A Review of Geological Energy Storage Technologies for Geothermal Energy Utilization

Geological thermal energy storage (TES) plays a vital role in the transition toward low-carbon and sustainable energy systems by mitigating the seasonal mismatch between renewable energy supply and heating/cooling demand. This paper systematically reviews recent advances in borehole (BTES), aquifer (ATES), mine/tunnel, and hybrid TES technologies, with a focus on their operational principles, system configurations, and integration into district energy networks. However, despite notable technical progress, the widespread deployment of geological TES remains constrained by site-specific geological heterogeneity, heat losses, clogging, and high upfront costs. Future research and development should prioritize the repurposing of existing underground infrastructure, the advancement of high-temperature and deep storage systems, the integration of digital and intelligent operation strategies, and the formulation of supportive policy and market frameworks. With continued innovation, geological TES holds substantial promise for enabling resilient, low-carbon, and cost-effective energy systems.