Transmission, Distribution & Storage

Grand Canonical Monte Carlo GCMC simulations are used to study the gravimetric and volumetric hydrogen storage capacities of different carbon nanopores shapes: Slit-shaped nanotubes and torusenes at room temperature 298.15 K and at pressures between 0.1 and 35 MPa and for pore diameter or width between 4 and 15 A. The influence of the pore shape or curvature on the storage capacities as a function of pressure temperature and pore diameter is investigated and analyzed. A large curvature of the pores means in general an increase of the storage capacities of the pores. While torusenes and nanotubes have surfaces with more curvature than the slit-shaped planar pores their capacities are lower than those of the slit-shaped pores according to the present GCMC simulations. Torusene a less studied carbon nanostructure has two radii or curvatures but their storage capacities are similar or lower than those of nanotubes which have only one radius or curvature. The goal is to obtain qualitative and quantitative relationships between the structure of porous materials and the hydrogen storage capacities in particular or especially the relationship between shape and width of the pores and the hydrogen storage capacities of carbon-based porous materials.

Development of probabilistic modelling tools to perform Bayesian inference and uncertainty quantification (UQ) is a challenging task for practical hydrogen-enriched and low-emission combustion systems due to the need to take into account simultaneously simulated fluid dynamics and detailed combustion chemistry. A large number of evaluations is required to calibrate models and estimate parameters using experimental data within the framework of Bayesian inference. This task is computationally prohibitive in high-fidelity and deterministic approaches such as large eddy simulation (LES) to design and optimize combustion systems. Therefore there is a need to develop methods that: (a) are suitable for Bayesian inference studies and (b) characterize a range of solutions based on the uncertainty of modelling parameters and input conditions. This paper aims to develop a computationally-efficient toolchain to address these issues for probabilistic modelling of NOx emission in hydrogen-enriched and lean-premixed combustion systems. A novel method is implemented into the toolchain using a chemical reactor network (CRN) model non-intrusive polynomial chaos expansion based on the point collocation method (NIPCE-PCM) and the Markov Chain Monte Carlo (MCMC) method. First a CRN model is generated for a combustion system burning hydrogen-enriched methane/air mixtures at high-pressure lean-premixed conditions to compute NOx emission. A set of metamodels is then developed using NIPCE-PCM as a computationally efficient alternative to the physics-based CRN model. These surrogate models and experimental data are then implemented in the MCMC method to perform a two-step Bayesian calibration to maximize the agreement between model predictions and measurements. The average standard deviations for the prediction of exit temperature and NOx emission are reduced by almost 90% using this method. The calibrated model then used with confidence for global sensitivity and reliability analysis studies which show that the volume of the main-flame zone is the most important parameter for NOx emission. The results show satisfactory performance for the developed toolchain to perform Bayesian inference and UQ studies enabling a robust and consistent process for designing and optimising low-emission combustion systems.

Since the addition of Al to high-Mn steels is known to reduce their sensitivity to hydrogen-induced delayed fracture we investigate possible trapping effects connected to the presence of Al in the grain interior employing density-functional theory (DFT). The role of Al-based precipitates is also investigated to understand the relevance of short-range ordering effects. So-called E21-Fe3AlC κ-carbides are frequently observed in Fe-Mn-Al-C alloys. Since H tends to occupy the same positions as C in these precipitates the interaction and competition between both interstitials is also investigated via DFT-based simulations. While the individual H–H/C–H chemical interactions are generally repulsive the tendency of interstitials to increase the lattice parameter can yield a net increase of the trapping capability. An increased Mn content is shown to enhance H trapping due to attractive short-range interactions. Favorable short-range ordering is expected to occur at the interface between an Fe matrix and the E21-Fe3AlC κ-carbides which is identified as a particularly attractive trapping site for H. At the same time accumulation of H at sites of this type is observed to yield decohesion of this interface thereby promoting fracture formation. The interplay of these effects evident in the trapping energies at various locations and dependent on the H concentration can be expressed mathematically resulting in a term that describes the hydrogen embrittlement

The effects of hot stamping (HS) and tempering on the hydrogen embrittlement (HE) behavior of a low-carbon boron-alloyed steel were studied by using slow strain rate tensile (SSRT) tests on notched sheet specimens. It was found that an additional significant hydrogen desorption peak at round 65–80 °C appeared after hydrogen-charging the corresponding hydrogen concentration (CHr) of the HS specimen was higher than that of the directed quenched (DQ) specimen and subsequent low-temperature tempering gave rise to a decrease of CHr. The DQ specimen exhibited a comparatively high HE susceptibility while tempering treatment at 100 °C could notably alleviate it by a relative decrease of ~24% at no expanse of strength and ductility. The HS specimen demonstrated much lower HE susceptibility compared with the DQ specimen and tempering at 200 °C could further alleviate its HE susceptibility. SEM analysis of fractured SSRT surfaces revealed that the DQ specimen showed a mixed transgranular-intergranular fracture while the HS and low-temperature tempered specimens exhibited a predominant quasi-cleavage transgranular fracture. Based on the obtained results we propose that a modified HS process coupled with low-temperature tempering treatment is a promising and feasible approach to ensure a low HE susceptibility for high-strength automobile parts made of this type of steel.

