Thermodynamic and Economic Assessment on the Supercritical Compressed Carbon Dioxide Energy Storage System coupled with Solar Thermal Storage

Abstract

In recent years, renewable energy, particularly solar energy and wind energy, has demonstrated robust growth worldwide. However, the intermittent nature of these energy sources causes significant challenges for the security and reliability of grid, which limits the penetration growth in power market. To enable a higher penetration of renewable energy sources and satisfy the demand for peak shaving and valley filling of the grid, one possibility is to couple them with energy storage systems. In this study, two supercritical compressed carbon dioxide energy storage systems coupled with concentrating solar thermal storage are proposed. One is a simple compression cycle, and the other is a split compression cycle. Both thermodynamic and economic performance have been investigated numerically. The effects of energy storage pressure, heating temperature, thermal oil mass flow rate and split ratio are discussed. The results indicate that under the designed condition, there exists a maximum energy storage efficiency for the simple cycle when the heating temperature is lower than 538.15K. Continuing to increase heating temperature, the efficiency first increases from 64% to 73.9% rapidly as the total pressure ratio rises from 3 to 5. However, the improvement of it will be limited after the pressure ratio exceeds 5. Besides, if the thermal oil mass flow rate rises, the efficiency also has a maximum value, which appears between 150kg/s and 160kg/s. Finally, for the split cycle, there exists an optimal value. And the optimal condition can promote the Dynamic Payback Period and Levelized Cost of Energy to fall about 2 years and 6.1% compared to the simple cycle.