Hydrogen energy system and underground hydrogen storage in depleted reservoirs

In a situation where the increase in greenhouse gas emissions in the atmosphere has unfavorably led to global warming, the production of energy from renewable and clean sources, instead of fossil fuels, has become very attractive worldwide. To replace traditional energy sources, hydrogen (H 2 ), as the most abundant element in the environment, has emerged as a recently developed energy carrier with a high calorific value. Due to its diverse applications, such as internal combustion engines and electric turbines, hydrogen is poised to become a cornerstone of global financial management in the current century. By examining and understanding hydrogen energy, realize that transitioning to a hydrogen-based economy will require an efficient, safe, and high-capacity storage system. This is why the most attractive hydrogen storage system globally is the underground storage system (USS), especially within depleted oil and gas reservoirs. Due to the unique features of hydrogen, such as high reactivity, slow kinetics, and the challenge of hydrogen adsorption/desorption temperatures, hydrogen storage faces numerous challenges. Therefore, in this study, a comprehensive review of the individual features of H 2 , hydrogen storage systems, and other influencing factors has been conducted. By accurately identifying existing mechanisms, capacities, and barriers, this study aims to inspire further research and contribute to the progress of the hydrogen economy. Additionally, this study presents, for the first time, a thorough review of H 2 sources and hydrogen storage mechanisms, providing a comprehensive overview of all critical stages of this industry.