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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]

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]

Hydrogen energy, characterized by its high calorific value and sustainability, represents a secondary clean energy source. It is predominantly stored, transported, and utilized through pipeline networks. However, a comprehensive optimization approach for the design for the ground pipeline network of hydrogen storage is currently lacking. This paper embarks on a systematic exploration of the layout, station type and parameter design for the ground pipeline network of hydrogen storage. Addressing various application perspectives, the study constructs two distinct pipeline network structures: the Star-Star Global Optimization Model (SSGO-Model) and the Star-Tree Global Optimization Model (STGO-Model). Three cases are discussed under six different constraint scenarios. These scenarios focus on layout optimization, variable capacity layout optimization, and the overall optimization of layout and parameters. An overall optimization strategy is proposed to solve the models. A detailed analysis of the iteration process, layout schemes, station and pipeline constraints, investment, and flow parameters of the pipeline network in the optimization results is presented. Through systematic analysis, the correctness and effectiveness of the model are verified, demonstrating the variability of optimization results under different topological structures and constraint conditions. Moreover, when conducting integrated optimization, the total investment is minimized, proving its superiority. The findings demonstrate the applicability of these models in guiding the construction for the ground pipeline network of hydrogen storage, thereby fostering the advancement of hydrogen storage technology. Concurrently, this research contributes significantly to the development of hydrogen energy, offering strategic insights and practical solutions for its efficient deployment. • Integrated optimization model for hydrogen storage ground pipeline network. • The model considers layout, station type and parameter design. • Overall optimization strategy is proposed. • Three cases verify optimization model. [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]

Hydrogen as a fuel of the future for mobile applications has the potential to increase energy efficiency and reduce emissions significantly (Groos et al., 2023 [1]). A main focus to enable hydrogen powered aviation is the efficient storage onboard (Prewitz et al., 2023 [2] ; Verstraete et al., 2010 [3] ; Prewitz et al., 2020 [4]). Especially the storage volume is a major challenge because of the rather low volumetric energy density of compressed or either liquified hydrogen in comparison with kerosene (Hassan et al., 2021 [5] ; Stetson et al., 2014 [6] ; Troeltsch et al., 2020 [7]). Glass capillaries have a high strength, also their geometry and low hydrogen permeability make them a suitable micro pressure tank (Prewitz et al., 2018; Veziroglu et al., 2003 [8] ; Meyer-Scherf, 2015 [9]). By combining glass capillaries and carbon fibers in a polymer matrix, a material composite could be developed that is both a structural element, contributing to load bearing, and a hydrogen tank at the same time. The synergetic use of the structure as storage could be a solution to tackle the problem of the increased required storage volume for hydrogen powered aviation. This paper presents a theoretical micromechanical analysis, the design and manufacturing process of the composite material, and the experimental results of tensile testing conducted on a glass capillary hybridized carbon fiber reinforced plastic (GCRP). The aim is to determine the influence of the glass capillary content on the tensile strength and tensile modulus of the GCRP. • Development of carbon fiber and glass capillary hybrid structural hydrogen storage. • Multipurpose utilization and potential synergetic effects could save weight. • Tensile mechanical properties shows degradation with increasing capillary fraction. [ABSTRACT FROM AUTHOR]

In this paper, certain issues envisaged in the framework of development of design methodology for intelligent autonomous distributed hybrid power complexes (ADHPC) with green hydrogen and energy storage, functioning in grid mode and in the mode of interaction with the global (national) grid (GN) have been solved. Depending on their energy deficit or surplus, relative to the global grid, ADHPCs can operate as a load or as an energy source, respectively, as follows: based on the analysis of the energy balance management process in the ADHPC, a reasonable choice of the structure of the system of accumulation and distribution of power flows (SADCF) was made from the point of view of increasing the reliability of its functioning and ensuring the physical feasibility of the energy balance management process in this structure, i.e. keeping the actual power consumption of the consumers close to the required rated power at each given time t. This is achieved by including a condenser connected to the SADCF system on its assembly and distribution bus and a storage system BS with double-level ((BS1, BS2), double-circuit ((BS1(1), BS1(2)), (BS2(1), BS2(2))) structure, whereby: BS1of the level 1 - to manage the capacity balance in the SADCF under normal ADHPC regime and the variation of green hydrogen and consumption capacities within their confidence intervals assessed at the design stage; BS2 of the level 2 - to coordinate ADHPC and GN modes of operation and to control, together with BS1 of the level 1, GN, diesel generator (DG), the power balance in the SADCF when the ADHPC fails and when RES and consumption power are outside their confidence intervals; alternating charge/discharge operation of the parallel circuits will extend the life of the BS system; – a comprehensive definition of optimal ADHPC system situational energy balance management task is formulated. [ABSTRACT FROM AUTHOR]

