Transmission, Distribution & Storage
Electrochemical Conversion Technologies for Optimal Design of Decentralized Multi-energy Systems: Modeling Framework and Technology Assessment
Apr 2018
Publication
The design and operation of integrated multi-energy systems require models that adequately describe the behavior of conversion and storage technologies. Typically linear conversion performance or fixed data from technology manufacturers are employed especially for new or advanced technologies. This contribution provides a new modeling framework for electrochemical devices that bridges first-principles models to their simplified implementation in the optimization routine. First thermodynamic models are implemented to determine the on/off-design performance and dynamic behavior of different types of fuel cells and of electrolyzers. Then as such nonlinear models are intractable for use in the optimization of integrated systems different linear approximations are developed. The proposed strategies for the synthesis of reduced order models are compared to assess the impact of modeling approximations on the optimal design of multi-energy systems including fuel cells and electrolyzers. This allows to determine the most suitable level of detail for modeling the underlying electrochemical technologies from an integrated system perspective. It is found that the approximation methodology affects both the design and operation of the system with a significant effect on system costs and violation of the thermal energy demand. Finally the optimization and technology modeling framework is exploited to determine guidelines for the installation of the most suitable fuel cell technology in decentralized multi-energy systems. We show how the installation costs of PEMFC SOFC and MCFC their electrical and thermal efficiencies their conversion dynamics and the electricity price affect the system design and technology selection.
Intermetallic Compounds Synthesized by Mechanical Alloying for Solid-State Hydrogen Storage: A Review
Sep 2021
Publication
Hydrogen energy is a very attractive option in dealing with the existing energy crisis. For the development of a hydrogen energy economy hydrogen storage technology must be improved to over the storage limitations. Compared with traditional hydrogen storage technology the prospect of hydrogen storage materials is broader. Among all types of hydrogen storage materials solid hydrogen storage materials are most promising and have the most safety security. Solid hydrogen storage materials include high surface area physical adsorption materials and interstitial and non-interstitial hydrides. Among them interstitial hydrides also called intermetallic hydrides are hydrides formed by transition metals or their alloys. The main alloy types are A2B AB AB2 AB3 A2B7 AB5 and BCC. A is a hydride that easily forms metal (such as Ti V Zr and Y) while B is a non-hydride forming metal (such as Cr Mn and Fe). The development of intermetallic compounds as hydrogen storage materials is very attractive because their volumetric capacity is much higher (80–160 kgH2m−3 ) than the gaseous storage method and the liquid storage method in a cryogenic tank (40 and 71 kgH2m−3 ). Additionally for hydrogen absorption and desorption reactions the environmental requirements are lower than that of physical adsorption materials (ultra-low temperature) and the simplicity of the procedure is higher than that of non-interstitial hydrogen storage materials (multiple steps and a complex catalyst). In addition there are abundant raw materials and diverse ingredients. For the synthesis and optimization of intermetallic compounds in addition to traditional melting methods mechanical alloying is a very important synthesis method which has a unique synthesis mechanism and advantages. This review focuses on the application of mechanical alloying methods in the field of solid hydrogen storage materials.
Storage System of Renewable Energy Generated Hydrogen for Chemical Industry
Nov 2012
Publication
Chemical industry is the base of the value chains and has strong influence on the competitiveness of almost all branches in economics. To develop the technologies for sustainability and climate protection and at the same time to guarantee the supply of raw material is a big challenge for chemical industry. In the project CO2RRECT (CO2 - Reaction using Regenerative Energies and Catalytic Technologies) funded by the German federal ministry of Education and Research carbon dioxide is used as the source of carbon for chemical products with certain chemical processes. Hydrogen that is needed in these processes is produced by electrolyzing water with renewable energy. To store a large amount of hydrogen different storage systems are studied in this project including liquid hydrogen tanks/cryo tanks high pressure tanks pipelines and salt cavities. These systems are analyzed and compared considering their storage capacity system costs advantages and disadvantages. To analyze capital and operational expenditure of the hydrogen storage systems a calculation methodology is also developed in this work.
