Feasibility analysis of utilising underground hydrogen storage facilities in integrated energy system: Case studies in China

Underground Hydrogen Storage (UHS) is regarded as a promising approach to achieve seasonal energy storage in the future, due to its synergy with surplus renewable energy generation. This paper proposes the idea of implementing an Integrated Energy System (IES) with UHS and other hydrogen related technologies, called Hydrogen Penetrated Energy System (HPES), and presents an intelligent planning procedure applicable to the HPES. Depleted oil/gas fields and salt caverns are selected as the study objects to explore the ability of UHS to achieve seasonal peak shaving, facilitate the renewable energy, and improve the energy system efficiency. Firstly, three regions in China are analysed in terms of geological conditions, resource endowment and load characteristics, to illustrate the feasibility of building a HPES in each of the analysed region. A two-stage planning method for the HPES is proposed and a detailed UHS model is established where the process of cushion gas accumulation is emulated and the influence of the diurnal temperature range is considered. Comprehensive case studies are subsequently carried out for typical cities or regions in Eastern, Northern and North-eastern China and the results demonstrate that the HPES can lower the cost, improve the energy efficiency and reduce the level of carbon dioxide emission to some extent. A lateral comparison also shows that the combination of salt cavern UHS and offshore wind power has a broad application prospect in the east coast of China, and the investment in the HPES scheme for Jintan can be recovered within 8 to 9 years. In addition, compared with the benchmark scheme without UHS and large penetration of renewables, the HPES scheme for Jintan can improve the primary energy efficiency by 22.26% and 27.75% in the first decade and second decade, reduce the carbon dioxide emission by more than 96%, and consume an average level of 95.85% of the offshore wind power. Although the investment payback period of HPES cases in north and northwest China is relatively long (20 years or more), significant return and benefits can be obtained in the long term.