Abstract

Exergy transmission characteristic of the compressed CO2 energy storage system is significant to evaluate the system performance while little attention has been paid to this analytical method in the literature. A CO2 energy storage cycle configured with a gas holder as a low-pressure gas reservoir and a liquid tank as a high-pressure gas reservoir is studied comprehensively. The exergy transmission characteristics and the cost uncertain analysis are considered. Results demonstrated that the round trip efficiency and levelized cost of storage are 71.2 % and 0.1286 $/kWh under optimal design parameters, respectively. Keeping the charge/discharge duration ratio close to 1 has a positive effect on optimizing the economic performance of the system. With the general exergy model of the whole system configured for the charge and discharge process, the study uncovers the fluctuations in the pertinent proportional ratios and exergy transfer efficiency in relation to important parameters. Except for the turbomachinery isentropic efficiency, which impacts nearly all efficiencies, the variation of each parameter only governs the modification of the exergy transfer efficiency for a specific term or a pair of terms. Furthermore, the thermal exergy efficiency of the discharge process and intercooler has a maximum value as the cold-side temperature difference of the high-temperature cooler changes to 27 °C.

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