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The escalating demand for renewable energy solutions and the imperative for efficient energy storage mechanisms have catalyzed the evolution of Power-to-X (PtX) technologies. Germany has the most PtX projects, accounting for 44% of all projects that have been reported. PtX encompasses a spectrum of processes engineered to convert surplus renewable energy into versatile energy carriers or chemical commodities, such as hydrogen, methane, or synthetic fuels. The Paramount to this domain is to synergistically harness renewable energy sources and hydrogen carriers to curtail waste and bolster sustainability. Central to achieving this synergy is the effective control of PtX processes, ensuring optimal performance, cost efficiency, and seamless integration within existing energy frameworks. This paper delves into the control processes and environmental prerequisites within the PtX landscape, elucidating key challenges, and strategies within this dynamic realm. While providing an initial overview of fundamental PtX process chains, this paper accentuates the critical role of geographical considerations. Subsequently, it conducts a thorough analysis of equipment modeling challenges, addressing performance metrics, operational requisites, and capital investments, particularly focusing on methanol and hydrogen production and storage. Through holistic examination, this paper endeavors to delineate the evolving landscape of PtX control processes and conditions, advancing our understanding of this expanding field. [Display omitted] • Comprehensive overview of PtX control process, challenges, strategies, and advancements. • Overview of PtX process chains and geographical conditions. • Analysis of equipment modeling challenges for methanol and hydrogen. • Addressing crucial storage challenges in PtX system. • Exploration of diverse influences on PtX control processes. [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]

Green hydrogen is crucial for society's access to peaceful, secure, and stable energy sources to flourish sustainably and get universal government support. To protect the environment and provide energy security, it is essential to use hydrogen as a sustainable fuel and energy source to cover the energy baseload. This paper investigates the developments of renewable energy (RE) and the potential for green hydrogen in the Middle East and North Africa (MENA) region. There is a considerable chance to use RE because of the MENA region's excellent solar radiation. On the other hand, many countries in the MENA region are classified as one of the poorest in water resources and are known to have water-energy challenges. This paper focuses on the water needed to produce hydrogen in countries with water scarcity. A strengths, weaknesses, opportunities, and threats (SWOT) analysis was performed for green hydrogen generation in the MENA, where recommendations for countries with a water-energy nexus can be made. Additionally, this paper offers suggestions for creating a sustainable hydrogen economy, such as cutting back on the domestic use of fossil fuels, subsidizing the renewable production industry, and supporting hydrogen manufacturing. • Green hydrogen production is highly affected by water scarcity. • SWOT analysis was performed on green hydrogen generation in the MENA. • Recommendations were provided on a country-by-country basis. [ABSTRACT FROM AUTHOR]

This study presents a bibliometric review focusing on the utilization of water electrolysis as a means of generating hydrogen as an energy carrier. The analysis includes research conducted over the past decade, covering from 2014 to 2023 (till August). Several key aspects are highlighted, including publication trends, the leading country in research output, journal rankings, and a citation analysis of papers related to water electrolysis. The findings reveal a notable increase in publication trends, with China emerging as the leading contributor in this research area. Furthermore, the International Journal of Hydrogen Energy is identified as the highest-ranked journal in terms of both publication number and citation impact. Additionally, the top ten most cited research articles and review papers are investigated to determine their influence within the field. To gain a deeper understanding of water electrolysis methods, the three primary approaches: alkaline water electrolysis (AWE), proton exchange membrane (PEM) electrolysis, and solid oxide electrolysis (SOE) is examined. The analysis emphasizes that PEM electrolysis is the most prevalent method for hydrogen generation, particularly when integrated with renewable energy sources such as solar and wind power due to its rapid response to electrical input fluctuation. Finally, the challenges and future directions of water electrolysis in hydrogen production are highlighted, including an exploration of economic and environmental considerations at large scale, offering insights into the path forward for advancing this technology sustainably. • A comprehensive bibliometric analysis of water electrolysis for hydrogen production. • Publication trends, journal rankings, and citation analysis are highlighted. • China is identified as the leading contributor in water electrolysis publications. • International Journal of Hydrogen Energy: the highest-ranked journal in this field. • Specific electrolysis methods, including AWE, PEM, and SOE are examined. [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 presented paper focuses on renewable energy-assisted electricity, hydrogen, and cold energy production. Solar energy is used as the energy source in the study. The organic Rankine cycle (ORC) is used for electricity generation, a proton exchange membrane electrolyzer (PEMe) for hydrogen production, and an ejector refrigeration system for cold energy production. The study is based on the exergy concept and examines thermo-economic and thermo-environmental analyses. The exergy efficiency of each equipment in the system is calculated from a holistic perspective. Considering the energy consumption values of the equipment in the whole system, the cost required for hydrogen production is calculated as 1.086 $/kg. Additionally, the exergy efficiency of the whole system is found to be 2.082 %. • Thermodynamic analysis of the solar-based hydrogen production system. • The exergy efficiency of the whole system is found as 2.082 %. • The cost of green hydrogen production is found as 1086 $/kg. [ABSTRACT FROM AUTHOR]

In response to climate change and the imperative for sustainable energy solutions, this study investigates the feasibility of producing green hydrogen and associated e-fuels (methane, methanol, and ammonia) using a renewable energy hybrid system in Dakhla, Morocco. Utilizing the System Advisor Model (SAM) software for simulation-based analysis, the research evaluates a hybrid system combining concentrated solar power (CSP) and photovoltaic (PV) plants against standalone counterparts. Various simulations comparing standalone PV and CSP plants with a novel CSP/PV hybrid concept were carried out. The hybrid system demonstrates significant promise, exhibiting increased annual energy yield and capacity factors up to 90%, leading to enhanced efficiency, performance, and cost savings with a Levelized Cost of Electricity (LCOE) approximating 17 cents/kWh. Furthermore, this paper conducts an in-depth exploration into the feasible production of hydrogen and its derived synthetic fuels utilizing hybrid renewable systems. The study provides a thorough examination of the production processes, yields, and efficiencies of hydrogen and its derivative e-fuels, with a focus on green hydrogen production through water electrolysis, CO2 hydrogenation, the Sabatier process, and the Haber-Bosch process. It sheds light on the potential applications of these fuels in the transportation sector, including in electric and hydrogen vehicles and aviation. The insights garnered are indispensable for crafting future strategies and policies in sustainable energy planning. These findings not only provide valuable direction for forthcoming initiatives in renewable energy but also underscore the pivotal role of hybridization in enhancing the efficient production and utilization of hydrogen within both renewable energy and transportation sectors. • PV and CSP systems to generate electricity for the Dakhla city was investigated. • A Hybrid system optimization has been proposed. • The Electricity surplus was used to produce hydrogen and hydrogen-based products. • Various scenarios for the heavy-duty application of e-fuel were presented and discussed. [ABSTRACT FROM AUTHOR]

