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This paper investigates an innovative study on the performance of a hybrid condensing boiler-fuel cell micro-cogeneration system for single residential applications. It combines experimental and dynamic numerical investigations including renewable energy for green hydrogen production and solid storage. Basing on the hourly measurements for a typical winter day, a dynamic model was developed and validated against different home heating need. Highlighting the influence home energy needs on fuel cell operating mode, it shows that single homes with low energy demand led to reduce the fuel cell's yearly operation below 50 %. In low-energy homes, a reduction in fuel cell size led to an increase in yearly operation to 60-70 % and achieved a 55 % electrical coverage rate. The integration of metal hydride hydrogen solid storage, powered by renewable sources, is emphasized. This setup increases heat demand, influencing fuel cell operation. In winter season, fuel cell operated for an average of 611 h, compared to 61 h in summer. System efficiency averaged 91 % annually, peaked at 95 % in summer, and sustained 93 % when both FC and condensing boiler were switched on. [Display omitted] • Modeling of a hybrid Boiler-Fuel Cell MCHP system for residential energy management. • Calibration of the FC-MCHP model using experimental data from a real MCHP unit. • Electrical and thermal coverage of the FC-MCHP unit with green hydrogen production and storage under different scenarios. • Strategies for optimal hydrogen consumption in in residential application. • Impact of solid-state hydrogen storage on FC-MCHP consumption and thermal management. [ABSTRACT FROM AUTHOR]

The cost of hydrogen production from environmentally friendly energy resources is a primary barrier to fully realizing a hydrogen economy. Therefore, a detailed analysis of hydrogen production costs from various sustainable routes is required. This paper presents a comparative economic study of hydrogen production using several nuclear reactors integrated with electrolysis hydrogen production methods. The Hydrogen Economic Evaluation Program (HEEP) software is used for comparing hydrogen production using different technologies. The HEEP tool was developed by International Atomic Energy Agency (IAEA) and offers comprehensive data for the different nuclear power plants, hydrogen production processes, and various storage and transportation options. The current study utilizes HEEP capabilities to evaluate the cost of nuclear hydrogen production and compare it with non-nuclear sources. Furthermore, it considers the cost of hydrogen storage and transportation options. The reactors considered are Advanced Pressurized Water Reactor (APWR) and High Temperature Gas-cooled Reactor (HTGR) to power low- and high-temperature electrolyzers. In addition, the costs of hydrogen produced using electricity from grid, solar, and wind are evaluated and compared with that of nuclear plants. It is found that the cost of hydrogen production and storage using Compressed Gas (CG) from an APWR plant is 8.2 $/kg for a plant capacity of 360 MWe; the cost is reduced to 6.06 $/kg when the capacity increased to 1117 MWe. It is also found that HTGR integrated with HTSE can produce hydrogen at 3.51 $/kg, which is slightly lower than the case of using the grid electricity, which costs 3.55 $/kg. • Studied costs of electrolysis hydrogen production using APWR and HTGR at different scales. • Compared costs of hydrogen production using nuclear, solar, wind, and grid electricity. • Considered additional costs for compression, liquefaction, and metal hydride storage options. • Evaluated and compared vehicle and pipeline transportation costs for 500 km. [ABSTRACT FROM AUTHOR]

