Modeling of Large-Scale Hydrogen Storage System Considering Capacity Attenuation and Analysis of Its Efficiency Characteristics

In the existing power system with a large-scale hydrogen storage system,there are problems such as low efficiency of electric-hydrogen-electricity conversion and single modeling of the hydrogen storage system.In order to improve the hydrogen utilization rate of hydrogen storage system in the process of participating in the power grid operation,and speed up the process of electric-hydrogen-electricity conversion.This article provides a detailed introduction to the mathematical and electrical models of various components of the hydrogen storage unit,and also establishes a charging and discharging efficiency model that considers the temperature and internal gas partial pressure of the hydrogen storage unit.These models are of great significance for studying and optimizing gas storage technology.Through these models,the performance of gas storage units can be better understood and improved.These studies are very helpful for improving energy storage efficiency and sustainable development.The factors affecting the charge-discharge efficiency of hydrogen storage units are analyzed.By integrating the models of each unit and considering the capacity degradation of the hydrogen storage system,we can construct an efficiency model for a large hydrogen storage system and power conversion system.In addition,the simulation models of the hydrogen production system and hydrogen consumption system were established in MATLAB/Simulink.The accuracy and effectiveness of the simulation model were proved by comparing the output voltage variation curve of the simulation with the polarization curve of the typical hydrogen production system and hydrogen consumption system.The results show that the charge-discharge efficiency of the hydrogen storage unit increases with the increase of operating temperature,and H2 and O2 partial voltage have little influence on the charge-discharge efficiency.In the process of power conversion system converter rectification operation,its efficiency decreases with the increase of temperature,while in the process of inverter operation,power conversion system efficiency increases with the increase of temperature.Combined with the efficiency of each hydrogen storage unit and power conversion system converter,the upper limit of the capacity loss of different hydrogen storage units was set.The optimal charge-discharge efficiency of the hydrogen storage system was obtained by using the Cplex solver at 36.46%and 66.34%.

AB_5-type Hydrogen Storage Alloy Modified with Ti/Zr Used as Anodic Materials in Borohydride Fuel Cell

Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hydrogen and enhance the utilization of borohydride, Ti/Zr metal powders has been added into the parent LmNi4.78Mn0.22 （where Lm is La-richened mischmetal） alloy （LNM） by ball milling and heat treatment methods. It is found that the addition of Ti/Zr metal powders lowers the electrochemical catalytic activity of the electrodes, at the same time, restrains the generation of hydrogen and enhances the utilization of the fuel. All the results show that the hydrogen generation rate or the utilization of the fuel is directly relative to the electrochemical catalytic activity or the discharge capability of the electrodes. The utilization of the fuel increases with discharge current density. It is very important to find a balance between the discharge capability and the utilization of the fuel.

1,4-Hydroquinone is a Hydrogen Reservoir for Fuel Cells and Recyclable via Photocatalytic Water Splitting

Photocatalytic splitting of water was carried out in a two-phase system. Nanocrystalline titanium dioxide was used as photocatalyst and potassium hexacyanoferrate(III)/(II) as electron transporter. Generated hydrogen was chemically stored by use of a 1,4-benzoquinone/1,4-hydroquinone system, which was used as a recyclable fuel in a commercialised direct methanol fuel cell (DMFC). The electrical output of the cell was about half compared to methanol. The conversion process for water splitting and recombination in a fuel cell was monitored by UV-Vis spectroscopy and compared to a simulated spectrum. Products of side reactions, which lead to a decrease of the overall efficiency, were identified based on UV-Vis investigations. A proof of principle for the use of quinoide systems as a recyclable hydrogen storage system in a photocatalytic water splitting and fuel cell cyclic process was given.

Structural and hydrogen storage capacity evolution of Mg_2FeH_6 hydride synthesized by reactive mechanical alloying

Mg-based metal hydrides are promising as hydrogen storage materials for fuel ce ll application. In this work,Mg2FeH6 complex hydride phase was synthesized by controlled reactive ball milling of 2Mg-Fe （atomic ratio） powder mixture in H2. Mg2FeH6 is confirmed to be formed via the following three stages: form ation of MgH2 via the reaction of Mg with H2,incubation stage and formation of Mg2FeH6 by reaction of fully refined MgH2 and Fe. The incubation stage is characterized by no traces of Mg or hydride crystalline phase by XRD. On the other hand,Mg is observed uniformly distributed in the milled powder by SEM-E DS. Also,almost the same amount of H2 as the first stage is detected stored i n the powders of the second stage by DSC and TGA.

