Hydrogen storage

Hydrogen storage in saline aquifers

The variation of the diffusion coefficient of H2 in brine in dependence on the total cation concentration from 0.5 mol/kgH2O to 5 mol/kgH2O at (a) T = 298 K and P = 1 atm and (b) T = 648 K and P = 218 atm.

Period 1.2021 – 12.2021

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Prof. Dr. Ingo Sass Leader
Applied Geothermal Engineering

Prof. Dr. Florian Müller-Plathe
Workgroup Theoretical Physical Chemistry

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Project description:

Germany is as part of the ‘Energiewende’ aiming to increase its share of renewable energies. However, renewable energies have fluctuations on daily and seasonal levels. Producing and storing H2 from the surplus electricity produced by renewable sources is one of the most promising solutions to stabilize the fluctuations in renewable energies production rate and secure the energy supply. To follow up this goal, here we examine the H2 storage in saline aquifers. Predicting the diffusion coefficient of hydrogen molecules at the conditions of saline aquifers is critical for modelling of hydrogen storage taking into account the interaction of hydrogen molecules with rocks and fluids. The diffusion coefficient of hydrogen molecules into chloride brine with different cations (Na+, K+, Ca2+) containing up to 5 mol/kgH2O concentration has been numerically investigated. We find that the temperature, pressure and properties of ions (compositions and concentrations) affect the hydrogen diffusion coefficient. In addition, to account for the pressure and composition of positive ions, combining the obtained MD results with five models of machine learning (ML) provide effective results to predict hydrogen diffusion. The resultant fitting equation from linear regression (LR) model compares well with other ML methods with slightly larger errors. Our work provides a promising route for a quick and cost-effective diffusion coefficient determination for multiple and complex brine solutions with a wide range of temperature, pressure and ion concentration by the combination of MD simulations and ML techniques. Numerical simulations used for examination of the behavior of injected gas. Results shows that CO2 as cushion gas would be lost due to the dissolution process and we need to replenish the CO2 in the system. Due to the low H2 solubility, the H2 loss in comparison to CO2 is negligible. This project builds a basis for a large proposal in which the study will be extended including the multiphase system (water + H2 + cushion gas).