This work highlights the recent advancements in the hydrogen value chain for the Middle East region by evaluating the feedstock, production technologies, storage options, delivery routes, and end-user applications. It discusses the national strategies for implementing the hydrogen value chain in the Middle East from 2020 to 2050. The challenges in the hydrogen value chain from techno-economic, safety, and social perspectives are also discussed in this study. Hydrogen production technologies are analyzed and compared. Steam-methane reforming has a high efficiency of 74% and a low hydrogen cost of $2.27/kg-H 2 , making it the most dominant technology for hydrogen production. Electrolysis has a lower efficiency of 60% and a higher hydrogen cost of $10.30/kg-H 2, with more potential for further improvments. Furthermore, hydrogen storage options are compared. Compressed gas and cryogenic liquid options have the highest storage capacities of 39.2 and 70.9 kg/m3, respectively. However, they are not entirely safe due to the high flammability of hydrogen. Two hydrogen explosion incidents are also reported, the first explosion at the Fukushima nuclear power plant in 2011 and the second in the Hindenburg fire in 1937. Metal hydrides propose a safer and more effective option, but they are still under research and development. For H 2 transportation options, pipelines and cryogenic tankers are the most conventional and efficient options (above 99%). Ships have the largest capacity of 10,000 tons per shipment and the maximum investment costs of 465M - 620M$ per barge, but they are not feasible. This review paper will help researchers and practitioners analyze the hydrogen value chain in a more systematic way for further improvements toward more practical applications. • Several Middle East countries have developed national strategies for the hydrogen economy. • Steam-Methane Reforming is the most widely used method for hydrogen production. • Electrolysis and photolysis need major technical advances to be commercialized. • Hydrogen delivery infrastructure requires further development for a future hydrogen economy. • Hydrogen Value Chain implementation has some techno-economic and safety and social challenges. [Display omitted] [ABSTRACT FROM AUTHOR]

Power-to-Power is a process whereby the surplus of renewable power is stored as chemical energy in the form of hydrogen. Hydrogen can be used in situ or transported to the consumption node. When power is needed again, hydrogen can be consumed for power generation. Each of these processes incurs energy losses, leading to a certain round-trip efficiency (Energy Out/Energy In). Round-trip efficiency is calculated considering the following processes; water electrolysis for hydrogen production, compressed, liquefied or metal-hydride for hydrogen storage, fuel-cell-electric-truck for hydrogen distribution and micro-gas turbine for hydrogen power generation. The maximum achievable round-trip efficiency is of 29% when considering solid oxide electrolysis along with metal hydride storage. This number goes sharply down when using either alkaline or proton exchange membrane electrolyzers, 22.2% and 21.8% respectively. Round-trip efficiency is further reduced if considering other storage media, such as compressed- or liquefied-H 2. However, the aim of the paper is to highlight there is still a large margin to increase Power-to-Power round-trip efficiency, mainly from the hydrogen production and power generation blocks, which could lead to round-trip efficiencies of around 40%–42% in the next decade for Power-to-Power energy storage systems with micro-gas turbines. • Round-trip e_ciency of P2P energy storage system with micro gas turbines between 22% and 29%.. • Literature review of hydrogen electrolysis systems available in the market. • Thermodynamic analysis of H2 compression with a speci_c energy consumption of around 10% of H2 energy content. • Hydrogen storage in high-pressure vessels, lique_ed and in metal hydrides. • Hydrogen transportation by Fuel Cell Electric Truck for an average distance of 200 km per trip. [ABSTRACT FROM AUTHOR]

Hydrogen storage technology plays an important role on the development of hydrogen fuel cell and lithium aluminum hydride is a powerful candidate for solid-state hydrogen storage materials. However, the high stability and slow dehydrogenation kinetics of LiAlH 4 hinder its application. In this paper, the two-step thermal decomposition properties of LiAlH 4 with and without Fe–Fe 2 O 3 catalysts are investigated. According to the master plots, the model of mample power law (Pn) and nucleation and growth (An) are the optimal mechanism functions for the two-step decomposition of LiAlH 4 , respectively. After doping catalysts, the activation energies decrease significantly. The theoretical and optimized kinetic method are consistent with each other on activation energy. And the latter can also yield other kinetic parameters for a more comprehensive kinetic modelling of LiAlH 4 decomposition. Furthermore, Fe–Al 2 O 3 and Fe–Al intermetallics generated during dehydrogenation might significantly improve the hydrogen release properties of LiAlH 4. • Thermal decomposition kinetics of LiAlH 4 is analyzed using nonisothermal method. • The kinetic parameters are obtained by the optimized kinetic method. • Synergistic catalytic effects of Fe and Fe 2 O 3 composites have been investigated. • Fe–Al 2 O 3 and Fe–Al intermetallics enhance the dehydrogenation properties. [ABSTRACT FROM AUTHOR]