Electrochemical properties of AB_5 type hydrogen storage alloy as anode electrocatalyst of PEMFC

The electrocatalytic properties of hydrogen storage alloy（HSA） MlNi3.65Co0.85Al0.3Mn0.3 substituting Pt as anode electrocatalyst of PEMFC was investigated. It is found that, after being optimized, the electrocatalytic abilities of the HSA is reasonably good, the current density of the HSA anode membrane and electrode assembly（MEA） reaches 168 mA/cm2 at 0.5 V and 232.4 mA/cm2 at 0.2 V, and its power density reaches the maximum value of 84 mW/cm2. The influence of operating temperature and hydrogen pressure on the electrocatalytic behavior of HSA anode MEA is also discussed. At 60 ℃ under 2.02×105 Pa H2, the HSA anode shows the best electrochemical properties.

Modeling and Simulation of Hydrogen Energy Storage System for Power-to-gas and Gas-to-power Systems

By collecting and organizing historical data and typical model characteristics,hydrogen energy storage system(HESS)-based power-to-gas(P2G)and gas-to-power systems are developed using Simulink.The energy transfer mechanisms and numerical modeling methods of the proposed systems are studied in detail.The proposed integrated HESS model covers the following system components:alkaline electrolyzer(AE),highpressure hydrogen storage tank with compressor(CM&H_(2) tank),and proton-exchange membrane fuel cell(PEMFC)stack.The unit models in the HESS are established based on typical U-I curves and equivalent circuit models,which are used to analyze the operating characteristics and charging/discharging behaviors of a typical AE,an ideal CM&H_(2) tank,and a PEMFC stack.The validities of these models are simulated and verified in the MicroGrid system,which is equipped with a wind power generation system,a photovoltaic power generation system,and an auxiliary battery energy storage system(BESS)unit.Simulation results in MATLAB/Simulink show that electrolyzer stack,fuel cell stack and system integration model can operate in different cases.By testing the simulation results of the HESS under different working conditions,the hydrogen production flow,stack voltage,state of charge(SOC)of the BESS,state of hydrogen pressure(SOHP)of the HESS,and HESS energy flow paths are analyzed.The simulation results are consistent with expectations,showing that the integrated HESS model can effectively absorb wind and photovoltaic power.As the wind and photovoltaic power generations increase,the HESS current increases,thereby increasing the amount of hydrogen production to absorb the surplus power.The results show that the HESS responds faster than the traditional BESS in the microgrid,providing a solid theoretical foundation for later wind-photovoltaic-HESS-BESS integration.

Hydrogen as a carrier of renewable energies toward carbon neutrality:State-of-the-art and challenging issues

Energy storage and conversion via a hydrogen chain is a recognized vision of future energy systems based on renewables and,therefore,a key to bridging the technological gap toward a net-zero CO_(2)emission society.This paper reviews the hydrogen technological chain in the framework of renewables,including water electrolysis,hydrogen storage,and fuel cell technologies.Water electrolysis is an energy conversion technology that can be scalable in megawatts and operational in a dynamic mode to match the intermittent generation of renewable power.Material concerns include a robust diaphragm for alkaline cells,catalysts and construction materials for proton exchange membrane(PEM)cells,and validation of the long-term durability for solid oxide cells.Hydrogen storage via compressed gas up to 70 MPa is optional for automobile applications.Fuel cells favor hydrogen fuel because of its superfast electrode kinetics.PEM fuel cells and solid oxide fuel cells are dominating technologies for automobile and stationary applications,respectively.Both technologies are at the threshold of their commercial markets with verified technical readiness and environmental merits;however,they still face restraints such as unavailable hydrogen fueling infrastructure,long-term durability,and costs to compete with the analog power technologies already on the market.

Hydrogen Storage Alloy and Carbon Nanotubes Mixed Catalyst in a Direct Borohydride Fuel Cell

In this study, carbon nanotubes （CNTs） were mixed with ABs-type hydrogen storage alloy （HSA）, as catalyst for an anode in a direct borohydride fuel cell （DBFC）. As comparision, a series of traditional carbon materials, such as acetylene black, Vulcan XC-72R, and super activated carbon （SAC） were also employed. Electrochemical measurements showed that the electrocatalytic activity of HSA was improved greatly by CNTs. The current density of the DI3FC employing the HSA/CNTs catalytic anode could reach 1550 mA.cm-2 （at -0.6 V vs the EIg/HgO electrode） and the maximum power density of 65 mW.cm-2 for this cell could be achieved at room temperature. Furthermore, the life time test lasting for 60 h showed that the cell displayed a good stability.

