Metal Hydride Hydrogen Compressor Research Articles

Optimization of Ti-Zr-Cr-Fe alloys for 45 MPa metal hydride hydrogen compressors using orthogonal analysis

A series of (Ti1-xZrx)yCr2-zFez (x=0.1, 0.2, 0.3; y=1, 1.05, 1.1; z=0.9, 1, 1.1) alloys has been designed by orthogonal experiments for a three-stage metal hydride hydrogen compressor. XRD results show that such alloys exist as a single C14 Laves phase, and SEM with energy-dispersive spectroscopy reveals a uniform distribution of the elements. The effects of substitution of Ti by Zr, of Cr by Fe, and over-stoichiometry on the hydrogen storage properties of the Ti-Zr-Cr-Fe alloys have been investigated by orthogonal analysis. With increasing Zr content and 2A/B ratio (1, 1.05, 1.1), the cell volume and enthalpy gradually increase, while the plateau pressure and hysteresis decrease. With increasing Fe content, the cell volume and enthalpy decrease, while the plateau pressure, plateau slope, and hysteresis all dramatically increase. The (Ti0.85Zr0.15)yCr2-zFez (y=1, 1.05, 1.1; z=0.9, 1, 1.1) alloys show the largest average hydrogen storage capacity at 1.73 wt%. Besides, a simple model is proposed to predict enthalpy, which is based on the unit cell volume and average electronegativity difference with hydrogen. Finally, the (Ti0.85Zr0.15)1.05Cr1.1Fe0.9 alloy has been selected for a three-stage metal hydride hydrogen compressor. Its maximum and usable storage capacities were evaluated as 1.75 wt% and 1.40 wt%, respectively, with a dissociation plateau pressure derived from the van’t Hoff equation of 45.5 MPa at 90 °C.

Demonstration of a single-stage metal hydride hydrogen compressor composed of BCC V40TiCr alloy

In this study, demonstration of a one-stage metal hydride hydrogen compressor (MH compressor) by using a BCC alloy was performed. It was estimated that V40Ti22Cr38 could compress approximately 1.6 wt% of hydrogen from 1.0 to 10 MPa in 20–140 °C temperature range from equilibrium theory via pressure-composition-isotherm measurements. For demonstration of an actual MH compressor, a kg-scale experimental system was set up; V40Ti22Cr38 (1.4 kg) was introduced into a 1-inch cylindrical vessel with a heat-medium flow tube outside. As a result, 1.0 MPa of hydrogen can be compressed into the hydrogen cylinder at >10 MPa by hydrogen absorption at 10 °C and desorption at 160 °C for 30 min each (1 cycle/h) to achieve a compression rate of 0.23 Nm3/h and indicate the potential of the practical MH compressors by using BCC alloy.

Investigation on Ti–Zr–Cr–Fe–V based alloys for metal hydride hydrogen compressor at moderate working temperatures

Ti0.85Zr0.17Cr1.2-xFe0.8Vx (x = 0–0.2), Ti0.85Zr0.17Cr1.2-yFe0.7+yV0.1 (y = 0–0.25) and Ti0.87-zZr0.15+zCr0.95Fe0.95V0.1 (z = 0–0.04) alloys for metal hydride hydrogen compressor at moderate working temperatures were prepared by induction levitation melting. Their microstructures and hydrogen storage properties were systematically investigated. The results show that all Ti–Zr–Cr–Fe–V based alloys have a single C14 Laves phase structure. As the V content in the Ti0.85Zr0.17Cr1.2-xFe0.8Vx (x = 0–0.2) alloys increases, better activation kinetics and larger hydrogen storage capacity are achieved, while the plateau pressure decreases and the plateau slope factor increases. Similarly, the hydrogen storage capacity, the plateau pressure and the plateau slope factor of the Ti0.87-zZr0.15+zCr0.95Fe0.95V0.1 (z = 0–0.04) alloys vary identically with Zr content increasing. Conversely, these three properties vary oppositely with increasing Fe content in the Ti0.85Zr0.17Cr1.2-yFe0.7+yV0.1 (y = 0–0.25) alloys. Among the studied alloys, Ti0.85Zr0.17Cr0.95Fe0.95V0.1 possesses the best overall properties for the designed moderate hydrogen compression application.

