Fast lateral hydrogen diffusion in magnesium-hydride films on sapphire substrates studied by electrochemical hydrogenography

Hydrogen diffusion in thin magnesium films in lateral film direction is studied by stepwise electrochemical loading via the change in optical light transmission (‘electrochemical hydrogenography’) during the dihydride formation. During the first loading step, the dihydride front propagation kinetics allows determining the lateral hydrogen diffusion coefficient in the film, by applying an analytical model and, alternatively, by comparison with finite-element simulations. Subsequent loading steps show a time lag behavior in the dihydride front propagation. Therefore, they can be regarded as permeation experiments. These subsequent loading steps can be explained by hydrogen diffusion along grain boundaries and by taking the Gaussian shape of the hydrogen site energy distribution in the grain boundaries into account. In average, an effective hydrogen diffusion coefficient of $3_{?2}^{+12}?{10}^{?12}\raisebox{1ex}{${\text{m}}^2$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$ was found in lateral film direction. This value is the highest value known for hydrogen diffusion in Mg-dihydride, at room temperature. Possible sources for this high lateral hydrogen diffusivity are discussed including preferential hydrogen diffusion along the Mg/Mg-oxide interface, anisotropy of diffusion coefficients and lowering of diffusion energy barrier upon anisotropic film expansion.     

A quantitative assessment of the hydrogen storage capacity of the UK continental shelf

Increased penetration of renewable energy sources and decarbonisation of the UK's gas supply will require large-scale energy storage. Using hydrogen as an energy storage vector, we estimate that 150 TWh of seasonal storage is required to replace seasonal variations in natural gas production. Large-scale storage is best suited to porous rock reservoirs. We present a method to quantify the hydrogen storage capacity of gas fields and saline aquifers using data previously used to assess CO₂ storage potential. We calculate a P50 value of 6900 TWh of working gas capacity in gas fields and 2200 TWh in saline aquifers on the UK continental shelf, assuming a cushion gas requirement of 50%. Sensitivity analysis reveals low temperature storage sites with sealing rocks that can withstand high pressures are ideal sites. Gas fields in the Southern North Sea could utilise existing infrastructure and large offshore wind developments to develop large-scale offshore hydrogen production.     

A Mass-Preserving Two-Step Lagrange–Galerkin Scheme for Convection-Diffusion Problems

Journal of Scientific Computing - In this paper, we propose and analyze a mixed finite element scheme for stationary inductionless magnetohydrodynamic equations on a general Lipschitz domain. We...     

Start-ups and firm in-migration: evidence from the Swedish wholesale industry

We use a data set covering 13,471 Swedish limited liability firms in the Swedish wholesale industries during 2000–2004 to ascertain the determinants of new start-ups and of in-migration of firms. Access to a large harbor, international airport or large railroad classification yard in the municipality nearly triples the number of start-ups and increases the expected number of in-migrating firms with 53 %. The presence of a university, many educated workers and low local taxes are also associated with more start-ups and firm in-migration.     

Geometrically non‐linear damage interface based on regularized strong discontinuity

The contribution of this paper concerns the fracture modelling of an interface with a fixed internal material surface in the context of geometrically non‐linear kinematics. Typical applications are composite laminates and adhesive/frictional joints in general. In the model development, a key feature is the concept of regularized strong discontinuity, which provides a regular deformation gradient within the interface. The deformation gradient within the interface is formulated in a multiplicative structure with a continuous part and a discontinuous part, whereby the interface deformation is interpreted as a transformation between the material damaged configuration and the actual spatial configuration. In analogy with the continuum formulation of hyper‐inelasticity, a constitutive framework is defined for the relation between the induced material traction and the displacement jump vector, which are defined on the material damaged interface configuration. Within this framework, a simple, but yet still representative, model for the delamination problem is proposed on the basis of a damage–plasticity coupling for the interface. The model is calibrated analytically in the large deformation context with respect to energy dissipation in mode I so that a predefined amount of fracture energy is dissipated. The paper is concluded with a couple of numerical examples that display the properties of the interface. Copyright © 2002 John Wiley & Sons, Ltd.