Hydrogen energy is one of promising non-polluting and renewable energy sources. In this paper, we present a first principal study of hydrogen storage in pure C 60 fullerene cage and Stone-Wales (SW) defective C 60 cages using density functional theory (DFT) with applying both the exchange functional B3LYP and the dispersion correction wb97xd at 6–31+g(d,2p) basis set. In addition, the counterpoise correction is applied, and the basis set superposition error is calculated. The calculations underscore that the hydrogenation binding energy of C 60 cages occurs through an endothermal process for C 60 H in with a hydrogen binding energy of 0.09 eV and through an exothermal process for C 60 H out , C 60 SW 66 H out , and C 60 SW 65 H out , cages with hydrogen binding energies of −2.17 eV, −2.96 eV, and −2.20 eV, respectively. Remarkably, for the first time, the intermediate hydrogen binding energy is found inside C 60 SW 66 H in fullerene, and C 60 SW 65 H in fullerene cages with energies of −0.26 eV and −0.81 eV, respectively. The hydrogen adsorption inside the cavity of C 60 SW 66 fullerene cage is thermodynamically possible below 289.8 K and entire pressure range considered. Our results highlight, for the first time, that the endohedral cavity of C 60 SW 66 is a promising new medium for hydrogen storage due to its binding energies (−0.26 eV) and its hydrogen storage weight percentage (5.3%) that are close to the optimal conditions specified by DOE for commercial use. In addition, this study opens up a new discovery of Stone-Wales defective C 60 fullerene for further endohedral cavity applications. • New insight into endohedral cavity of Stone Wales C 60 SW 66 is reported. • For the first time, a new promising medium for hydrogen storage inside cavity of C 60 SW 66 is proved. • Binding energies of −0.26 eV and hydrogen storage weight percentage up to 5.3% are achieved inside the cavity of C 60 SW 66. • This study opens a new discovery of the SW defective C 60 fullerene for further endohedral cavity applications. [ABSTRACT FROM AUTHOR]

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

Renewable energy production through electrolysis of water to obtain "green hydrogen" has gained interest as a clean energy storage option. However, integrating variable renewable energy resources into the grid poses challenges to maintaining energy balance and stability. In this paper, a hybrid energy storage system combining short-term battery energy storage system and long-term hydrogen-based energy storage system is proposed for an isolated DC microgrid with a structure similar to a hydrogen refueling station. Passivity-Based Control (IDA-PBC) is utilized for power converters regulation, ensuring global stability based on Lyapunov theory while accounting for the nonlinear characteristics of the physical system. The control strategy is designed to ensure a reliable supply of electrical energy to the loads, preserve the quality of electrical variables in the network, and secure the safe operation of system components. Additionally, to safeguard devices from overvoltage, a Sliding Mode Reference Conditioning loop (SMRC) is proposed. It intervenes only when there is a potential risk of exceeding predefined boundaries. Simulations results under demanding conditions demonstrate the effectiveness of incorporating hydrogen energy storage systems with IDA-PBC and SMRC for this class of problems. • An isolated MG with H2 storage, typical structure of a refueling station, was modeled. • The IDA-PBC ensures the stability of the nonlinear and complex MG. • SMRC ensures overvoltage protection in the bus. • The control confirms that H2 storage integrated with RES contributes to MG stability. [ABSTRACT FROM AUTHOR]

Transportation is an economic sector that contributes significantly to global warming due to its high consumption of fossil fuels, and sustainably produced hydrogen is a major contender for an alternative clean energy source. Public transit is vital for environmental sustainability via reducing individual vehicle usage and traffic congestion, and the prospect of powering buses using hydrogen fuel has been extensively studied lately. This paper seeks to comprehensively review the current status of research on hydrogen-powered buses considering triple bottom line sustainability perspectives. A brief technical overview of prospective environmentally benign hydrogen production processes has been presented. Technological, economic, and environmental findings and research trends seen in recent analyses on hydrogen-powered buses have been summarized, along with the status quo of global hydrogen refuelling stations. Identified focal points for future studies include performance enhancements, refuelling infrastructure propagation, and policy formulation. The conclusions derived from this review will benefit the accelerated deployment of hydrogen-fuelled public transit fleets. • Environmentally benign hydrogen production is reviewed techno-economically. • The prospects of using hydrogen for public bus transport are discussed thoroughly. • Blue and green hydrogen production are likely to coexist in the hydrogen economy. • Costs and energy consumption of hydrogen-powered buses need improvement. • Refuelling facility deployment and public awareness of safety should be enhanced. [ABSTRACT FROM AUTHOR]

The development of efficient, stable and low-cost catalysts for hydrogen evolution reaction (HER) is one of the major difficulties in water electrolysis. It is also the key to realizing the large-scale production of hydrogen energy, a renewable and clean energy source. In recent years, metal-organic frameworks (MOFs) have attracted much attention as novel precursors for preparing water electrolysis catalysts due to their high porosity and large specific surface area. In this paper, we use ZIF-67 as a precursor and modify it by doping transition metal elements Fe and Ni. Afterwards, Fe–Ni–CoSe 2 @NC is synthesized by a thermal selenization process. The results show that the HER overpotential of the catalyst after modification is reduced by 50%, and the efficiency of water electrolysis is significantly improved. Moreover, the catalyst has good stability under alkaline condition and is more economical than the expensive Pt-based catalysts, which provides more possibilities for industrial applications. [Display omitted] • The catalysts prepared by ZIF-67 as a precursor have large specific surface area. • Co-doping of Fe and Ni greatly improves the electrochemical activity of CoSe 2 @NC. • Fe–Ni–CoSe 2 @NC has relatively good stability and obvious economic advantage. [ABSTRACT FROM AUTHOR]