Utilization of Energy Storage and Hydrogen in Power and Energy Systems:Viewpoints from Five Aspects

Decarbonizing power systems is crucial to mitigating climate change impacts and achieving carbon neutrality.Increasing renewable energy supply can reduce greenhouse gas emissions and accelerate the decarbonization process.However,renewable energy sources(RESs)such as wind and solar power are characterized by intermittency and often non-dispatchability,significantly challenging their high-level integration into power systems.Energy storage is acknowledged as a vital indispensable solution for mitigating the intermittency of renewables such as wind and solar power and boosting the penetrations of renewables.In the CSEE JPES Forum,five well-known experts were invited to give keynote speeches,and the participating experts and scholars had comprehensive exchanges and discussions on energy storage technologies.Specifically,the views on the design,control,performance,and applications of new energy storage technologies,such as the fuel cell vehicle,water electrolysis,and flow battery,in the coordination and operation of power and energy systems were analyzed.The experts also provided experience that could be used to develop energy storage for constructing and decarbonizing new power systems.

Synthesis of nanostructured Mg_2FeH_6 hydride and hydrogen sorption properties of complex

Reactive mechanical alloying(RMA)was carried out in a planetary ball mill for the synthesis of ternary hydride Mg2FeH6 for hydrogen storage.The formation mechanism of Mg2FeH6 in RMA process and the sorption properties of the products were investigated.The results show that Mg2FeH6 has a yield ratio around 80%,and a grain size below 10 nm in the powder synthesized by milling 3Mg+Fe mixture for 150 h under the hydrogen pressure of 1 MPa.The synthesized powder possesses a high hydrogen capacity and good sorption kinetics,and absorbs 4.42%(mass fraction)of hydrogen within 200 s at 623 K under the hydrogen pressure of 4.0 MPa.In releasing hydrogen at 653 K under 0.1 MPa,it desorbs 4.43%(mass fraction)of hydrogen within 2 000 s.The addition of Ti increases the hydrogen desorption rate of the complex in the initial 120 s of the desorption process.

Value assessment of hydrogen-based electrical energy storage in view of electricity spot market

Hydrogen as an energy carrier represents one of the most promising carbon-free energy solutions.The ongoing development of power-to-gas(Pt G)technologies that supports large-scale utilization of hydrogen is therefore expected to support hydrogen economy with a final breakthrough.In this paper,the economic performance of a MW-sized hydrogen system,i.e.a composition of water electrolysis,hydrogen storage,and fuel cell combined heat and power plant(FCCHP),is assessed as an example of hydrogen-based bidirectional electrical energy storage(EES).The analysis is conducted in view of the Danish electricity spot market that has high price volatility due to its high share of wind power.An economic dispatch model is developed as a mixed-integer programming(MIP)problem to support the estimation of variable cost of such a system taking into account a good granularity of the technical details.Based on a projected technology improvement by 2020,sensitivity analysis is conducted to illustrate how much the hydrogen-based EES is sensitive to variations of the hydrogen price and the capacity of hydrogen storage.

Use of hydrogen storage in an off-grid system for implementing a renewable-energy system

This paper presents the purpose,advantages,system constitution,operation method and estimation results of using hydrogen storage in a small-scale electric power(off-grid)system when renewable energy sources are introduced.It is assumed that all electricity is supplied from renewable energy sources without using a diesel generator that requires fossil fuels.In other words,for a small-scale electric power system on a remote island,a power-supply system comprising a photovoltaic power-generation system,storage battery,hydrogen-production system,storage tank and a fuel cell is considered.The condition under which the total construction cost is minimized by considering the equipment capacity,operation method of the battery and fuel cell as parameters is investigated.The results demonstrate that the construction cost can be reduced by applying the method of surplus magnification and hydrogen storage.The initial cost is~70%when hydrogen storage is added as compared with the case in which a storage battery alone is used.Such a cost-effective system can contribute to Japan’s self-reliance with regard to the energy sector in the future.

2022 roadmap on hydrogen energy from production to utilizations

Hydrogen has been always the hot topic,which drives a lot of researchers to study and explore hydrogenrelated projects and fields.The first subfield is hydrogen production with green and cost-effective means.Some methods have been intensively used for high-efficient hydrogen production,i.e.,catalytic chemical hydrogen generation,electrocatalytic hydrogen evolution,photocatalytic hydrogen evolution,photo-electrocatalytic hydrogen evolution.Most of them are driven by various catalysts.Moreover,the hydrogen storage is also an important question,which is also a present research hot topic,although the history is long with several decades.Hydrogen fuel cells have also obtained great attention due to the zero emissions.The related research mainly focuses on the cell systems and electrocatalysts used.Under this background,we invite some excellent research groups to write this progress on hydrogen from production to utilizations.Finally,we believe that this roadmap on hydrogen can give some useful guidance in future research.

