With the increasing proportion of renewable energygeneration in the power system, its intermittence and volatility promote the development of Energy Storagesystems. Liquid Air Energy Storage (LAES) has attracted wide attention due to its many unique advantagesincluding high energy density, geographical-constraint free and a highly competitive capital cost. However, its efficiency is not high, mainly due to the lack of cold energy to cool the air, and the systemâ€™s liquid rate is low (about 70%). On the other hand, liquified natural gas (LNG) is an efficient and well-developed technology to store and transport natural gas after purification and liquefaction, which has a lot of cold energy that can be used to help cool the air. In this study, LNG is directly involved in the air-cooling process. According to the LNG inlet temperature, the recoverable energy cold in the discharging air is stored in different tanks. The thermodynamic model of the system is established, and the optimal mass flow rate of propane and LNG is studied. Performance of the system under different working conditions with or without LNG is analyzed. The result shows that it should increase the mass flow rate of propane on the premise of ensuring the temperature of the cold storage tank; The efficiency of the independent LAES system is still less than 51%, ignoring the disadvantages of high heat storage temperature under high energy storage pressure. However, under the optimal LNG supply mass flow rate, the recommended charging pressure is 8MPa, the energy release pressure is 16MPa, the liquid rate is up to 89.35%, and the system efficiency is 68.83%. In addition, optimal LNG flow rates under various operating pressures are provided to guide engineering practice.
Keywords Energy storage, Liquid air, LNG cold energy, Cycle efficiency