Optimizing compressed air energy storage with organic Rankine cycle and ejector refrigeration for sustainable power and cooling provision

Abstract

In the pursuit of sustainable energy systems, integrating storage technologies is crucial. Compressed air energy storage (CAES) emerges as a significant option for ensuring reliable power supply during peak hours. This study focuses on a configuration combining a CAES unit with two integrated organic Rankine cycle and ejector refrigeration units (ORCERC). The primary objective is to ensure adequate power supply during peak hours in the discharge period, while also providing cooling capacity to enhance system flexibility and efficiency. The proposed system is evaluated from thermodynamic, exergoeconomic, and exergoenvironmental perspectives to determine optimal operating conditions for the CAES unit. A fluid selection process identified a suitable zeotropic mixture, R141b/Hexane, as the working fluid for both ORCERCs. The results demonstrate a net power production of 20,749.91 kW and a cooling load of 1448.23 kW, with cost and exergoenvironmental impact rates of $1193.59/h and 143.42 Pt/h, respectively. Additionally, the configuration achieves an exergy round-trip efficiency of 65.85 % and a payback period of 2.88 years. Increasing the HTES temperature from 1150 to 1250 K improved both the round-trip efficiency (RTE) and exergetic round-trip efficiency (ERTE) from 52.22 % to 53.39 % and 62.98 %–63.71 %, respectively, while reducing the product cost and exergoenvironmental impact rate from $1128 to $1117/h and 134.35 to 127.93 Pt/h, respectively. Three triple-objective optimization scenarios were considered, yielding diverse outcomes, each contributing unique insights into the system's performance and potential improvements.