Experimental investigation on the output performance of a micro compressed air energy storage system based on a scroll expander

Compressed air energy storage (CAES) has attracted substantial attention due to its advantages, including low cost, long lifespan, and low environmental pollution. This paper establishes a test bench for a micro CAES system based on a scroll expander and employs experimental methods to investigate the effects of key parameters—regulated pressure, rotation speed, torque, volume flow rate (VFR), and expansion ratio on the output performance and energy conversion efficiency of the scroll expander and generator. The experimental results indicate that the power output of the scroll expander initially increases and then decreases with the increase of torque, rotation speed, expansion ratio, and VFR. The compressed air consumption rate (CACR) of the scroll expander initially decreases, stabilizes, and finally slightly increases with the increase of torque and expansion ratio. The CACR of the scroll expander slightly decreases at first, then flattens out, and eventually linearly increases trend with the increase of rotation speed and VFR. The power output of the generator initially increases to a peak value and then declines with changes in torque, rotation speed, expansion ratio, and VFR. The energy conversion efficiency of the generator first increases to the maximum value and then decreases with the increase of torque and rotation speed. To achieve high-efficiency operation, the generator should operate within a medium-to-low torque and a medium-to-high-speed range, with a maximum efficiency of approximately 95 %.