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Hydrogen/methane mixtures draw attention due to the idea of the injection of hydrogen into natural gas networks and biological production of biohythane by one- and two-step anaerobic fermentation/digestion methods. It is hard to extract hydrogen from dilute mixtures with methane by traditional separation processes, since hydrogen is the minor component with low partial pressure. Metal hydrides selectively absorb hydrogen and offer an opportunity to overcome the limitations of traditional separation methods. In the present paper, we present experimental results on the separation of a dilute mixture of hydrogen (10%) with methane in a flow-through metal hydride reactor with inlet mixture pressure of 0.95 MPa by the LaNi 4.8 Mn 0.3 Fe 0.1 intermetallic compound. Hydrogen was separated in one step with roundtrip (absorption/desorption) recovery of 74%. An exergetic analysis of the metal hydride separation of a binary mixture containing hydrogen was implemented and equations for hydrogen recovery and exergy efficiency of separation are obtained. Thermodynamic analysis shows that the exergy efficiency of the metal hydride purification has a clear maximum at hydrogen concentrations around 5–20%. The advantage of metal hydride purification is the absorption of the minor fraction from the feed, thus it is preferable for dilute mixtures and could be feasible for practical applications. With the use of low potential or waste heat to drive the reaction, it is possible to increase the efficiency of hydrogen purification by metal hydrides. The maximum exergy efficiency is 61% for 0.8 MPa outlet pressure, taking into account the quality of involved heat flows. • H 2 (10%)/CH 4 mixture was separated by LaNi 4.8 Mn 0.3 Fe 0.1 with 74% H 2 recovery. • Equations for the exergy efficiency of separation and the hydrogen recovery are obtained. • Exergy efficiency has maximum at H 2 concentration 5–20%. • Metal hydride purification has advantage for dilute H 2 mixtures. [ABSTRACT FROM AUTHOR]

Emerging technologies of the 21st Century introduced bi-directional flows between a big number of uncontrollable and unpredictable generators together with a need for energy storage (ES) capable of solving instability issues. With the aim of developing new control methodologies, Skoltech developed a Smart Grid laboratory that includes a variety of energy generators, and storage systems. The capabilities of the grid were expanded with a metal hydride (MH) ES and 1 kW fuel cell. MH ES performs at the near ambient temperatures and relatively low pressure, it has adjustable properties, satisfactory gravimetric H 2 density, and a simple thermal management. However, existing technologies require an external heat source, which cannot serve the purpose of autonomous microgrid applications. The aim of this research was to develop and test an air heated metal hydride energy storage system that utilizes the internal waste heat of the system. Based on low power MH ES system experiments [1] and waste heat investigations [2], an air heated system with 1 m3 H 2 MH reactor was developed and tested. The experiments were performed in the system that also includes 1 kW fuel cell and an electrolyzer. Obtained results show higher efficiency rate of the system due to waste heat utilization from the air-cooled polymer electrolyte membrane (PEM) FC, ensure mobility for autonomous applications, and open the opportunity for further research in the field of power system control. • 1 kWh hydrogen energy storage prototype was successfully developed and tested. • A novel concept of the fuel cell output hot air utilization is proved. • The internal waste heat of the system replaced an external heating agent. • Air heated metal hydride storage ensures the autonomy of the system. • A prototype was created for the supply systems for the Far East settlements in Russia. [ABSTRACT FROM AUTHOR]

The metal hydride reactor filled with 5 kg of the AB 5 -type (LaFe 0.5 Mn 0.3 Ni 4.8 ) alloy was investigated with respect to the hydrogen discharge rates classified using C-rate value, which is discharge of the maximum hydrogen capacity 750 st L within 1 h. The reactor cannot be fully discharged with a constant flow rate, for each temperature of hot water and flow rate there exists a moment of crisis at which the hydrogen flow drops under the constant value. The nominal capacity of the reactor reaches 80% of maximum capacity if sufficient heat transfer is provided. The simple balance model of a metal hydride reactor is developed based on the assumption of uniform temperature and pressure inside a metal hydride bed. The model permits to predict behavior of the metal hydride reactor in different operation regimes, quantitative agreement is obtained for low C-rates (less than 4) and sub-critical modes. [ABSTRACT FROM AUTHOR]