Hydrogen energy storage systems (HESS) play an essential role in Microgrid (MG) systems to address the inherent generation characteristics of renewable energy sources. Also, the integration of Demand Response (DR) into the Energy Management System (EMS) of a renewable-based Multi-Microgrid (MMG) can lead to substantial technical and economic benefits. This paper proposes a modified optimization algorithm for optimizing MMG Energy Management (EM). The proposed algorithm is a modified version of the Student Psychology-Based Optimization (SPBO) technique called Modified Student Psychology-Based Optimization (MSPBO). This modification aims to improve issues such as slow convergence, low solution accuracy, lack of diversity, and getting stuck in local optima. The proposed MSPBO method incorporates a local escape operator and a collaborative student class to achieve a better balance between exploiting known solutions and exploring new possibilities. The MSPBO algorithm is applied to address the EM challenge within a MMG context. Considering the integration of renewable sources as Wind turbines and solar photovoltaic and the HESS, the EM problem is formulated as a two-stage multi-objective optimization: minimizing the operating cost of conventional generators and power transactions cost in addition to the cost of HESS, while maximizing operator benefits and peak load reduction. This multi-objective problem is tackled using a hybrid ε-lexicography–weighted-sum approach that avoids the need for normalization. The performance of the proposed MSPBO is evaluated using CEC 2017 benchmark test functions, utilizing various statistical measures such as best, average, worst, rank, and standard deviation (SD) of fitness values, along with Wilcoxon's rank-sum test. The MSPBO technique is compared with other optimization algorithms for these test functions, highlighting its efficiency and adeptness in achieving a harmonious trade-off between exploiting known solutions and exploring new ones. Furthermore, the MSPBO method is applied to solve two case studies. In Case 1, which involves a single stage with conventional demand response optimization, the results achieved using MSPBO are benchmarked against other optimization techniques, revealing its superior efficacy in addressing the EM challenge. In Case 2, a more complex two-stage multi-objective problem is tackled using MSPBO, and the assessment of the integration of HESS in the MMG is evaluated. In the second stage, there is a notable enhancement in peak load reduction percentage (PRP), from 13.9% to 16.13% without the HESS and from 12.68% to 16.46% with the integration of HESS. [ABSTRACT FROM AUTHOR]

Increasing greenhouse gas emissions and the increase in renewable energy sources in electricity generation have led to an increasing interest in hydrogen in recent years. As an energy storage solution for renewable energy, hydrogen can contribute to decarbonizing industries and transportation sectors as well as balancing energy systems. In this paper, the primary objective is to examine different methods for producing hydrogen depending on the primary energy source. In addition, it evaluates the economic and environmental performance of three types of hydrogen, known as hydrogen colors, and the significant obstacles to widespread fuel cell adoption. The key finding is that hydrogen's environmental benefits depend heavily on how hydrogen is produced and what fuel is used to produce it. Green hydrogen can only be produced using wind, solar photovoltaic (PV), and hydroelectric power. The emissions from other sources, such as blue hydrogen that uses carbon capture, utilization, and storage (CCUS) or electrolysis using electricity from the grid, are significantly higher than those from grey hydrogen. Furthermore, establishing an international hydrogen market will reduce costs and allow hydrogen to be produced in optimal locations. Lastly, a key unresolved question is whether hydrogen, whatever its color, is economically competitive in any sector of the energy system, despite all external costs associated with it. A policy framework that supports technological advancements, cost reductions, and future priorities will determine hydrogen's success in the future. The transition from grey hydrogen to green hydrogen should be facilitated by this framework. [ABSTRACT FROM AUTHOR]

Nowadays, renewable energy sources are integral to programs for the development of electric power systems. It is established that modern renewable generation units and energy storage systems utilize power electronic-based interfaces, such as voltage source converters, to convert power. On the one hand, the utilization of a voltage source converter provides certain advantages, such as the absence of a direct link to the network, the ability to operate on all quadrants of the PQ diagram, and the possibility of connecting renewable generation units to a weak network. On the other hand, the widespread use of renewable generation units utilizing voltage source converters reduces the overall inertia of the electric power system. However, excessive use of power electronic converters in the network leads to a significant increase in harmonic pollution, thereby introducing fresh challenges to ensuring safe and stable operation of the electric power system. To ensure the dependable operation of an electric power system with renewable energy sources units and energy storage systems based on the voltage source converter, it is essential to update the control system of the voltage source converter to meet the requirements for traditional generation as part of the electric power system. This paper presents the outcome of the power oscillation damping controller application implemented in the voltage source converter, which enhances the electric power system's stability. [ABSTRACT FROM AUTHOR]

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

Hydrogen is expected to be a game changer in the fight against climate change, being able to support the clean energy transition through a variety of roles: decarbonizing different hard-to-abate industrial sectors (such as steel, cement production) and transport (in long haul vehicles, maritime transport, and aviation), direct use as a fuel, chemical feedstock or in the form of synthetic fuels, and providing the ability to integrate with hybrid energy systems and renewables, enhancing energy storage and tapping the full potential of renewable energy sources. As a consequence, a substantial expansion in hydrogen production, due to rise in the demand, is expected by 2050, with all the generation coming from zero-carbon processes (electrolysis/thermochemical cycles using clean electricity and heat) or from a low-carbon production process using steam methane reforming with carbon capture and storage. Nuclear energy can be capitalized on both electricity and heat to provide a clean and reliable source of hydrogen through various processes. There are currently various demonstration projects undergoing in several countries to showcase the use of nuclear energy to produce clean hydrogen, considering both the current reactor fleet and advanced reactors. This paper provides an overview of these projects, giving an insight on the potential use of nuclear energy for hydrogen production and the current status of existing projects. It also highlights the activities of the International Atomic Energy Agency on technical and economic assessment of hydrogen production using nuclear energy for near term deployment. • Hydrogen is anticipated to be a game-changer in the fight against climate change. • Nuclear energy is positioned favourably to serve the developing hydrogen economy. • A single 1000 MW nuclear reactor could produce more than 200,000 t of H2 per year. • Several countries are considering nuclear hydrogen demonstration projects. • The IAEA has multiple resources available for nuclear hydrogen production. [ABSTRACT FROM AUTHOR]

Alkaline water electrolysis has become the most promising solution for hydrogen production considering certain factors such as cost, lifetime and maturity of technology. By developing the large-scale hydrogen production by alkaline water electrolysis as the energy buffering, the consuming pressure of the power system caused by the growing penetration of renewable energy sources such as wind and solar energy can be relieved effectively. However, when the alkaline water electrolysis is integrated with renewable energy sources, the unclear underlying mechanism and interaction characteristics limit large-scale application for hydrogen production. Aiming at this problem, from the aspects of efficiency and consistency, power regulation flexibility and gas purity, this paper studies safety and efficiency problems about the wide-range operation of alkaline water electrolyzers driven by renewable energy sources. The corresponding mechanism analyses are carried out and possible solutions for the future research are given, which are expected to provide a comprehensive review and useful guide for this research topic. • The mechanism of the inefficiency of alkaline water electrolyzers in low load is revealed. • Power regulation flexibility of alkaline water electrolyzers is improved by the advanced energy management. • Possible solutions to solve the poor gas purity of alkaline water electrolyzers are provided. [ABSTRACT FROM AUTHOR]

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

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]

