Cryogenic energy storage characteristics of a packed bed at different pressures

A packed bed cryogenic energy regenerator is investigated for use in a cryogenic energy storage (CES) system. With liquid nitrogen used as the working fluid, the cryogenic energy storage characteristics of the packed bed are investigated at pressures of 0.1 MPa and 6.5 MPa. The packed column is 1500 mm in height with a 345 mm inner diameter, and is made of 16 mm thick stainless steel. Granite pebbles about 9 mm in size are used as the medium for energy storage. The transient axial and radial temperature distributions of the packed bed were measured, and the results show that the transient temperature axial distribution exhibits a typical thermocline behavior at both low and high pressures. The temperature distribution does however vary significantly at the different pressures.