An experimental study on small-scale for solar hydrogen production system via a Proton Exchange Membrane electrolysis under a desert climatic condition in Ouargla region (South-East of Algeria) has been carried out, the target of this study has been first to evaluate hydrogen production by water analysis and to store the solar energy which has had the form of a hydride-metal hydrogen, after that, to investigate the performance of sophisticated commercial electrolyser (HG-60)powered by photovoltaic panels via the Power Management Unit (PMU) as a power conditioner, this paper has also a mathematical models based on real-time experiments were used to simulate both the photovoltaic system and PEM electrolyser work, along with attempting to direct linking strategy with the same experimental components of photovoltaic panels and commercial electrolyser, it was found through this study, the addition of the number of commercial electrolyser with the bank of four HG-60 stacks in series. More effective considering the improving voltage matching, with power transfer efficiency reach to 99%, also another factor is the photovoltaic panels slope on panel output power and hydrogen productivity are theoretically examined, where the proper selection of optimal tilt angle has an importance for collecting the maximum hydrogen amount, eventually, over the experiment span, the real-amount of hydrogen vented over experiment course is around 92.54l. • Experiments were used to modelling the solar hydrogen production system components. • The performance of PEM electrolyser powered by PV system was investigated. • A direct and indirect coupling PV/HG-60 water electrolyser system is investigated. • Hourly hydrogen production simulations for various panels slope levels are presented. • Panels slope angles effect on the PV/HG-60 performance is examined. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, sodium borohydride (NaBH4) is examined as a method of hydrogen storage and transport, and compared with hydrogen obtained from fossil sources. This chemical hydride has a very high storage density capability due to its large hydrogen content. Hydrogen is released as the main product of the reaction of NaBH4 with water, with sodium metaborate (NaBO2) as a by-product. The main disadvantage of the process is the production cost of the borohydride. In this paper, an economic analysis is carried out of the production, storage and transport of hydrogen from NaBH4 and from fossil fuels. Finally, a comparison is presented between various vehicles fuelled by petrol, hydrogen and sodium borohydride. [Copyright &y& Elsevier]

Abstract: Simulation and design of hydrogen storage systems based on metal hydrides require appropriate quantitative kinetic description. This paper presents an empirical kinetic model for the two-step hydrogen desorption of sodium alanate material doped with aluminium-reduced TiCl4, produced in kg-scale. The model is based on kinetic data obtained by volumetric titration measurements within a range of experimental conditions varying from 0 bar to 35bar and from 100°C to 190°C. It is shown that while the first desorption step is a zero-order reaction, the second desorption step follows the Johnson–Mehl–Avrami (JMA) equation with n =1. The predictions of the model are validated by experimental results and are used to asses the pressure–temperature (p–T) performance of the desorption steps against selected hydrogen supply criteria. This paper complements a previous paper of this investigation that presented the kinetic model of the corresponding hydrogen absorption of sodium alanate material. [Copyright &y& Elsevier]

Abstract: The use of Nickel–Metal Hydride (Ni–MH) batteries for traction application in electric and hybrid vehicles is on the rise. High-rate charge/discharge characteristics are important parameters for electric vehicle applications. The ability to reduce charging time is essential in these traction applications. In this paper, the performance of assembled Ni–MH batteries (1.2V, 0.5Ah specimen cells) when subjected to different charging rates is described. Changes in battery voltage during charging were monitored with a particular emphasis on the quest for fast recharge characteristics. The charging curves reveal the formation of different types of phases. Hydrogen evolution resulted in flat charge profile after certain amount of overcharging. The changes in discharge level after different rates of charging are insignificant. This paper describes the fast rechargeability of assembled Ni–MH cells under various fast-charge regimes. [Copyright &y& Elsevier]

