Hydrogen Storage System Research Articles

Recent Development of Physical Hydrogen Storage: Insights into Global Outlook and Future Applications.

Transition of global energy market towards an environment-friendly sustainable society requires a profound transformation from fossil fuel to zero carbon emission fuel. To cope with this goal production ofrenewable energy is accelerating worldwide. Research in renewable energy from production and storage to practical utilization requires an organized approach. One of the best renewable energy carrier is the hydrogen, due to its clean combustion and abundance. Nonetheless, its storage is a critical challenge to its success. Hydrogen must be stored long after being produced and transported to a storage site. Physical hydrogen storage is vital among hydrogen storage modes, and its shortcoming needs to overcome for its successful and economic benefits. This review intends to discuss the techniques and applications of physical hydrogen storage in the state of compressed gas, liquefied hydrogen gas, and cold/cryo compressed gas concerning their working principle, chemical and physical properties, influencing factors for physical hydrogen storage, and transportation, economics, and global outlook. Insights of several probable physical hydrogen storage (PHS) systems are highlighted. The outcomes of this review envisioned that the PHS still necessitates technological advancements despite having remarkable success. The Liquid Hydrogen Gas storage marks better sustainability than Compressed and Cryo Compressed Gas. The physical hydrogen storage method can store hydrogen in tanks in any state (liquid or gas) under 20 K for the liquid state and ambient temperature for the gaseous state The Bibliographic analysis depicts that the research in hydrogen rising with time and mostly the research in conducted in USA with 231 articles. Prospects and challenges with lessons learned and the limitation opens the door to further research, which would be helpful for efficient and long-term physical hydrogen storage.

Hydrogen energy storage system integrated with the surplus energy from Hydropower plant in the context of Nepal: A parametric study

Abstract With the search for emission-free energy sources, hydrogen is considered a reliable alternative to store energy from renewable sources like wind, solar, thermal, and hydropower. Hydrogen has minimal environmental implications and can be stored and transported whenever there is an energy demand that other intermittent sources cannot suffice. This project aims to study the integration of hydropower with a hydrogen production and storage plant in Nepal to utilize excess energy supply that will exceed the country’s demand shortly. The excess power from the hydropower will be used to produce hydrogen from the water coming out from the tailrace. This water will also be a coolant for cooling the hydrogen before passing to the storage unit. This parametric analysis shows the effect of variation in the hydrogen inlet pressure before it enters the compressor unit and the impact of variation in storage tank pressure on the energy and exergy efficiency of the overall hydrogen production and storage system. In the first case, the inlet pressure varies from 0 to 20 MPa at three different constant storage pressures 40 MPa, 60 MPa, and 90 MPa. An increase in inlet pressure gradually increases energy and exergy efficiencies, but an increase in storage pressure lowers this efficiency. The reduction is more significant at a high value of inlet pressure. In the second case, the storage pressure varies between 20-80 MPa with constant inlet pressure at 0.1 MPa, 1 MPa, and 5 MPa. The increase in storage pressure gradually reduces efficiency, whereas the higher inlet pressure has higher efficiency. Hydrogen fills the gap between supply and demand of energy, so considering hydrogen production with multiple-stage compression and integration of three sources of energy: wind, solar, and hydropower has an excellent prospect for consistent and low carbon emission solutions.

A day‐ahead energy management strategy for electric vehicles in parking lots considering multi‐scenario simulations and hydrogen storage system