Designing self-sufficient renewable energy systems is becoming a key issue in the energy sector due to modern energy goals. Due to the variability of renewable energy sources, very often it is necessary to adopt hybrid configurations of renewable energy systems and advanced energy storage to achieve self-sufficiency. However, the adoption of complex and novel systems, including technologies as photovoltaic, wind turbines, biomass gasifiers, hydrogen energy storage, must to be founded on a comprehensive analysis of the system operation under different conditions and its energy and economic performance in the investigated case study. Therefore, the aim of the present paper is carry out a comprehensive feasibility analysis of a novel hybrid renewable energy system achieving a high self-sufficiency level. The system integrates a wind turbine and photovoltaic panels to match the energy load of a tourist resort in Agkistro, Greece. Energy exceeding the load is directed to the energy storage system based on the battery and hydrogen tank. As backup energy source, a wood gasifier is used. The investigation is performed by means of a numerical model developed in TRNSYS software allowing one to simulate dynamically the system and to assess its energy and economic performance. The goal achieved during the simulation of the system was to ensure at least 97% of energy demand from renewable sources. Moreover, a parametric analysis of the storage system is presented. It is found that payback period of the installation varies in the range between 11 and 15 years, for systems configurations allowing to satisfy 90–98% of the users energy yearly demand from renewables. The achieved results allows one to evaluate the feasibility of the proposed system from both an energy and economic point of view. • Island energy systems in Greece. • Hybrid energy system with both battery and hydrogen energy storage. • 97% reduction of energy produced from fossil fuels with 30% of energy curtailed. • Parametric study concerning sizes of the energy storage. [ABSTRACT FROM AUTHOR]

This paper explores the use of Solar Chimney Power Plants (SCPPs) for the production of green hydrogen as a means to store excess electrical energy generated from renewable energy resources (RESs). The proposed structure produces electrical energy and distilled water by heating the air under the SCPP. The electrolyzer is integrated into the seawater pool and installed at the solar chimney's base. The weather conditions at the proposed location of the SCPP including solar radiation, temperature, humidity, and wind speed, are analyzed to assess their impact on the performance of the SCPP. The potential applications and economic feasibility of the SCPP are discussed, considering its contribution to renewable energy generation and the benefits of hydrogen as a clean energy carrier. The results show that solar radiation levels and favorable temperature profiles play an important role in the performance of the SCPP. The SCPP could produce 380,263 kW h of electrical energy and 139,443 tons of distilled water annually. The results also showed that the SCPP could produce 13,000 kg of green hydrogen and 173,224 kg of oxygen annually. The revenue generated from the production of H 2 and O 2 has improved the levelized cost of energy (LCOE) for the SCPP to 0.51 $/kWh and made it compete with other energy production facilities. Monthly variations in electrical energy, H 2 , O 2 , and distilled water production, highlight the dependence of hydrogen production on solar intensity and temperature. Overall, the research demonstrates the potential of SCPPs and hydrogen production as a sustainable and efficient solution for storing and utilizing excess renewable energy. [Display omitted] • Solar-electrolysis system combing solar chimney & electrolysis station is proposed. • The system produces green hydrogen, oxygen, desalinated water, and electricity. • The solar-electrolysis system was modeled using MATLAB mathematical modeling. • The system produced 380 MW h, 13 ton H 2 , 173.3 ton O 2 , and 139,443 ton water per year. [ABSTRACT FROM AUTHOR]

In a 100% renewable energy scenario, power generation fluctuates, requiring management and control of this generation. Storage is presented as a solution to regulate production discontinuity. In particular, seasonal storage can compensate for long-term fluctuations and serve as a necessary complement to short-term storage management. Due to the potential role of hydrogen in the decarbonization of energy production systems, this research attempts to analyse the levelized cost of storage (LCOS) of this energy carrier as a solution to long-term electricity requirements. The research focuses on the analysis of the total Power-to-Power (P2P) process cost, all factors affecting the input of electricity up to the output of electricity after the conversion of the hydrogen are considered. A transformation of the surplus electricity to hydrogen through a PEM electrolyzer is proposed in this paper. This hydrogen would be stored seasonally in salt caverns. Finally, a gas-to-energy transformation using gas turbines or fuel cells is contemplated. The analysis presents highly competitive results in terms of cost, demonstrating the system's competitiveness and potential: the turbine powered by 100% hydrogen solution appears to be more cost effective than the fuel cell solution: 0.207€/kWh and 0.284€/kWh respectively. Hydrogen storage presents itself as the most cost-effective long-term alternative in the near future, even better than pumped hydro, compressed air or batteries. • LCOS: Levelized Costs of Storage for a large-scale and long-term system. • The use of hydrogen as an energy carrier to store electrical energy from renewable sources at large scale. • Long-term storage of hydrogen in salt caverns. • Transformation of stored hydrogen into electricity through turbine and fuel cells. [ABSTRACT FROM AUTHOR]

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

After a natural disaster, electrical grids might go into a self-healing mode to restore service and reconnect any customers that lost power. In the self-heal system, the fast operation and restoring the critical loads (CLs) during a fault by available resources can increase the flexibility and resilience of the network. In addition to renewable energy sources and electric vehicles (EVs) storage devices, the hydrogen storage system and the process of converting hydrogen into electric energy by micro-gas turbine (MGT) have been modeled in order to assess the impact of this storage system in electrical loads restoration in critical conditions. Self-healing functionality is enhanced by using alternative and novel energy sources. In such a situation, how to interact with the stochastic nature of network components will be challenging. This paper formulates the optimal service restoration (SR) problem using chance-constrained Adaptive Distributionally Robust Optimization (ADRO) to address the ambiguities introduced by the uncertain parameters. A tri-level robust optimization model is developed such that the optimal switching in the network until clearing the fault is determined at the upper level, and the maximization of the SR based on the load demand values is determined at the lower level. The proposed method is demonstrated by simulation results on the modified Civanlar test system. In an equal operating condition and considering β = 3, it can be seen that the initial hydrogen State of the Tank (SoT) by 50 % can improve the load restoration by 7.5 % compared to the uncharged hydrogen tank. By increasing the initial SoT to the nominal value (10 Kg), the load restoration can increase to 13.2 %. [Display omitted] • Customized hydrogen into electric energy conversion model is developed in the energy management field. • Each uncertain parameter is considered ambiguous in the manner that follows an unknown but bounded distribution. • EVs, PHEVs, flexible loads, and the coordinated operation of the hydrogen-to-power system are all taken into account simultaneously. • A tri-level MILP model is formulated to determine the service restoration schedule. • CVaR is employed to effectively deal with the uncertainty of the parameters. [ABSTRACT FROM AUTHOR]

