Techno-economic assessment on a multi-stage compressed carbon dioxide energy storage system with liquid storage

Abstract

Energy storage system is capable of solving the intermittent and volatility problems of renewable energy and can also perform peak-shaving and valley-filling of the grid. A compressed gas energy storage by storing liquid carbon dioxide possesses the merits of high energy density and competitive efficiency, which makes it a promising overground energy storage technology. However, the problems this technology faced with are narrow compression/expansion processes, high storage pressure and liquefying the gaseous carbon dioxide. Therefore, a liquid carbon dioxide storage system with low-pressure storage and extended working process is suggested in this work. Furthermore, a comprehensive evaluation is conducted on the system from both thermodynamic and economic aspects. The effects of charge and discharge pressures, CO2 mass flow ratio, system operation years, annual cycle times, discount rate, inflation rate and electricity price in different cities on system performance are analyzed. The results indicate that by increasing the charge and discharge pressures there is a maximum round trip efficiency of 56.23% and a peak energy density of 19.90 kWh/m3, respectively. In addition, the analysis of the electricity prices in four different cities on the economic action over the system shows that Shenzhen has the lowest levelized cost of energy (0.0907 $/kWh), Beijing can obtain the highest net present value of 35.314 million dollars and complete cost recovery in the shortest time of 4.84 years.