Renewable hydrogen is considered as one of the key technologies that may be needed to fully decarbonise our economies, providing the high-temperature heat, fuels and feedstock that might not be possible to electrify. Several pilot projects are underway, and some assessments of the economics of green hydrogen have been published. However, most of them have assessed the costs of producing renewable hydrogen in large-scale, grid-connected units. Another option, pointed by many as a robust strategy in the early stages, is to produce hydrogen locally, in "hydrogen valleys", to serve industrial demand. In this paper, the economics of the different technical configurations and strategies that might be used for this decentralised, variable-demand option are analysed, accounting for the impact that a non-constant operation may cause on the operational efficiency of electrolysers, and for the potential benefits of local hydrogen storage. Our results show that when hydrogen demand is variable, production costs are higher compared to the constant demand case, due to the higher electrolyser size required. Electricity price optimization plus hydrogen storage can be a valuable option in some cases, although the cost benefit is negligible (about 1%) unless price volatility in the market increases with higher RES shares, or investment costs decrease significantly. Sourcing electricity exclusively from a dedicated renewable power plant can only become competitive if electricity market prices rise as observed recently or triggered by increasing CO 2 prices. • Different production strategies are compared to minimise H 2 production costs. • Faraday efficiency increases costs for variable electricity generation. • Electricity price optimization is best for H2 valleys, although compression costs may change this. • Direct H 2 production from renewable plants is not competitive with current prices. [ABSTRACT FROM AUTHOR]

Metal borohydrides exhibit remarkable hydrogen storage capabilities. Nevertheless, the practical application of metal borohydrides as onboard hydrogen storage materials is constrained owing to their elevated hydrogen release temperatures, limited reversibility, and sluggish kinetics. This paper presents an overview of the current research advancements concerning the hydrogen storage capacity of metal borohydrides and the measures employed to improve their properties, encompassing ionic substitution, nano-methods, catalytic doping, and the construction of composite systems. Lastly, this article scrutinizes the challenges and prospects associated with metal borohydrides, proposes methodologies to augment their hydrogen storage capabilities, and furnishes guidelines for further research on metal borohydrides and the broader hydrogen storage domain. • Hydrogen storage is the major barrier to the widespread adoption of hydrogen energy. • Storage via metal borohydrides results in high capacities. • Borohydrides face difficulty in stability and reversibility. • Storage targets must be achieved through various modification methods. [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 investigates an innovative study on the performance of a hybrid condensing boiler-fuel cell micro-cogeneration system for single residential applications. It combines experimental and dynamic numerical investigations including renewable energy for green hydrogen production and solid storage. Basing on the hourly measurements for a typical winter day, a dynamic model was developed and validated against different home heating need. Highlighting the influence home energy needs on fuel cell operating mode, it shows that single homes with low energy demand led to reduce the fuel cell's yearly operation below 50 %. In low-energy homes, a reduction in fuel cell size led to an increase in yearly operation to 60-70 % and achieved a 55 % electrical coverage rate. The integration of metal hydride hydrogen solid storage, powered by renewable sources, is emphasized. This setup increases heat demand, influencing fuel cell operation. In winter season, fuel cell operated for an average of 611 h, compared to 61 h in summer. System efficiency averaged 91 % annually, peaked at 95 % in summer, and sustained 93 % when both FC and condensing boiler were switched on. [Display omitted] • Modeling of a hybrid Boiler-Fuel Cell MCHP system for residential energy management. • Calibration of the FC-MCHP model using experimental data from a real MCHP unit. • Electrical and thermal coverage of the FC-MCHP unit with green hydrogen production and storage under different scenarios. • Strategies for optimal hydrogen consumption in in residential application. • Impact of solid-state hydrogen storage on FC-MCHP consumption and thermal management. [ABSTRACT FROM AUTHOR]

