Thermodynamic simulation and economic analysis of a novel liquid carbon dioxide energy storage system

Compressed carbon dioxide energy storage systems have attracted much attention due to their high energy storage density and no geographical restrictions. This paper proposes a novel liquid carbon dioxide energy storage system based on the conventional transcritical compressed carbon dioxide energy storage system, where a condenser is adopted to liquefy the carbon dioxide in the high-pressure storage tank and a booster pump is added to flexibly regulate the turbine inlet pressure in the energy release process. Detailed mathematical models of the energy storage systems are established and verified. The effects of some decision parameters on the round-trip efficiency, energy generated per unit volume of storage, and the Levelized cost of electricity are studied by parameter analysis. Finally, both the conventional and novel carbon dioxide energy storage systems are optimized and compared in terms of thermodynamics and economics. Single-objective optimization reveals that the round-trip efficiency and energy generated per unit volume of storage of the novel system are 0.55%pt. (percentage point) and 9.45 times higher than those of the conventional system, respectively. Multi-objective optimization results show that the round-trip efficiency, energy generated per unit volume of storage, and Levelized cost of electricity of the novel system are 2.58%pt. higher, 19.19 times higher, and 1.41 % lower than those of the conventional system respectively, indicating that the novel system has better-balanced performance. Exergy analysis indicates that the largest exergy destructions occur in the cold energy storage units.