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Micro Fuel cells or microfluidic fuel cells (μMFCs) are one of the most promising power supplies for portable electronics. However, the necessary electrode spacing is required to prevent fuel-crossover and maintain the stable operation, introducing the unavoidable ohmic resistance and retarding the miniaturization. Herein, we propose a novel μMFC device combining the cellulose paper as separator, with selective catalysts at the cathode side to eliminate the unwanted side reactions and increase the system compactness. One single reactant solution containing fuel and electrolyte is applied to keep the device stable operation. The power-generation properties are evaluated in typical alkaline conditions. A great construction simplification makes the device a substantial high-power density of 2.14 W cm−3 and maximum current density of 15.82 A cm−3. The μMFC stacks are arranged in series and parallel manners, which delivers a maximum power output of 23.6 mW and current of 194.6 mA. It is expected that innovative and customizable performance from commercial paper and low-cost carbonaceous catalysts can provide a forum for future advancement in chip-based electrochemical energy generation and storage devices. • Filter paper served as a membrane for μMFC is proposed. • The electrode-pair distance is greatly minimized (∼140 μm). • The optimized μMFC delivers an ultrahigh power density of 2.14 W cm−3. • The μMFC stacks power output of 23.6 mW and current output of 194.6 mA are achievable. [ABSTRACT FROM AUTHOR]

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]

To tackle the carbon emission problem, the exploitation of renewable energy resources (RESs) with zero emissions has gained much importance. In this context, hydrogen has become an important resource to involve itself in distributed energy resources (DERs) to generate electricity, energize vehicles, and heat our living areas. The utilization of hydrogen technologies is indispensable due to their procurement, environmental friendliness, and high efficiency for DERs. A challenging area in the field of hydrogen energy technologies is extracting efficient power and integration to DERs. This paper investigates how to model and operate a proton exchange membrane fuel cell (PEMFC) stack in a DER application to establish a living lab facility for educational and research purposes by covering Power-to-X (P2X). The PEMFC model of the studied system is designed in a MATLAB/Simulink environment and implemented in an experimental testbed. Thus, a fuel cell (FC) unit as a complementary source is preferred to be used near a photovoltaic (PV) array, a small-scale wind turbine (WT), and a lead acid battery energy storage system (BESS) by creating a P2X concept to form a living lab platform. Beyond the model, regarding the experimental part, a PV array, a WT, and a BESS are combined with a PEMFC module that is rated output of 1200 W. Expect for all systems, the FC part is emphasized in this study. Also, a dynamic model of the mentioned PEMFC is proposed and verified. • Importance of hydrogen energy is focused on its advantages, future role, potential, and challenges. • FC unit as a complementary source is evaluated by creating a P2X concept. • This platform is designed to meet the energy needs of research-education, diversify the supply, increase energy independence. • Energy procurement is supplied via green energy during a lesson, which is noteworthy and instructive. • Feasibility of combined PV/WT/BESS/PEMFC system is investigated. [ABSTRACT FROM AUTHOR]

The necessity of employing renewable energy sources within microgrid-based Power-to-X (P2X) systems has been emphasized by the imperatives of reducing global warming and fossil fuel consumption. Due to their numerous advantages, solar and wind energy have acquired prominence in contemporary power systems. However, their intermittent nature presents challenges. To overcome these challenges, energy storage devices are utilized. Batteries, however, are plagued by issues such as high maintenance needs, self-discharge, and diminishing storage capacity with age. Consequently, investigating alternatives such as hydrogen storage has become a financially viable option, especially for high-power applications. However, the intrinsically slow dynamics of hydrogen production from electricity contrast with the rapid responses of contemporary power electronic devices. This paper presents a versatile technique for optimizing hydrogen production in the presence of stochastic fluctuations in solar irradiance and wind speed. The proposed method combines a modified version of the Symbiotic Differential Whale Optimization Algorithm (m-SDWOA) with power converters to maximize production from renewable sources and electrolyzers. Using extensive simulations to demonstrate the efficacy of the proposed method by comparing its performance to that of the Whale Optimization Algorithm (WOA) and Particle Swarm Optimization (PSO). The results demonstrate the superior performance of the m-SDWOA-integrated method and pave the way for improved hydrogen generation in microgrid-based P2X systems. • Innovative control framework coordinates WT, PV, BESS, and HESS. • Maximizes hydrogen production while maintaining power quality. • Efficient controllers stabilize DC-bus voltage amidst WT/PV variability. • Ensures consistent, reliable power supply in microgrid. • Efficient energy management via m-SDWOA for resource optimization. [ABSTRACT FROM AUTHOR]

The Proton Exchange Membrane Fuel Cell - Mechanical Heat Pump - Combined Heat and Power (PEMFC-MHP-CHP) system is a reliable energy supply solution, which can operate independently of the grid during emergencies or be used for peak shaving and load leveling in renewable energy networks. This paper proposes two system structures, namely the separated and integrated systems and establishes MATLAB/Simulink models. Then, a sensitivity analysis is conducted, examining system design and operation. The results show that the separated system can satisfy basic heating and electricity demands without an external power supply at −14.5 °C. Increasing the number of cells by 20, reducing one room's heat load (36 m2), or increasing the current density by 0.1 A/cm2 results in reductions in compressor power consumption ranging from 1.76 % to 2.91 %, 7.42 %–10.57 %, and 6.52 %–16.88 %, respectively. On the other hand, the integrated system has higher power consumption but can operate smoothly at lower temperatures than the separated system. It is suitable for integration with auxiliary power devices in low-temperature environments. The PEMFC's heat output minimally affects system efficiency. Reducing the number of rooms improves system performance, with each reduction of one room decreasing compressor power consumption by 5.43 %–8.55 %. Meanwhile, two design options are identified based on the power supply and hot water demands. Further research and development can enhance the efficiency and performance of these systems, promoting their wider use in the future. • Established MATLAB/Simulink models for the PEMFC-MHP-CHP system. • Demonstrated better performance and stable heating capacity compared to conventional CHP systems. • Provided insights into advantages and limitations of separated and integrated systems. • Conducted a thorough performance analysis under load fluctuations for energy supply and peak shaving. • Proposed system design and operational options based on sensitivity analysis. [ABSTRACT FROM AUTHOR]

Hydrogen production from renewable energy sources is one of the important means to solve the world energy crisis. In the past decades, many experts and scholars have made different reviews on electrolyser and hydrogen production power supply. However, few articles have reviewed the actual industrial products of electrolyser and hydrogen production power supply from the perspective of industry. Therefore, this paper reviews the hydrogen production power supply and electrolyser used in practical engineering projects. It is helpful for experts and scholars to understand the development status of hydrogen production power and electrolyser in the industry and to further develop industrial products more suitable for practical applications. • This paper reviews the products of electrolyzers and hydrogen power sources. • This paper expounds the development situation of hydrogen production key products. • This paper summarizes the future development direction of water electrolysis. • This paper helps scholars to propose methods with practical significance. • This paper has guiding value for industrial equipment selection. [ABSTRACT FROM AUTHOR]

In the contemporary global discourse on environmental and developmental issues, the dual challenges of sustainable green energy and water supply stand paramount. These elements are vitally intertwined with the socio-economic vitality of the world. Notably, regions plagued by freshwater scarcity are increasingly turning to desalination which consists of a reliable and unconventional water source. The intersection of renewable energy with desalination and water purification processes presents a compelling synergy. This approach is particularly pertinent in areas where freshwater shortages coexist with abundant solar energy availability. Additionally, these technologies boast the advantage of low operational and maintenance costs. This paper delves into the design, optimization and financial analysis of a novel, standalone hybrid energy system, integrating photovoltaic and fuel cell technologies, for an agriculture farm situated in Kairouan, Tunisia. Unlike conventional systems, this model foregoes battery storage in favour of hydrogen storage, generated through water electrolysis powered by solar energy. This system harnesses solar energy for direct electrical power generation and hydrogen gas production. A segment of the generated electricity is allocated to electrolysis for green hydrogen production. In times of solar unavailability, the stored hydrogen is reconverted to electricity via a fuel cell. An intriguing aspect of this system is the utilization of saline well water, which, due to its high salt content, necessitates purification through desalination to prevent damage to the electrolysis unit and to render it suitable for agricultural irrigation. [Display omitted] • The production of green hydrogen, water and electricity for agriculture farm in Tunisia is analyzed. • The Levelized cost of green hydrogen produced in the PV farm is 2.25 €/kg. • A PV hydrogen Farm station with a capacity of 140 kW produces 1991 kg of green hydrogen and 235 MW h of electricity yearly. [ABSTRACT FROM AUTHOR]