With the extensive utilization of fossil fuels, environmental concerns have been growing. Hydrogen-powered vehicles (HPVs) as well as hydrogen refueling stations (HRSs) are expected to proliferate to alleviate the pollution. In order to promote the economic valibity of HRSs, this paper proposes an optimal scheduling model for distributed HRSs to maximize HRSs' revenue during a day. HRSs serves both the mobility sector with fuel individually and the power system with reserve demand response collaboratively. The elaborated operating of electrolysers and relaxed control of hydrogen storage are involved to enhance practicability and flexibility of the scheduling. Considering that this model has multiple variables, intractable high-dimension nonlinear constraints, a transfer multi-agent reinforcement learning algorithm is developed. The algorithm consists of two parts: the one is the multi-agent optimization method by transforming multi-decision optimization into a multi-agent optimization; the other is to transfer the empirical knowledge of the source task to reinforcement learning according to the similarity between the source task and the target task, making it cut down the blindness of exploration and accelerate convergence. Numerical studies reveal that participating in the reserve services market collaboratively increases overall revenues of HRSs by up to 32.90%, and the computation time is sharply shortened by approximately 34 times compared to the basic reinforcement learning. • A joint operation model of distributed HRSs is proposed to lift revenue by 32.90%. • Relaxed control of hydrogen storage is utilized to minimize service deviation. • An evolutionary transfer reinforcement learning shortens solving time by 34 times. [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]

Green hydrogen, proposed as a sustainable alternative for conventional fuels, has gained utmost importance due to its reduced carbon footprint and potential application in maintaining balance between energy generation and demand. Utilization of hydrogen-based systems are challenged by cost effective storage methods. Bio-hydrogen storage technologies using cryogenic and adsorptive methods are discussed in this review paper, along with their operating conditions and storage capacities. An analysis of operational challenges and recent advancements in hydrogen storage techniques is presented. With a storage pressure of 70 MP, cryogenic hydrogen is almost twice as dense as compressed hydrogen. Technical challenges such as material cost and explosion risk can be addressed by hydrogen adsorption on activated carbon active sites. Maximum hydrogen storage capacity are reported by activated carbon obtained from Chitosan (6.77 wt%), Bamboo (6.6 wt%) and African palm shell (6.5 wt%) at 77 K and 4–20 Mpa. Further, nanotechnology approaches are presented in detail for increasing hydrogen storage capacity in pristine Si and Mg. The future perspectives in terms of technological, and economic aspects are discussed. • Detailed review on hydrogen storage methods is presented. • Role of cryogenics and adsorptive media are discussed. • The comparative performance of various methods is tabulated. • Existing research gap and future perspectives are analyzed. [ABSTRACT FROM AUTHOR]

This paper discusses the technical and economic feasibility of a renewable energy-based system, aimed to replace the traditional diesel engines implemented on a pushed and pusher bulk carrier barge. This barge has a challenging navigational route in the Nile River from Alexandria to Aswan and vice versa. It is scheduled to complete 30 trips annually while carrying 850 tons/trip. The system is based on photovoltaic panels, and was selected with its excess energy to be stored primarily in the form of H 2 gas through electrolysis, and batteries (i.e. Power to Gas technology) to be later converted back to electrical energy through fuel cells. Hence, an operation algorithm was formulated to optimize the performance of the system by defining operating modes that use solar energy, hydrogen energy, batteries, or hybrid energy coming from multiple sources that result in an internal rate of return (IRR) of 15.1% and overall efficiency of 57.9%. This high efficiency is due to the nature of water current that flows from south to north of Egypt, therefore, causing a significant reduction in power demand in the trip from Aswan to Alexandria that requires 11,980 kW h, compared to the trip from Alexandria to Aswan that requires 21,064 kW h. • Zero emission solution combining solar energy, hydrogen generation and fuel cell propulsion for a barge in Nile River. • Preparation to achieve the 7th goal of sustainable development ensuring green propulsion in Nile River cargo transport. • Efficient use of natural resources, solar energy and water current from south to north of Egypt. • Integrating electrolizer, fuel cell, solar energy pv, batteries, and hydrogen storage to form an autonomous barge. [ABSTRACT FROM AUTHOR]

