The key feature of Adiabatic Compressed Air Energy Storage (A-CAES) is the reuse of the heat generated from the air compression process at the stage of air expansion. This increases the complexity of the whole system since the heat exchange and thermal storage units must have the capacities and performance to match the air compression/expansion units. Thus it raises a strong demand in the whole system modelling and simulation tool for A-CAES system optimisation. The paper presents a new whole system mathematical model for A-CAES with simulation implementation and the model is developed with consideration of lowing capital cost of the system. The paper then focuses on the study of system efficiency improvement strategies via parametric analysis and system structure optimisation. The paper investigates how the system efficiency is affected by the system component performance and parameters. From the study, the key parameters are identified, which give dominant influences in improving the system efficiency. The study is extended onto optimal system configuration and the recommendations are made for achieving higher efficiency, which provides a useful guidance for A-CAES system design.

The paper presents the mathematical models of an A-CAES system components and developed a new whole system model of A-CAES with low temperature thermal storage. The model is implemented in Matab/Simulink software environment. With the system model developed in the paper, the system energy efficiency is analysed, especially, a comprehensive study is performed on how much the system parameter variations affect the system overall efficiency. From the analysis, it is found that the isentropic efficiencies of compressors and turbines and the heat transfer rates of HEXs are the key parameters to give the dominant influences on the system efficiency. In addition to system parameters, the system configuration can also lead to system efficiency improvement. From the study, multi-stage compression and expansion can improve system efficiency but it does not mean the system can have unlimited number of stages. Regulating the A-CAES charging time and discharging time via flow control can also lead to different system efficiencies. These are considered as the important factors for efficient system design in practice. The results from optimal design study of low temperature A-CAES systems show that the system cycle efficiency and the heat energy recycle efficiency can potentially reach to around 68% and 60% respectively. The results confirm that the current relative low efficiency of CAES systems can be improved to address the main concern of CAES system design and deployment.

The results have been published on Applied Energy 162 (2016) 589–600.