Global Trade of Hydrogen: What is the Best Way to Transfer Hydrogen Over Long Distances?
Aug 2022
Publication
As a manufactured fuel hydrogen can be produced in a decentralized way in most countries around the world. This means even in a net zero economy the global trade of hydrogen could look quite different to the current international trade in fossil fuels including natural gas. With further declines in the costs of renewable electricity and electrolyzers regions which have lower cost renewable electricity may develop an economic advantage in the production of low-cost hydrogen but for hydrogen to become a globally traded commodity the cost of imports needs to be lower than the cost of domestic production. Unlike oil or natural gas transporting hydrogen over long distances is not an easy task. Hydrogen liquefaction is an extremely energy-intensive process while maintaining the low temperature required for long-distance transportation and storage purposes results in additional energy losses and accompanying costs. The upside is that hydrogen can be converted into multiple carriers that have a higher energy density and higher transport capacity and can potentially be cheaper to transport over long distances. Among the substances currently identified as potential hydrogen carriers suitable for marine shipping liquid ammonia the so-called ‘liquid organic hydrogen carriers’ in general (toluene-methylcyclohexane (MCH) in particular) and methanol have received the most attention in recent years. This paper compares the key techno-economic characteristics of these potential carriers with that of liquified hydrogen in order to develop a better understanding of the ways in which hydrogen could be transported overseas in an efficient manner. The paper also discusses other factors beyond techno-economic features that may affect the choice of optimum hydrogen carrier for long distance transport as well as the global trade of hydrogen.
Hydrogen Stress Cracking Behaviour in Dissimilar Welded Joints of Duplex Stainless Steel and Carbon Steel
Jun 2021
Publication
As the need for duplex stainless steel (DSS) increases it is necessary to evaluate hydrogen stress cracking (HSC) in dissimilar welded joints (WJs) of DSS and carbon steel. This study aims to investigate the effect of the weld microstructure on the HSC behaviour of dissimilar gas-tungsten arc welds of DSS and carbon steel. In situ slow-strain rate testing (SSRT) with hydrogen charging was conducted for transverse WJs which fractured in the softened heat-affected zone of the carbon steel under hydrogen-free conditions. However HSC occurred at the martensite band and the interface of the austenite and martensite bands in the type-II boundary. The band acted as an HSC initiation site because of the presence of a large amount of trapped hydrogen and a high strain concentration during the SSRT with hydrogen charging. Even though some weld microstructures such as the austenite and martensite bands in type-II boundaries were harmless under normal hydrogen-free conditions they had a negative effect in a hydrogen atmosphere resulting in the premature rupture of the weld. Eventually a premature fracture occurred during the in situ SSRT in the type-II boundary because of the hydrogen-enhanced strain-induced void (HESIV) and hydrogen-enhanced localised plasticity (HELP) mechanisms.
Hydrogen Storage in Geological Formations—The Potential of Salt Caverns
Jul 2022
Publication
Hydrogen-based technologies are among the most promising solutions to fulfill the zero-emission scenario and ensure the energy independence of many countries. Hydrogen is considered a green energy carrier which can be utilized in the energy transport and chemical sectors. However efficient and safe large-scale hydrogen storage is still challenging. The most frequently used hydrogen storage solutions in industry i.e. compression and liquefaction are highly energy-consuming. Underground hydrogen storage is considered the most economical and safe option for large-scale utilization at various time scales. Among underground geological formations salt caverns are the most promising for hydrogen storage due to their suitable physicochemical and mechanical properties that ensure safe and efficient storage even at high pressures. In this paper recent advances in underground storage with a particular emphasis on salt cavern utilization in Europe are presented. The initial experience in hydrogen storage in underground reservoirs was discussed and the potential for worldwide commercialization of this technology was analyzed. In Poland salt deposits from the north-west and central regions (e.g. Rogóźno Damasławek Łeba) are considered possible formations for hydrogen storage. The Gubin area is also promising where 25 salt caverns with a total capacity of 1600 million Nm3 can be constructed.