AbstractThis article investigated the charge and discharge management structure of electric vehicles (EVs) in intelligent parking lots (IPLs). It seems that with the expansion of renewable energy sources (RESs) as clean energy and investigation of the effects of EVs on the operation and planning of future distribution networks around the way EVs exchange energy with each other and the upstream network operator, RESs such as solar and wind sources, along with hydrogen storage are essential. Therefore, a new stochastic multi‐scenario approach for charge/discharge management of EVs parked in IPL was proposed, in which a newly developed model for the IPL with a hydrogen storage system (HSS) consisting of a fuel cell, an electrolyzer, and a hydrogen storage tank was presented. In the proposed model, the constraints of upstream network and power balance constraints, with the operating constraints related to the IPL, including EVs, renewable energy sources, and the hydrogen storage system, were formulated as the most important objectives of the optimization problem. The optimization algorithm, Competitive Swarm Optimizer (CSO), was formulated for implementation, and its results were compared with those of the PSO and GWO algorithms. The CSO must handle a variety of practical, large‐scale optimization problems. Based on the obtained results, the excess energy purchased from the upstream network or renewable sources was used as hydrogen storage for consumption during peak hours. As expected, the technical constraints and financial goals of the system were met, and the proposed system was evaluated on a 33‐bus network. As the expected benefits will be the most beneficial with the presence of renewable sources, the final profit will be reduced by taking into account uncertainty for charge/discharge management in EVs such as the uncertainty of electric load, market price, wind turbine, and photovoltaic cell sources. Nonetheless, the profit obtained from renewable resources is preferable to losses resulting from the uncertainty of the system, and according to expectation, the performance of the system for managing the optimal charging and discharging of EVs in the IPL will be acceptable with the maximum profit for the grid.

Solar–Hydrogen-Storage Integrated Electric Vehicle Charging Stations with Demand-Side Management and Social Welfare Maximization

The reliable operation of a power system requires a real-time balance between supply and demand. However, it is difficult to achieve this balance solely by relying on supply-side regulation. Therefore, it is necessary to cooperate with effective demand-side management, which is a key strategy within smart grid systems, encouraging end-users to actively engage and optimize their electricity usage. This paper proposes a novel bi-level optimization model for integrating solar, hydrogen, and battery storage systems with charging stations (SHS-EVCSs) to maximize social welfare. The first level employs a non-cooperative game theory model for each individual EVCS to minimize capital and operational costs. The second level uses a cooperative game framework with an internal management system to optimize energy transactions among multiple EVCSs while considering EV owners’ economic interests. A Markov decision process models uncertainties in EV charging times, and Monte Carlo simulations predict charging demand. Real-time electricity pricing based on the dual theory enables demand-side management strategies like peak shaving and valley filling. Case studies demonstrate the model’s effectiveness in reducing peak loads, balancing energy utilization, and enhancing overall system efficiency and sustainability through optimized renewable integration, energy storage, EV charging coordination, social welfare maximization, and cost minimization. The proposed approach offers a promising pathway toward sustainable energy infrastructure by harmonizing renewable sources, storage technologies, EV charging demands, and societal benefits.

Integrated planning of hydrogen supply chain and reinforcement of power distribution network for accommodating fuel cell electric vehicles

Fuel cell electric vehicles (FCEVs) hold great promise for achieving sustainable and environmentally friendly transportation. However, their widespread adoption depends on the efficient development of the hydrogen supply chain (HSC) required for refueling these vehicles. Given the interdependence between the HSC and power distribution networks (PDNs), this paper presents an innovative model to jointly plan the HSC and reinforce PDNs. In this new model, the inherent uncertainties related to wind energy generation, load demand, and FCEV consumption are modeled. Furthermore, coordinating the planning of hydrogen storage and battery energy storage systems is incorporated. The results underscore the critical importance of simultaneous planning for the HSC and PDN reinforcement. Moreover, the findings reveal that hydrogen storage alone can provide sufficient energy arbitrage, leading to a 9.6% reduction in total costs compared to the scenario where storage is disregarded.

Exploring hydrogen storage safety research by bibliometric analysis

The application of hydrogen energy is affected by the safety of hydrogen storage system. To grasp the current status of research and application in the research field of hydrogen storage safety and explore its research development trend, data analysis techniques, such as co-occurrence, co-citation, and burst detection, were adopted to conduct bibliometric analysis of the relevant literature. The study results show that the research hotspots of hydrogen storage safety mainly concentrate on six aspects: the stability of metal hydride hydrogen storage materials, the study of thermal management and stress relief in metal hydride reactors, the safety analysis of hydrogen fuel cells and hydrogen leakage monitoring, the analysis of leakage and explosion risks in hydrogen refueling stations, the study of filling pressure and temperature distribution in hydrogen storage tanks, and the study of safety issues in underground hydrogen storage. Mg-based hydride stability and underground hydrogen storage risk analyses are current research frontiers in hydrogen storage safety.

