The save and effective storage of hydrogen in geological formations is an important part towards the implementation of renewable energy use. Due to fluctuating power supply from wind or solar plants, it is envisaged to use excess energy for electrolytical hydrogen production and the subsequent temporary storage in geological formations, as buffer for energy at “high-demand-low-production-times”.
The preferred geological storage formations are either salt deposits or porous sandstones with a gas-tight caprock. To date, these formations are generally confirmed to be appropriate for natural gas storage. However, the deviant physical properties of hydrogen, in terms of density, viscosity and hence mobility, require a reassessment of migration characteristics in these rocks.
For this purpose, an experimental set-up was designed, constructed and tested to quantify hydrogen migration rates in rocks. It comprises two gas chambers, separated by a through flange, containing the epoxy-embedded sample section with an exposed area of 7 cm². The retentate chamber is filled with a gas mixture of 2 Vol% hydrogen in synthetic air at 0.1 MPa. The permeate chamber contains air and includes an amperometric hydrogen sensor. Since there is no pressure gradient, the driving force for hydrogen movement is solely the concentration gradient between both sides of the rock sample. The hydrogen break-through and transport rates are monitored. In initial tests, core pieces of various length of sandstone and salt at dry and wet conditions are employed. The results approve the functional capability of the set-up and allow for a first-approach characterisation of hydrogen gas transport.