Performance investigation of solar-assisted supercritical liquid carbon dioxide energy storage systems

At present, Liquid carbon dioxide energy storage (LCES) plays an important role in stabilizing renewable energy fluctuations and maintaining grid stability due to its high energy density, no geographical restrictions, and low environmental impact. However, the efficiency of LCES is relatively low and its economic performance is poor. Coupled with solar energy can effectively solve these problems. Based on this, this article proposes a new liquid carbon dioxide energy storage system integrated with tower solar energy and waste heat recovery system (WHRS). Thermodynamic performance and economic feasibility analyses are conducted to evaluate the system performance. Compared to the reference LCES system, the energy efficiency of the novel system has increased by 15.85 %. Although the energy efficiency has decreased by 0.44 % compared to the system only coupling WHRS, the energy generated per unit volume of storage (EGV) has increased by 17.58 kWh/m3, and the system's power output has also been significantly enhanced. In addition, the economic performance of the system is competitive, with a dynamic payback period (DPP) of 6.2 years, a 30-year net present value (NPV) of 4.91 M$, an internal rate of return (IRR) of 19.15 %, and a levelized cost of energy (LCOE) of 0.1998 $/kWh, indicating strong profitability. In addition, the influences of the inlet temperature of turbine 1, energy storage pressure, energy release pressure, electricity price fluctuations, and different regions on system performance are also analyzed.