Numerical Modelling of H2 Storage with Cushion Gas of CO2 in Subsurface Porous Media: Filter Effects of CO2 Solubility
Jun 2022
Publication
The central objective of this study is to improve the understanding of flow behaviour during hydrogen (H2) storage in subsurface porous media with a cushion gas of carbon dioxide (CO2). In this study we investigate the interactions between various factors driving the flow behaviour including the underlying permeability heterogeneity viscous instability and the balance between the viscous and gravity forces. In particular we study the impact of CO2 solubility in water on the level of H2 purity. This effect is demonstrated for the first time in the context of H2 storage. We have performed a range of 2D vertical cross-sectional simulations at the decametre scale with a very fine cell size (0.1 m) to capture the flow behaviour in detail. This is done since it is at this scale that much of the mixing between injected and native fluids occurs in physical porous media. It is found that CO2 solubility may have different (positive and negative) impacts on the H2 recovery performance (i.e. on the purity of the produced H2) depending on the flow regimes in the system. In the viscous dominated regime the less viscous H2 may infiltrate and bypass the cushion gas of CO2 during the period of H2 injection. This leads to a quick and dramatic reduction in the H2 purity when back producing H2 due to the co-production of the previously bypassed CO2. Interestingly the impurity levels in the H2 are much less severe in the case when CO2 solubility in water is considered. This is because the bypassed CO2 will redissolve into the water surrounding the bypassed zones which greatly retards the movement of CO2 towards the producer. In the gravity dominated scenario H2 accumulates at the top of the model and displaces the underlying cushion gas in an almost piston-like fashion. Approximately 58% of H2 can be recovered at a purity level above 98% (combustion requirements by ISO) in this gravity-dominated case. However when CO2 solubility is considered the H2 recovery performance is slightly degraded. This is because the dissolved CO2 is also gradually vaporised during H2 injection which leads to an expansion of mixing zone of CO2 and H2. This in turn reduces the period of high H2 purity level (>98%) during back-production.
Mathematical Modeling of Unstable Transport in Underground Hydrogen Storage
Apr 2015
Publication
Within the framework of energy transition hydrogen has a great potential as a clean energy carrier. The conversion of electricity into hydrogen for storage and transport is an efficient technological solution capable of significantly reducing the problem of energy shortage. Underground hydrogen storage (UHS) is the best solution to store the large amount of excess electrical energy arising from the excessive over-production of electricity with the objective of balancing the irregular and intermittent energy production typical of renewable sources such as windmills or solar. Earlier studies have demonstrated that UHS should be qualitatively identical to the underground storage of natural gas. Much later however it was revealed that UHS is bound to incur peculiar difficulties as the stored hydrogen is likely to be used by the microorganisms present in the rocks for their metabolism which may cause significant losses of hydrogen. This paper demonstrates that besides microbial activities the hydrodynamic behavior of UHS is very unique and different from that of a natural gas storage.
Emerging Electrochemical Energy Conversion and Storage Technologies
Sep 2014
Publication
Electrochemical cells and systems play a key role in a wide range of industry sectors. These devices are critical enabling technologies for renewable energy; energy management conservation and storage; pollution control/monitoring; and greenhouse gas reduction. A large number of electrochemical energy technologies have been developed in the past. These systems continue to be optimized in terms of cost life time and performance leading to their continued expansion into existing and emerging market sectors. The more established technologies such as deep-cycle batteries and sensors are being joined by emerging technologies such as fuel cells large format lithium-ion batteries electrochemical reactors; ion transport membranes and supercapacitors. This growing demand (multi-billion dollars) for electrochemical energy systems along with the increasing maturity of a number of technologies is having a significant effect on the global research and development effort which is increasing in both in size and depth. A number of new technologies which will have substantial impact on the environment and the way we produce and utilize energy are under development. This paper presents an overview of several emerging electrochemical energy technologies along with a discussion some of the key technical challenges.
