvantages, and potential adjustments in making a process that is fit for future development. Aside from directly using the hydrogen produced from these processes in fuel cells, streams rich with hydrogen can also be utilised in producing ethanol, methanol, gasoline as well as various chemicals of high value. This paper provided a brief summary on the current and developing technologies of hydrogen that are noteworthy. Image 1 • Alternative energy resources and sustainable energy systems. • Hydrogen demand market and its transmission and distribution briefly discussed. • Hydrogen production methods are reviewed and recent advances were mentioned. • The future directions on hydrogen production were stressed in the conclusions. [ABSTRACT FROM AUTHOR]

Among the few lessons learned presented in the literature, authors put in evidence the on-going need to investigate on station components and their integration. The specific power consumption of station units with on-site hydrogen generation is often subject to uncertainty, and it would have been desirable to find more details about the energy contribution of each component. To address this gap, this paper focuses on the development of a mathematical modeling as a dynamic and multi-physical design tool to predict the energy performance of hydrogen production systems. Particularly, the model aims to describe and analyze the energy performance of two different electrolyzer technologies (PEM and Alkaline), integrated with a compressor system and gaseous buffer storage. Multiple tank options and a switching strategy are investigated, as well as a control system to simulate a real infrastructure operation. Auxiliaries and components related to the thermal management system have been also included. A carbon-footprint analysis follows the energy one, focusing on the CO 2 emission reduction. Comparisons between literature data and model show that the hydrogen system proposed model is suitable to evaluate systems with respect to energy efficiency and system performance. The model could be a powerful tool for exploring control strategies and understanding the contributions to the overall energy consumption from the various internal components as a guide to researchers aiming for improved performance. • Hydrogen Production Modeling via PEM and Alkaline water electrolysis. • Development of a dynamic and multi-physical design tool for hydrogen infrastructure. • Implementation of safety procedures for production, compression, and storage. • The tool is based on scalable and reusable blocks, with a flexible and fast approach. • Hydrogen infrastructure carbon footprint for emission reduction investigation. [ABSTRACT FROM AUTHOR]

Rheological properties of substrates significantly affect energy consumption and hydrogen production potential in the process of hydrogen production with stirring. Hence, the rheological properties of corn stover hydrolysate with diverse concentrations and its hydrogen producing capacities under intermittent stirring conditions were investigated in this paper. The results showed that corn stover hydrolysate exhibited pseudo-plastic flow behavior at total solid (TS) of 2.76%–7.65%, and was well fitted by the Power law model. Among four intermittent stirring modes, intermittent stirring C2 (static time: stirring time is 2:1) obtained the highest hydrogen yield of 57.63 ± 1.75 mL g−1 VS, which was 18.97% higher compared with static-culture. Moreover, the maximum hydrogen production rate of intermittent stirring C2 increased by 65.05% compared to continuous stirring. It's a feasible way to improve hydrogen production performance with proper intermittent stirring. • The rheological properties of corn stover hydrolysate were studied. • The Power law model described the flow behavior well. • The bio-hydrogen producing capacity under intermittent stirring were studied. • Proper intermittent stirring mode was identified. [ABSTRACT FROM AUTHOR]

Engine performance parameters, including fuel conversion efficiency (FCE), power, torque and specific fuel consumption (SFC), can be affected by variables such as ignition timing (IGT), injection timing (IT) and hydrogen volume fraction (H2%). In this paper an engine fueled with different H2/CNG blend rations from 0 to 50% volume under ignition and injection timing at different speeds were investigated. For model validation, the engine operating conditions were simulated using the AVL fire software and compared with experimental results. The statistical comparison showed that there was no significant difference between them. Also, a support vector machine (SVM) was used to study the engine's behavior according to the variables studied. The SVM model predicted the FCE, power, torque, SFC and CO with error of less than 4%. The Genetic Algorithm (GA) was used to find optimal IGT, IT and H2% values to achieve optimum engine performance. Therefore, the results showed that the optimum engine operating conditions depend on the engine speed. Also, the results showed that independent variables (IT, IGT and H2%) maximize the engine performance and minimize SFC and CO emission. So that the optimum use of hydrogen in this research at different engine speeds was between 20% and 30%. • Effect of hydrogen fuel in direct injection engine was studied. • Use of HCNG fuel can improve engine performance and exhaust emissions. • The SVM model could predict the engine performance and CO with error of less than 4%. • Ignition timing, injection timing and hydrogen volume fraction at different engine speeds. [ABSTRACT FROM AUTHOR]