Analysis of safety technical standards for hydrogen storage in fuel cell vehicles

Fuel cell vehicles are considered as the direct alternative to fuel vehicles due to their similar driving range and refueling time. The United Nations World Forum for Harmonization of Vehicle Regulations (UN/WP29) released the Global Technical Regulation on Hydrogen and Fuel Cell Vehicles (GTR13) in July 2013, which was the first international regulation in the field of fuel cell vehicles. There exist some differences between GTR13 and the existing safety technical specifications and standards in China. This paper studied the safety requirements of the GTR13 compressed hydrogen storage system, analyzed the current hydrogen storage safety standards for fuel cell vehicles in China, and integrated the advantages of GTR13 to propose relevant suggestions for future revision of hydrogen storage standards for fuel cell vehicle in China.

Development and assessment of a floating photovoltaic-based hydrogen production system integrated with storage options

The integrated system approach utilized in the current study represents an innovative approach to harnessing solar energy through a floating photovoltaic-based integrated plant featuring a diverse array of energy storage options. As part of this research, a solar energy system integrating both floating and concentrating solar technologies was designed at the specified site. Despite the constraints presented by the cold temperature at the chosen location, particularly during the winter months when solar irradiation is restricted, strategies are employed, such as exploiting the high albedo effect caused by the freezing of the water body, optimizing the application of solar radiation, and assuring the system's resilience and energy efficiency. Floating photovoltaic and concentrated solar panels are integral components of this advanced system, which is supplemented by underground hot and cold storage units, underground hydro-pumped storage, a multi-effect desalination system with freshwater storage, a lithium bromide absorption cooling system, and an alkaline electrolysis system for hydrogen and oxygen storage. This comprehensive energy strategy includes diverse storage and production technologies. The thermodynamic analyses and assessments employing the Engineering Equation Solver and the System Advisor Model provide some quantitative performance evaluations. The study considers time-dependent operational characteristics, illustrates the water withdrawal rates, energy and exergy efficiencies of the heating space temperature, inverter efficiency, GHI irradiance, mass, and volume values of the heat transfer fluid in both hot and cold tanks within thermal energy storage, annual cooling generation over a year, power production, hydropower storage, and hydrogen storage over a year. The system's concentrated solar panels are projected to generate an annual AC output of 180.79 GWh, with a yearly water usage of 14,055 m3, while floating panels are predicted to provide 7000 kWh with a 0.85 performance ratio. The overall energy efficiency of the current system is determined to be 51.76 %, and the exergy efficiency is found to be 55.41 %, respectively. Optimizing energy efficiency, utilizing diverse storage solutions, and utilizing aquatic environments minimizes environmental impact, and time-dependent analysis enhances perceptions of performance throughout different times and circumstances.

Conceptual design and optimization of integrating renewable energy sources with hydrogen energy storage capabilities

Systems are inherently tied to uncertainty, which necessitates the development of designs and schedules that accommodate this unpredictability. Particularly in modern power systems, the variable efficiency of numerous factors, including pricing, underscores the need for uncertainty modeling. In the meantime, the incorporation of EVs (electric vehicles) into the electrical grid is advancing, with these vehicles being recognized for their role in reducing dependency on fossil energies and enhancing the resilience, stability and efficiency of the grid. However, the rapid growth of the EV sector necessitates thoughtful strategies from decision-makers to manage its expansion effectively, particularly considering the environmental implications associated with the life cycle of EVs, including their charging and discharging processes. This research introduces the conceptual design and optimization approach utilizing a hybrid bat algorithm and differential evolution algorithm (BA-DEA) to improve the efficiency and resilience of EV-smart parking lots under the unpredictable conditions caused by grid pricing fluctuations within the DRP (demand response program). The technique effectively modulates daily costs by adjusting loads among peak and off-peak periods. Key features of the proposed approach include a non-dominated sorting model, innovative variable identification, a memory-based selection process, and the application of fuzzy theory to identify optimal Pareto outcomes. This methodology is not only swift in converging to a solution but also demonstrates a high likelihood of reaching the global optimum. Modeling considerations for smart hydrogen storage systems (SHSSs) incorporate significant constraints, notably those associated with electrolyzers, fuel cells, and storage capacities. The algorithm's effectiveness is validated in scenarios involving parking facilities and multiple uncertain resources, demonstrating a robust reduction in specific cost indicators and adjustments in cost dynamics when DRP is considered. Specifically, the algorithm achieves a substantial 42% decrease in cost variability when DRP is excluded, and a 46.9% reduction in cost variability when DRP is included, despite a minor 5% increase in average cost. These outcomes underscore the proposed system's capability to improve resilience and thermal performance under fluctuating conditions, making it a promising solution for future smart energy systems. Further, the results exhibited the complex interplay between cost optimization and operational adjustments in response to demand-side management.