Metal Hydroborates: From Hydrogen Stores to Solid Electrolyte
Nov 2021
Publication
The last twenty years of an intense research on metal hydroborates as solid hydrogen stores and solid electrolytes are reviewed. It is shown that from the most promising application in hydrogen storage due to their high gravimetric and volumetric capacities the focus has moved to solid electrolytes due to high cation mobility in disordered structures with rotating or tumbling anions-hydroborate clusters. Various strategies of overcoming the strong covalent bonding of hydrogen in hydroborates for hydrogen storage and disordering their structures at room temperature for solid electrolytes are discussed. The important role of crystal chemistry and crystallography knowledge in material design can be read in the cited literature.
Quantitative Monitoring of the Environmental Hydrogen Embrittlement of Al-Zn-Mg-based Aluminum Alloys via Dnyamic Hydrogen Detection and Digital Image Correlation
Mar 2021
Publication
In this study a novel analytical system was developed to monitor the environmental hydrogen embrittlement of Al-Zn-Mg-based aluminum alloys dynamically and quantitatively under atmospheric air pressure. The system involves gas chromatography using a SnO2-based semiconductor hydrogen sensor a digital image correlation step and the use of a slow strain rate testing machine. Use of this system revealed that hydrogen atoms are generated during the plastic deformation of Al-Zn-Mg alloys caused by the chemical reaction between the water vapor in air and the alloy surface without oxide films. Digital image correlation also clarified that the generated hydrogen atoms caused numerous localized grain boundary cracks on the specimen surface resulting in a localized grain boundary fracture. The amount of hydrogen atoms evolved from the embrittled fracture surface was 2.7 times as high as that from the surface without embrittlement.
A Numerical and Graphical Review of Energy Storage Technologies
Dec 2014
Publication
More effective energy production requires a greater penetration of storage technologies. This paper takes a looks at and compares the landscape of energy storage devices. Solutions across four categories of storage namely: mechanical chemical electromagnetic and thermal storage are compared on the basis of energy/power density specific energy/power efficiency lifespan cycle life self-discharge rates capital energy/power costs scale application technical maturity as well as environmental impact. It’s noted that virtually every storage technology is seeing improvements. This paper provides an overview of some of the problems with existing storage systems and identifies some key technologies that hold promise.
Investigation on the Changes of Pressure and Temperature in High Pressure Filling of Hydrogen Storage Tank
May 2022
Publication
Hydrogen as fuel has been considered as a feasible energy carry and which offers a clean and efficient alternative for transportation. During the high pressure filling the temperature in the hydrogen storage tank (HST) may rise rapidly due to the hydrogen compression. The high temperature may lead to safety problem. Thus for fast and safely refueling the hydrogen several key factors need to be considered. In the present study by the thermodynamics theories a mathematical model is established to simulate and analyze the high pressure filling process of the storage tank for the hydrogen station. In the analysis the physical parameters of normal hydrogen are introduced to make the simulation close to the actual process. By the numerical simulation for 50 MPa compressed hydrogen tank the temperature and pressure trends during filling are obtained. The simulation results for non-adiabatic filling were compared with the theoretically calculated ones for adiabatic conditions and the simulation results for non-adiabatic filling were compared with the simulation ones for adiabatic conditions. Then the influence of working pressure initial temperature mass flow rate initial pressure and inlet temperature on the temperature rise were analyzed. This study provides a theoretical research basis for high pressure hydrogen energy storage and hydrogenation technology.