Abstract: In this paper the properties of Mg–Al alloys in relation to hydrogen storage are reviewed. The main topics of this paper are materials preparation, hydrogen capacity, thermodynamics of hydride formation, and the kinetics of hydride formation and decomposition. Hydrogenation of Mg–Al leads to disproportionation with the formation of magnesium hydride and metallic aluminum as the final product. Experimental evidence renders this process reversible. It is observed that the enthalpy of hydride formation of magnesium is lowered upon alloying with Al due to a slightly endothermic disproportionation reaction. Further, it is found that the kinetics of hydrogenation, as well dehydrogenation, may be significantly improved by alloying compared to pure Mg. The expense of these improvements of the hydrogenation/dehydrogenation properties is a lower gravimetric hydrogen density in the hydrogenated product. [Copyright &y& Elsevier]

This paper presents a mathematical model to study opportunities for simultaneous passive thermal management of an integrated PEM fuel cell and metal hydrogen (MH) storage system by thermal bridging of these two components, using heat pipes. The thermal coupling arrangement is expected to be promising, because, as more power is drawn from the PEMFC, more heat is generated that can be used to enhance the rate of release of hydrogen from the MH storage. Heat pipes can provide an effective passive thermal bridge for this purpose on account of their high thermal conductivity, and thus avoid parasitic energy penalties associated with active methods of cooling. The main components modelled analytically in MATLAB in this study are the PEMFC, heat pipes, and MH hydrogen storage. This simulation has been used to size the heat pipe system needed for thermal coupling of a 500 W PEMFC and MH storage canisters. The performance improvement of the MH system after receiving the fuel cell heat, and the cooling capacity of the MH system to be used as heat sink for thermal management of the fuel cell stack, has been studied. The MH canisters used to supply hydrogen to this stack each had the maximum supply capability of 2.5 slpm at 25 °C, while the fuel cell demand was 7.2 slpm at its rated power (500 W). The results show that just under 20% of the total cooling load of the stack (i.e. ∼880 W) at its maximum power point is demanded by the MH canisters (∼170 W) to achieve the required hydrogen discharge rate of 7.2 slpm at 35 °C provided the MH canisters are thermally well insulated. [ABSTRACT FROM AUTHOR]

The present paper focuses on the elaboration of LaTi 2 Cr 4 Ni 5 -based intermetallic compounds by mechanical alloying from LaNi 5 and TiCr 2 precursors and their characterization as negative electrode materials in Nickel-metal hydride (Ni-MH) batteries. The structural properties of the phases were determined by X-ray diffraction and quantified from the Rietveld refinement data. The increase of the milling time up to 25 h leads to the highest abundance of the LaTi 2 Cr 4 Ni 5 phase, estimated at 66 wt%, and a complete elimination of the LaNi 5 intermetallic precursor. The electrochemical techniques were applied to characterize the electrochemical behavior of prepared LaTi 2 Cr 4 Ni 5 -based compounds. The maximum discharge capacity was 115 mAh g −1 and the average capacity retention was equal to 77% upon 60 charge/discharge cycles, indicating a high electrochemical stability in the alkaline solution. The values of the hydrogen diffusion coefficient are equal to 4.18 × 10 −8 and 7.17 × 10 −8 cm 2 s −1 after 8 h and 20 h of milling durations, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a metal hydride hydrogen storage reactor is analyzed from heat and mass transfer and entropy generation points of view. A transient two dimensional energy equation along with suitable reaction kinetics and entropy balance equation is solved numerically. Results are obtained keeping hydrogen flow rates constant during absorption and desorption. For a fixed mass of metal hydride in the reactor the amount of hydrogen transferred and the time in which the transfer takes place are kept fixed. Using the mathematical model the entropy generated during the process and the external cooling and heating fluid requirements are obtained. Results show how improvement in the design and/or operating conditions leads to reduced cooling and heating requirements and lower entropy generation. For the system considered in the study the internal heat transfer characteristics of the hydride bed are seen to influence the reactor performance significantly. With improved bed heat transfer the required heat transfer fluid temperature during desorption can be reduced and that during absorption can be increased significantly. This automatically leads to lower entropy generation and a more economic system operation. It is expected that the methodology proposed and the results presented in this study will be useful in the optimal design of metal hydride reactors for a variety of practical applications, including hydrogen storage. [Copyright &y& Elsevier]

