Underground hydrogen storage and its roadmap and feasibility in India toward Net-Zero target for global decarbonization

The world is combating climate change by adopting a low-carbon energy mix and pursuing a net-zero target. Being the third-largest CO2 emitter, net-zero target for India is crucial for global decarbonization. Hydrogen is a promising fuel for the future to aid in this transition, but its storage is a significant challenge. Surface-based storage options are inadequate and expensive, making underground hydrogen storage (UHS) in geological for -mations a more practical solution for its ample storage capacity and economic feasibility. Herein, this review critically investigates (i) the possibility of surplus renewable energy storage in India, (ii) UHS's applicability to store this surplus energy, and (iii) scientific aspects, feasibility, and challenges with suitable geological storage locations for storage of hydrogen in India. This review starts with briefing 'net-zero' at both the global and national (India) levels. The urgency for green energy is highlighted by the disparity between the Human Development Index and ecological footprint. The Indian hydrogen market and the production of green hydrogen from renewable resources are also discussed. The review discusses UHS storage types, reservoir and fluid pa-rameters, and flow behavior, including physiochemical, geochemical, and microbial interactions. Based on the geological basins and formation, availability and capacity of renewable energy sources, the potential of UHS in India is analysed. This review also provides vital information including technical data, regulations, initiatives, and policies needed to explore the opportunity of UHS and its development. Finally, the article presents chal-lenges and opportunities for UHS development and emphasizes the need for continued research and development.