New Insights into Hydrogen Uptake on Porous Carbon Materials via Explainable Machine Learning
Apr 2021
Publication
To understand hydrogen uptake in porous carbon materials we developed machine learning models to predict excess uptake at 77 K based on the textural and chemical properties of carbon using a dataset containing 68 different samples and 1745 data points. Random forest is selected due to its high performance (R2 > 0.9) and analysis is performed using Shapley Additive Explanations (SHAP). It is found that pressure and Brunauer-Emmett-Teller (BET) surface area are the two strongest predictors of excess hydrogen uptake. Surprisingly this is followed by a positive correlation with oxygen content contributing up to ∼0.6 wt% additional hydrogen uptake contradicting the conclusions of previous studies. Finally pore volume has the smallest effect. The pore size distribution is also found to be important since ultramicropores (dp < 0.7 nm) are found to be more positively correlated with excess uptake than micropores (dp < 2 nm). However this effect is quite small compared to the role of BET surface area and total pore volume. The novel approach taken here can provide important insights in the rational design of carbon materials for hydrogen storage applications.
Hydrogen as a Long-Term Large-Scale Energy Storage Solution to Support Renewables
Oct 2018
Publication
This paper presents a case study of using hydrogen for large-scale long-term storage application to support the current electricity generation mix of South Australia state in Australia which primarily includes gas wind and solar. For this purpose two cases of battery energy storage and hybrid battery-hydrogen storage systems to support solar and wind energy inputs were compared from a techno-economical point of view. Hybrid battery-hydrogen storage system was found to be more cost competitive with unit cost of electricity at $0.626/kWh (US dollar) compared to battery-only energy storage systems with a $2.68/kWh unit cost of electricity. This research also found that the excess stored hydrogen can be further utilised to generate extra electricity. Further utilisation of generated electricity can be incorporated to meet the load demand by either decreasing the base load supply from gas in the present scenario or exporting it to neighbouring states to enhance economic viability of the system. The use of excess stored hydrogen to generate extra electricity further reduced the cost to $0.494/kWh.
Techno-economic Evaluation on a Hybrid Technology for Low Hydrogen Concentration Separation and Purification from Natural Gas Grid
Jul 2020
Publication
Hydrogen can be stored and distributed by injecting into existing natural grids then at the user site separated and used in different applications. The conventional technology for hydrogen separation is pressure swing adsorption (PSA). The recent NREL study showed the extraction cost for separating hydrogen from a 10% H2 stream with a recovery of 80% is around 3.3e8.3 US$/kg. In this document new system configurations for low hydrogen concentration separation from the natural gas grid by combining novel membrane-based hybrid technologies will be described in detail. The focus of the manuscript will be on the description of different configurations for the direct hydrogen separation which comprises a membrane module a vacuum pump and an electrochemical hydrogen compressor. These technological combinations bring substantial synergy effect of one another while improving the total hydrogen recovery purity and total cost of hydrogen. Simulation has been carried out for 17 different configurations; according to the results a configuration of two-stage membrane modules (in series) with a vacuum pump and an electrochemical hydrogen compressor (EHC) shows highest hydrogen purity (99.9997%) for 25 kg/day of hydrogen production for low-pressure grid. However this configuration shows a higher electric consumption (configuration B) due to the additional mechanical compressor between the two-stage membrane modules and the EHC. Whereas when the compressor is excluded and a double skin Pd membrane (PdDS) module is used in a single stage while connected to a vacuum pump (configuration A5) the hydrogen purity (99.92%) slightly decreases yet the power consumption considerably improves (1.53 times lower). Besides to these two complementary configurations the combination of a single membrane module a vacuum pump and the electrochemical compressor has been also carried out (configuration A) and results show that relatively higher purity can be achieved. Based on four master configurations this document presents a different novel hybrid system by integrating two to three technologies for hydrogen purification combined in a way that enhances the strengths of each of them.
