Investigation on performance improvement of small scale compressed-air energy storage system based on efficient radial-inflow expander configuration

Distributed power generation systems powered by compressed air energy storage can be considered as one of the effective solutions for high energy demand. In this regard, the key component for such systems is the expander where the overall system efficiency has been affected by the expander performance. Therefore, this work outlines a novel integrated methodology to predict the performance characteristics of the radial-inflow expander for small scale compressed air energy storage CAES system for low mass flow rate applications. The integrated methodology combines the mean-line design and 3D CFD simulations for the expander with thermodynamics analysis for CAES system. The expander mean-line design is verified against the data available in open literature and compared with the delivered results from the CFD simulations using ANSYS-CFX. Moreover, comprehensive parametric studies are carried out based on the CFD analyses under design and off-design conditions in terms of rotational speed, expander inlet temperature and expansion ratio in order to investigate the effect of those conditions beside the geometric parameters on the expander and system performance. The delivered results from CFD simulations and CAES system analyses highlighted that radial-inflow expander with CAES can be used for distributed power generation. The expander performance maps based on CFD analyses exhibited that the maximum power and efficiency were 3.282 kW and 76.70% respectively with CASE system efficiency of 12.46% and the system round trip efficiency of 59.08%.