The transition from fossil fuels to renewable energy sources is seen as an essential step toward a more sustainable future. Hydrogen is being recognized as a promising renewable energy carrier to address the intermittency issues associated with renewable energy sources. For hydrogen to become the "ideal" low or zero-carbon energy carrier, its storage and transportation shortcomings must be addressed. This paper will provide the current large-scale green hydrogen storage and transportation technologies, including ongoing worldwide projects and policy direction, an assessment of the different storage and transportation methods (compressed hydrogen storage, liquid hydrogen, blending hydrogen into natural gas pipelines, and ammonia as green hydrogen carrier), as well as economic factors that influence the viability of large-scale green hydrogen storage and transportation. The results of our study highlight several significant findings concerning the cost, challenges, and potential advancements in the green hydrogen storage and transportation field. Our analysis demonstrates that the cost associated with storing and transporting green hydrogen is anticipated to decrease over time due to technological advancements and economies of scale being achieved. However, the commercialization of this technology requires addressing challenges related to storage methods, transportation modes, efficiency optimization, and technology adoption. For example, our research highlights the need for thorough technical and economic evaluations of using salt caverns for hydrogen storage. The efficiency of hydrogen storage and transportation utilizing existing infrastructure, such as storage tanks and natural gas pipelines. By elucidating these aspects, our research contributes valuable insights that can guide future endeavors toward achieving a sustainable and economically viable green hydrogen industry. • Role of government support in green hydrogen storage remains crucial. • Different storage and transportation methods is analyzed and compared. • Cost of hydrogen is expected to decrease for economies of scale. [ABSTRACT FROM AUTHOR]

Hydrogen, as a carbon-free energy carrier, has emerged as a crucial component in the decarbonization of the energy system, serving as both an energy storage option and fuel for dispatchable power generation to mitigate the intermittent nature of renewable energy sources. However, the unique physical and combustion characteristics of hydrogen, which differ from conventional gaseous fuels such as biogas and natural gas, present new challenges that must be addressed. To fully integrate hydrogen as an energy carrier in the energy system, the development of low-emission and highly reliable technologies capable of handling hydrogen combustion is imperative. This study presents a ground-breaking achievement - the first successful test of a micro gas turbine running on 100% hydrogen with NOx emissions below the standard limits. Furthermore, the combustor of the micro gas turbine demonstrates exceptional fuel flexibility, allowing for the use of various blends of hydrogen, biogas, and natural gas, covering a wide range of heating values. In addition to a comprehensive presentation of the test rig and its instrumentation, this paper illuminates the challenges of hydrogen combustion and offers real-world operational data from engine operation with 100% hydrogen and its blends with methane. • Hydrogen's potential as an alternative, carbon-free fuel for micro gas turbines is assessed. • The obstacles of utilizing hydrogen fuel in a micro gas turbine are addressed and the necessary modifications are presented. • Data from successful tests of a micro gas turbine running on hydrogen blends ranging up to 100% hydrogen is presented. • NOx emissions below the standard limits were achieved with the new setup. • The study's outcomes could aid researchers and developers in incorporating hydrogen as a carbon-free energy carrier. [ABSTRACT FROM AUTHOR]

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

Argentina has a wide availability of renewable resources, which provides important advantages for the hydrogen vector incorporation. The province of Córdoba is an excellent model case for the study of the rapid incorporation of hydrogen as fuel, to replace 20% V/V of natural gas consumed in vehicular use. This does not involve major changes in infrastructure or modifications to the vehicles. This paper computes and analyzes the levelized cost of hydrogen with the emissions associated for each part of the complete hydrogen supply chain. Two different production sources were used: renewable energies sources and the Argentine electrical grid; and two production pathways: in situ and centralized production. Comparing the same volume of proposed hydrogen compressed natural gas and current CNG, a cost decrease in the majority of the scenarios and a CO 2 eq emission reduction ranging from 19.5 to 8.2% are achieved, even if the hydrogen is produced using the carbon-intensive grid electricity. • The Production of hydrogen to replace part of the CNG used in vehicles is proposed. • Levelized cost of hydrogen and the emissions associated was assessed. • The study includes the entire supply chain from production to the filling station. • The use of HCNG results in a reduction of emissions in all the studied scenarios. • The new fuel is economically favorable, becoming relevant for rapid energy transition. [ABSTRACT FROM AUTHOR]

Energy plays a crucial role in human life as it is necessary for survival and enables us to perform daily activities. The passage of time has driven progress, with various tools, machines, and devices created to facilitate human affairs. Everything is very dependent on Energy. Unfortunately, the prevalent reliance on fossil fuels as the primary energy source has resulted in an environmental disparity attributed to greenhouse gas emissions. Besides, the depletion of fossil fuel reserves is a long-term concern for nations involved in fossil fuel production including Malaysia, which necessitates a delicate equilibrium between escalating energy demands and escalating pollution levels. This review paper aims to highlight the potential of renewable energy based on green hydrogen in Malaysia. The energy scenario in Malaysia has been reviewed by discussing energy demand, current population, energy policy synopsis, conventional energy sources, carbon emissions, and the direction of renewable energy in Malaysia. Besides, the conceptual framework for hydrogen as renewable energy was discussed covering the hydrogen economy, production technology, storage, and energy production using green hydrogen. Finally, potential applications for using hydrogen energy have been presented so that the future direction of using this alternative energy can be well planned in Malaysia. •An overview of hydrogen energy as Malaysian alternative energy is comprehensively discussed. •The hydrogen energy prospects are described in detail such as hydrogen economy, production, and consumption. •The progress of hydrogen energy implementation in Malaysia is studied towards embarking on this effort. [ABSTRACT FROM AUTHOR]

The problems of energy shortage, severe pollution, and global warming are becoming increasingly severe. Renewable energy systems with hydrogen have been widely used. In recent years, much literature has described the energy management of renewable energy systems with hydrogen in a comprehensive way. However, most of them are proposed and discussed from an academic point of view. There are likewise several different approaches and ideas in the patents that address the energy management of hydrogen renewable energy systems. Moreover, most patents are oriented toward industrial applications and still need to be reviewed and analyzed. To fill this gap, this paper reviews relevant US patents to find potential and industrial hydrogen applications and energy management strategies in renewable energy systems. The work presented in this paper will provide solutions and guidance in solving energy management problems in renewable energy systems. • Review of U.S. patents for hydrogen-containing renewable energy systems management methods. • Review of U.S. patents for application of hydrogen-containing. • Energy management strategy based on object classification. • The industry mainly adopts rules-based energy management strategies. [ABSTRACT FROM AUTHOR]