Abstract: Metal hydride systems are utilized in many practical applications such as hydrogen storage, heat pumps, etc. The establishment of a metal hydride system requires the expression of reaction rate for the first step design, from an engineering standpoint. However, improper experimental determination of intrinsic kinetics usually leads to significant errors in the kinetic data. This paper presents a novel methodology of estimating these errors based on the entropy generation analysis. For this purpose, numerical simulation is performed taking into account the experimental conditions for a real case. The results showed that if the operating conditions (i.e. hydrogen pressure, heat transfer coefficient) and the size of the experimental setup are not chosen properly, the kinetic data obtained from the experiments will be largely misled. Therefore it should be carefully taken into account in order to minimize the relative errors induced on the kinetic data. [Copyright &y& Elsevier]

Abstract: Hydrogen release from hydrolysis of LiNH2BH3, NaNH2BH3, LiH–NH3BH3 and NaH–NH3BH3 respectively was investigated in this paper. It is shown experimentally that LiNH2BH3 and NaNH2BH3 hydrolysis can release 3equiv. of hydrogen at 25°C. Hydrolysis of LiNH2BH3 or NaNH2BH3 exhibits greatly improved kinetics in comparison with neat NH3BH3 hydrolysis. The electronic and structural changes from NH3BH3 to [NH2BH3]− play a crucial role in the improvements. The mechanism of LiNH2BH3 and NaNH2BH3 hydrolysis is the combination of H+ and OH− ions of water with the polar ions of LiNH2BH3 and NaNH2BH3. The process of LiH–NH3BH3 and NaH–NH3BH3 hydrolysis comprises two steps: LiH or NaH first reacts with water and then the generated heat initiates thermohydrolysis of NH3BH3. LiH or NaH hydrolysis is prior to the reaction of LiH or NaH with NH3BH3. Our results show a novel strategy to promote hydrogen release kinetics of LiNH2BH3 and NaNH2BH3. Furthermore, our results also present a novel noncatalytic method for hydrogen release from NH3BH3 by co-hydrolyzing it with other highly exothermic hydrides. [Copyright &y& Elsevier]

Abstract: The metal hydride heat transformer shows great potential for the low-grade heat recovery. However, the heat output is variable, and these dynamics have to be taken into account in realistic applications. In this paper, a new index called true temperature boost is introduced together with conventional indices to assess the performance of the heat transformer system. Detailed analyses are carried out using a mathematical model that authors developed, investigating effects of key design and operating factors on the system’s performance. The amount of hydrogen transferred between coupled reactors is found to be crucial to obtain a high coefficient of performance, while specific heating power is very sensitive to the cycle time. On the true temperature boost, the driving force of reaction and the heat transfer conditions exert the most significant effects. [Copyright &y& Elsevier]

Abstract: In small hybrid wind systems, excess wind energy is stored for later use during the deficit power generation. Excess wind energy can be stored as hydrogen in a metal hydride storage bed and reused later to generate power using a fuel cell. This paper deals with the discharge dynamics of the coupled fuel cell and metal hydride storage bed during the power extraction. Thermal coupling of the fuel cell and metal hydride bed is also discussed. The waste heat generated in the fuel cell is removed using a water coolant. The exit fuel cell coolant stream is passed through the metal hydride storage bed to supply the necessary heat required for desorption of hydrogen from the bed. This will also lead to a reduction in the load on the radiator. The discharge dynamics and the thermal management of the coupled system are demonstrated through a system simulation model developed in Matlab/Simulink platform. [Copyright &y& Elsevier]

