Full dynamic simulation of an adiabatic compressed air energy storage plant with radial-flow packed-bed storage and an organic Rankine cycle unit

Abstract

[EN]This work analyzes several adiabatic compressed air energy systems (ACAES) configurations with a thermodynamic time-dependent model. ACAES systems allow for large-scale energy storage, with fast response times and high output power. However, despite being a promising technology, few works have been done in systematically modeling the unsteady dynamic operation and integrating all components in ACAES plants. The developed model in this work can simulate the thermodynamic behavior of the plant components individually and their integration into an ACAES plant as a whole. The influence of an additional organic Rankine cycle on the round-trip efficiency of the plant is also studied. A comparison of the performance of several plant arrangements is obtained under a unified framework, filling an observed gap in the reported literature. Particular results include the centrifugal compression train working along the peak-line efficiency, the analysis and comparison of pressure drops in packed-bed subsystems used as thermal energy storage: axial or radial, and the optimization of the inlet pressure in the Rankine evaporator. As a conclusion, pressure drops in the radial packed-beds are found to be about 20% lower than in axial packed-beds, and global round-trip efficiencies can be improved by about 2%–3% (reaching values of 0.78) by selecting a suitable symmetrical configuration or by coupling a Rankine cycle. This increase in efficiency is due to the notable reduction in destroyed exergy when an optimized organic Rankine is used for heat recovery instead of discharging heat by an intercooler device.