Study on the operation and energy demand of dual-stage Metal Hydride Hydrogen Compressors under effective thermal management

For the commercial viability of a hydrogen-based transportation, hydrogen infrastructure is key. One of the major issues of hydrogen infrastructure is related to the deployment and costs of the Hydrogen Refuelling Stations (HRSs), where up to 40% of the cost is related to hydrogen compression. The introduction of Metal Hydride Hydrogen Compressors (MHHCs) in the HRSs as compression elements is a potential technology to reduce operational costs, ensure noiseless operation and increase efficiency, if renewable-based thermal energy (and/or industrial waste heat) is supplied to the system. In this work, four different two-stage MHHCs are introduced and examined in terms of compression ratio, hydrogen flow rate (compression duration), thermal energy requirements and efficiency. In addition, for comparison purposes, a three-stage MHHC is also studied. The properties of five different materials are used for the individual compression stages of the MHHCs, where all the necessary thermodynamic properties are extracted experimentally and incorporated in a commercial Multiphysics software. The unsteady heat and mass transfer equations are employed for the development of the numerical model. The hydrogenation/dehydrogenation kinetics and the temperature profile were validated against solid experimental results. In addition, to improve and accelerate the storage/release kinetics, an internal thermal management scenario has been introduced. The results show that for compression at the temperature range of 10–90 °C, the most favourable two-stage compression case (Case 3) showed a compression ratio of 11.18 ÷ 1, an isentropic efficiency of 4.54% with a thermal energy demand of 322 kJ/molH2 and a cycle time of almost 34 min.

Alloy selection for multistage metal-hydride hydrogen compressors: A thermodynamic model

A thermodynamic model is presented to aid the selection of compatible pairs of hydrogen storage alloys for service in a multi-stage metal-hydride compressor. The model is built around the concept of an ideal compressor in which all pairs of hydrides operate between the same working temperatures. The key feature of the model is a link between the thermodynamic characteristics of the hydrides in each pair (the entropy change ΔS and enthalpy change ΔH when the hydride is formed from the metal) that results from requiring that the heated low-pressure hydride is able to desorb to the cooled high-pressure metal at a unique intermediate pressure. This necessary linking places severe constraints on the choice of alloys, since ΔS and ΔH cannot be freely chosen and are in fact strongly correlated for hydrides with similar operating temperatures. The model is based on the van ‘t Hoff relation, which is derived from first principles and shown to be only approximately valid at the high hydrogen pressures of interest for vehicle filling stations. Pressure hysteresis and plateau slope are incorporated into the model. A case study of a two-stage compressor is presented, based on the curved van ‘t Hoff line and the experimentally determined effects of pressure hysteresis and plateau slope.

Modelling of metal hydride hydrogen compressors from thermodynamics of hydrogen – Metal interactions viewpoint: Part I. Assessment of the performance of metal hydride materials

This work presents a model to determine productivity and heat consumption of hydrogen compression utilising metal hydrides (MH) by using Pressure – Composition – Temperature (PCT) diagrams of the MH materials at defined operating conditions – temperatures and hydrogen pressures. The present Part I is focused on the analysis of hydrogen compression performances of several AB5- and AB2-type intermetallic alloys which, when operating between temperatures of 20 and 150 °C, provide H2 compression up to 500 atm, with a cycle productivity about 100 NL H2/kg MH and compression ratio of up to 10, at H2 suction pressure below 10–15 atm, or up to 5 at higher suction pressures.We show that calculated cycle productivities of hydrogen compression are related to the operating conditions and significantly vary for the different MH materials, even though showing similar trends in their changes. The cycle productivity of MH material increases with decrease of the cooling temperature, decrease of the discharge pressure, increase of the heating temperature and increase of the suction pressure. When hydrogen pressure approaches plateau pressures for H2 absorption at cooling or H2 desorption at heating, the changes of the cycle productivity become very pronounced. Particularly, the compression productivity becomes very sensitive to the P-T variations when the isotherms show presence of “flat” pressure plateaux which are characteristic for the ideal PCT diagrams of the MH. Thus, in the latter case, even minor changes in P-T result in a dramatic variation of the cycle productivity and when aiming at increased efficiency of the process, a strict P-T control is required.