This paper presents a novel off-grid hybrid renewable energy system integrated with hydrogen production and retired electric vehicle (EV) batteries for combined power and heat supply to a small rural community. The system consists of photovoltaic (PV) panels, evacuated tube solar collectors, a proton exchange membrane fuel cell (PEMFC), an alkaline electrolyzer, compressed hydrogen storage tanks, and reused lithium-ion batteries from EVs. A new battery model is developed in the Transient System Simulation Program (TRNSYS) to capture the capacity degradation of retired batteries. A two-stage energy management strategy is proposed to regulate power flow and maximize solar energy utilization. The system is optimized for minimum power supply disruption, hot water supply disruption, energy waste, and annualized costs over a 20-year lifetime using a multi-objective NSGA-II algorithm coupling MATLAB and TRNSYS. Optimization results reveal tradeoffs between the competing objectives. Dynamic simulations show the water tank temperature fluctuates between 20 and 100 °C with mean values dropping slightly in later years due to battery degradation. Energy waste from components rises in later years for the same reason. The replacement interval for a retired EV battery module is around 2.5 years. The integrated system proves feasible for off-grid combined power and heat supply using solar energy and retired EV batteries as storage, though battery degradation impacts long-term performance. • Integrates solar, hydrogen, retired EV battery for off-grid power and heat supply with optimized storage and backup. • Utilizes multi-objective optimization to balance system reliability, waste minimization, and costs through Pareto solutions. • Implements long-term performance over twenty years to provide insights into component lifetimes and replacement needs. [ABSTRACT FROM AUTHOR]

A dedicated grid-tied offshore hybrid energy system for hydrogen production is a promising solution to unlock the full benefit of offshore wind and solar energy and realize decarbonization and sustainable energy security targets in electricity and other sectors. Current knowledge of these offshore hybrid systems is limited, particularly in the integration, component control, and allocation aspects. Therefore, a grid-integrated analytical model with a power dispatch allocation strategy between the grid and electrolyzer for the co-production of hydrogen from the offshore hybrid energy system is developed in this paper. While producing hydrogen, the proposed offshore hybrid energy system supplies a percentage of its capacity to the onshore grid facility, and the amount of the electricity is quantified based on the electricity market price and available total offshore generation. The detailed controls of each component are discussed. A case study considers a hypothetical hybrid offshore energy system of 10 MW situated in a potential offshore off the NSW of Australia based on realistic metrological data. A grid-scale proton-exchange membrane electrolyzer stack is used and a model predictive power controller is implemented on the distributed hydrogen generation scheme. The model is helpful for the assessment or optimization of both the economics and feasibility of the dedicated offshore hybrid energy farm for hydrogen production systems. • Modeling of a grid-integrated analytical model of an OHES for hydrogen co-production. • Development of a power dispatch allocation strategy for the proposed OHES. • Development of detailed controls of each component used in the proposed OHES. • Demonstrations of a case study considering 10 MW OHES situated in offshore off the NSW of Australia. [ABSTRACT FROM AUTHOR]

This comprehensive review delves into the utilization of ultrasound for hydrogen generation, emphasizing the key mechanisms and techniques involved. One of the focal points of the study is the exploration of the generation and detection of cavitation bubbles, which are induced by ultrasound waves. An in-depth overview of various experimental setups that employ ultrasound technology for hydrogen production is also provided. A comparative analysis of these setups reveals differences in crucial parameters such as acoustic intensity, liquid temperature, and frequency. These are the key parameters identified as significant determinants affecting the hydrogen yield and efficiency. This review paper also highlights the potential applications of sonohydrogen as a viable energy resource. While challenges such as the high costs of ultrasound equipment and the need for efficient catalysts exist, the inherent benefits make sonohydrogen a compelling subject for future research and development. The study shows that there is no one-size-fits-all approach, accentuating the importance of understanding these parameters for optimizing the process of hydrogen production. Although the technology is primarily in the experimental phase, existing research indicates that the sonohydrogen production holds considerable potential for large-scale applications. [Display omitted] • The study explores ultrasound's role in enhancing hydrogen production. • The article reviews various experimental setups and comparing them. • The manuscript identifies key parameters affecting sonohydrogen production. • The study discusses the potential dimensions of sonohydrogen options and future research directions. • It examines scaling sonohydrogen production challenges for industrial use. [ABSTRACT FROM AUTHOR]

The authors have developed an autonomous hydrogen energy complex and analyzed its economic efficiency. The developed energy complex is multifunctional. The main result of the work is the production and supply of electricity to the power system during hours of increased load. In addition, the low-power steam turbines included in the energy complex can provide plant-wide backup of the NPP's own needs in the event of a station blackout: based on the experimental data of the Balakovo NPP, it was previously shown that one power unit with a low-power turbine using the energy of the residual heat from the reactor can for a long time to provide electricity to required power units. Thanks to the installation of low-power turbines as part of the hydrogen energy complex, their constant warm state and self-sufficiency will be ensured by generating electricity for the power grid or for own needs in the normal mode. The paper considers options for installing an autonomous hydrogen power complex with and without replacing expensive external heat exchangers of the system for passive removal of heat from the reactor core. The efficiency of an alternative option without installing a storage system with the sale of off-peak electricity to the power system, which, in the option with AHC, is used to generate hydrogen/oxygen by electrolysis, depending on the tariff for off-peak electricity, is also calculated. Due to the lack of existing analogues of the hydrogen energy complex, several options for the proposed investment were considered. The results of the study revealed that the replacement of expensive equipment of the passive heat removal system significantly increases the economic efficiency of the proposed redundancy system. For the accepted options for capital investments, the boundary values of the off-peak selling tariff for electricity are shown, at which the use of the storage system is more efficient in comparison with the sale of nightly electricity to the power system. [ABSTRACT FROM AUTHOR]

The ongoing transition from fossil fuel-based electricity generation toward green energy relying on the intermittent renewable energy sources indispensably requires development of novel energy conversion and storage methods. Depending on a particular location and local resources, pumped storage, lithium- or sodium-ion batteries, compressed air energy storage, as well as the so called power-to-gas (P2G) technologies may be applied. Taking into account the abundant solar energy resources available in the northwestern China, such as Ningxia hui autonomous region, and local water resources coming from the Yellow River, a power-to-hydrogen (P2H2) distributed energy conversion system is proposed in this paper, which is based on a high-efficiency reversible Solid Oxide Cell (rSOC). The conducted studies comprise tests with simulated current based on the actual photovoltaic power station data, and with usage of the as-obtained Yellow River water for the electrolysis mode without any pretreatment. It is documented that the reversible operation is beneficial, and the tested cell can operate for a prolonged time. Of importance, Na, Ca, Mg, and Si elements remain in an evaporator, and do not contaminate the cell, while higher than the initial boron concentration can be found in the condensed exhaust gases. The respective operational parameters of the system correspond to an electrolysis current density loading up 433.3 mA cm−2 for 4 h, as well as fuel cell operation mode with a current density of 8.3 mA cm−2 for 12 h. It is found that the average voltage losses in the electrolysis cell and fuel cell mode are 0.27 %/cycle and 0.886 %/cycle, respectively, indicating that the lifetime of the cells can be more than 800 h. The reported studies demonstrate validity of applying rSOC-based P2H2 system, especially if abundant photovoltaic power and water resources are available. [Display omitted] • The Yellow River water was utilized by rSOC for the first time. • The designed test current was modeled with local photovoltaics. • The P2H2 nearby consumption system can reversibly operate for over 800 h. • The degradation rates in SOFC mode are lower than those in SOEC mode. • The Yellow River water has no significant effect on the degradation rate. [ABSTRACT FROM AUTHOR]