Precooling technology is a widely used method for increasing the flight speed of turbojet engines. To solve the problems of oversized fuel tank and engine performance degradation caused by the low density of hydrogen fuel, a new precooled engine cycle based on hydrogen production technology from ammonia cracking is proposed. To evaluate the engine performances, a thermodynamic model and a test platform are established. The study shows that the test heat sink of ammonia is 4.12 MJ at 620.5 °C, and the upper boundaries of heat sink and hydrogen production rate of ammonia are higher than other chemical fuels. Besides, the optimized fuel ratio is set to 2.0, and the best compressor pressure ratio could be obtained at the point with the highest engine performances Further, the maximum flight Mach number of precooled engine is Ma 4.69, and compared with GE90 and J-58 engines, the carbon emission of precooled engine could be reduced by 94.15% and 72.95% respectively. Moreover, by increasing the cold storage degree, the engine performance can be further improved especially at high pressure ratio. Overall, the research of this paper is hopeful to provide a new idea and necessary theoretical support for the development of high-performance supersonic aero-engine. • A new precooled engine cycle based on hydrogen production technology is proposed. • The test heat sink of ammonia reaches 4.12 MJ at 620.5 °C. • The maximum flight Mach number of precooled engine is Ma 4.69. • The carbon emission of precooled engine could be reduced by 94.15%. • The method to improve the engine performances through clod storage is also proposed. [ABSTRACT FROM AUTHOR]

Economical hydrogen storage and transportation contribute to hydrogen energy utilization. In this paper, for economically distributing hydrogen from the hydrogen plant to the terminal hydrogen refueling station, considering the daily hydrogen demand and transportation distance, firstly a comprehensive techno-economic analysis of the point-to-point hydrogen storage and transportation system based on compressed gas hydrogen (GH), liquid hydrogen (LH), pipeline hydrogen (PH), and liquid organic hydrogen carriers (LOHC) is investigated, respectively. The optimal economical point-to-point energy storage and transportation modes under various transportation distance and daily hydrogen demand are obtained. Then the economic analysis of different hydrogen storage and transportation modes under 1-to-N hydrogen storage and transportation scenario is conducted, which can significantly decrease the cost of LH storage and transportation mode. To step further, the 1-to-N relay hydrogen storage and transportation scenario is constructed to improve the applicability and reduce the unit cost. The economic analysis of 14 kinds of feasible combinations of hydrogen storage and transportation modes is systematically assessed. Regarding to the transportation distance and daily hydrogen demand, the optimal economical 1-to-N relay energy storage and transportation modes are identified. This study may contribute to rationally design and application for economic hydrogen storage and transportation systems. [Display omitted] • The economics of point-to-point hydrogen storage and transportation scenario is investigated. • The economics of the 1-to-N hydrogen storage and transportation scenario is analyzed. • 1-to-N relay hydrogen storage and transportation scenario is constructed to improve economic applicability. • 1-to-N relay hydrogen storage and transportation scenarios may exhibit obvious economic advantage. [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]

This paper introduces a Techno-Economic Assessment (TEA) on present and future scenarios of different energy storage technologies comprising hydrogen and batteries: Battery Energy Storage System (BESS), Hydrogen Energy Storage System (H 2 ESS), and Hybrid Energy Storage System (HESS). These three configurations were assessed for different time horizons: 2019, 2022 and 2030, under both on-grid and off-grid conditions. For 2030, a sensitivity analysis under different energy scenarios was performed, covering other trends in on-grid electric consumption and prices, CO 2 taxation and the evolution of hydrogen technology prices from 2019 until 2030. The selected case study is the Research Park Zellik (RPZ), a CO 2 -neutral sustainable Local Energy Community (LEC) in Zellik, Belgium. The software HOMER (Hybrid Optimisation Model for Electric Renewable) has been selected to design, model and optimise the defined case study. The results showed that BESS was the most competitive when the electric grid was available among the three possible storage options. Additionally, HESS was overall more competitive than H 2 ESS-only, regardless of the grid connection mode. Finally, as per HESS, hydrogen was proved to play a complementary role when combined with batteries, enhancing the flexibility of the microgrid and enabling deeper decarbonisation by reducing the electricity bought from the grid, increasing renewable energy production and balancing toward an island operating mode. • Assessment of hybrid energy storage systems for future energy scenarios. • Sensitivity analysis with different technical, economic, and environmental KPIs. • Analysis of the effects of the connection and capacity access to the electric grid. • Application to a real case study: a CO2-neutral Local Energy Community. [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]