Hydrogen has been long known to provide a solution toward clean energy systems. With this notion many efforts have been made to find new ways of storing hydrogen. As a result decades of studies has led to a wide range of hydrides that can store hydrogen in a solid form. Applications of these solid-state hydrides are well-suited to stationary applications. However the main challenge arises in making the selection of the Metal Hydrides (MH) that are best suited to meet application requirements. Herein we discuss the current state-of-art in controlling the properties of room temperature (RT) hydrides suitable for stationary application and their long term behavior in addition to initial activation their limitations and emerging trends to design better storage materials. The hydrogen storage properties and synthesis methods to alter the properties of these MH are discussed including the emerging approach of high-entropy alloys. In addition the integration of intermetallic hydrides in vessels their operation with fuel cells and their use as thermal storage is reviewed.

Hydrogen embrittlement susceptibility ratios calculated from slow strain rate tensile tests have been employed to study the response of three high-strength mooring steels in cold and warm synthetic seawater. The selected nominal testing temperatures have been 3 °C and 23 °C in order to resemble sea sites of offshore platform installation interest such as the North Sea and the Gulf of Mexico respectively. Three scenarios have been studied for each temperature: free corrosion cathodic protection and overprotection. An improvement on the hydrogen embrittlement tendency of the steels has been observed when working in cold conditions. This provides a new insight on the relevance of the seawater temperature as a characteristic to be taken into account for mooring line design in terms of hydrogen embrittlement assessment.

This paper presents a simplified procedure to analyse the Hydrogen Induced Cracking (HIC) of structural steels by means of the Small Punch Test (SPT). Two types of notched specimens were used: one with through-thickness lateral notch and another with surface longitudinal notch. The results for conventional specimens were compared with those for hydrogen pre-charged specimens. For this purpose two different methods to introduce hydrogen in the specimens were used: cathodic/electrochemical pre-charging and pressurized gaseous hydrogen pre-charging. The results obtained with both methods are also discussed.

Fracture failure caused by hydrogen embrittlement (HE) is a major concern for the system reliability and safety of hydrogen storage vessels which are generally made of 2.25Cr1Mo0.25V steel. Thus study of the influence of pre-charged hydrogen on fracture toughness of as-received 2.25Cr1Mo0.25V steel and weld is of significant importance. In the current work the influence of hydrogen on fracture toughness of as-received 2.25Cr1Mo0.25V steel and weld was systematically studied. Base metal (BM) and weld metal (WM) specimens under both hydrogen-free and hydrogen-charged conditions were tested using three-point bending tests. Hydrogen was pre-charged inside specimens by the immersion charging method. The J-integral values were calculated for quantitatively evaluating the fracture toughness. In order to investigate the HE mechanisms optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the microstructure of BM and WM specimens. The results revealed that the presence of pre-charged hydrogen caused a significant decrease of the fracture toughness for both BM and WM specimens. Moreover the pre-charged hydrogen led to a remarkable transition of fracture mode from ductile to brittle pattern in 2.25Cr1Mo0.25V steel.

Underground storage is a method of storing large amounts of renewable energy that can be converted into hydrogen. One of the fundamental problems associated with this process concerns determining the timing and amount of injected gas in the first filling period for the operation of an underground storage facility. Ascertaining the hydrogen flow rate is essential to ensure that the capillary and fracturing pressures are not exceeded. The value of the flow rate was assessed by modelling the injection of hydrogen into a deep aquifer. The best initial H2 injection period was found to be five months. The volume of the cushion gas and the total storage capacity expanded with the extension of the first filling period length. The working capacity grew as the depth increased reaching maximum values at depths of approximately 1200e1400 m. This depth was considered optimal for storing hydrogen in the analysed structure.

In this podcast David Ledesma talks with Rahmat Poudineh and Martin Palovic about their paper on integrating hydrogen into the European energy transfer infrastructure landscape. As hydrogen is expected to play an important role in European plans towards climate neutrality adequate hydrogen transport (and storage) infrastructure needs to be established. However hydrogen transport infrastructures are costly and have a long lead time. Furthermore hydrogen can be transported via a variety of means: it can be transported as a gas via pipelines or liquid via road rail and sea or even converted to derivatives such as ammonia or methanol for long distance transportation. It is also possible to transfer electrical energy instead of hydrogen and produce hydrogen in a decentralized way. From a system perspective all these infrastructures represent elements of a grand hydrogen ‘polygrid’ that will be the backbone of the future decarbonized energy system. This raises the fundamental question of how to prevent inefficiency and infrastructure redundancy across different modes of hydrogen transport. The task is made more challenging by technological uncertainty the unpredictability of future supply and demand for hydrogen network externality effects and investment irreversibility of grid-based infrastructures. In this podcast we discuss three possible coordination approaches to optimise future cross-sectoral investment into hydrogen transport infrastructure and highlight their strengths and shortcomings.

The podcast can be found on their website.