Thermodynamics analysis of a novel compressed air energy storage (CAES) system combined with SOFC-MGT and using low grade waste heat as heat source

Abstract

As modern societies face increasing energy demands and a complex smart grid with multiple inputs of traditional and intermittent renewable energy power generation systems, the need for energy storage systems has become a general trend. Among these systems, compressed air energy storage (CAES) has received extensive attention due to its low cost and high efficiency. This study proposes a novel design framework for a hybrid energy system comprised of CAES system, gas turbine, and high-temperature solid oxide fuel cells, aiming for power generation and energy storage solutions. The overall model of the hybrid power generation system was constructed in Aspen Plus, and the mass balance, energy balance, and thermodynamic properties of the thermal system were simulated and analyzed. The results demonstrate that the hybrid system utilizes the functional complementarity of CAES and solid oxide fuel cells (SOFC), resulting in the cascade utilization of energy, flexible operation mode and increased efficiency. The overall round trip efficiency of the system is 63%, and the overall exergy efficiency is 67%, with a design net power output of 12.5 MW. Additionally, thermodynamic analysis shows that it is advisable to operate the system under higher compressor and turbine isentropic efficiencies, and optimal SOFC/MGT (Micro Gas Turbine) split air flow rates. The results of this article provide guidance for designing innovative hybrid systems and system optimization.