The global energy issue is undergoing transformation owing to various factors, such as climate change and geopolitics. In the long term, the primary pathways to achieve sustainable energy development remain the clean energy and global cooperation. As the largest energy consumption centers, the Asia Pacific and North America possess complementary energy profiles and developmental needs for cooperation. This paper analyses various electricity or hydrogen transmission technologies suitable for the Pacific Rim energy system. The liquid hydrogen superconducting energy pipelines possess the potential to fulfill the demands of long-distance and large-scale energy transmission. Building upon this technology, a super energy pipeline project connecting East Asia and North America across 12 time zones was proposed. It is composed of pipelines and relay energy stations, which can realize large-scale storage and transportation of renewable energy as well as the diversified energy supply at terminals. The techno-economic evaluation of the project has been comprehensively conducted, and the investment can be recovered within 10 years. The project is expected to boost the progress of renewable energy, ensure regional energy security and promote the sustainable development of global energy. [Display omitted] • Proposes cross-continental energy transmission scheme for Pacific Rim. • Highlights the potential of liquid hydrogen superconducting energy pipelines. • Identifies the future requirements for the energy storage and transmission. • Presents a review of the existing global energy mix. [ABSTRACT FROM AUTHOR]

The circulating current in the non-isolated power supply composed of an AC current converter and a DC current converter affects the normal operation of the power supply for electrolytic hydrogen production characteristics testing. This paper proposes a novel topology without circulating current by using half bridge circuit. First, the circulating current in the traditional non-isolated circuit with a full bridge circuit is analyzed, and the loop of the circulating current is obtained. The influence of the DC side voltage of AC current converter on the circulating current is analyzed. Then, through the equivalent circuit, the circulating current loop has been removed and a novel topology is presented. The circulating current in the proposed topology can be eliminated. The proposed analysis results and topology have been verified through simulation and experimental results. • A power supply composed of two paralleled converters has a DC circulating current. • The circulating current is determined by the DC voltage of the full bridge circuit. • A proposed half bridge circuit can effectively suppress the DC circulating current. • The circulating current suppression is not affected by the load dynamic process. [ABSTRACT FROM AUTHOR]

This paper focuses on the design and use of a control system for a renewable energy production plant based on hydrogen. The proposed control system aims at ensuring the stability and smooth functionality of the plant, which consists of a (i) photovoltaic system connected to an electrolyzer through a battery, (ii) a DC/DC step down transformer, and (iii) an electrolyzer heat exchange system. In this study, solar irradiance is the main system input, and hydrogen production the main output. Since the system utilizes solar energy as input, it depends on the random input of solar irradiance, ambient temperature, and wind flow. Furthermore, the electrolyzer's functionality is subject to several operational variables including cell voltage, current, temperature, and pressure. The electrolyzer heat exchange system operates at specified water temperatures and flow rates. The DC/DC output voltage, and therefore the voltage supplied to the electrolyzer, is regulated by changing its duty cycle. To regulate hydrogen production in the renewable energy production plant, an efficient control system is required. Accordingly, in this work, a control system is designed accounting for three different electrolyzer technologies, alkaline, PEM (proton exchange membrane), and E-TAC (electrochemical - thermally activated chemical water splitting). Subsequently, the effectiveness of the control system is analyzed using Matlab and Simulink models. The main results indicate that the battery is a crucial element in the whole system as it supplies the necessary energy to the electrolyzer. By regulating the appropriate components, the proposed control system proved capable of minimizing power fluctuations and increasing system efficiency up to 20% depending on ambient conditions. Additionally, the results indicate E-TAC and PEM efficiencies 13% and 7% higher than alkaline, respectively. [Display omitted] • Design of a control system for three different electrolyzer technologies. • Use of control systems for electrolyzer voltage and heat exchange. • Photovoltaic system connected to an electrolytic one through a battery. • Proposed control system increases system efficiency up to 20%. [ABSTRACT FROM AUTHOR]

The electricity production from Renewable Energy (RE) in isolated locations requires long-term energy storage systems. To that end, Hybrid Energy Storage Systems (HESS), through a combination of hydrogen and batteries, can benefit from the different advantages of both technologies. This paper presents a hybrid Power-to-Power (PtP) Optimal Power Dispatch (OPD) model for isolated systems with no electric grid access. Currently, the electricity supply in such cases is usually based on a mix of RE as the primary energy source sustained by a diesel genset acting as a backup generator. In this context, the model delivers the hourly energy flows between renewable production sources, energy storage devices and the electrical load, which minimises costs and Green House Gases (GHG) emissions. For validation purposes, the model was tested through its application to a case study in an isolated area in the Canary Islands, Spain. The results show that the algorithm calculates the hourly OPD successfully for a given plant sizing, considering the defined operational states of the different assets. These operational constraints showed a decrease in the PtP round-trip efficiency of 5.4% and a reduction of the hydrogen production of 9.7%. Finally, the techno-economic analysis of the results proves that the combination of hydrogen and batteries with RE production is a feasible alternative to phasing out fossil fuels for the selected case study – reducing the diesel generator usage down to 1.2% of the yearly energy supply. • Novel multi-state optimal power dispatch model for power-to-power energy systems. • Multi-year techno-economic evaluation of an off-grid case study. • Phasing out fossil fuels with renewable energy-based hybrid energy storage systems. • Hydrogen technology contributes to a lower levelized cost of energy. • High initial investment cost was a significant entry barrier to deploying hydrogen. [ABSTRACT FROM AUTHOR]

This paper presents a novel energy management strategy (EMS) to control a wind-hydrogen microgrid which includes a wind turbine paired with a hydrogen-based energy storage system (HESS), i.e., hydrogen production, storage and re-electrification facilities, and a local load. This complies with the mini-grid use case as per the IEA-HIA Task 24 Final Report, where three different use cases and configurations of wind farms paired with HESS are proposed in order to promote the integration of wind energy into the grid. Hydrogen production surpluses by wind generation are stored and used to provide a demand-side management solution for energy supply to the local and contractual loads, both in the grid-islanded and connected modes, with corresponding different control objectives. The EMS is based on a hierarchical model predictive control (MPC) in which long-term and short-term operations are addressed. The long-term operations are managed by a high-level MPC, in which power production by wind generation and load demand forecasts are considered in combination with day-ahead market participation. Accordingly, the hydrogen production and re-electrification are scheduled so as to jointly track the load demand, maximize the revenue through electricity market participation and minimize the HESS operating costs. Instead, the management of the short-term operations is entrusted to a low-level MPC, which compensates for any deviations of the actual conditions from the forecasts and refines the power production so as to address the real-time market participation and the short time-scale equipment dynamics and constraints. Both levels also take into account operation requirements and devices' operating ranges through appropriate constraints. The mathematical modeling relies on the mixed-logic dynamic (MLD) framework so that the various logic states and corresponding continuous dynamics of the HESS are considered. This results in a mixed-integer linear program which is solved numerically. The effectiveness of the controller is analyzed by simulations which are carried out using wind forecasts and spot prices of a wind farm in center-south of Italy. • Design of control algorithms for islanded and grid-connected microgrids. • Development of hierarchical MPCs to target long-term and short-term operations. • Tracking the load demand and maximizing the revenue via electricity markets. • Minimization of the HESS operational costs. [ABSTRACT FROM AUTHOR]

The number of hydrogen refuelling stations worldwide has increased to over 700 due to the rapid development of green hydrogen energy. The risk assessment of hydrogen refuelling stations is indispensable to prevent accidents, and its foundation is accident scenarios screening. Although the integrated energy supply station containing fuels such as hydrogen, compressed natural gas (CNG), methanol eliminates the need for building hydrogen refuelling stations separately, the risk assessment for these complex systems has not been comprehensively studied. This paper proposes a scenario screening approach for identifying potential hazards in multi-fuel integrated energy supply stations. The risk of the processing unit was evaluated, and the leakage scenarios were pre-screened to identify credible leakage scenarios that adhere to the principle of maximum credibility by considering the frequency of occurrence and severity of consequences in two parts. Based upon acquired credible leakage scenarios, secondary screening of possible accident consequences was conducted by calculating the value of the credible factor to obtain the final maximum credible accident scenarios (MAS). Credible factors are derived from the accident probability, consequence severity, population density and asset density. By comparing the values of the credible factors, the accident scenarios with a low probability or low severity were eliminated, and the accident scenarios with the highest credible factors of each unit were retained as the MAS that require further consequence simulation analysis. The results offer a crucial foundation for the consequences and risk assessment of integrated energy supply stations. • Potential consequences of accidents caused by hydrogen and other fuel leaks. • Credible scenarios for fuel leaks are identified. • Maximum credible accident scenarios are determined. • Hydrogen compressor and associated piping are most susceptible to jet fires and explosions. [ABSTRACT FROM AUTHOR]

