Thermo-economic analysis on trans-critical compressed CO2 energy storage system integrated with the waste heat of liquid-cooled data center

Compressed CO2 energy storage (CCES) technology has the advantages of high energy storage density, low economic cost, low carbon emission, which is suitable for the construction of large-scale and long-time energy storage system. Besides, as a scene with massive heat, the electricity consumption of servers in data center is mostly converted into heat. Thus, the purpose of this work is to integrate a trans-critical compressed CO2 energy storage system with the waste heat of data centers, so as to improve the system performance and reduce the operating cost of data center. Based on different operating principles of compressors, a single-stage compression system (System-CP) and a double-stage compression system (System-VP) are constructed. To analyze and compare the energy and exergy performance of these two systems under design conditions, a quasi-dynamic model is developed by considering the variations of pressure and temperature in the storage tank. On this basis, an economic model is developed to obtain the economy performance for the systems. The obtained results show that the round-trip efficiency (RTE) of System-CP and System-VP are 64.67 % and 67.41 %, respectively. For the energy storage capacity 15 MW x 5 h, volumes of high-pressure S-CO2 storage tank are 314,387.51 m3 and 287,982.91 m3 for System-CP and System-VP, respectively. Thereby, the energy storage density (ESD) of System-CP and System-VP are 0.24 kW & sdot;h/m3 and 0.26 kW & sdot;h/m3, respectively. Meanwhile, the total capital cost (TCC) is $477.84 x 106 for System-CP, and $437.41 x 106 for System-VP, and the corresponding payback period (PBP) are 14.76 years and 12.39 years respectively. Further, the effect of key parameters on systems performance is revealed. The results show that with the decrease of slip-pressure range decreases, RTE, TCC and the volume of storage tanks increase linearly.