Reliable off-grid power supply utilizing green hydrogen

Green hydrogen produced from wind,solar or hydro power is a suitable electricity storage medium.Hydrogen is typically employed as mid-to long-term energy storage,whereas batteries cover short-term energy storage.Green hydrogen can be produced by any available electrolyser technology[alkaline electrolysis cell(AEC),polymer electrolyte membrane(PEM),anion exchange membrane(AEM),solid oxide electrolysis cell(SOEC)]if the electrolysis is fed by renewable electricity.If the electrolysis operates under elevated pressure,the simplest way to store the gaseous hydrogen is to feed it directly into an ordinary pressure vessel without any external compression.The most efficient way to generate electricity from hydrogen is by utilizing a fuel cell.PEM fuel cells seem to be the most favourable way to do so.To increase the capacity factor of fuel cells and electrolysers,both functionalities can be integrated into one device by using the same stack.Within this article,different reversible technologies as well as their advantages and readiness levels are presented,and their potential limitations are also discussed.

Hydrogen technologies and developments in Japan

The successful development of hydrogen-energy technologies has several advantages and benefits.Hydrogen-energy development could prevent global warming as well as ensure energy security for countries without adequate energy resources.The successful development of hydrogen would provide energy for transportation and electric power.It is a unique energy carrier,as it can be produced from various energy sources such as wind,fossil fuels and biomass and,when it is combusted,it emits no CO_(2)emissions.The other advantage is the wide distribution of resources globally that can be used to produce hydrogen.In Japan,the Ministry of Economy,Trade and Industry(METI)published a‘Strategic Roadmap for Hydrogen and Fuel Cells’in 2014,with a revised update published in March 2016.The goal of the roadmap is to achieve a hydrogen society.The roadmap aims to resolve technical problems and secure economic efficiency.The roadmap has been organized into the following three phases:Phase 1-Installation of fuel cells;Phase 2-Hydrogen power plant/mass supply chain;Phase 3-CO_(2)-free hydrogen.This paper reports on the current status of fuel cells and fuel-cell vehicles in Japan and gives a description and status of the R&D programmes along with the results of global energy model study towards 2050.

氢能技术及其在车用领域应用现状综述

化石燃料的快速消耗迫切地需要寻找绿色清洁的替代能源,氢能是一种来源丰富、绿色低碳、应用广泛的二次能源,具有高能量、无污染的特性,是当下重要的工业原料。本文较为全面地分析了氢能的制取与储存,并且围绕氢能在车用领域的应用,因为在碳峰值和碳中和的背景下,内燃机行业的发展正面临着最好的转型机遇。加快氢发动机关键技术的研发和应用已成为世界各国政府和各大汽车企业的重要战略。本文对比了氢燃料电池与氢燃料内燃机的特点,对未来氢能源利用的产业化前景进行了分析。

车用氢能发展难点与对策

“双碳”目标背景下,国内加快能源转型步伐,交通运输业作为第三大碳排放行业,加快向电、氢转型。分析了国内氢燃料电池汽车和加氢站的发展现状,从产业链的角度深入剖析了国内车用氢能发展的“车贵”“氢贵”“站贵”等三大痛点,认为深层次的原因是燃料电池、车辆生产和加氢站设备生产存在技术瓶颈,关键零部件仍然依赖进口,加氢站建设及运营成本高,电解水等制氢成本高等。最后,从行业发展的角度,分别提出了降低车用氢能成本的突破路径,指导行业良性发展。

基于多端口直流变压器的氢燃料电池-储能协调控制策略

面向氢燃料电池在微网领域日趋广泛的应用,依托宁波慈溪氢电耦合直流微网示范工程中的风/光/氢燃料电池直流互联系统,研究其氢燃料电池接入的核心设备——三端口直流变压器的端口功率协调控制策略。为缩短仿真时间,提出并采用了一种适用于多模块串并联多有源桥结构直流变压器的开关周期平均模型,并应用该等效简化模型提出了一种燃料电池-储能混合供电系统能量协调控制策略。该控制策略可根据储能系统荷电状态、各端口功率容量、燃料电池动态响应速度等因素对各端口功率指令进行优化调整与智能分配,避免燃料电池发电功率过快变化、储能系统过充过放,并最大化氢能发电占比。经实际样机测试与MATLABSimulink仿真验证,该协调控制策略在直流变压器的多种控制模式下均有良好的工作性能,功率控制端口的实际功率可以跟随快速变化的指令值,负荷突变时电压控制端口的实际电压波动均能控制在4%以下。