At present, energy shortage and environmental pollution are becoming more and more serious. If environmental governance and energy supply can be combined, it will be more consistent with the long-term concept of sustainable development. Urea electrooxidation may achieve the degradation of pollutants and the conversion of energy supply, urea oxidation occurs at the anode and hydrogen evolution occurs at the cathode. However, the electrochemical oxidation process of urea requires the transfer of six electrons, and the reaction rate is slow. The electrocatalyst is a key factor in improving the reaction kinetics. In this context, catalysts used in urea electrocatalytic oxidation in recent years are reviewed in this paper. The application of the electrocatalyst in electrolytic hydrogen production, urea wastewater treatment, urea fuel cells and urea sensors are described in detail. In addition, the future research directions, research emphases and areas needing improvement of these catalysts are discussed. [Display omitted] • Urea electrooxidation has double benefits of environmental protection and energy supply. • Electrocatalysts for urea electrooxidation in alkaline electrolytes are reviewed. • The applications of electrocatalyst in the electrooxidation of urea are demonstrated. [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]

This paper presents a framework for the efficient design and evaluation of a standalone hybrid renewable energy system (HRES) to meet the energy requirements of a rural community in the north-eastern region of Nigeria. The proposed microgrid system incorporates solar photovoltaic, wind turbines, biomass gasifier, fuel cell, and Battery storage. The sizing of each component is determined through the utilization of real local meteorological data and the load demand over a year, employing the Levy flight-salp swarm algorithms (LF-SSA). The optimization objective is to minimize the annualized system cost (ASC) of the HRES, while also considering the reliability constraint of Loss of power supply probability (LPSP). The comparative outcomes demonstrate that the LF-SSA surpasses other examined algorithms, namely the salp swarm, genetic algorithm, and HOMER software by achieving substantial cost savings of $29033, $50796, $191771 respectively in relation to the proposed HRES. The result further shows that, the LF-SSA provides the lowest LCOE of $0.933162/kWh, in contrast to SSA at $0.947737/kWh, GA at $0.958660/kWh, and HOMER at $1.075351/kWh. Additionally, the results indicate that the implemented Energy Management System (EMS) has successfully facilitated the establishment of an environmentally friendly and cost-effective energy system. • An efficient energy storage system is essential for managing intermittent energy supply. • The fuel cell can generate DC power by combining hydrogen with oxygen. • The amount of power generated by a PV panel depends on temperature and solar radiation intensity. • Deterministic rule-based controllers operate based on pre-defined rules. • Energy Management System coordinate the flow of power between different components. [ABSTRACT FROM AUTHOR]

Hydrogen is a type of clean secondary energy, and the hydrogen energy supply is vital to regional energy development. Guangdong is at the forefront of hydrogen energy deployment in China, and aims to achieve peak carbon by 2030. However, hydrogen production research is challenging due to complex technical routes, technical maturity levels, life-cycle carbon emissions, and costs. Multi-time-scale research is necessary to explore optimal production paths and their contributions to CO 2 emission reduction. This study discussed key technologies and the technical maturity of five hydrogen production routes: production from industrial byproducts and coal, wind, hydro-, and photovoltaic power. Policy scenarios were designed to investigate the potential of these routes and technology deployment intensity under medium- and long-term scenarios. This paper proposes a roadmap for hydrogen development and provides a reference for hydrogen production planning in Guangdong. This methodology can be applied in other regions for hydrogen energy development research. • Key technology maturity of the hydrogen production routes was evaluated. • Roadmap of hydrogen production in Guangdong Province was designed. • A method for research of hydrogen supply scenarios was proposed. [ABSTRACT FROM AUTHOR]

Hydrogen is expected to be a key energy carrier in the global energy transition. A promising method of hydrogen production is water electrolysis powered by nuclear energy. This energy source can also be used in other hydrogen production technologies, such as copper-chlorine cycle. Proper comparison of various hydrogen production methods from the sustainability perspective requires the use of analysis in a global balance boundary. The paper presents a comparison of sustainability of various hydrogen generation methods, with emphasis on the methods exploiting nuclear energy. Instead of local energy efficiency, the index of Thermo-Ecological Cost (TEC) is proposed. TEC is a measure of the depletion of non-renewable resources burdening the production of a given product. Other criteria used in the assessment are: availability of energy supply (capacity factor), cumulative greenhouse gas emissions and resources to production ratio. In addition, water electrolysis and copper-chlorine cycle have been considered cogeneration processes, providing oxygen as a useful by-product. Taking into account all the criteria suggests that obtaining hydrogen with the use of nuclear technologies will provide a fair, long-term compromise compared to other hydrogen generation technologies. • Sustainability of H 2 production methods utilizing nuclear energy is investigated. • Technologies are evaluated in global balance boundary using Thermo-Ecological Cost. • Multiple criteria are applied to properly compare hydrogen production methods. • Nuclear-based H 2 can be considered more sustainable than renewable-based H 2. [ABSTRACT FROM AUTHOR]

Clean energy resources will be used more for sustainability improvement and durable development. Efficient technologies of energy production, storage, and usage results in reduction of gas emissions and improvement of the world economy. Despite 30% of electricity being produced from wind energy, the connection of wind farms to medium and large-scale grid power systems is still leading to instability and intermittency problems. Therefore, the conversion of electrical energy generated from wind parks into green hydrogen consists of an exciting solution for advancing the development of green hydrogen production, and the clean transportation sector. This paper presents a techno-economic optimization of hydrogen production for refueling fuel cell vehicles, using wind energy resources. The paper analyses three configurations, standalone Wind-Park Hydrogen Refueling Station (WP-HRS) with backup batteries, WP-HRS with backup fuel cells, and grid-connected WP-HRS. The analysis of different configurations is based on the wind potential at the site, costs of different equipment, and hydrogen load. Therefore, the study aims to find the optimized capacity of wind turbines, electrolyzers, power converters, and storage tanks. The optimization results show that the WP-HRS connected to the grid has the lowest Present Worth Cost (PWC) of 6,500,000 €. Moreover, the Levelized Hydrogen Cost (LHC) of this solution was found to be 6.24 €/kg. This renewable energy system produces 80,000 kg of green hydrogen yearly. • Wind to green hydrogen represents an interesting solution for greenhouse gas reduction. • Three configurations of wind-park stations designed for green hydrogen production are analyzed. • Grid-connected wind park consists of an optimal solution for the wind park hydrogen station. • The Levelized cost of hydrogen production using a 5 MW grid-connected wind park is 6.24 €/kg. [ABSTRACT FROM AUTHOR]

This paper outlines the optimal design of a hybrid system that includes wind turbines, solar panels, and a fuel cell to successfully meet the load's requirements. All cost components of the system, including load loss and expenditure for operation and maintenance, have been taken into consideration. A modified version of Ruddy Turnstone Optimization Algorithm is applied to determine the ideal equipment capacity for the hybrid system. Comparison and analysis are done between the optimization results and the outcomes obtained through evolutionary techniques. Moreover, the proposed technique is tested on a case study from Egypt and a comparison is made with existing Hybrid Firefly/Harmony Search method from literature. According to the results, both modified Ruddy Turnstone Optimization and Hybrid Firefly/Harmony Search methods have produced satisfactory outcomes. While the production cost slightly increased using the Hybrid Firefly/Harmony Search methodology, the system's dependability level has improved significantly, thereby ensuring reliable load supply. The results of a loss of power supply possibility comparison using 0.5%, 1%, and 2% of the modified Turnstone Optimization algorithm versus Hybrid Firefly/Harmony Search method approach yields a minimum cost of energy of 0.0798, 0.0739, and 0.0573 $/kWh, respectively. • Combined WT, PV, and FC system is described to satisfy the load's requirement. • System includes load loss cost as well as original investment cost for O&M. • Modified Ruddy Turnstone Optimizer is used for determining ideal equipment capacity. • The method is performed to a studied case in Egypt. • Comparison is conducted between the outcomes and HFA/HS method. [ABSTRACT FROM AUTHOR]