The most important hydrogen energy storage technologies, developed between 1974 and 2022, now enable the quality operation of global power grids that integrate alternative energy facilities (wind power, solar power, geothermal power, etc.). With the continuous large-scale penetration of converter-interfaced generation (CIG), based on the combined use of renewable energy sources (RES) and hydrogen energy storage systems (ESS), into practical power systems, the dynamic characteristics of the latter change significantly. New challenges with the power system control and stability arise due to the specific CIG properties. A positive-sequence time-domain simulation is frequently used to solve them. However, the known simplifications and limitations are inevitably applied in case of such simulation. These become critical for the CIG with RES and hydrogen ESS models due to their fast dynamics. Therefore, the validation of such simulation results becomes relevant. This paper proposes a novel validation approach based on the use of a benchmark tool Hybrid Real-Time Power System Simulator (HRTSim) instead of field measurements. A major feature of the proposed approach is the possibility of a guaranteed validation of the benchmark tool using any state of the modeled power system. A hybrid implementation of a detailed three-phase model of CIG is also developed for the HRTSim, which provides an adequate simulation of the full range of dynamic processes. The results of validation of a positive-sequence simulation of a practical power system with CIG, which includes both RES and hydrogen ESS, using the developed approach presented in this paper have allowed to identify the causes of calculation errors, as well as factors affecting them. [ABSTRACT FROM AUTHOR]

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

Concerns about energy security, energy prices and climate change led scientific research towards sustainable solutions to fossil fuel as renewable energy sources coupled to hydrogen as energy vector and carbon capture and conversion technologies. Among the technologies investigated in the last decades, biomass gasification acquired great interest owing to the possibility to obtain low cost and CO 2 negative emission hydrogen production from a large variety of everywhere available organic wastes. Upstream and downstream treatment were then studied in order to maximize hydrogen yield, reduce the content of organic and inorganic contaminants under the admissible levels for the technologies which are coupled with, capture, and convert carbon dioxide. However, studies which analyse a whole process made of all those technologies is still missing. In order to fill this lack, the present paper investigated the coexistence of Hydrothermal Carbonization (HTC), Sorption Enhance Gasification (SEG), Hot Gas Cleaning (HGC), and CO 2 conversion by Dielectric Barrier Discharge (DBD) plasma reactor for H 2 production from biomass waste by means of Aspen Plus software. The proposed model aimed to identify and optimise the performance of the plant by varying operating parameters (such as temperature, CaO/biomass ratio, separation efficiency, etc.). The carbon footprint of the global plant is 2.3 kg CO 2 /kg H 2 , lower than the latest limit value imposed by the European Commission to consider hydrogen as "clean", that was set to 3 kg CO 2 /kg H 2. The hydrogen yield referred to the whole plant is 250 g H2 /kg BIOMASS. • A global simulation model for SEG, HTC, HGC and plasma for H 2 production was developed. • The carbon footprint of the global plant is 2.3 kg CO 2 /kg H 2. • The hydrogen yield referred to the whole plant is 250 g H2 /kg BIOMASS. [ABSTRACT FROM AUTHOR]

Hydrogen has the potential to be considered almost the cleanest fuel of the future and a key contributor toward a low-carbon economy. This latter can be achieved through the production of green hydrogen by electrolysis using renewable energy sources. This work investigates the production of green hydrogen using solar PV-electrolysis configuration. Three different photovoltaic technologies including monocrystalline (m-Si), polycrystalline (p-Si) and amorphous (a-Si) have been used in this study. The aim of this paper is to identify the most suitable PV system for hydrogen production in mountain temperate climate conditions. Therefore, a performance assessment of the aforementioned PV systems has been conducted using data collected for an operation period of 6 years. In addition, the rate of degradation of each technology has been determined, and its effects on hydrogen generation and cost have been examined. The obtained results have shown that p-Si technology has the lowest degradation rate of (0.28%), followed by m-Si (0.41%), and a-Si (0.75%). In addition, key metrics including the levelized cost of energy (LCOE) as well as the levelized cost of hydrogen (LCOH) have been calculated. The findings indicate that the lowest LCOE and LCOH are achieved by p-Si (0.021 $/kWh, 3.59 $/kg), followed by a-Si technology (0.027 $/kWh, 4 $/kg), and m-Si (0.032 $/kWh, 4.34 $/kg). Therefore, the results demonstrates that p-Si is the most cost-effective and favorable technology for hydrogen production in the considered temperate climate. • Hydrogen production of 3 PV technologies under mountain climate of Morocco. • Performance evaluation under real weather conditions over an operation period of 6 years. • PV Degradation impact on hydrogen production. • The most cost-effective PV system for hydrogen production is p-Si. [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]

Hydrogen supplying to industrial users is currently the major hydrogen business worldwide and the demand for hydrogen is almost entirely supplied from fossil fuels. In the last years a widespread interest on hydrogen has grown as energy vector for the decarbonization of multiple sectors, including industry, transport and buildings. Nevertheless, the impact of natural gas and other fossil fuels substitution with hydrogen is highly affected by the mix of different technologies and energy sources applied for hydrogen generation. The paper aims to investigate current CO 2 emissions related with hydrogen generation in Australia and Italy by means of PEM and alkaline technologies; and to evaluate the potential impact considering cell characteristics variation and 3 scenarios based on energy mix. A sensitivity analysis is performed to identify the critical parameters. Based on experimental data, the energy consumption for hydrogen production using PEM technology is more sensitive to cell voltage compared to current density, which indicates the importance of cell manufacturing and electrolyte resistance. In addition, by performing sensitivity analysis regarding energy sources scenarios it is found that carbon dioxide emission in Australia is more sensitive to renewable energy sources rather than Italy. [Display omitted] • Importance of manufacturing and electrolyte resistance because of high PEM energy consumption sensitivity to cell voltage. • Predicted emission in 2030 is 5–10 kg CO 2 using PEM/alkaline technology in Italy. • 18% reduction of national electricity grid CO 2 emission in Australia is predicted. (In 2030 in comparison to 2019). [ABSTRACT FROM AUTHOR]

Integration of renewable energy sources (RES) together with energy storage systems (ESS) changes processes in electric power systems (EPS) significantly. Specifically, rate of change and the lowest values of operating conditions during the emergencies are got influenced. Such changes can cause incorrect actions of relay protection (RP) as it was designed and adjusted with no regard for influence of RES and ESS. Detailed research on processes during the different normal and abnormal modes in both EPS and primary transducers and also in RP devices should be done to take preventive actions. To do this research mathematical modeling based on detailed and authentic models of all elements including RP should be used. HRTSim (which was developed by authors) software for simulating EPS provides the opportunity to create such models of EPS of any size without simplifications and limits. Using of this instrument together with detailed mathematical models of RP which were developed before provided the opportunity to investigate them rigorously in RES-integrated EPS. Settings providing adequate action of RP in certain conditions were performed as a result of this investigation. Fragments of these investigations are performed in this paper. Results of these investigations would be useful for designing new methods and tools of RP adjustment. General structure of a grid-connected combined renewable energy system with a hydrogen storage system. [Display omitted] [ABSTRACT FROM AUTHOR]