Abstract: This paper describes the design, fabrication and performance evaluation of a high efficiency, compact heater that uses the catalytic oxidation of hydrogen to provide heat to a hydrogen storage system. The heater was designed to transfer up to 30kW of heat from the catalytic reaction to the hydrogen storage system via a recirculating heat transfer fluid. The catalytic heater consists of three main parts: 1) the reactor, 2) the gas heat recuperator, and 3) oil and gas flow distribution manifolds. The reactor and recuperator are integrated, compact, finned-plate heat exchangers to maximize heat transfer efficiency and minimize mass and volume. Detailed, three-dimensional, multi-physics computational models were used to design and optimize the system. At full power the heater was able to catalytically combust a 10% hydrogen/air mixture flowing at over 80 cubic feet per minute and transfer 30kW of heat to a 30 gallon per minute flow of oil over a temperature range from 100°C to 220°C. The total efficiency of the catalytic heater, defined as the heat transferred to the oil divided by the inlet hydrogen chemical energy, was determined to exceed the design goal of 80% for oil temperatures from 60°C to 165°C. [Copyright &y& Elsevier]

Abstract: This paper describes the ultrasonic irradiation on the hydrolysis of magnesium hydride to enhance hydrogen generation; the effects of the ultrasonic frequency and the sample size on the hydrogen generation were mainly examined. In the experiments, three MgH2 particle and nanofiber samples were soaked in distilled water and ultrasonically irradiated at frequencies of 28, 45, and 100 kHz. Then, the amount of hydrogen generated was measured. We found that the low frequency of ultrasonic irradiation and the relatively small sample size accelerated the hydrolysis reaction MgH2 + 2H2O = Mg(OH)2 + 2H2 + 277 kJ. In particular, the MgH2 nanofibers exhibited the maximum hydrogen storage capacity of 14.4 mass% at room temperature at a frequency of 28 kHz (ultrasound irradiation). The results also experimentally validated that a combination of ultrasonic irradiation and MgH2 hydrolysis is considerably effective for efficiently generating hydrogen without heating and adding any agent. [Copyright &y& Elsevier]

Abstract: Chemical hydrides have already been pointed out as great potential hydrogen storage materials. In this paper, the hydrolysis of two solid hydrides, namely sodium borohydride (NaBH4) and lithium hydride (LiH) was studied to check their performance as hydrogen generators. The simplicity of the reactor design, the absence of high pressure or very high temperatures as well as the benignity of the spent fuel make this hydrogen storage approach conceptually feasible. Several devices have been developed and tested. The devices have been designed to generate hydrogen flows in the 0.5–1.0 L min−1 range. Batches up to 500 g of sodium borohydride powder were hydrolyzed with liquid water. 10.0 wt. % nickel acetate was used as catalyst. Hydrogen flows in the desired range have been continuously produced for several hours (up to 30 h). Due to the high reactivity lithium hydride was hydrolyzed without any catalyst. In this case batches of about 50 g have been hydrolyzed with steam for 4 h. [Copyright &y& Elsevier]

Abstract: Hydrogen generation by hydrolysis of hydrogenated Mg3LaNi0.1, and Mg3LaNi0.1Al0.1 in pure water at room temperature has been investigated and compared with that of Mg3La. It has been found that hydrolysis reaction rate of those hydrides, which are obtained by induction melting and then hydrogenated, is fast when they are immersed in pure water. The highest hydrogen yield is 1024 ml/g for hydrogenated Mg3LaNi0.1. The kinetics of hydrogen production reaction for hydrogenated Mg3LaNi0.1, and Mg3LaNi0.1Al0.1 hydrides at 298 K was also measured. The effect for addition of Ni and Al was also discussed in this paper. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a two-dimensional mathematical model to evaluate transient heat and mass transfer in a metal hydride tank (hereinafter MHT) with metal foam heat exchanger. The model is validated by comparison with experimental data. A good agreement is obtained. A study of the geometric and the operating parameters of the metal foam (such as base material, pore size and relative density) has been carried out to identify their influence on the performance of the charging process of the MHT. After that, the model was used as a tool to predict the performance of the hydrogen-charging process of two configurations of MHTs with metal foam heat exchangers. The obtained results showed that the reduction of the storage time due to the metal foam heat exchanger can be more important when the MHT is equipped with a concentric heat exchanger tube. [Copyright &y& Elsevier]

