Theoretical evaluation of round-trip efficiency of solid gravity energy storage systems

Solid gravity energy storage (SGES) is a method of energy storage technology that combines the prospects of operation safety, cost-effectiveness, and adaptive application. There are different systems within the SGES technology, which are grouped into three categories: mountain gravity energy storage (MGES), underground cavern energy storage (UCES), and structural building energy storage (SBES). However, there is a lack of studies comparing the round-trip efficiency of these SGES systems. To address this issue, this study first conducted academic review on differing SGES technologies, and simplified physical models were established to derive corresponding theoretical equations for determining the round-trip energy storage efficiency. Then, primary factors of influence on energy storage efficiency along with technical benefits and drawbacks of each system were then analyzed, revealing a variety of possible effects on efficiency and how to best utilize each SGES system, based on theoretical data.