Chemical-based Hydrogen Storage Systems: Recent Developments, Challenges, and Prospectives.

Hydrogen (H2) is being acknowledged as the future energy carrier due to its high energy density and potential to mitigate the intermittency of other renewable energy sources. H2 also ensures a clean, carbon-neutral, and sustainable environment for current and forthcoming generations by contributing to the global missions of decarbonization in the transportation, industrial, and building sectors. Several H2 storage technologies are available and have been employed for its secure and economical transport. The existing H2 storage and transportation technologies like liquid-state, cryogenic, or compressed hydrogen are in use but still suffer from significant challenges regarding successful realization at the commercial level. These factors affect the overall operational cost of technology. Therefore, H2 storage demands novel technologies that are safe for mobility, transportation, long-term storage, and yet it is cost-effective. This review article presents potential opportunities for H2 storage technologies, such as physical and chemical storage. The prime characteristics and requirements of H2 storage are briefly explained. A detailed discussion of chemical-based hydrogen storage systems such as metal hydrides, chemical hydrides (CH3OH, NH3, and HCOOH), and liquid organic hydrogen carriers (LOHCs) is presented. Furthermore, the recent developments and challenges regarding hydrogen storage, their real-world applications, and prospects have also been debated.

Stable Pt/MgAl2O4 catalysts for efficient production of H2 from cyclohexane dehydrogenation

Cyclohexane as liquid organic hydrogen carriers has attracted considerable interest in the field of hydrogen storage technology. However, the innovation of efficient catalyst for producing H2 through cyclohexane dehydrogenation remains a substantial challenge. In this study, we have successfully developed Pt/MgAl2O4 catalysts exhibiting outstanding catalytic performance in cyclohexane dehydrogenation. Notably, the optimal catalyst Pt/MgAl2O4-700 achieves cyclohexane conversion of 89.1 % and benzene selectivity of over 99 % at 345 °C, resulting in a high hydrogen evolution rate of 933 mmol/gPt/min. Moreover, this catalyst exhibits remarkable long-term stability, with no evident loss of activity in 225-hour dehydrogenation reaction. The catalyst was characterized by XRD, N2 adsorption–desorption, STEM, XPS, NH3-TPD, CO-FTIR and H2-TPR techniques, which provides detailed structure information for elucidation of structure–activity relationship. The spinel structure and moderate acid density of the support enable highly dispersed Pt species at the surface of MgAl2O4. This results in the formation of ultra-small and sintering-resistant Pt particles that exhibit exceptional activity in cyclohexane dehydrogenation. Additionally, the presence of positively charged Ptδ+ species in Pt/MgAl2O4 facilitates the rapid desorption of benzene product. This effectively prevents the formation of coke arising from benzene dehydrogenation, which ensures to achieve high stability. These findings provide valuable knowledge for the rational design of efficient metal-based catalysts for liquid organic hydrogen carriers in hydrogen storage systems.

