Transmission, Distribution & Storage

Hydrogen interaction with metal atoms is of prime focus for many energy related applications like hydrogen storage hydrogen evolution using catalysis etc. Although hydrogen binding with many main group alkaline and transition metals is quite well understood its binding properties with lanthanides are not well reported. In this article by density functional theory studies we show how a rare earth metal cerium binds with hydrogen when decorated over a heteropolar 2D material hexagonal boron nitride. Each cerium adatom is found to bind eight hydrogen molecules which is a much higher number than has been reported for transition metal atoms. However the highest binding energy occurs at four hydrogen molecules. This anomaly therefore is investigated in the present article using first-principles calculations. The number density of hydrogen molecules adsorbed over the cerium adatom is explained by investigating the electronic charge volume interactions owing to a unique geometrical arrangement of the guest hydrogen molecules. The importance of geometrical encapsulation in enhancing electronic interactions is explained.

In order to reduce anthropogenic global warming governments around the world have decided to reduce CO₂ emissions from fossil fuels dramatically within the next decades. In moderate and cold climates large amounts of fossil fuels are used for space heating and domestic hot water production in winter. Although on an annual base solar energy is available in large quantities in these regions least of the solar resource is available in winter when most of the energy is needed. Therefore solutions are needed to store and transfer renewable energy from summer to winter. In this paper a seasonal energy storage based on the aluminium redox cycle (Al3+→Al→ Al3+) is proposed. For charging electricity from solar or other renewable sources is used to convert aluminium oxide or aluminium hydroxide to elementary aluminium (Al3+→Al). In the discharging process aluminium is oxidized (Al→Al3+) releasing hydrogen heat and aluminium hydroxide or aluminium oxide as a by-product. Hydrogen is used in a fuel cell to produce electricity. Heat produced from the aluminium oxidation process and by the fuel cell is used for domestic hot water production and space heating. The chemical reactions and energy balances are presented and simulation results are shown for a system that covers the entire energy demand for electricity space heating and domestic hot water of a new multi-family building with rooftop photovoltaic energy in combination with the seasonal Al energy storage cycle. It shows that 7–11 kWp of photovoltaic installations and 350–530 kg Al would be needed per apartment for different Swiss climates. Environmental life cycle data shows that the global warming potential and non-renewable primary energy consumption can be reduced significantly compared to today's common practice of heating with natural gas and using electricity from the ENTSO-E network. The presumptive cost were estimated and indicate a possible cost-competitiveness for this system in the near future.

A solid-state hydrogen storage material comprising ammonia borane (AB) and polyethylene oxide (PEO) has been produced by freeze-drying from aqueous solutions from 0% to 100% AB by mass. The phase mixing behaviour of AB and PEO has been investigated using X-ray diffraction which shows that a new ‘intermediate’ crystalline phase exists different from both AB and PEO as observed in our previous work (Nathanson et al. 2015). It is suggested that hydrogen bonding interactions between the ethereal oxygen atom (–O–) in the PEO backbone and the protic hydrogen atoms attached to the nitrogen atom (N–H) of AB molecules promote the formation of a reaction intermediate leading to lowered hydrogen release temperatures in the composites compared to neat AB. PEO also acts to significantly reduce the foaming of AB during hydrogen release. A temperature-composition phase diagram has been produced for the AB-PEO system to show the relationship between phase mixing and hydrogen release.

Among the several typologies of storage technologies mainly on different physical principles (mechanical electrical and chemical) hydrogen produced by power to gas (P2G) from renewable energy sources complies with chemical storage principle and is based on the conversion of electrical energy into chemical energy by means of the electrolysis of water which does not produce any toxic or climate-relevant emission. This paper aims to pinpoint the potential uses of renewable hydrogen storage systems in Europe analysing current and potential locations regulatory framework governments’ outlooks economic issues and available renewable energy amounts. The expert opinion survey already used in many research articles on different topics including energy has been selected as an effective method to produce realistic results. The obtained results highlight strategies and actions to optimize the storage of hydrogen produced by renewables to face varying electricity demand and generation-driven fluctuations reducing the negative effects of the increasing share of renewables in the energy mix of European Countries.

Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine – the metal hydride material itself – should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage hydrogen sorption kinetics and effective thermal conductivity) the thermodynamics of the metal–hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimised to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors reduction of slope of the isotherms and hysteresis increase of cycling stability and life time together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation.<br/>The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal–hydrogen systems suitable for the hydrogen compression; and (b) applied aspects including their consideration from the applied thermodynamic viewpoint system design features and performances of the metal hydride compressors and major applications.