Developing a thriving hydrogen industry will depend on public and community support. Past research, mainly focusing on the acceptance of hydrogen fuelling stations and cars, suggests that people generally support hydrogen energy technology (HET). Few studies have, however, considered how people think about other components of the hydrogen supply chain (i.e., technologies required to make, store, transport and use hydrogen). Moreover, there has been limited research investigating how people interpret and develop beliefs about HET after being presented with technical information. This paper attempts to address these research gaps by presenting the findings from four face-to-face focus group discussions conducted in Australia. The findings suggest that people have differing views about HET, which depends on the type of technology, and these views influence levels of support. The study also revealed concerns about a range of other factors that have yet to be considered in hydrogen acceptance research (e.g., perceived water use, efficiency and indirect benefits). The findings highlight the value of qualitative research for identifying salient beliefs that shape attitudes towards HET and provide recommendations for future research and how to effectively communicate with the public and communities about an emerging hydrogen industry. • Focus group discussions with Australians about whole hydrogen supply chain. • Generally positive, but tentative, attitudes toward hydrogen overall. • Stronger support for industrial applications over domestic/household applications. • Concerns raised about hydrogen's efficiency and its conflict with other technologies. • Support for more research and pilot projects to provide tangible evidence. [ABSTRACT FROM AUTHOR]

This paper presents a study that focuses on alleviating the impacts of grid outages in Ethiopia. To deal with grid outages, most industrial customers utilize backup diesel generators (DG) which are environmentally unfriendly and economically not viable. Grid-integration of hybrid renewable energy systems (HRES) might be a possible solution to enhance grid reliability and reduce environmental and economic impacts of utilizing DG. In this study, an optimization of grid integrated HRES is carried out for different dispatch and control strategies. The optimal power supply option is determined by performing comparative analysis of the different configurations of grid integrated HRES. The result of the study shows that grid integrated HRES consisting of photovoltaic and wind turbine as renewable energy sources, and battery and hydrogen as hybrid energy storage systems is found to be the optimal system to supply the load demand. From the hydrogen produced on-site, the FC generator and FCEVs consume 143 620 kg/yr of hydrogen which is equivalent to 394 955 kg/yr gasoline fuel consumption. This corresponds to saving 1 184 865 kg/yr of CO 2 emissions and 605 703 $/yr revenue. Besides, this system yields 547 035.4 $/yr revenue by injecting excess electricity to the grid. The study clearly shows the economic and environmental viability of this new technology for implementation. • Modeling and optimization of grid-integrated HRES including grid-reliability and dispatch control. • Storage of excess electricity produced from renewable energy sources in batteries. • Onsite production of renewable hydrogen with excess electricity produced from renewable energy sources. • The role of renewable hydrogen for simultaneous decarbonization of electricity and transportation sectors. • Minimizing overall operating costs by injecting excess electricity to the grid. [ABSTRACT FROM AUTHOR]

Establishing an industrial park-integrated energy system (IN-IES) is an effective way to reduce carbon emission, reduce energy supply cost and improve system flexibility. However, the modeling of hydrogen storage in traditional IN-IES is relatively rough. In order to solve this problem, an IN-IES with hydrogen energy industry chain (HEIC) is proposed in this paper. Hydrogen production, transportation, and storage technologies are applied in HEIC. Firstly, a novel long-term hydrogen storage model considering different time steps is presented. Secondly, hydrogen compressor models considering different pressure ratios are further employed. On this basis, the impact of the HEIC on the planning and operation results of IN-IES is studied. Finally, the superiority and the effectiveness of the proposed model and planning method are verified by simulation cases. • The hydrogen energy industry chain including hydrogen production, storage, and transportation technologies. • A novel long-term hydrogen storage model is proposed that considers different time steps. • Different hydrogen compression levels are utilized to hydrogen compressor models. [ABSTRACT FROM AUTHOR]

In this paper, a multi-objective mixed-integer linear programming model is developed to design a hybrid PV-hydrogen renewable energy system considering two objective functions; minimizing total life costs and loss probability of power supply. The decisions of the hybrid system include the number of PV panels, the number of hydrogen tanks, the number of electrolyzers, the number of fuel cells, and quantity of hydrogen stored over time. An exact method embedded in GAMS software is used to solve the developed model. The model is validated using an electrical testing lab in Saudi Arabia with hourly power demand. Different plans are chosen from the obtained optimal Pareto solutions. For example, one of the plans found that a hybrid system with 212 PV panels, 617 hydrogen tanks, 30 electrolyzers, and 21 fuel cells is sufficient to satisfy the electrical testing lab load with an annual cost of $61663, the loss of power supply probability is 10%, and the CO 2 saving of 214,882 kg of CO 2. The results indicated the feasibility of combining an electrolyzer, hydrogen tank storage, and fuel cell with a renewable energy system; however, the cost of energy generated is still high because of the high investment cost. Furthermore, the findings revealed that hydrogen technologies are appealing as an energy storage solution for intermittent renewable energy systems and in other applications such as transportation, residential, and industrial sectors. In addition, the findings demonstrated the possibility of using renewable energy as a source of energy, namely, in Saudi Arabia. However, weather conditions, geomorphological conditions, and climatic dependence on hydrogen fuel cell technology can harm the energy yields produced by renewable energy systems. • Design a multi-objective hybrid PV-Hydrogen storage renewable energy system. • Evaluate the performance of the proposed model based on a real case study. • Help the decision-maker in analyzing alternative trade-offs. • The LCOE ranges between 0.143 and 0.160 $/kWh for generated plans. • The annual CO 2 savings range between 197,351 and 227,905 kg of CO 2. [ABSTRACT FROM AUTHOR]

Population growth and the expansion of industries have increased energy demand and the use of fossil fuels as an energy source, resulting in release of greenhouse gases (GHG) and increased air pollution. Countries are therefore looking for alternatives to fossil fuels for energy generation. Using hydrogen as an energy carrier is one of the most promising alternatives to replace fossil fuels in electricity generation. It is therefore essential to know how hydrogen is produced. Hydrogen can be produced by splitting the water molecules in an electrolyser, using the abondand water resources, which are covering around ⅔ of the Earth's surface. Electrolysers, however, require high-quality water, with conductivity in the range of 0.1–1 μS/cm. In January 2018, there were 184 offshore oil and gas rigs in the North Sea which may be excellent sites for hydrogen production from seawater. The hydrogen production process reported in this paper is based on a proton exchange membrane (PEM) electrolyser with an input flow rate of 300 L/h. A financially optimal system for producing demineralized water from seawater, with conductivity in the range of 0.1–1 μS/cm as the input for electrolyser, by WAVE (Water Application Value Engine) design software was studied. The costs of producing hydrogen using the optimised system was calculated to be US$3.51/kg H 2. The best option for low-cost power generation, using renewable resources such as photovoltaic (PV) devices, wind turbines, as well as electricity from the grid was assessed, considering the location of the case considered. All calculations were based on assumption of existing cable from the grid to the offshore, meaning that the cost of cables and distribution infrastructure were not considered. Models were created using HOMER Pro (Hybrid Optimisation of Multiple Energy Resources) software to optimise the microgrids and the distributed energy resources, under the assumption of a nominal discount rate, inflation rate, project lifetime, and CO 2 tax in Norway. Eight different scenarios were examined using HOMER Pro, and the main findings being as follows: The cost of producing water with quality required by the electrolyser is low, compared with the cost of electricity for operation of the electrolyser, and therefore has little effect on the total cost of hydrogen production (less than 1%). The optimal solution was shown to be electricity from the grid, which has the lowest levelised cost of energy (LCOE) of the options considered. The hydrogen production cost using electricity from the grid was about US$ 5/kg H 2. Grid based electricity resulted in the lowest hydrogen production cost, even when costs for CO 2 emissions in Norway, that will start to apply in 2025 was considered, being approximately US$7.7/kg H 2. From economical point of view, wind energy was found to be a more economical than solar. • Overview of hydrogen production technologies. • Assessment of cost of desalination processes in relation to the total hydrogen production costs. • Investigation of applicability of offshore hydrogen production from seawater. • To assess the green hydrogen production potential offshore. [ABSTRACT FROM AUTHOR]