Hydrogen storage integrated in off-grid power systems: a case study

This paper investigates the feasibility and benefits of integrating hydrogen storage systems into off-grid power systems. As a case study, a stand-alone microgrid located on a small island in southeastern Sardinia (Italy) and already equipped with a photovoltaic (PV) system coupled with batteries is chosen.To evaluate the integration benefits of the two storage systems (hydrogen and batteries) and the optimal sizing of the hydrogen storage section, a parametric analysis with a simulation model implemented in the MATLAB environment has been carried out. Results show that the optimal integration between the two storage systems is found by imposing a share of the batteries (18 kWh, 50% of the overall battery capacity) to exclusively supply the load demand (called battery energy buffer). In these conditions, an almost 100% self-sufficiency of the microgrid can be achieved by a hydrogen generator with the lowest size considered (2.4 kW), a hydrogen storage volume of 10 m3 and a fuel cell, mainly able to completely cover the night loads, of 1.5 kW. This sizing leads to a Levelized Cost of Electricity (LCOE) for the hydrogen section of about 10.5 €/kWh.

Comparative analysis of hydrogen production, accumulation, distribution, and storage systems

The global energy demand in the world continues to grow and environmental pollution caused by fossil fuels becomes increasingly serious, the development and utilization of new energy sources has become a hot topic of global concern. The development and utilization of new energy sources is one such possible solution, which can provide clean, renewable energy and thus reduce the impact on the environment. Hydrogen, as a clean, productive, carbon-free secondary energy source, has the potential to be used as a fuel and essential substance for different fields such as heating, transportation, industry, and power generation. As the international community strives to achieve a shift toward a more eco-conscious and sustainable future, hydrogen has received extensive research and attention due to its abundant resources and environmentally friendly properties. The main objective of this study was to describe and comparatively analyze the efficient production, accumulation, distribution and storage of hydrogen. Today the production of hydrogen is centered on the creation or extraction of hydrogen from primary energy sources. The accumulation of hydrogen involves the preservation of surplus hydrogen for subsequent utilization. The distribution of hydrogen encompasses the conveyance and delivery of hydrogen. The storage systems for hydrogen pertain to the technologies and infrastructure employed to retain hydrogen for future deployment. In complex, these constituents establish a comprehensive hydrogen value chain that facilitates the generation, preservation, and distribution of hydrogen as a sustainable and environmentally friendly energy solution. Keywords: comparative analysis, hydrogen, production, accumulation, distribution, storage systems.

Grid variability and value assessment of long-duration energy storage under rising photovoltaic penetration: Evidence from Japan

Using high-resolution grid power balance and market data, this work investigates the effects of rising solar photovoltaic generation on the variability of large-scale net grid load and spot prices, and conducts an analysis of the potential balancing profits of various grid-scale energy storage systems. Analysis results show the correlation between PV (photovoltaic) generation and electricity demand has been identified as a significant factor influencing spot price value. As PV penetration increases, the value of spot prices experiences a notable decline, with values declining to nearly zero when the share of hourly PV generation surpasses 70 %. The volatility of electricity spot prices has a substantial impact on utilization rates and economic profits of energy storage systems employed for grid energy balancing. Despite the lower roundtrip efficiency, reversible hydrogen storage system can offer positive benefits. The longer storage duration offers the advantage of capturing greater dispatch profits by exploiting price differences over extended periods. Considering the time-varying nature of spot prices, the rated power capacity of the storage system plays a significant role in determining its utilization rates. The larger rated charging and discharging ability of the storage system allows for more effective utilization of price fluctuations, resulting in greater profitability.

Distributed fiber optic strain sensing for structural health monitoring of 70 MPa hydrogen vessels

We report on the development and testing of 70 MPa hydrogen pressure vessels with integrated fiber optic sensing fibers for the automotive use. The paper deals with the condition monitoring of such composite pressure vessels using the optical backscatter reflectometry (OBR) which was applied for a distributed fiber optic strain sensing along fully integrated polyimide-coated single-mode glass optical fiber (SM-GOF). The sensing fibers were embedded into the vessel structure by wrapping them over the inside polymer liner during the manufacturing process of the outside carbon fiber reinforced polymer (CFRP). Detecting local strain events by the integrated fiber optic sensors might be an opportunity for monitoring the material degradation. Regarding the investigation of the ageing behavior, both ambient hydraulic cycling tests and slow burst tests were conducted on 70 MPa pressure vessels with embedded fiber optic sensors. The achieved results contribute to the knowledge about material fatigue to guarantee the safe usage during the entire lifetime of the composite hydrogen storage vessels. The presented work stands in context of the European Horizon 2020 research project SH2APED focused on the development of an innovative hydrogen storage system composed of an assembly of nine 70 MPa tubular pressure vessels used as an automotive battery pack.