Considering the high calorific value and low-carbon characteristics of hydrogen energy, it will play an important role in replacing fossil energy sources. The production of hydrogen from renewable energy sources for electricity generation and electrolysis of water is an important process to obtain green hydrogen compared with classic low-carbon hydrogen production methods. However, the challenges in this process include the high cost of liquefied hydrogen and the difficulty of storing hydrogen on a large scale. In this paper, we propose a new route for hydrogen storage in metals, namely, electricity generation from renewable energy sources, electrolysis to obtain metals, and subsequent hydrogen production from metals and water. Metal monomers facilitate large-scale and long-term storage and transportation, and metals can be used as large-scale hydrogen storage carriers in the future. In this technical route, the reaction between metal and water for hydrogen production is an important link. In this paper, we systematically summarize the research progress, development trend, and challenges in the field of metal to hydrogen production. This study aim to aid in the development of this field. • A new route for hydrogen storage and production via metals on a large scale is proposed. • Electrolysis to obtain metals by green electricity, and subsequent hydrogen production from metals and water. • Metal monomers facilitate large-scale and long-term storage and transportation. • Metals can be used as large-scale hydrogen storage carriers in the future. • Metal-water hydrogen production can make full use of renewable energy without carbon dioxide. [ABSTRACT FROM AUTHOR]

Given global warming, which limits the use of classical energy sources, renewables can provide a solution to the dilemma between environmental protection and sustainable economic growth. In this complex and changing context, green hydrogen can become a promising link between renewable energy sources and end users. However, although hydrogen has a high gravitational energy density, it has a very low volumetric energy density. This challenge requires hydrogen compression at several stages in the supply chain from electrolysis units to conversion, storage, and distribution. Recently, many studies have focused on hydrogen compression technologies. This paper provides an overview of recent advances in large-scale hydrogen compression. First, the role of hydrogen compression in providing clean energy for the future is explored. Then the thermodynamic concept of hydrogen compression is investigated. Gaining a proper understanding of compressor operating conditions in various operations in the large hydrogen industry is the next focus of this paper. Later, the capabilities and limitations of available mechanical compressors for the hydrogen industry, including reciprocation and centrifugal, are summarized. Finally, research gap and recommended new areas in this field are recognized. The presented insightful concepts provide students, experts, researchers, and decision-making working on large-scale hydrogen industry with the state of the art in hydrogen compressors industry. • Green hydrogen is a promising link between production and use of renewables. • Low molecular weight of hydrogen makes compression a crucial step in the green hydrogen chain. • Various operations in this industry need compressors with output pressures of 20 bar–200 bar. • Only reciprocating and centrifugal compressors can handle the required capacity in this industry. • Review of resources proves rapid progress in the design and reliability of hydrogen compressors. [ABSTRACT FROM AUTHOR]

Hydrogen is a potential future solution addressing global warming, climate change, and energy security challenges. It efficiently allows for storing excess renewable energy and generating heat and electricity without increasing greenhouse gas emissions. It can create a practical pathway to replace fossil fuel vehicles and move toward a net-zero transport sector. Various hydrogen strategies and industry roadmaps have been developed to identify key goals, set targets for progress, and develop strategic plans to remove barriers. As identified through these documents, the development of consistent national and international codes and standards and the creation of clear procedures and regulations are essential for the safe implementation and adaptation of hydrogen systems, leading to the successful process of hydrogen sector. This paper provides a comprehensive and critical review of the different aspects of hydrogen safety to advance hydrogen regulations, codes, and standards. While it summarises the key international hydrogen frameworks, the main focus of the paper is on Australian plans, progress, and working groups for hydrogen deployment that will help future green energy society. • The safety developments affect the cost of Australian hydrogen scaling targets. • Training and safety developments are essential to achieve public trust in Australia. • Better community engagement is needed to move from hydrogen planning to its development. • Data-based tools assist the development of hydrogen safety procedures in Australia. [ABSTRACT FROM AUTHOR]

This paper proposes a system modeling and performance analysis of a renewable hydrogen energy hub (RHEH) connected to an ac/dc hybrid microgrid (MG). The proposed RHEH comprises a photovoltaic (PV)-based renewable energy source (RES) as the primary source, a proton exchange membrane fuel cell (PEMFC) as the secondary power source, and a proton exchange membrane electrolyzer (PEMELZ) that can generate and store hydrogen in a hydrogen tank. All these resources are directly connected at the dc bus of the ac/dc microgrids. The PEMFC operates and utilizes the hydrogen from the hydrogen tank when the energy generated by RES cannot meet the load demand. A coordinated power flow control approach has been developed for the RHEH to mitigate the mismatch between generation and demand in the ac/dc microgrid and produce renewable hydrogen when renewable power is in excess. The paper also proposes a modified hybrid Perturb & Observe-Particle Swarm Optimization (Hybrid PO-PSO) algorithm to ensure the maximum power point tracking (MPPT) operation of the PV and the PEMFC. The operation of the proposed RHEH is validated through simulations under various critical conditions. The results show that the proposed RHEH is effective to maintain the system power balance and can provide power-to-hydrogen and hydrogen-to-power when required. • Modeling and performance analysis of a RHEH connected to a hybrid microgrid. • Development of a coordinated power flow control approach for the RHEH. • Development of a modified Hybrid PO-PSO algorithm to ensure the MPPT operation. • Justification of the proposed RHEH under various critical conditions. [ABSTRACT FROM AUTHOR]

With the increasing depletion of conventional energy sources and their detrimental environmental hazards, it is imperative to search for sustainable alternative clean energy sources. In the recent decades, hydrogen has emerged as potential source of clean energy. One of the potential alternatives to achieve the objective is the designing and characterization of materials for hydrogen-storage energy applications. In this regard, metal-bearing hydrides are the most promising candidates. For instance, magnesium-bearing hydrides are the focus of current research work owing to high hydrogen capacity of 7.6 wt%. In this paper, we first time report density functional-based quantum theoretical analysis to explore the potential of Mo-doped magnesium hydrides MgH 2 :Mo for optoelectronic and hydrogen-storage applications. For the quantum computations of the required optoelectronics and energy storage properties, we employed all-electron methods within generalized gradient approximation (GGA). Besides applying GGA approximation to account for the electronic correlated effects, we employed the Hubbard potential U (= 4 eV) for onsite repulsive Coulomb force. We predict that 10% doping by weight of Mo into MgH 2 suppresses its insulating band gap of 4.9 eV to semiconducting band gap of order 3.15 eV for spin up and 0.15 eV for spin down. As such the doping of Mo can tune the the bandgap, structural, electronic and optoelectronic properties of MgH 2 considerably for potential applications. • Quantum-computational analysis of MgH 2 :Mo for optoelectronic & hydrogen-energy applications. • To account for electronic correlation, GGA + U method is employed. • Band gap of MgH 2 :Mo suppresses to 3.15 eV (0.15 eV) for spin up (down). • Suppression of bandgap & thermodynamic stability may enhance kinetic & hydrogen release efficiency. • MgH 2 shows larger hydrogen-storage capacity (7.98%) than MgH 2 :Mo (1.778%). [ABSTRACT FROM AUTHOR]

