Design, Experimental Investigation, and Thermodynamic Performance Analysis of a Small-Scale Compressed Air Energy Storage System for Off-Grid and Rural Electrification Applications

Abstract

Energy storage is the critical enabling technology for reliable renewable energy supply from intermittent solar and wind sources, particularly for off-grid and rural applications where grid backup is unavailable. Compressed Air Energy Storage (CAES) offers an attractive alternative to electrochemical battery storage for small-scale off-grid systems, with advantages including long cycle life (>10,000 cycles with no degradation), use of non-toxic and widely available working fluid (air), low self-discharge, and potential for waste heat recovery from the compression process. This paper presents the design, fabrication, and comprehensive experimental Characterisation of a small-scale CAES test facility comprising a two-stage reciprocating compressor (750 W, 8 bar maximum), a 200-litre mild steel storage vessel (15 bar rated), and a vane-type pneumatic expander motor (1.2 kW rated) instrumented with pressure transducers, RTD temperature sensors, a vortex flow meter, and a torque-speed sensor for full system energy accounting. Experiments were conducted at five storage pressure levels (4 to 12 bar) and two expander speeds (500 and 800 rpm), characterising charging energy, discharge energy, round-trip efficiency, and exergy efficiency. The complete thermodynamic model incorporating isothermal, adiabatic, and actual (polytropic) compression and expansion processes is developed and compared with experimental measurements. Maximum round-trip efficiency of 50.0% is achieved at 10 bar storage pressure, consistent with theoretical predictions accounting for compressor inefficiency (76.7–79.8%), expander inefficiency (64.2–76.2%), and heat losses during storage and discharge. An inter-stage air preheating strategy using recovered compressor aftercooler heat improves round-trip efficiency by 4.2 percentage points at 10 bar. The experimental dataset and efficiency analysis provide a validated technical foundation for the design of CAES systems coupled with solar photovoltaic generation for rural off-grid electrification applications in India.

Cite as:

Patil Sanket T. (2026). Design, Experimental Investigation, and Thermodynamic Performance Analysis of a Small-Scale Compressed Air Energy Storage System for Off-Grid and Rural Electrification Applications. Advancement in Mechanical Engineering and Technology, 9(2), 40–49. https://doi.org/10.5281/zenodo.21820464