This short review discusses the classification, pressure concentration isotherm (PCI) characterisation and applications of metal hydrides. Special attention is paid to describe the design criterion and fabrication of Sievert's apparatus and PCI characterisation methods of metal hydrides. Different classes of metal hydrides and their properties are broadly discussed. Also, some of the important applications of metal hydrides are presented. The absorption and desorption PCIs of four Lanthanum based alloys namely La0.9Ce0.1Ni5, La0.8Ce0.2Ni5, LaNi4.7Al0.3 and LaNi4.6Al0.4 are measured using volumetric method in the temperature range of 20 to 80 °C. Later, different PCI simulation models are compared, and Zhou's model is used to simulate the experimentally measured PCIs at different temperatures. It is found that the simulation results are in good agreement with the experimentally measured results. Copyright © 2016 John Wiley &amp; Sons, Ltd. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Vinod Kumar Sharma

Department of Thermal and Energy Engineering

School of Mechanical Engineering

Vellore Campus

Anil Kumar E.

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

International Journal of Energy Research

A novel high entropy alloy (HEA) i.e. AlCrFeMnNiW is synthesized via high-energy planetary ball milling with an average crystallite size of 10.37 nm. The morphology study of hydrogenated and dehydrogenated HEA is carried out through Scanning Electron Microscope (SEM). The HEA is charged with hydrogen using inhouse Sievert's Apparatus which results to be maximum hydrogen storage capacity of 0.615 wt% at atmospheric pressure and temperature. The dehydrogenation of the sample is performed through thermogravimetry (TG) at different scanning rate. The crystalline structure (i.e. lattice parameters) and chemical composition of HEA is studied using X-Ray Diffraction (XRD) and Energy Dispersive X-Ray analysis (EDX) respectively. The unit cell volume of as-prepared alloy is estimated as 0.03131 nm3 whereas the average crystallite size as 10.37 nm. It is observed that the unit cell volume is increased by 0.67% and crystallite size decreased by 10.8% upon hydrogenation whereas it is then decreased by 0.2% and increased by 6.7% respectively upon dehydrogenation. Activation energy during hydrogen desorption is found to be −8.161 kJ/mol. The enthalpy and entropy of the mixing are estimated to be −2.645 kJ/mol and 1.793 R J/mol K. © 2019 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Synthesis and characterization of hydrogenated novel AlCrFeMnNiW high entropy alloy

The requirement of simultaneous heating and cooling effects at different zones of a building demands for the development of an energy-efficient air-conditioning system for heating and cooling outputs. In order to fulfil this requirement, a novel multistage hydrogen-alloy–based sorption heat pump (H-A SHP) for space air-conditioning is proposed in the present work. The proposed system produces multiple cooling and heating outputs at 20°C and 45°C, respectively, with single heat input at 160°C. A set of MmNi5, La0.8Ce0.2Ni5, MmNi4.4Al0.6, and LaNi4.6Al0.4 metal hydrides (MHs) is chosen to operate at the above-mentioned temperature range with hydrogen as working fluid. The proposed system can completely eliminate the requirement of conventional compressor because it operates using waste heat, and useful outputs (cooling-heating) result from reaction enthalpies (MH + H2 interaction). The thermodynamic and heat-hydrogen transfer analyses of H-A SHP are carried out through finite volume approach, in which heat and mass transfer equations are solved to foresee the variations in MH bed temperature, hydrogen concentration, and heat interactions during cycle operation as well as the amount of cooling and heating outputs delivered to the air-conditioning space. The numerical code is validated with experimental pressure-concentration isotherms (PCIs) measured through Sievert's apparatus. The maximum heat exchange during the cooling and heating processes, at a particular instant of time, is observed as 257.5 and 286.1 W with cooling temperature of 10°C and heating temperature of 53°C, respectively. The thermodynamic performance is estimated as 178.5 kJ of cooling effect, 265.5 kJ of upgraded heat with overall coefficient of performance (COP) of 6.8, and overall specific alloy output of 396.5 W/0.34 kg of alloy. © 2019 John Wiley & Sons Ltd

Thermodynamic and heat‐hydrogen transfer analyses of novel multistage hydrogen‐alloy sorption heat pump

In the present study, a novel four alloys three-stage hydrogen based sorption heat transformer (4A – HSHT) is proposed to achieve higher heating output and efficiency with wide range of operating temperatures. The 4A – HSHT system can able to produce multiple heating outputs compared to conventional single stage metal hydride heat transformer (MHHT) with higher COP. The screening of metal hydrides is carried out to identify the best suited working pair for 4A – HSHT which results in the pair of La0.9Ce0.1Ni5 – MmNi4.4Al0.6 – LaNi4.7Al0.3 – MmNi3.7Co0.7Mn0.3Al0.3 hydrides for operating temperature range of 180 °C for heating output, 140 °C for heat supply and 45 °C for heat sink. The thermodynamic performance of 4A – HSHT is investigated using experimentally measured pressure concentration isotherm (PCI) and thermodynamic properties of chosen metal hydrides. The thermodynamic performance i.e. COP, specific heat output and heating capacity are estimated as 0.75, 81.8 W/kg and 0.9 kW, respectively for 2.75 kg of each alloy with 64 min of cycle time followed by the discussion on effects of heating output temperature on COP and specific heat output. The detailed flow chart demonstrating the methodology of material selection and thermodynamic simulation is presented. In addition, the various issues related to the implementation of practical devices based on metal hydride sorption systems are discussed including recent developments. © 2019 Elsevier Ltd

Applied Thermal Engineering

Studies on thermodynamic performance of three stage sorption heat transformer

Fulltext

Energy Storage

Performance investigation of metal hydride based heat transformer

Hydrogen storage in carbon materials—A review

Metal hydrides for energy applications - classification, PCI characterisation and simulation

Energetic evaluation of hydrogen storage in metal hydrides

Journal of Alloys and Compounds

Niche applications of metal hydrides and related thermal management issues

Intermetallics

Studies on La based intermetallic hydrides to determine their suitability in metal hydride based cooling systems

Influence of dynamic operating conditions on the performance of metal hydride based solid sorption cooling systems

Journal	Data powered by TypesetInternational Journal of Energy Research
Publisher	Data powered by TypesetWiley
ISSN	0363-907X
Open Access	0