Density and speed of sound measurements of aqueous solutions of potassium formate, potassium bicarbonate and their mixtures

Potassium formate and potassium bicarbonate are currently subject of research in a variety of new potential technical applications. One example of this is the use of the mixture of both salts in solution as a reversible hydrogen storage system and thus as a potential renewable energy carrier. In order to develop these new technologies, knowledge of the thermophysical properties of the individual salt solutions and mixtures is essential. Due to the limited data available in literature, which are only available for the single salt solutions, measurements of density and speed of sound as well as mathematical correlations based on the data were carried out in order to predict the behaviour of the salt solutions as a function of concentration and temperature. Good approximation equations were found for both properties, which agree with the existing data in the literature and result in deviations well below 1 % over wide concentration and temperature ranges. The large number of measurements, the clear trends in the results and the good agreement with existing data from the literature allow to assume that reliable predictions of concentration, and thus degree of hydrogen charging, can be realized utilizing density measurements. With the help of this fundamental research, it will not only be possible to investigate the newly discussed applications in more detail in the future, but also enable more precise design calculations, models and simulations. In addition, material properties that result from the measured variables or are related to them, such as thermal expansion or isentropic compressibility, can be analysed.

Computational study to investigate effectiveness of titanium substitution in CaFeH3 perovskite-type hydride: An approach towards advanced hydrogen storage system

In recent years, there has been increased interest in hydrogen storage due to the numerous advantages hydrogen offers as an energy source. This study explores the structural, hydrogen storage, electronic, elastic, mechanical, and optical properties of Ca1-xTixFeH3 through DFT. After Ti substitution in the host material, structure phase transformation occurs: cubic → pseudo-cubic → cubic. Study compounds are thermodynamically stable and experimentally synthesizable according to the calculated negative formation energies. Gravimetric hydrogen storage capacities for different concentrations of Ti (x = 0, 0.11, 0.33, 0.55, 1) were calculated as 2.963, 2.938, 2.843, and 2.753 wt%, respectively. The investigation focuses on understanding the material's BS, Fermi level, and DOS, elucidating its metallic characteristics, and non-zero DOS at the Fermi level contributing to electrical and thermal conductivity. Elemental partial density of states reveals hybridization effects with Ti doping, affecting the valence band's atomic contributions. Using cubic symmetry, C11, C12, and C14 elastic constants were used to describe mechanical characteristics, and the Born criteria were met. Thus, mechanical stability was demonstrated for these compounds. Optical analyses exhibit changes concerning Ti concentrations and energy levels, including absorption spectra, conductivity, reflectivity, dielectric function, refractive index, energy loss function, and extinction coefficient. These findings shed light on the material's response to incident radiation and potential applications in hydrogen storage and optoelectronic devices.

Influence of hydrogen sulfide on gas-water interface in underground hydrogen storage: A molecular dynamics study

In this study, we investigate the dynamics of interfacial tension (IFT) between residual pore water and gas mixtures containing H2, CH4, and H2S within subsurface porous media, essential for underground hydrogen storage (UHS) systems. Utilizing molecular dynamics simulations, we established specific IFT correlations across a spectrum of H2S concentrations, ranging from 5 % to 80 %, under the conditions of 14.5 MPa and 343 K. Our results demonstrate a marked decrease in IFT, with a notable 12 % reduction observed even at a minimal H2S concentration of 5 % for H2S-H2 mixtures, contrasting with a 6 % reduction in H2S-CH4 mixtures, and reaching a saturation point at concentrations exceeding 80 %. The presence of CH4 at the interface mitigates the reduction in IFT caused by H2S, underscoring the complexity of gas interactions in subsurface storage. These insights into the molecular dynamics at the gas-water interface carry significant implications for the optimization of UHS operations, informed by the substantial variations in IFT with different H2S concentrations.