Modelling of metal hydride hydrogen compressors from thermodynamics of hydrogen – Metal interactions viewpoint: Part II. Assessment of the performance of metal hydride compressors

Performance of the thermally-driven metal hydride hydrogen compressor (MHHC) is defined by (a) its H2 compression ratio and maximum output H2 pressure; (b) throughput productivity/average output flow rate; (c) specific thermal energy consumption which determines H2 compression efficiency. In earlier studies, the focus of the R&D efforts was on the optimisation of the design of the MH containers and heat and mass transfer in the MH storage and compression system aimed at shortening the time of the H2 compression cycle. This work considers an important but insufficiently studied aspect of the development of the industrial-scale thermally driven MHHC's – selection of the materials and optimisation of the materials performance. Further to the operation in the specified pressure/temperature ranges, materials selection should be based on the estimation of the productivity of the compression cycle, and specific heat consumption required for the H2 compression, which together determine the process efficiency.The current work presents a model to determine productivity and heat consumption for a single- and multi-stage MHHC's which is based on use of Pressure – Composition – Temperature (PCT) diagrams of the utilized metal hydrides at defined operating conditions – temperatures and hydrogen pressures – and main operational features of the MHHC (number of stages, amounts of the MH materials used, cycle time). In Part I of this work [Lototskyy, Yartys, et al., Int J Hydrogen Energy, DOI: 10.1016/j.ijhydene.2020.10.090], we showed that the calculated cycle productivities significantly vary for the different materials. Analysis of the system performance carried out in this work (Part II) shows that the throughput productivity and efficiency of a multi-stage MHHC also depends on the types and amounts of the used MH materials in the multi-stage compressor layout. This has been analysed for a number of the most practically important AB5 and Laves type AB2 hydrogen storage alloys integrated into the MHHC's.A comparison of experimentally measured performances of single-, two- and three-stage industrial-scale MHHC's developed by the authors earlier shows their satisfactory agreement with the modelling results thus demonstrating a high value of the presented method for the proper materials selection during development of the MHHC. As an important future development, the work presents a performance evaluation of a two-stage MHHC for H2 compression operating in the pressure range from 30 to 500 atm at operating temperatures between 20 and 150 °C.

МЕТАЛОГІДРИДНИЙ АКУМУЛЯТОР-КОМПРЕСОР ВОДНЮ З АВТОМАТИЧНОЮ СИСТЕМОЮ УПРАВЛІННЯ ТА КОНТРОЛЮ

A project of metal hydride hydrogen compressor is presented, which can be used as an element of refueling complexes, hydrogen storage and compression systems. The capacity of the developed sample is 40 kg of hydrogen, the mass is 4,8 ton, and the maximum compression pressure is 15 MPa. The base metal hydride material on the basis of which this compressor battery model is developed is LaNi4.5Al0.5. the sorption capacity of hydrogen of which is determined experimentally, and is at least 1.38 % by weight. A feature of the developed compressor battery is the use of air cooling, the presence of an automatic monitoring and control system, I allow a number of operations to be performed in automatic mode, and the use of software, electrical and automatic protection against overpressure. Each accumulator-compressor is made in the form of a steel box in which six blocks (capsules) are placed. The block, respectively, is made in the form of a steel coaxial multilayer cylinder, on the outer side of which there is a heating element and a layer of thermal insulation. In the middle of the cylinder is a sealed capsule filled with metal hydride material. Capsules are interconnected with the collector through a piping system. Also, the piping system is equipped with an inlet valve connecting the volume formed with an external receiver. The battery-compressor is equipped with an external receiver, to which a hydrogen, vacuum, nutrient and consumable outline is connected. Each circuit is equipped with an electromagnetic valve, as well as measuring devices, which makes it possible to carry out automatic control of parameters and automatic control of the device in accordance with the operating mode. A list of equipment is presented, on the basis of which a system of automatic control and monitoring, a block diagram of the main operating modes, an interface of the developed software are developed. Depending on the mode chosen by the operator, the automatic control and monitoring system allows activation of metal hydride materials, purification of contaminants of harmful impurities, sorption and desorption of hydrogen.