Toxic emissions from waste thermal treatments are a major issue that in several countries hinders a full waste cycle. This paper addresses the specific topic of a sustainable exploitation of the refuse derived fuel (RDF). Because concerns still arise when using RDF as fuel, a new approach for its exploitation, the RDF hydrogasification for producing synthetic natural gas (SNG), is discussed herein. The process has been simulated with Aspen code. The best operating conditions to maximize methane yield, under thermodynamic equilibrium conditions, have been studied while the composition of the obtained SNG has been verified in order to comply with the requirements of the methane grid. Furthermore, the analysis looked at the effect of the hydrogen excess in promoting the methane yield and the reduction of the dioxins formation. The energy analysis of the process, that has considered the use of commercial alkaline electrolysers for producing hydrogen, has been found to be mainly affected by the electric power consumption and has exhibited values of energy efficiency around 61%. Finally, a preliminary assessment of the economic competitiveness of this process has been done in order to clarify if the benefits from costs avoided for waste disposal could be the breakthrough in making RDF a sustainable competitive fuel. • Gasification of refuse derived fuel with electrolytic hydrogen is modelled via Aspen. • Synthetic natural gas is produced with a yield of 65 wt%. • The process exhibits an energy efficiency of 61%. • Best operating conditions (300 °C and 30 bar) inhibit the formation of toxic emissions (dioxins). [ABSTRACT FROM AUTHOR]

The investment in the hydrogen infrastructure for hydrogen mobility has lately seen a significant acceleration. The demand for energy and cost efficient hydrogen liquefaction processes has also increased steadily. A significant scale-up in liquid hydrogen (LH 2 ) production capacity from today's typical 5–10 metric tons per day (tpd) LH 2 is predicted for the next decade. For hydrogen liquefaction, the future target for the specific energy consumption is set to 6 kWh per kg LH 2 and requires a reduction of up to 40% compared to conventional 5 tpd LH 2 liquefiers. Efficiency improvements, however, are limited by the required plant capital costs, technological risks and process complexity. The aim of this paper is the reduction of the specific costs for hydrogen liquefaction, including plant capital and operating expenses, through process optimization. The paper outlines a novel approach to process development for large-scale hydrogen liquefaction. The presented liquefier simulation and cost estimation model is coupled to a process optimizer with specific energy consumption and specific liquefaction costs as objective functions. A design optimization is undertaken for newly developed hydrogen liquefaction concepts, for plant capacities between 25 tpd and 100 tpd LH 2 with different precooling configurations and a sensitivity in the electricity costs. Compared to a 5 tpd LH 2 plant, the optimized specific liquefaction costs for a 25 tpd LH 2 liquefier are reduced by about 50%. The high-pressure hydrogen cycle with a mixed-refrigerant precooling cycle is selected as preferred liquefaction process for a cost-optimized 100 tpd LH 2 plant design. A specific energy consumption below 6 kWh per kg LH 2 can be achieved while reducing the specific liquefaction costs by 67% compared to 5 tpd LH 2 plants. The cost targets for hydrogen refuelling and mobility can be reached with a liquid hydrogen distribution and the herewith presented cost-optimized large-scale liquefaction plant concepts. [ABSTRACT FROM AUTHOR]

Because of highly increasing energy consumption, environmental issues and lack of common energy sources, the use of renewable energy sources especially wind power generation technology is increasing with significant growth in the world. But due to the variable nature of these sources, new challenges have been created in the balance between production and consumption of power system. The hydrogen energy storage (HES) system by storing excess wind power through the technology of power to hydrogen (P2H) and delivering it to the electricity network through hydrogen-based gas turbine at the required hours reduces not only wind alternation but can play an important role in balancing power production and consumption. On the other hand, power consumers by participating in demand response (DR) programs can reduce their consumption at peak load or wind power shortage hours, and increase their consumption at low-load or excess wind power hours to reduce wind power spillage and system energy cost. This paper proposes a stochastic security constrained unit commitment (SCUC) with wind energy considering coordinated operation of price-based DR and HES system. Price-based DR has been formulated as a price responsive shiftable demand bidding mechanism. The proposed model has been tested on modified 6-bus and 24-bus systems. The numerical results show the effect of simultaneous consideration of HES system and price-based DR integrated with wind energy on hourly generation scheduling of thermal units. As a result there is some reduction in wind generation power spillage and daily operation cost. • HES system increased wind power dispatch and reduced daily operation cost. • DR was considered as a price-responsive shiftable demand bidding mechanism. • Proposed DR increased social welfare and reduced wind spillage and operation cost. • Stochastic SCUC problem was solved for coordinated HES system, DR and wind. [ABSTRACT FROM AUTHOR]