Imbalance costs caused by forecasting errors are considerable for grid-connected wind farms. In order to reduce such costs two onsite storage technologies i.e. power-to-hydrogen-to-power and lithium battery are investigated considering 14 uncertain technological and economic parameters. Probability density distributions of wind forecasting errors and power level are first considered to quantify the imbalance and excess wind power. Then robust optimal sizing of the onsite storage is performed under uncertainty to maximize wind-farm profit (the net present value). Global sensitivity analysis is further carried out for parameters prioritization to highlight the key influential parameters. The results show that the profit of power-to-hydrogen-to-power case is sensitive to the hydrogen price wind forecasting accuracy and hydrogen storage price. When hydrogen price ranges in (2 6) €/kg installing only electrolyzer can earn profits over 100 k€/MWWP in 9% scenarios with capacity below 250 kW/MWWP under high hydrogen price (over 4 €/kg); while installing only fuel cell can achieve such high profits only in 1.3% scenarios with capacity below 180 kW/MWWP. Installing both electrolyzer and fuel cell (only suggested in 22% scenarios) results in profits below 160 k€/MWWP and particularly 20% scenarios allow for a profit below 50 k€/MWWP due to the contradictory effects of wind forecasting error hydrogen and electricity price. For lithium battery investment cost is the single highly influential factor which should be reduced to 760 €/kWh. The battery capacity is limited to 88 kW h/MWWP. For profits over 100 k€/MWWP (in 3% scenarios) the battery should be with an investment cost below 510 €/kWh and a depth of discharge over 63%. The power-to-hydrogen-to-power case is more advantageous in terms of profitability reliability and utilization factor (full-load operating hours) while lithium battery is more helpful to reduce the lost wind and has less environmental impact considering current hydrogen market.

Renewable methanol obtained from CO₂ and hydrogen provided from renewable energy was proposed to close the CO₂ loop. In industry methanol synthesis using the catalyst CuO/ZnO/Al₂O₃ occurs at a high pressure. We intend to make certain modification on the traditional catalyst to work at lower pressure maintaining high selectivity. Therefore three heterogeneous catalysts were synthesized by coprecipitation to improve the activity and the selectivity to methanol under mild conditions of temperature and pressure. Certain modifications on the traditional catalyst Cu/Zn/Al₂O₃ were employed such as the modification of the synthesis time and the addition of Pd as a dopant agent. The most efficient catalyst among those tested was a palladium-doped catalyst 5% Pd/Cu/Zn/Al₂O₃. This had a selectivity of 64% at 210 °C and 5 bar.

In the current study the effect of hydrogen atoms on the intergranular failure of α-iron is examined by a molecular dynamics (MD) simulation. The effect of hydrogen embrittlement on the grain boundary (GB) is investigated by diffusing hydrogen atoms into the grain boundaries using a bicrystal body-centered cubic (BCC) model and then deforming the model with a uniaxial tension. The Debye Waller factors are applied to illustrate the volume change of GBs and the simulation results suggest that the trapped hydrogen atoms in GBs can therefore increase the excess volume of GBs thus enhancing intergranular failure. When a constant displacement loading is applied to the bicrystal model the increased strain energy can barely be released via dislocation emission when H is present. The hydrogen pinning effect occurs in the current dislocation slip system <111>{112}. The hydrogen atoms facilitate cracking via a decrease of the free surface energy and enhance the phase transition via an increase in the local pressure. Hence the failure mechanism is prone to intergranular failure so as to release excessive pressure and energy near GBs. This study provides a mechanistic framework of intergranular failure and a theoretical model is then developed to predict the intergranular cracking rate

In the research the corrosion and mechanical properties as well as susceptibility to hydrogen embrittlement of two casing pipe steels were investigated in order to assess their serviceability in corrosive and hydrogenating environments under operation in oil and gas wells. Two carbon steels with different microstructures were tested: the medium carbon steel (MCS) with bainitic microstructure and the medium-high carbon steel (MHCS) with ferrite–pearlite microstructure. The results showed that the corrosion resistance of the MHCS in CO2-containing acid chloride solution simulating formation water was significantly lower than that of the MCS which was associated with microstructure features. The higher strength MCS with the dispersed microstructure was less susceptible to hydrogen embrittlement under preliminary electrolytic hydrogenation than the lower strength MHCS with the coarse-grained microstructure. To estimate the embrittlement of steels the method of the FEM load simulation of the specimens with cracks was used. The constitutive relations of the true stress–strain of the tested steels were defined. The stress and strain dependences in the crack tip were calculated. It was found that the MHCS was characterized by the lower plasticity on the stage of the neck formation of the specimen and the lower fracture toughness than the other one. The obtained results demonstrating the limitations of the usage of casing pipes made of the MHCS with the coarse-grained ferrite/pearlite microstructure in corrosive and hydrogenating environments were discussed.

Hydrogen (H2) as a cleaner fuel has been suggested as a viable method of achieving the decarbonization objectives and meeting increasing global energy demand. However successful implementation of a full-scale hydrogen economy requires large-scale hydrogen storage (as hydrogen is highly compressible). A potential solution to this challenge is injecting hydrogen into geologic formations from where it can be withdrawn again at later stages for utilization purposes. The geostorage capacity of a porous formation is a function of its wetting characteristics which strongly influence residual saturations fluid flow rate of injection rate of withdrawal and containment security. However literature severely lacks information on hydrogen wettability in realistic geological and caprock formations which contain organic matter (due to the prevailing reducing atmosphere). We therefore measured advancing (θa) and receding (θr) contact angles of mica substrates at various representative thermo-physical conditions (pressures 0.1-25 MPa temperatures 308–343 K and stearic acid concentrations of 10−9 - 10−2 mol/L). The mica exhibited an increasing tendency to become weakly water-wet at higher temperatures lower pressures and very low stearic acid concentration. However it turned intermediate-wet at higher pressures lower temperatures and increasing stearic acid concentrations. The study suggests that the structural H2 trapping capacities in geological formations and sealing potentials of caprock highly depend on the specific thermo-physical condition. Thus this novel data provides a significant advancement in literature and will aid in the implementation of hydrogen geo-storage at an industrial scale.