Experimental investigation on compressor performance in compressed air energy storage system under variable working conditions

Compressed air energy storage system has the advantages of high reliability, low cost, flexible layout, and negligible environmental impact. Meanwhile, the low efficiency of compressed air energy storage system is a key obstacle currently faced by researchers all around the world. Compressor and expander are the key components of compressed air energy storage system; thus, their efficiency directly affects the compressed air energy storage system efficiency. In order to improve the economic performance of compressed air energy storage system, this study proposes an expander/compressor integration based on pneumatic motor. The overall performance of the compressor under dynamic conditions, which are represented by the pressure change of the air tank and the load fluctuation, is investigated through experiments. The effect of torque, air tank pressure, mass flow rate, and rotating speed on compressor power consumption and energy conversion efficiency are studied. The experimental results show that the power consumed by the compressor increases with the increasing of torque, air tank pressure, mass flow rate, and rotating speed. When the rotation speed is 2700 r/min and the torque is 4 N·m, the work consumed by the compressor reaches the maximum value of approximately 1095 W. The maximum energy efficiency value of η1, η2, η3, and η4 are approximately 73.7%, 90%, 56.8%, and 52%, respectively.