The shortage of fossil energy has become a growing global concern. It is particularly important to make full use of the infinite solar energy resources, and transform them into sustainable and clean energy. The development of hydrogen energy has become a feasible solution to solve the energy shortage problem. The preparation of photocatalysts featuring efficient charge transfer channels and high hydrogen production activity provides a pathway for the development of hydrogen energy. In this paper, we report for the first time the direct assembly of 2D ZnIn 2 S 4 (ZIS) nanosheets on the surface of CoTiO 3 (CTO). The synthesized CoTiO 3 /ZnIn 2 S 4 (CTO/ZIS) photocatalyst features a direct Z-scheme charge transfer channel, which enhances the separation rate of photogenerated carriers, and accelerates the photocatalytic H 2 evolution (PHE) rate. Without the assistance of any co-catalyst, the PHE rate of prepared CoTiO 3 /ZnIn 2 S 4 was as high as 5.21 mmol g−1 h−1. Moreover, the H 2 evolution rate of CoTiO 3 /ZnIn 2 S 4 almost did not decrease significantly after four consecutive 4 h cycles. This investigation provides a valuable approach for the exploitation of novel and efficient Z-scheme photocatalysts in the application of solar energy to hydrogen energy conversion. Using the Z-scheme CoTiO 3 /ZnIn 2 S 4 photocatalyst, water is decomposed under visible light irradiation to produce large amounts of H 2. The conversion of solar energy to hydrogen energy is realized. [Display omitted] • This is the first report of in situ assembly of ZnIn 2 S 4 nanosheets on CoTiO 3 surface. • The as-prepared CoTiO 3 /ZnIn 2 S 4 showed a new Z-scheme heterojunction. • The CoTiO 3 /ZnIn 2 S 4 heterojunction displayed an improved photocatalytic hydrogen evolution rate. [ABSTRACT FROM AUTHOR]

Nowadays the trend of increasing the generation units based on renewable energy sources in the electric power system can be observed. Obviously, this is due to the intensifying level of consumer load and demand for electricity. However, renewable generation is characterized by intermittent energy production, which can cause and potential imbalance between generation and demand, especially during off-peak periods. Therefore, in order to ensure a reliable power supply to consumers, it is necessary to use a maneuverable reserve of capacity, such as energy storage systems, in conjunction with the renewable energy source unit. Over the past 10 years, the energy storage market has grown by almost 50%: the installed capacity of energy storage system in the world is about 5 GW. Analysis of the literature on the subject determines the need to study the impact of these devices on the parameters of electric power systems and one of the primary tasks is to determine the optimal location and capacity of energy storage system in the power system. This paper presents the result of solving the task of determining the optimal parameters of a hydrogen energy storage system using the particle swarm optimization method for example a test scheme radial distribution system – 33 bus IEEE. The choice of the type of energy storage is based on such advantages of a hydrogen energy storage system as environmental friendliness, high energy capacity and the ability to store electricity for a long period of time. In addition, compared to lithium-ion batteries, hydrogen energy storage systems have a long life time of about 25 years, during this period of time there is no degradation and significant deterioration of its properties. All these advantages of hydrogen as an energy carrier allow to take into account not only the criterion of total value of active power losses and its maximum reduction respectively, but the possibility and economic efficiency of partial use of the stored hydrogen for other needs when determining the optimal scenario of their operation in the process of discharge. [ABSTRACT FROM AUTHOR]

Nowadays, the scheme of a stand-alone microgrid utilizing renewable energy is regarded as an effective approach to guarantee the power supply of an off-grid system. However, the intermittent nature of renewables brings new challenges to the determination of the optimal operation point for a hybrid energy system (HES). To address this issue, this paper proposes a subsection bi-objective optimization dynamic programming strategy for the HES consisting of photovoltaic, fuel cell, electrolyzer, hydrogen storage system, and battery bank. Within the proposed strategy, reasonable rule-based judgment is introduced to reduce the complexity of system control. Moreover, dynamic programming is selected to obtain the global optimal power distribution scheme. Meanwhile, a multi-objective genetic algorithm strategy is designed for comparative analysis. The results in two typical cases indicate the proposed strategy can improve photovoltaic utilization by 0.95% and 0.0003%, and fuel economy by nearly 50%. [Display omitted] • The hybrid energy system is modeled to clarify the operation mechanism. • Subsection bi-objective optimization dynamic programming is proposed. • Rule-based judgment is introduced to reduce the complexity of the optimization. • Two-staged optimization is implemented to improve fuel economy and utilization. [ABSTRACT FROM AUTHOR]

In modern power systems, the reliability of energy supplies is a real challenge for the operators. The emergence of renewable energy resources, along with multi-career users, requires multi-career systems. In this regard, the energy hub (EH) as an integrated system can be used to increase the reliability of the system. The power-to-gas (P2G) and P2G storage are two practical technologies to achieve high efficiency in energy systems. In this paper, the contribution is optimal scheduling of stochastic problem in EH system amalgamated with CHP unit, P2G storage, thermal storage, boiler, wind power, and electrical storage to supply the heat, gas, and power loads by regarding demand response program (DRP). For the electrical loads, the load shifting strategy is considered to minimize the operational cost of the EH system. In order to manage related uncertainties about electricity price, wind power, and electrical loads, the downside risk constraint (DRC) method is applied to investigate the EH system function. According to the obtained results, by increasing approximately 2.8% of the operational cost, the risk level can be reduced remarkably. And also, almost 10% of the energy shifted from peak hours to the off-peak time after DRP is applied. • Optimization of power, heat and gas energy consumption in an energy hub. • Energy hub system is integrated with power-to-gas storage. • All uncertainty parameter are modeled via scenario based stochastic programming. • Downside risk constrained approach is proposed for risk modeling in energy hub. • Risk-averse and risk-neutral strategies are compared with each other. [ABSTRACT FROM AUTHOR]

This paper reviews the prospect to institute the inter-state hydrogen energy system on selected countries in Asia-Pacific region, through individual evaluation from the nexus of technology, social and economy perspectives, and further utilizing the respective strengths to identify the inter-state hydrogen network strategy in Asia-Pacific region, or 'Asia-Pacific Hydrogen Valley'. Domestic energy self-sufficiency based on the existing energy sources produced nationally is also considered in the review. In looking into the prospective of hydrogen energy system adoption, four indicators are set based on domestic energy capacity, national wealth, society development and research and development (R&D), which are generalized according to the population size of the country. Countries of assessment are Indonesia, Malaysia, Brunei Darussalam, Philippines, Singapore, Vietnam, Thailand, Japan, South Korea, Australia and New Zealand. This study reveals that nations with active hydrogen policies and high R&D capacity could lead the strategy, while countries with high capacity in primary energy supply and economy advantage would benefit the group in catering the energy and commercial resources, respectively. Social acceptance is another critical aspect, as countries with high social security index could potentially reduce the risk of public rebuttal against the energy system transformation. This paper also extensively discusses the existing energy profile, policies and strategies of each country, which become the basis in potential identification of the country to adopt the new hydrogen energy system in the future. • This study characterizes nation's role in potential inter-state hydrogen network. • Japan, South Korea, Australia, New Zealand may lead the inter-state hydrogen network. • Singapore and Brunei Darussalam hold potential as key players in capital resources. • Australia, Brunei Darussalam, Indonesia are amongst the potential energy suppliers. • Low-tariffs countries are enticing for hydrogen infrastructures institution. [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]

This paper evaluates the potential of grid services in France, Italy, Norway and Spain to provide an alternative income for electrolysers producing hydrogen from wind power. Grid services are simulated with each country's data for 2017 for energy prices, grid services and wind power profiles from relevant wind parks. A novel metric is presented, the value of curtailed hydrogen, which is independent from several highly uncertain parameters such as electrolyser cost or hydrogen market price. Results indicate that grid services can monetise the unused spare capacity of electrolyser plants, improving their economy in the critical deployment phase. For most countries, up-regulation yields a value of curtailed hydrogen above 6 €/kg, over 3 times higher than the EU's 2030 price target (without incentives). However, countries with large hydro power resources such as Norway yield far lower results, below 2 €/kg. The value of curtailed hydrogen also decreases with hydrogen production, corresponding to the cases of symmetric and down-regulation. • Defined a metric independent of electrolyser cost or hydrogen price, which are a large source of uncertainty. • Analysed the potential for grid services in multiple markets with real data for prices and wind power. • Presented the separate contribution of grid services, spot prices and tariffs in the value of curtailed hydrogen. [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 deals with the emission reduction in synthesis-gas production by better integration and increasing the energy efficiency of a high-temperature co-electrolysis unit combined with the Fischer-Tropsch process. The investigated process utilises the by-product of Fischer-Tropsch, as an energy source and carbon dioxide as a feedstock for synthesis gas production. The proposed approach is based on adjusting process streams temperatures with the further synthesis of a new heat exchangers network and optimisation of the utility system. The potential of secondary energy resources was determined using plus/minus principles and simulation of a high-temperature co-electrolysis unit. The proposed technique maximises the economic and environmental benefits of inter-unit integration. Two scenarios were considered for sharing the high-temperature co-electrolysis and the Fischer-Tropsch process. In the first scenario, by-products from the Fischer-Tropsch process were used as fuel for a high-temperature co-electrolysis. Optimisation of secondary energy sources and the synthesis of a new heat exchanger network reduce fuel consumption by 47% and electricity by 11%. An additional environmental benefit is reflected in emission reduction by 25,145 tCO 2 /y. The second scenario uses fossil fuel as a primary energy source. The new exchanger network for the high-temperature co-electrolysis was built for different energy sources. The use of natural gas resulted in total annual costs of the heat exchanger network to 1,388,034 USD/y, which is 1%, 14%, 116% less than for coal, fuel oil and LPG, respectively. The use of natural gas as a fuel has the lowest carbon footprint of 7288 tCO 2 /y. On the other hand, coal as an energy source has commensurable economic indicators that produce 2 times more CO 2 , which can be used as a feedstock for a high-temperature co-electrolysis. This work shows how in-depth preliminary analysis can optimise the use of primary and secondary energy resources during inter-plant integration. [Display omitted] • Transition to sustainable energy and share of high hydrogen-containing fuels. • Inter-plant integration via by-products recycling and better heat recovery was proposed. • Methodology combined process integration and process modification principles. • Unified process flow diagram for different fuel types was developed. • In-depth integrated syngas production consumes 47% less energy and saves 25,145 tCO 2 /y. [ABSTRACT FROM AUTHOR]

