Phase equilibrium, thermodynamics, hydrogen-induced effects and the interplay mechanisms in underground hydrogen storage

Abstract

T., Sun, S. Phase equilibrium, thermodynamics, hydrogen-induced effects and the interplay mechanisms in underground hydrogen storage. Abstract: Global attention has shifted back to hydrogen, the ultimate green alternative energy, due to the intensifying extreme climate and greenhouse impacts. It is now a promising energy carrier for large-scale underground hydrogen storage, which may benefit the peak-shaving of electric grids and the supply from other sustainable energies. The prospects of underground hydrogen storage are bright due to the abundance of subsurface formations such as depleted oil and gas reservoirs, saline aquifers, and salt caverns and the traditional energy industry's extensive underground procedures and management knowledge. However, hydrogen's unique thermodynamic and chemical properties pose challenges as well, requiring further research and modeling to provide a firm basis and validate engineering practice. Some typical concerns, like hydrogen embrittlement, have long plagued industry. The intricate and difficult-to-reach nature of the underground makes fundamental mechanics, mathematical modeling, and numerical simulation essential tools for further advancement. Integration of experiments and simulations at the multi-scale (molecular, pore, and Darcy) provides data support and solution validation for the pursuit of comprehensive descriptions and accurate predictions of hydrogen storage and extraction processes. Given this, our paper reviews the thermodynamic properties of hydrogen, focuses on the phase equilibrium processes at different scales in underground hydrogen storage, and introduces the related mathematical models and simulation methods. Based on recent research progress and comparing four typical trapping mechanisms in carbon capture, utilization and storage, we highlight some unique hydrogen-induced effects: (1) compositional grading; (2) competitive adsorption; (3) hydrogen-induced rock alteration, in conjunction with phase equilibrium issues, discuss their interplay mechanisms, offering constructive insights for further in-depth research.