Structural responses of energy storage pile foundations under thermal-mechanical loadings

Abstract

Recently studies have investigated feasibilities to configure pile foundations as energy storage media using a small-scale compressed air energy storage technology. These studies consider that storage temperatures of compressed air can be lowered entirely down to ambient temperatures through a cooling process. This assumption may not be feasible and economical due to the efficiency of the cooling process. As an alternative option, a higher storage temperature can be allowed by reducing the cooling time, which can cause additional thermal-mechanical loadings to the pile foundation. This paper investigates structural responses of reinforced concrete pile foundations subjected to combined structural, compressed air pressure, and thermal-mechanical loadings through nonlinear dynamic heat transfer and thermal-mechanical analyses. Several parameters were studied, including pile spacing, pile inner diameters, and concrete grades. Analysis results show that thermal-mechanical loading can reduce critical tensile stresses and change stress distributions in the pile section originated from compressed air pressure. Design recommendations were made to determine an optimal storage temperature and an allowable loading cycle for the energy storage pile foundation.