The current energy supply depends on fossil fuels which have increased carbon dioxide emissions leading to global warming and depleted non-renewable fossil fuels resources. Hydrogen (H 2) fuel could be an eco-friendly alternative since H 2 consumption only produces water. However, the overall impacts of the H 2 economy depend on feedstock types, production technologies, and process routes. The existing process technologies for H 2 production used fossil fuels encounter the escalation of fossil fuel prices and long-term sustainability challenges. Therefore, biohydrogen production from renewable resources like biomass wastes and wastewaters has become the focal development of a sustainable global energy supply. Different from other biohydrogen production studies, this paper emphasizes biohydrogen fermentation processes using different renewable sources and microorganisms. Moreover, it gives an overview of the latest advancing research in different biohydrogen process designs, modeling, and optimization. It also presents the biohydrogen production routes and kinetic modeling for biohydrogenation. • Review on biohydrogen process design, modelling, and optimization. • Comparison of biohydrogen process designs including continuous, batch, or semi-batch processes. • Kinetic equations with optimized parameters are hard to be converted into universal predictive models. • Identification of some possible future research directions. [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]

In this paper, a new geothermal-based multigeneration system is designed and investigated in both thermodynamic and economic analyses. The reason to select the geothermal source is that geothermal power is a renewable and sustainable power resource, and also it is not weather dependent. The proposed geothermal-based multigeneration plant is able to produce power, heating, cooling, swimming pool heating, and hydrogen. The main idea in this renewable-based multigeneration system is to create valuable products by using waste heat of subsystems. Then, by applying thermodynamic analyses, the energy and exergy performances of proposed multigeneration system are computed. Also, parametric work has been performed in order to see the impacts of the reference temperature, geothermal fluid temperature, and geothermal water mass flow rate. Finally, exergo-economic analysis based on exergy destruction or thermodynamic losses is done to gain more information about the system and to evaluate it better. According to the calculations, the overall plant's energy and exergy performances are 32.28% and 25.39%. Economic analysis indicates that hydrogen production cost can be dropped down to 1.06 $/kg H 2. [Display omitted] • A new geothermal energy-based plant is developed for multigeneration. • Thermodynamic and economic analyses are given for more effective design. • Overall energy and exergy efficiencies are computed as 32.28% and 25.39%. • The impact of working parameters on the plant performance is analyzed. [ABSTRACT FROM AUTHOR]

Hydrogen energy storage systems (HydESS) and their integration with renewable energy sources into the grid have the greatest potential for energy production and storage while controlling grid demand to enhance energy sustainability. This paper presents a bibliometric analysis based on a comprehensive review of the highly cited articles on HydESS to provide a detailed insight into future directions and applications. The study was carried out by using the Scopus database search engine to look for filtered keywords in the HydESS and related research. It can be demonstrated that the HydESS literature expanded rapidly from 2016 to 2021 compared to 2011 to 2015. It is found that 89.17% of published articles explained control and test systems-based methods, whereas 10.83% of publications discuss review assessments. Our analysis of highly cited articles on HydESS highlights several aspects, such as methods and systems, issues, difficulties, and challenges to establishing current constraints and research gaps. This evaluation can enhance operational performance, environmental friendliness, energy savings, uninterrupted power supply service, cost benefits, on-site generation, and adaptability. It would be beneficial for technology development and the growth of the hydESS industry. This study may act as a guideline not only for academics in determining the line of research and generating additional discoveries, but also for the government in formulating financial strategies. • Top-cited hydrogen energy storage system articles are reviewed under specific conditions. • Hydrogen storage integrated grids have the potential for energy sustainability. • A historical overview of hydrogen storage was analyzed using the Scopus database. • This survey has exhibited a developing hydrogen storage and renewable energy fields of research. • Bibliometric analysis was used to identify potential future research directions. [ABSTRACT FROM AUTHOR]

The paper provides an assessment of the current wind energy potential in Ukraine, and discusses developmental prospects for wind-hydrogen power generation in the country. Hydrogen utilization is a highly promising option for Ukraine's energy system, environment, and business. In Ukraine, an optimal way towards clean zero-carbon energy production is through the development of the wind-hydrogen sector. In order to make it possible, the energy potential of industrial hydrogen production and use has to be studied thoroughly. Ukraine possesses huge resources for wind energy supply. At the beginning of 2020, the total installed capacity of Ukrainian wind farms was 1.17 GW. Wind power generation in Ukraine has significant advantages in comparison to the use of traditional sources such as thermal and nuclear energy. In this work, an assessment of the wind resource potential in Ukraine is made via the geographical approach suggested by the authors, and according to the «Methodical guidelines for the assessment of average annual power generation by a wind turbine based on the long-term wind speed observation data». The paper analyses the long-term dynamics of average annual wind speed at 40 Ukrainian weather stations that provide valid data. The parameter for the vertical wind profile model is calculated based on the data reanalysis for 10 m and 50 m altitudes. The capacity factor (CF) for modern wind turbine generators is determined. The CF spatial distribution for an average 3 MW wind turbine and the power generation potential for the wind power plants across the territory of Ukraine are mapped. Based on the wind energy potential assessment, the equivalent possible production of water electrolysis-derived green hydrogen is estimated. The potential average annual production of green hydrogen across the territory of Ukraine is mapped. It is concluded that Ukraine can potentially establish wind power plants with a total capacity of 688 GW on its territory. The average annual electricity production of this system is supposed to reach up to 2174 bln kWh. Thus, it can provide an average annual production of 483 billion Nm3 (43 million tons) of green hydrogen by electrolysis. The social efficiency of investments in wind-hydrogen electricity is presented. Image 1 • Assessment of wind potential and electrolysis of green hydrogen in Ukraine. • Ukraine has the potential to build 688 GW of WPP capacity on its territory. • Ukraine can provide 43 m tons of green hydrogen annual production by electrolysis. • Map of potential distribution of annual green hydrogen production in Ukraine. • Investments' social efficiency of in wind-hydrogen electricity. [ABSTRACT FROM AUTHOR]

