Status and challenges of deep geothermal exploitation and energy storage technology: a comprehensive review

Abstract

Geothermal energy is a green source of power that offers a promising solution to achieving a net-zero emissions target. Deep geothermal energy resources primarily consist of Hot Dry Rock (HDR) resources, which have the potential to scale up their exploitation by Enhanced Geothermal Systems (EGS). Additionally, there has been an increased interest in utilizing HDR reservoirs as a large-scale renewable energy storage solution because to its potential to contribute to the improvement of energy efficiency by stabilizing fluctuations in the supply and demand for heat energy. This work presents a comprehensive review of deep geothermal energy exploitation, focusing on the development of EGS and its role in energy storage systems. The paper discusses the geological distribution and classification of geothermal thermal energy resources. The exploitation status of HDR and supercritical geothermal is examined. This study also explores the methods of heat storage and compressed air energy storage in deep geothermal reservoirs. It highlights the technical challenges of deep geothermal energy development in the process of drilling, completion, heat exchange, and energy storage. Recommendations are provided for further research directions, including (a) deep geothermal resources evaluation and reservoir characterization; (b) deep geothermal well construction; (c) integration of deep geothermal energy with variable renewable energy sources; and (d) energy system operation optimization.