Hydrogen storage systems performance and design parameters using response surface methods and sensitivity analysis

DesignDesign of metal hydride-based hydrogen storage reactors is often performed using numerical/experimental modelling which is computationally/economically difficult. This paper investigates the applicability of Response Surface Methodology (RSM) coupled Local/Global Sensitivity Analysis (L/GSA) to investigate – i) the applicability of advanced RSMs in predicting the responses for storage systems efficiently, ii) the applicability of advanced RSMs to perform L/GSA to identify the sensitive input design parameters based on their effect on the Outputs of Interests (OIs), i.e., reaction fraction (i.e., C) and bed temperature (i.e., T), and iii) the dependence of importance ranking of design parameters on the employed L/GSA methodology. The study is conducted in two stages. In the first stage, the most accurate RSM was identified among fourteen traditional and advanced RSMs, i.e., radial basis, kriging, quadratic, moving least square, support vector machine etc., employing a measure of precision, i.e., Nash–Sutcliffe Efficiency (NSE). RSMs were constructed based on the values of OIs estimated using finite element simulation using COMSOL software for random realizations of inputs generated via Latin Hypercube Sampling (LHS). In the second stage, the importance ranking of design parameters was estimated for both OIs using six different L/GSAs based on the input-output relationships estimated in stage one. All the codes of RSMs and L/GSAs were written and validated in MATLAB. Finite element simulations of the random realizations were performed using COMSOL software. For the present study, NSEs of the considered RSMs were ranging between 0.6262-0.8544 and 0.4652–0.8081 for C and T respectively, indicating the importance of selection of appropriate RSM. RBF-augmented Compact-I and kriging were the most accurate RSMs with NSEs approximately 10%–20 % higher to those of frequently used polynomial RSM. Time (t) and mass of hydrogen to be stored (MH) were the most; and external temperature (Text) and porosity (E) were the least sensitive inputs corresponding to C and T, with differences of 80–90 % in the sensitivity indices respectively. The ranking prediction was highly dependent upon the employed L/GSA methodology, with Morris's screening observed to be the least accurate. The RSM methods described in this study help to design and investigate the metal hydride reactors for various applications (space heating, hydrogen storage, storage for vehicular application, metal hydride compressor) without undergoing detailed mathematical modelling of the system. The proposed methodology may significantly assist the designers to focus (or vary) on the sensitive inputs only during the physical modelling of systems to improve their performance. This sensitivity analysis is helpful to find out the most advance sensitivity analysis method which can be used to find out the most sensitivity parameter which can be varied according to their rankings to achieve the required performance of metal hydride reactor for the particular application. The advanced RSMs assist to identify these sensitive inputs quickly by reducing the mathematical efforts in the L/GSA by providing the accurate input-OIs relationships based on the limited numerical simulations. This will significantly save the resources and time of industries required in physical modelling/numerical simulations significantly, which otherwise would have been invested on investigating the non-sensitive inputs.

Optimization of energy and hydrogen storage systems in geothermal energy sourced hybrid renewable energy system

Research on renewable energy systems has accelerated in recent years due to the exhaustibility of fossil fuels and the damage they cause to the environment. Renewable energy sources such as wind, solar, and geothermal are used for energy production. In this study, a hybrid system design was created using wind, solar, and geothermal energy. The study offered the opportunity to produce electricity from low-temperature geothermal energy. Optimization of a hybrid system with geothermal energy in this study presents an innovative approach. Additionally, an energy storage system was added to the system for hydrogen production from the excess energy. The system met the required electrical load of 1983.040 MWh/yr and excess electricity was 362.077 MWh/yr in total electricity of 2402.572 MWh/yr. The excess electricity produced was used in hydrogen production, and hydrogen production was 3423 kg/yr. The levelized energy cost of the hybrid system was obtained as $0.561. In a rural area with geothermal resources, this new hybrid system is quite reasonable in terms of both meeting the electricity needs using renewable energy and uninterrupted use by storing excess energy and hydrogen.