Performance of a compressed-air energy storage pile under various operation conditions

Abstract

Compressed air energy storage (CAES) has been re-emerging over the last decades as a viable energy storage option, and the authors have recently explored the idea of utilizing building foundations (termed as CAES piles) as small-scale storage media for the air charge and load-bearing elements under simplified conditions. This paper extends the authors' preceding work and conducts a series of finite element analyses to investigate the impact of various operation conditions, such as heat management, ground profiles, and pile-head fixities, on the performance of a CAES pile. The analysis results show that a greater axial pile displacement and a greater tensile stress are induced in the CAES pile during the air charge as the surrounding soil becomes weaker. Adiabatic and diabatic heat management conditions yield greater axial pile displacements but smaller tensile stresses in the pile during the air charge than an ideal isothermal condition. Having a restraint at the pile head (i.e., fixed-head condition) or at the pile base (i.e., hard rock layer beneath the pile base) leads the CAES pile to move toward a direction where there is a less restraint and such a constraint induces compressive stress in the pile during the air charge, eventually reducing the magnitude of the tensile stress in the pile when fully pressurized. The maximum tensile stress developing in the pile during the air charge does not exceed the lower bound of yield strengths of steels commonly used for conventional pipe piles but the analysis results suggest that higher-grade steels would be more advantageous for CAES piles to secure some safety margins.