Novel scroll tip modification: development and validation of scroll expander for compressed-air energy storage

• A novel Lip Spoiler scroll tip improves scroll expander performance for CAES systems. • Compared with other tips, the LS scroll shortens scroll length and removes suction blockage. • Simulation and experiment agree well, validating a deterministic 1-D MATLAB scroll model. • At ambient conditions, LS raises efficiency from 69 % to 72 % and power from 141 W to 176 W. Scroll expanders are promising components for micro-scale Compressed-Air Energy Storage (mCAES) systems due to their compactness, oil-free operation, and high efficiency. However, their performance is highly sensitive to both scroll geometry and the matching of built-in volume ratio (Rv) with operating pressure. This study investigates a novel scroll tip modification called Lip Spoiler (LS) and is aimed at improving expansion ratio, eliminating suction blockage, and enabling efficient expansion within shorter scroll lengths. A fully deterministic 1-D MATLAB model was adapted and experimentally validated using three scroll expander prototypes with different built-in volume ratios (Rv = 3.5, 3.0, and 2.5). Results show that reducing Rv from 3.5 to 2.5, in consistent with a 3-bar a inlet pressure, achieves adaptive expansion, leading to a 12 % increase in isentropic efficiency and a 27 % improvement in power output. Incorporating the LS tip design at Rv = 2.5 further enhances performance, reaching 72 % efficiency and 176 W output, representing a 32 % power gain compared to the baseline design. These findings demonstrate that both precise volume ratio selection and scroll tip optimization are critical for maximizing scroll expander performance in CAES systems, offering a scalable and efficient solution for renewable energy storage.