The demand for H 2 increases rapidly with the gradual recognition of the potential of H 2 as an important secondary energy. At present, coal gasification is the main way to obtain hydrogen on a large scale and at a low cost in China. The underground coal gasification (UCG), as a kind of in-situ utilization technology that can exploit the unreachable deep coal resources, could become an alternative H 2 production pathway. This paper presents comparative study of energy utilization and resource consumption in H 2 production by UCG and typical surface coal gasification (SCG) technology, namely Lurgi fixed bed gasification, with 1.2 billion Nm3/a throughput of H 2 as example, to offer corresponding data support. The efficiency and the amount of resources consumed in constructing and operating each coal-to-hydrogen system under different conditions have been researched from exergetic point of view, which is not reported in existing literatures. In this paper, the exergy efficiency is calculated to be 40.48% and 40.98% for hydrogen production using UCG and SCG. The result indicates the competitiveness of UCG in the field of hydrogen production comparing with widely used coal gasification technology. The resource consumption is measured by cumulative exergy consumption (CExC), which is 8.17E+10 MJ and 6.57E+10 MJ for H 2 production from UCG and SCG. The result shows that although the H 2 production from UCG has higher CExC, it can significantly reduce the resource consumption of equipment comparing with H 2 production from SCG, indicating its advantage in total investment. It is found that the exergy efficiency increases with the rise in H 2 O-to-O 2 and O 2 -to-CO 2 ratio, while the value of CExC decreases with the appreciation of H 2 O-to-O 2 ratio yet increases as the O 2 -to-CO 2 ratio rises. In addition, the sensitivity analysis of production capacity reveals that the exergy efficiency gap and CExC gap between hydrogen production by UCG and SCG diminishes at smaller scale production capacities, showing that UCG is more suitable for small-scale hydrogen production. • A resource consumption comparison of H 2 production from UCG and SCG is conducted. • Exergy is analyzed with 1.2 billion Nm3/a throughput of H 2 as example. • Exergy efficiency of UCG-H 2 reaches 40.48%, comparable to 40.98% for SCG-H 2. • UCG-H 2 significantly reduces CExC of equipment compared to SCG-H 2. • Effects of key operational parameters on system's performances are investigated. [ABSTRACT FROM AUTHOR]

Conventional productions of large volume of hydrogen from fossil based resources continue to play a key role in the hydrogen economy. This paper recalls the contribution of these conventional technologies with new technological development and researches. Providing gradual integration of renewable solutions into large-scale production, some emerging developments in the use of the renewable based feedstock and energy resources in reforming processes in order to bridge the gaps from conventional use of fossil feedstock to improve various conversion processes were discussed. This paper focuses on high temperature process technologies for producing hydrogen via non-renewable resources and various industrial technologies and processes (700 °C and above) for the beneficiation of the available carbonaceous feedstocks like natural gas, other hydrocarbons (other fossil based options), coal etc. The paper concludes with the analysis of some development gaps in hydrogen production from various resources, which interplays between the renewable and non-renewable resources as well as likely future trends that should be expected in the hydrogen market in the next decades. Image 1 • Wide range of hydrogen utilizations are key drivers to its increasing demand. • Fossil based hydrogen production continues to play dominate role in the hydrogen economy. • By production volume and technological advancement, reforming of natural gas takes the lead. • Non-renewable resources beneficiations via high temperature processes were discussed. • Emerging developments in industrial scale reforming with renewable solutions were assessed. [ABSTRACT FROM AUTHOR]

Gasification process is considered as one of the best routes of energy recovery from biomass by producing syngas mostly including H 2 , CO, and CH 4. Biomass as the main renewable energy resources has great advantages regarding its diversity, availability, and sustainability for supplying energy needs in heat, electricity production, biofuel production for transportation, etc. Various gasifiers based on the gasifying process and agents have been examined. This paper reviewed the theory of biomass gasification by comparing and analyzing different gasification models-designs and configurations, also different operational conditions. It aimed to bring a holistic approach for hydrogen rich syngas production based on the present technologies, techno-economic analysis, and industrial/commercialization pathways. The biomass gasification technologies need to be improved for hydrogen production regarding the global environmental and economic issues. The review provided better insights into the enhancement of syngas production from biomass. [Display omitted] • Biomass gasification for hydrogen rich syngas production was reviewed. • Various gasification models regarding the different designs and configurations were studied. • The impact of different operating conditions on biomass gasification was critically assessed. [ABSTRACT FROM AUTHOR]

Hybrid renewable based power generation has emerged as a major breakthrough in electrical power system due to their capability of providing competitive and carbon free electricity to the consumer. This paper presents techno-economic analysis of a grid connected solar photovoltaic-fuel cell based hybrid energy system to supply the electrical load demands of a small shopping complex located at the University campus in India. The proposed system has been designed by considering the cost of energy purchase and sold to the utility grid and further ensuring the smooth power flow management between elements of the system and the utility grid. A simplified mathematical modeling of the proposed hybrid energy system, including power and hydrogen management has been presented to access the potential of hydrogen based energy systems. Component sizing to optimize the net present cost of the proposed system has been performed employing three meta-heuristic algorithms, i.e. , artificial bee colony, particle swarm optimization and a hybrid of both. The experimental results obtained from three algorithms have been compared in terms of cost effectiveness of the system. The hybrid system has been designed to cater the total electricity demand of 135 M W h / y r of a small community center. It has emerged from the simulation results that the total electricity demand could be met with a 106 k W solar photovoltaic, 8 k W fuel cell, 45 k W electrolyzer and a 150 k g of hydrogen tank. The proposed grid connected system has 30 k W grid purchase and 25 k W grid sale capacities, respectively. In this paper, grid sale and purchase capacities have been considered as a decision variable along with other system component sizing. Loss of power supply probability is minimized along with objective function i.e., levelized cost of electricity (LCOE) using the exterior penalty method. It is evident from the results that the proposed system is economically viable with a LCOE of 0.104 $ / k W h. It has emerged from the results that the proposed hybrid energy system may be helpful to promote hydrogen and solar based energy system to reduce the reliance on the overburden grid, particularly, in developing countries. [ABSTRACT FROM AUTHOR]

The rapidly growing of population in the developing countries and their lack of access to electricity, especially in the remote or rural areas, is causing huge challenges for on energy production. Energy is an enabler and a reliable energy supply is critical to sustainable socio-economic development for any nation. Most of Chad's people live in villages with no particular power supply system. Exploiting renewable energies is the only means of fostering development and improving people's welfare. This paper attempts at proposing an energy profile and storage model for Chad in vast remote towns. The paper addresses the key energy gap that is hindering on the development of such systems, it models and assess the potential on electricity generation and using hydrogen as surplus power storage system. A techno-econo-environmental survey on a solar-wind hybrid system in 25 towns in Chad is undertaken using NASA data and HOMER Software. Several hybrid scenarios of energy production and storage is analyzed. The results showed that in the electricity generation scenario, the average total NPC for the studied stations was $ 48164 and the average LCOE was $0.573. The lowest LCOE was related to Aouzou station with 0.507 $/kWh and the highest LCOE was obtained for Bol station with 0.604 $/kWh. In the simultaneous electricity and hydrogen generation scenario, the cheapest hydrogen ($4.695/kg) was produced in the "Grid" scenario, which was the same for all of the stations, with a total NPC of $2413770. The most expensive hydrogen ($4.707/kg) was generated in the "Grid-Wind" scenario and Bol stations with a total NPC of $2420186. The paper develops cost effective models for all hybrid systems combination for both electricity and hydrogen generation across Chad. These findings could help policy makers, investors and other developmental agencies make informed choices on energy access for sustainable development for rural communities in Sub Saharan Africa. • The wind turbine alone was the superior choice at no station in Chad. • The lowest LCOE (0.507 $/kWh) was associated with Aouzou station. • The lowest COH (4.695 $/kg) was associated with Grid scenario. • In electricity generation scenario, Abeche has the lowest emission (63.1 kg/year). • In hydrogen generation scenario, Aouzou has the lowest emission (1109 kg/year). [ABSTRACT FROM AUTHOR]

In this paper, optimal size and power exchange of a grid-connected diesel generator-photovoltaic-fuel cell (diesel/PV/FC) hybrid energy system is investigated by multi-objective optimization for a community in Kerman, Iran. To optimally size hybrid system, number of system components (PV panels, diesel generators, electrolysers, FCs and hydrogen tanks) are considered as decision variables. In this paper, to optimize power exchange between the hybrid system and grid, two other decision variables are introduced: selling coefficient and purchase coefficient. Selling and purchase coefficients are defined to optimize the amount of electricity sold to the grid and the amount of electricity purchased from the grid, respectively. In order to optimally design the hybrid system, multi-objective optimization has been considered with respect to three objectives: levelized cost of energy (LCOE), loss of power supply probability (LPSP) and renewability. Based on simulation results, it can be drawn that when the hybrid system can sell/buy energy to/from the grid, (1) by decreasing non-renewable energy source usage, the value of LPSP increases, (2) by decrease of non-renewable energy usage, value of LCOE increases and (3) using FC system leads to increasing LCOE. • Multi-objective optimization of a grid connected diesel/PV/FC. • Introducing selling and purchase coefficients in size optimization problem. • Considering renewability as an objective function. • Optimization of power exchange between hybrid system and grid. [ABSTRACT FROM AUTHOR]