Introducing Power-to-H3: Combining Renewable Electricity with Heat, Water and Hydrogen Production and Storage in a Neighbourhood
Oct 2019
Publication
In the transition from fossil to renewable energy the energy system should become clean while remaining reliable and affordable. Because of the intermittent nature of both renewable energy production and energy demand an integrated system approach is required that includes energy conversion and storage. We propose a concept for a neighbourhood where locally produced renewable energy is partly converted and stored in the form of heat and hydrogen accompanied by rainwater collection storage purification and use (Power-to-H3). A model is developed to create an energy balance and perform a techno-economic analysis including an analysis of the avoided costs within the concept. The results show that a solar park of 8.7 MWp combined with rainwater collection and solar panels on roofs can supply 900 houses over the year with heat (20 TJ) via an underground heat storage system as well as with almost half of their water demand (36000m3) and 540 hydrogen electric vehicles can be supplied with hydrogen (90 tonnes). The production costs for both hydrogen (8.7 €/kg) and heat (26 €/GJ) are below the current end user selling price in the Netherlands (10 €/kg and 34 €/GJ) making the system affordable. When taking avoided costs into account the prices could decrease with 20–26% while at the same time avoiding 3600 tonnes of CO2 a year. These results make clear that it is possible to provide a neighbourhood with all these different utilities completely based on solar power and rainwater in a reliable affordable and clean way.
NewGasMet - Flow Metering of Renewable Gases (Biogas, Biomethane, Hydrogen, Syngas and Mixtures with Natural Gas): Report on the Impact of Renewable Gases, and Mixtures with Natural Gas, on the Accuracy, Cost and Lifetime of Gas Meters
May 2022
Publication
For the usage of domestic gas meters with combustible gases like hydrogen natural gas or mixtures of hydrogen and natural gas in public grids the metrological behaviour of the gas meters has to fulfil the requirements described in the Measuring Instrument Directive (MID). The MID requires also that a measuring instrument shall be suitable for the application. The tightness of a meter is required in order to obtain correct results in case of accuracy tests but also for an application in the grid or for durability tests to avoid risks such as explosive gas mixtures. Due to the different properties of renewable gases leak tightness to one gas mixtures does not necessarily imply leak tightness for other gases. Hydrogen molecules are smaller than those in conventional natural gas which can more easily result in a gas leakage. The EMPIR project NEWGASMET includes beside metrological investigations also a durability test with hydrogen. In order to carry out these activities but also for further hydrogen leakage investigations for instance the investigation of proper seal materials used in the gas meter installation a reliable gas tightness test was developed.
Reversible Hydrogenation of AB2-type Zr–Mg–Ni–V Based Hydrogen Storage Alloys
Feb 2021
Publication
The development of hydrogen energy is hindered by the lack of high-efficiency hydrogen storage materials. To explore new high-capacity hydrogen storage alloys reversible hydrogen storage in AB2-type alloy is realized by using A or B-side elemental substitution. The substitution of small atomic-radius element Zr and Mg on A-side of YNi2 and partial substitution of large atomic-radius element V on B-side of YNi2 alloy was investigated in this study. The obtained ZrMgNi4 ZrMgNi3V and ZrMgNi2V2 alloys remained single Laves phase structure at as-annealed hydrogenated and dehydrogenated states indicating that the hydrogen-induced amorphization and disproportionation was eliminated. From ZrMgNi4 to ZrMgNi2V2 with the increase of the degree of vanadium substitution the reversible hydrogen storage capacity increased from 0.6 wt% (0.35H/M) to 1.8 wt% (1.0H/M) meanwhile the lattice stability gradually increased. The ZrMgNi2V2 alloy could absorb 1.8 wt% hydrogen in about 2 h at 300 K under 4 MPa H2 pressure and reversibly desorb the absorbed hydrogen in approximately 30 min at 473 K without complicated activation process. The prominent properties of ZrMgNi2V22 elucidate its high potential for hydrogen storage application.
Reliable Off-grid Power Supply Utilizing Green Hydrogen
Jun 2021
Publication
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.
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