The expected increase of hydrogen fuel cell vehicles has motivated the emergence of a significant number of studies on Hydrogen Refuelling Stations (HRS). Some of the main HRS topics are sizing, location, design optimization, and optimal operation. On-site green HRS, where hydrogen is produced locally from green renewable energy sources, have received special attention due to their contribution to decarbonization. This kind of HRS are complex systems whose hydraulic and electric linked topologies include renewable energy sources, electrolyzers, buffer hydrogen tanks, compressors and batteries, among other components. This paper develops a linear model of a real on-site green HRS that is set to be built in Zaragoza, Spain. This plant can produce hydrogen either from solar energy or from the utility grid and is designed for three different types of services: light-duty and heavy-duty fuel cell vehicles and gas containers. In the literature, there is a lack of online control solutions developed for HRS, even more in the form of optimal online control. Hence, for the HRS operation, a Model Predictive Controller (MPC) is designed to solve a weighted multi-objective online optimization problem taking into account the plant dynamics and constraints as well as the disturbances prediction. Performance is analysed throughout 210 individual month-long simulations and the effect of the multi-objective weighting, prediction horizon, and hydrogen selling price is discussed. With the simulation results, this work shows the suitability of MPC for HRS control and its significant economic advantage compared to the rule-based control solution. In all simulations, the MPC operation fulfils all required services. Moreover, results show that a seven-day prediction horizon can improve profits by 57% relative to a one-day prediction horizon; that the battery is under-sized; or that the MPC operation strategy is more resolutive for low hydrogen selling prices. [Display omitted] • Model Predictive control application for green hydrogen refuelling station. • Linear modelling of green hydrogen refuelling station. • Parameter sensitivity analysis of the multi-objective function. • Prediction horizon sensitivity analysis. • Model Predictive Control performance advantage compared to rule-based control. [ABSTRACT FROM AUTHOR]

The production of hydrogen is still a major challenge, due to the high costs and often also environmental burdens it generates. It is possible to produce hydrogen in emission-free way: e.g. using a process of electrolysis powered by renewable energy. The paper presents the concept of a research, experimental stand for the storage of renewable energy in the form of hydrogen chemical energy with the measurement methodology. The research involves the use of proton exchange membrane electrolysis technology, which is characterized by high efficiency and flexibility of energy extraction for the process of electrolysis from renewable sources. The system consist of PV panel, PEM electrolyzer, battery, programmable logic controller system and optional a wind turbine. Preliminary experimental tests results have shown that the electrolyzer can produce in average 158.1 cc/min of hydrogen with the average efficiency 69.87%. • Zero-emission hydrogen production is possible. • Hydrogen production using a proton exchange membrane (PEM) electrolyzer for Polish conditions. • Proposal for experimental studies on hydrogen production. [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]

This paper presents the results research on the optimal fuel compositions and the control parameters of the spark ignition engine fueled with syngas-biogas-hydrogen for the purpose of setting up a flexible electronic control unit for the engine working in a solar-biomass hybrid renewable energy system. In syngas-biogas-hydrogen mixture, the optimal content of hydrogen and biogas is 20% and 30%, respectively. Exceeding these thresholds, the improvement of engine performance is moderate, but the pollution emission increases strongly. The optimal advanced ignition angle is 38°CA, 24°CA, and 18°CA for syngas, biogas, and hydrogen, respectively. With the same content of hydrogen or biogas in the mixture with syngas, the advanced ignition angle of the hydrogen-syngas blend is less than that of the syngas-biogas blend by about 4°CA at the engine speed of 3000 rpm. The derating power of the engine is 30% and 23% as switching from the hydrogen and biogas fueling mode to the syngas fueling mode, respectively. However, NO x emission of the engine increase from 200 ppm (for syngas) to 2800 ppm (for biogas) and to over 6000 ppm (for hydrogen). The optimal advanced ignition angle, the optimal equivalence ratio of the syngas-biogas-hydrogen fuel mixture vary within the limits of the respective values for syngas and hydrogen. To improve the engine efficiency and reduce pollutant emissions, the loading control system of the engine should prioritize the adjustment of the fuel flow and then the adjustment of the air-fuel mixture flow. [Display omitted] • Optimal advanced ignition angle is 38°CA, 24°CA, 18°CA for syngas, biogas, hydrogen. • Optimal content of hydrogen and biogas in mixture with syngas is 20% and 30%. • Derating power is 30% and 23% as switching from hydrogen, biogas to syngas. • NO x emissions are 200 ppm, 2800 ppm, and 6000 ppm for syngas, biogas, and hydrogen. • Flexible electronic control unit is needed for engine operating in solar-biomass. [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]

In the present paper a techno-economic hydrogen production and transportation costs to export from Colombia to Europe and Asia were determined using the open-source Python tools, such as WindPowerLIB, PVLIB, ERA5 weather data, and the Hydrogen-2-Central (H2C) model. Calculations were performed as well for Chile, for comparison as a regional competitor. In addition, a detailed overview of Colombia's energy system and national efforts for a market ramp-up of renewable energy and hydrogen is provided. The application of the model in different scenarios shows Colombia's potential to produce green hydrogen using renewable energies. The prices estimated are 1.5 and 1.02 USD/kgH 2 for 2030 and 2050 with wind power, and 3.24 and 1.65 USD/kgH 2 for 2030 and 2050 using solar energy. Colombia can become one of the most promising hydrogen suppliers to Asian and European countries with one of the lowest prices in the production and transportation of green hydrogen. [Display omitted] • Open-source models were used to obtain costs of H 2 production and transportation. • LCOH of green H 2 using wind energy is 1.63 and 1.11 USD/kgH2 by 2030 and 2050. • LCOH of green H 2 using solar energy is 3.72 and 1.89 USD/kgH2 by 2030 and 2050. • Exporting H 2 to Asia by 2030 and 2050 costs 3.47 and 2.9 USD/kg, respectively. • Exporting H 2 to Europe by 2030 and 2050 costs 3.1 and 2.55 USD/kg, respectively. [ABSTRACT FROM AUTHOR]