Abstract: Although alane (AlH3) has many interesting properties as a hydrogen storage material, it cannot be regenerated on-board a vehicle. One way of overcoming this limitation is to formulate an alane slurry that can be easily loaded into a fuel tank and removed for off-board regeneration. In this paper, we analyze the performance of an on-board hydrogen storage system that uses alane slurry as the hydrogen carrier. A model for the on-board storage system was developed to analyze the AlH3 decomposition kinetics, heat transfer requirements, stability, startup energy and time, H2 buffer requirements, storage efficiency, and hydrogen storage capacities. The results from the model indicate that reactor temperatures higher than 200°C are needed to decompose alane at reasonable liquid hourly space velocities, i.e.,>60h−1. At the system level, a gravimetric capacity of 4.2wt% usable hydrogen and a volumetric capacity of 50gH2/L may be achievable with a 70% solids slurry. Under optimum conditions, ∼80% of the H2 stored in the slurry may be available for the fuel cell engine. The model indicates that H2 loss is limited by the decomposition kinetics rather than by the rate of heat transfer from the ambient to the slurry tank. [Copyright &y& Elsevier]

Abstract: This paper deals with how the Hydrogen Energy may play a crucial role in taking care of the environmental scenario/climate change. The R&D efforts, at the Hydrogen Energy Center, Banaras Hindu University have been described and discussed to elucidate that hydrogen is the best option for taking care of the environmental/climate changes. All three important ingredients for hydrogen economy, i.e., production, storage and application of hydrogen have been dealt with. As regards hydrogen production, solar routes consisting of photoelectrochemical electrolysis of water have been described and discussed. Nanostructured TiO2 films used as photoanodes have been synthesized through hydrolysis of Ti[OCH(CH3)2]4. Modular designs of TiO2 photoelectrode-based PEC cells have been fabricated to get high hydrogen production rate (∼10.35lh−1 m−2). However, hydrogen storage is a key issue in the success and realization of hydrogen technology and economy. Metal hydrides are the promising candidates due to their safety advantage with high volume efficient storage capacity for on-board applications. As regards storage, we have discussed the storage of hydrogen in intermetallics as well as lightweight complex hydride systems. For intermetallic systems, we have dealt with material tailoring of LaNi5 through Fe substitution. The La(Nil − x Fe x )5 (x =0.16) has been found to yield a high storage capacity of ∼2.40wt%. We have also discussed how CNT admixing helps to improve the hydrogen desorption rate of NaAlH4. CNT (8mol%) admixed NaAlH4 is found to be optimum for faster desorption (∼3.3wt% H2 within 2h). From an applications point of view, we have focused on the use of hydrogen (stored in intermetallic La–Ni–Fe system) as fuel for Internal Combustion (IC) engine-based vehicular transport, particularly two and three-wheelers. It is shown that hydrogen used as a fuel is the most effective alternative fuel for circumventing climate change. [Copyright &y& Elsevier]