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 increasing heterogeneity and scalability of the Internet of everything, especially, the Energy Internet (EI), is a prompt for novel engineering paradigms. The current infrastructure of hardware technologies besides the available software stack is becoming obsolete for handling the advanced requirements of the smart energy ecosystem. Accordingly, software definitions of the Internet of Things (IoT) stack functions are gaining interest to provide more flexible and scalable implementations. This paper investigates a sophisticated softwarization explicit hybrid model predictive control strategy for energy storage facility systems through the accessor design pattern. This strategy is presumed to support and facilitate the integration of higher-level analytic and control functionalities within the IoT stack at edges and nodes. Simulation is conducted with the Ptolemy II software to evaluate the execution semantics of the proposed strategy. In addition, real-time experiments on a lab-scale hydraulic tank process with both abrupt and gradual commands test scenarios showed the efficiency and reliability of the accessor-based controllers for achieving the control objectives for the benchmark storage facility with an abstract implementation. The analysis shows that this process can serve as a benchmark to mimic the charge and discharge cycles of storage elements in EI ecosystems. • A new paradigm for hydrogen energy storage interfacing within energy Internet ecosystems is proposed and investigated. • An actor-oriented approach is applied for implementing real-time control systems of hydrogen storage. • Software-defined model predictive control is implemented within a Node.js accessor host. • A benchmark process is developed as an emulator for hydrogen energy storage to evaluate the accessors design pattern. [ABSTRACT FROM AUTHOR]

In this paper we investigate the nature of hydrogen diffusion in substoichiometric TiC using simulations. Specifically, we examine how well connected the carbon structural vacancies are in TiC x using percolation theory and how many structural carbon vacancies are connected to the surface of TiC x. This provides direct insight into the number of sites available for hydrogen storage and the interconnected nature of the carbon vacancy network. We also compute the binding energies and migration energies of hydrogen in TiC x using density functional theory. This is conducted over a range of carbon concentrations from nearly stoichiometric TiC to Ti 2 C and includes the differences in vacancy ordering. We find that the migration energy of hydrogen in TiC x generally decreases with carbon loss and is associated with the tetrahedral interstices near them but that the binding energy of hydrogen to TiC x is independent of carbon concentration. Furthermore, we show that this migration path can occur through the tetrahedral interstices, which is influenced by local carbon concentration. These results also demonstrate the vacancy ordered R 3 ¯ m Ti 2 C structure does not possess any more superior ability to store or transport hydrogen than the F d 3 ¯ m Ti 2 C structure. • Hydrogen insertion in TiC x should occur for carbon concentrations below TiC 0.7. • The energy barriers for hydrogen diffusion drop with carbon concentration. • Hydrogen diffusion occurs from carbon vacancy to tetrahedral interstice. • It is easier to diffuse hydrogen into ordered F d 3 ¯ m Ti 2 C than R 3 ¯ m Ti 2 C. [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]

The safety of hydrogen directly affects the use of hydrogen refueling stations and public acceptance of hydrogen energy. This paper presented a methodology for the optimal design of the minimum height, width, and safety distance of the firewall of the hydrogen refueling station under various leakage pressures. The obtained relationship between distances and different hydrogen storage pressures is essential for directing the design of hydrogen refueling stations and firefighters to carry out the rescue. Results from numerical simulation showed that the firewall should be 2 m taller than the leakage hole to prevent the hydrogen jet fire from spreading back. The distance before and behind the firewall presented a linear relationship with the leakage pressure. The specific safe distances behind the firewall were 8.4, 8.5, 9.2, and 9.3 m. The firewall width exhibited a non-linear relationship with the leakage pressure. The specific values were 2.5 m for 35 or 45 MPa and 3 m for 70 or 90 MPa. • Methodology for the optimal design of firewalls in hydrogen refueling stations is determined. • The firewall should be 2 m higher than the leakage hole. • Firewalls can deflect flames and prevent them from spreading behind walls. • The distance before and behind the firewall increases with the increase of hydrogen storage pressures. [ABSTRACT FROM AUTHOR]