Experimental behaviour of a three-stage metal hydride hydrogen compressor

A three-stage metal hydride hydrogen compressor (MHHC) system based in AB2-type alloys has been set-up. Every stage can be considered as a Sieverts-type apparatus. The MHHC system can work in the pressure and temperature ranges comprised from vacuum to 250 bar and from RT to 200 °C, respectively. An efficient thermal management system was set up for the operational ranges of temperature desired. It drops temperature shifts due to hydrogen expansion during stage coupling and hydrogen absorption/desorption in the alloys. Each reactor consists of a single and thin stainless-steel tube to maximize heat transfer. These were filled with similar amount of AB2 alloy. The MHHC system was able to produce a compression ratio as high as 84.7 for inlet and outlet hydrogen pressures of 1.44 and 122 bar for a temperature span of 23 °C – 120 °C.

Metal hydride hydrogen compressors for energy storage systems: layout features and results of long-term tests

This work summarises the results of development and long-term testing of two prototype models of industrial-scale metal-hydride thermal sorption hydrogen compressors, TSC1-3.5/150 (up to 11 Nm3 h−1; water cooling/steam heating) and TSC2-3.5/150 (up to 15 Nm3 h−1; heating and cooling by circulating oil). Both compressors have a two-stage layout utilising LaNi5 for the stage 1 and La0.5Ce0.5Ni5 for stage 2, thus providing hydrogen compression from 0.35 to 15 MPa at a cooling temperature of about 20 °C and a heating temperature between 150 °C and 160 °C. The compressors were operating for one year each and exhibited a satisfactory performance. The results of this work can be used in various medium-to-large scale hydrogen compression applications, including renewable energy systems.

Numerical investigation on the operation and energy demand of a seven-stage metal hydride hydrogen compression system for Hydrogen Refuelling Stations

In the present work, a numerical analysis on the performance of a seven-stage metal hydride hydrogen compression (MHHC) system is introduced, presented and discussed. The operation efficiency and cost along with the reliability of hydrogen compression is of great importance for the future commercial availability of Hydrogen Refuelling Stations (HRS); thus, significant improvements in hydrogen compression must be achieved and novel methods and approaches are being investigated in that respect. MHHC's offer distinct advantages over conventional mechanical compressors and the present paper aims at contributing to the efficient design and upscaling of such device via advanced numerical simulations of a seven-stage MHHC. The numerical model was supported by and validated with solid experimental data. Furthermore, several different operational temperature ranges for the compressor were examined and the importance of the proper operation conditions is discussed in terms of temperature evolution, pressure profile, cycle duration, compression ratio, thermal energy demand and efficiency.

Analysis of the Design Calculation of a Membrane-Catalytic Converter for Producing High-Purity Hydrogen from Biodiesel Fuel

The results of the verification confirmed the main parameters of the design calculation of a membrane catalytic converter for the production of high-purity hydrogen from the products of steam reforming of biodiesel fuel. A technological regime is suggested for excluding the deposition of carbon and removing hydrogen-product under vacuum using a metal hydride hydrogen compressor.