Abstract: This paper describes the direct synthesis of magnesium hydride (MgH2) nanofibers by hydriding chemical vapor deposition (HCVD), in which the effect of hydrogen pressure on the production rate, the composition and the shape of products obtained were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET). The XRD patterns showed that the main product in each case was MgH2; in particular, the products formed at 2, 3 and 4MPa were highly pure. In contrast, at a hydrogen pressure of 1MPa, unhydrided Mg was deposited along with MgH2. The SEM images also revealed orientation of the as-deposited products; higher pressures of 3 and 4MPa caused the formation of straight and curved nanofibers, and lower ones of 1 and 2MPa, highly curved nanofibers and nanorods with a few straight nanofibers. With pressurizing hydrogen, not only the BET specific surface areas of the products but also the production rate increased. The results also appealed that HCVD could control the shape/size of MgH2 nanofibers by changing the pressure via only a single operation. [Copyright &y& Elsevier]

Abstract: This paper describes the Self-Ignition Combustion Synthesis (SICS) of the hydrogen storage alloy Ti1.15FeO x (x =0, 0.024, and 0.050) in a hydrogen atmosphere and the obtained product''s hydrogenation properties. Ti, Fe, and α-Fe2O3 powders were mixed to produce Ti1.15FeO x and uniformly heated to the eutectic temperature 1358K for self-ignition, which occurred after the hydrogenation and decomposition of Ti. The X-ray diffraction results for the final product had TiFeH0.06 and Fe2Ti as the major and minor phases, respectively. The hydrogen storage capacity of the product at a hydrogen pressure of 5MPa was 1.18–1.50m%. As the value of x increased, the capacity gradually decreased. However, the initial hydrogenation kinetics of the product improved. In contrast, the equilibrium pressure for the product was almost unaffected. These results demonstrate that SICS is quite effective for producing O-doped TiFe alloys as well as TiFe without rare metal. The procedure offers many benefits of releasing tough activation treatment, minimizing operation time, and saving energy. [Copyright &y& Elsevier]

Abstract: Hydrogen is an energy carrier which can be used for the storage of intermittent and renewable energy sources. In this paper, the general characteristics of an integrated and automated hydrogen-based auxiliary power unit (APU) are presented. A PEM water electrolyzer (production capacity ranging from zero up to 1Nm3 H2/h), which can be powered by a panel of photovoltaic cells, is used to produce hydrogen at day hours. Hydrogen is dried and stored in hydride reservoir tanks (the storage capacity of individual reservoirs is 1Nm3 H2). Then hydrogen is used for the co-generation of heat and electricity at night hours using a PEM fuel cell (1kW maximum output power). The main electrochemical and technological features of the overall system are presented. This kind of APU can potentially be used as an electric power source for domestic applications, for the production of electricity on remote sites or as a mobile hydrogen refuelling station for transport applications in urban areas. [Copyright &y& Elsevier]

Abstract: In this paper, Al was partially substituted by Ni in the Zintl phase alloy SrAl2 and the structural and hydrogenation characteristics of the SrAl2−x Ni x (0≤ x ≤0.4) alloys were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and hydrogenation measurements. The alloy consisted of a single Zintl phase of SrAl2 when x =0. However, partial substitution of Al by Ni resulted in multiphase structure of the alloys. When x =0.1, the alloy was composed of SrAl2, Sr5Al9, SrAl and AlNi phases. With the increase of x, the amount of SrAl2 and Sr5Al9 phases decreased, while the amount of SrAl and AlNi phases increased. Hydrogenation measurements were made at 473K under 3MPa hydrogen pressure. It was interesting to find that the hydriding kinetics of the alloy was improved greatly after Ni substitution, which could be attributed to the catalysis of AlNi phase. [Copyright &y& Elsevier]

Abstract: Cycloalkanes are good candidate media for hydrogen storage (6.5wt% and ). A novel approach for the supply of hydrogen, through liquid organic hydrides (LOH) using catalytic reaction pair of dehydrogenation of cycloalkanes and hydrogenation of corresponding aromatics is a useful process for supply of hydrogen. Hydrogenation of aromatics is relatively well-established process. However, the efforts are needed to develop efficient catalyst for dehydrogenation of cycloalkanes. In this paper we review the dehydrogenation of cycloalkanes as useful reaction for storage of hydrogen in chemical hydrides. [Copyright &y& Elsevier]