Energy and Performance Analysis of a Novel Near-Isothermal Pneumatic Compressed Air Energy Storage System

Today, renewable energy is receiving increasing global attention. However, the operation of such energy systems is associated with several challenges, including natural uncertainty and intermittency at different times of the day. Furthermore, to overcome these challenges, there is an increasing interest in developing energy storage systems. Compressed air energy storage (CAES) is considered a promising, cost-effective, and environmentally friendly technology. The present study proposes a novel CAES system distinct from conventional designs. The proposed storage system can store energy by feeding the excess electrical energy to a motor to drive a large-diameter piston to compress and store air in a container. Then, the energy is extracted when needed by releasing the piston to drive the generator back. This study evaluates the feasibility via a thermodynamic model of all components. We examine the effects of (i) piston speed and piston-air volume ratio, (ii) initial pressure, and (iii) container volume. We also assess how container volume scales with the maintained initial pressure. Results are compared against an adiabatic baseline. The results demonstrate that near-isothermal compression/expansion can improve energy density and storage efficiency by generating two times more recoverable work than the adiabatic in the same volume, and an efficiency of 76% can be reached, while the realistic efficiency achieves around 50%. It also shows that the volume of the container for an amount of energy depends on the initial pressure maintained before the charging cycle. As a result, when the initial pressure increases, the volume of the container required decreases, and for the same volume, the results show that more energy can be stored by maintaining the initial pressure. Therefore, this system could be considered an attractive solution to the integration of intermittent renewable energy sources.