Development of a high-pressure Ti-Mn based hydrogen storage alloy for hydrogen compression

This work focuses on the selection and development of high-pressure Ti-Mn based alloy for a domestic 2-stage Metal Hydride Hydrogen Compressor (MHHC) capable of compressing hydrogen from 15 bar to over 350 bar with a maximum operating temperature of 130 °C. Thermodynamic, kinetics and hydrogen storage characteristics of Ti-Mn based alloy were shown to be very sensitive to the alloy's composition. Stability of the hydride phase could be significantly reduced by increasing the Mn content of the alloy and contracting the C14 Laves phase unit cell volume, therefore meeting the required thermodynamic for the target MHHC. The structure and hydrogen capacity of the alloy remained almost constant even after 1000 hydrogen absorption and desorption cycles at room temperature. A significant reduction in the hydrogen absorption plateau slope of the modified high-pressure alloy was achieved by increasing the C14 Laves phase proportion. As a result, effective improvement in the hydrogen sorption kinetics of the modified alloy was observed with most of the hydrogen ab/desorbed in less than 5 min. Although compositional modification showed to be beneficial for lowering the hydrogen absorption plateau slope in high-pressure alloys, the level of hysteresis seemed to be mainly dominated by the alloys thermodynamic.

Numerical and experimental study of heat-and-mass transfer processes in two-stage metal hydride hydrogen compressor

This work presents a hybrid model for the simulation of heat and mass transfer in metal hydride (MH) reactors. The model combines “lumped” approach based on mass and energy conservation for the gas phase with detailed consideration of the heat and mass exchange processes in the solid. The developed calculation procedure was realised numerically and integrated in a combined model of a two-stage MH hydrogen compressor (MHHC). Experimental validation based on the data available in the literature, the results of testing two types of MH reactors for H2 compression, as well as a small-scale two-stage MHHC, demonstrated the qualitative and quantitative agreement of calculated and experimentally measured dependencies.

Metal hydride hydrogen compressors: Current developments & early markets

Abstract Compression is one of the most critical issues related to almost all hydrogen storage methods and its subsequent usage. Hydrogen compression is only part of the so-called “Hydrogen Value Chain”, but it is crucial for overcoming the entry barriers for a “Hydrogen Economy”. It is widely accepted that there is a strong need for significant improvements in efficiency, durability and reliability of hydrogen compressors as well as for cost reductions, The basic scope of this work is to present the current developments on Metal Hydride Hydrogen Compressors (MH2C) and try to evaluate from both technical and economical point of view the potential integration of MH2C in real power systems comprising Renewable Energy Sources and Hydrogen technologies. In this work, certain target markets for the MH2 compressor are identified, while all technical and financial issues of its integration in complete power systems have been assessed. Through a preliminary analysis of potential markets for the MH2 Compressor, it is shown that there are three major niche markets: (i) Chemical industry, by utilisation of waste industrial and/or available renewable heat; (ii) Hydrogen filling stations for vehicles and (iii) RES & H2 autonomous power systems for remote communities (e.g. off-grid islands). A specific case study (the Greek island of Milos) is analysed in detail (using the HOMER software tool) with the aim of increasing RES penetration. A RES & hydrogen storage power supply system is proposed and examined from an economic, environmental and social perspective drawing the relevant conclusions.

Simulation and design of a three-stage metal hydride hydrogen compressor based on experimental thermodynamic data

A semi-empirical method was developed to design a three stage Metal Hydride Hydrogen Compressor (MHHC) through the determination of thermodynamic properties of several hydrides. As a first step, three AB2-type alloys that satisfy operation conditions were selected from published thermodynamic data entailing over 200 single plateau hydrides. These alloys were synthetized by arc melting and characterized by X-Ray Powder Diffraction (XRPD), Scanning Electron Microscopy (SEM) and Energy Dispersion X-ray spectroscopy (EDX). Absorption and desorption Pressure-composition-Isotherms (P-c-I) were determined between 23 and 80 °C to characterize their thermodynamic properties. Subsequently, an algorithm that uses these experimental data and a real equation of state for gaseous H2 was implemented to simulate the volume, alloy mass, pressure and temperature of operation for each compressor stage, while optimizing the compression ratio and total number of compressed H2 moles. Optimal desorption temperatures for the three stages were identified within the range of 110–132 °C. A system compression ratio (CR) of 92 was achieved. The number of H2 moles compressed, the alloy mass and volume of each stage depend linearly on the volume of the external tank in which the hydrogen is delivered.

