Design and performance analysis of a novel compressed air–liquid CO2 energy storage

The application of aboveground artificial tank frees the compressed air energy storage (CAES) from geographical limitations, while one significant issue is how to reduce the price of storage tanks and achieves high efficiency concurrently. The compressed CO2 energy storage (CCES) with flexible gas holder may be an effective and economic proposal, but it can only be used in sparsely populated areas due mainly to the huge size of flexible gas holder. Therefore, this study reports a new aboveground energy storage system with a small footprint, high efficiency and low investment cost. This system is an integration of CAES and CCES by arranging the CCES flexible gas holder into the CAES air chamber. With this configuration, the isobaric CAES is ensured and the size of flexible gas holder is significantly lessened. The integrated system is systematically evaluated in the view of a technical and economic standpoint. It is found that the system efficiency is 67.47 % (charge and discharge pressures being 5.5 MPa), which is increased by 12 % of the CAES efficiency (charge pressure being 10 MPa and discharge pressure being 3.5 MPa). One of the deficiencies of the proposed system may be the larger gas storage volume, which is 1.27 times of that in the CAES system. The system levelized cost of storage is 0.1491 $/kWh, representing a 14.05 percent reduction compared to that of the CAES system. More importantly, the system gas storage pressure is only 5.5 MPa, carrying about half of that in the CAES system. The reliability and safety of the energy storage plant is extensively intensified.