Cycling stability of RNi5 (R = La, La+Ce) hydrides during the operation of metal hydride hydrogen compressor

This work presents results of the experimental studies (XRD, SEM, PCT) of hydride forming intermetallides used in the first (LaNi5) and the second (La0.5Ce0.5Ni5) stages of industrial-scale metal hydride hydrogen compressor providing H2 compression from 3.5 to 150 atm with the productivity about 10 Nm3/h. During the operation, both materials underwent 18,180 hydrogenation/dehydrogenation (h/d) cycles which included H2 absorption at the pressure of 3.5 atm (LaNi5) and 35–38 atm (La0.5Ce0.5Ni5) at T = 15–20 °C followed by H2 desorption at the pressure of 35–38 atm (LaNi5) and 150 atm (La0.5Ce0.5Ni5) at T = 150–160 °C. It was found that the observed ∼30% drop of the productivity of the compressor by the end of its operation is associated with a degradation of the first stage hydride material (LaNi5) under conditions specified above. The cycling resulted in the appearance of Ni and LaH2+x phases in addition to the parent intermetallide. In turn, the cycled LaNi5 exhibited more than 20% lower hydrogen storage capacity than the alloy at the beginning of the cycling; the cycling was also found to result in a noticeable sloping of initially flat plateau. Conversely, the degradation effects in La0.5Ce0.5Ni5 were found to be much less pronounced, in spite of the higher operating H2 pressures. The observed effect was associated with the decrease of thermodynamic driving force (TDF) of AB5 disproportionation in H2 when substituting La with Ce.

Industrial-scale metal hydride hydrogen compressors developed at the South African Institute for Advanced Materials Chemistry

This work provides an overview of R&D activities at South African Institute for Advanced Materials Chemistry (SAIAMC) on metal hydride hydrogen compression technology with a focus on engineering solutions for industrial-scale applications. A summary of layout features, as well as test / operation results are presented for industrial-scale prototypes of: (i) 1-stage H2 compressor for refueling station (50–200 bar, up to 13 Nm3/h), and (ii) 3-stage H2 compressor (3–200 bar, up to 5 Nm3/h). The developed systems provide hydrogen compression utilizing low-grade steam (T=120–140 °C) and cooling water (T=15–25 °C) available at sites of industrial customers.

Technical Performance of a Hybrid Thermo-Electrochemical System for High Pressure Hydrogen Compression

A novel alternative to high-pressure mechanical hydrogen compression has been proposed. The alternative technology employs a two-stage, hybrid, thermo-electrochemical system based on electrochemical and metal hydride hydrogen compression technologies. A technical analysis was performed to evaluate the performance of both the electrochemical low-pressure stage (100 bar) and the metal hydride high-pressure stage (875 bar). The performance of several membrane and metal hydride candidate materials was evaluated and the best candidate materials were identified. A model of the integrated, two-stage system was developed that found that all or most of the waste heat from the electrochemical stage can be used to fully drive the metal hydride stage, thereby, improving the overall efficiency of the combined process.

Numerical analysis of candidate materials for multi-stage metal hydride hydrogen compression processes

A numerical study on multistage metal hydride hydrogen compression (MHHC) systems is presented and analyzed. Multistage MHHC systems use a combination of different materials to increase the final compression ratio at the end of the compression process. In the current work a numerical model is proposed to describe the operation of a complete three-stage MHHC cycle, which can be divided in seven steps (for a three-stage compression system): first stage hydrogenation process, sensible heating of first stage, coupling process between the first and the second stage, sensible heating of the second stage, second coupling with the upcoming sensible heating of the third stage material and finally the delivery of high pressure hydrogen to a high pressure hydrogen tank. Three scenarios concerning the combination of different materials for the compression stages are introduced and analyzed in terms of maximum compression ratio, cycle time and energy consumption. According to the results, the combination of LaNi5 (stage 1), MmNi4.6Al0.4 (stage 2) and a novel synthesized AB2-Laves phase intermetallic (stage 3) present a compression ratio 22:1 while operating between 20 and 130 °C.