Performance analysis of liquid air energy storage with enhanced cold storage density for combined heating and power generation

Abstract

Liquid air energy storage (LAES), as a grid-scale energy storage technology, is promising for decarbonization and carbon-neutrality of energy networks. In the LAES, off-peak electricity or renewable energy is stored in the form of liquid air (i.e. air liquefaction); when electricity is needed, the liquid air is evaporated to generate electricity and meanwhile releases a great deal of cold energy in a temperature range of 85-300 K. The released cold energy is usually recovered for improving the air liquefaction, where fluids are popular as both cold recovery and storage media with the benefits of straightforward control strategy and high efficiency. However, two kinds of fluids are usually required to work together for cold recovery and storage (baseline LAES) as single fluid is not able to work in such a large temperature span (85–300 K). This leads to a four-tank configuration, making the cold storage bulky and complex. To address this issue, this paper investigates various fluids and it is found that their temperature ranges could be extended when they are under pressure (i.e., pressurized fluids). This makes it possible to recover and store the cold energy from liquid air by single pressurized fluid with a two-tank configuration, thus increasing cold storage density and decreasing capital cost. Therefore, a novel LAES configuration is proposed and analysed with pressurized propane (1 MPa) as an example for cold recovery and storage. Simulation results show that the proposed LAES system increases the volumetric cold storage density by ∼52% and improves the system energy storage density by 16.7% compared to the baseline LAES system . This saves the capital cost of cold storage by 37% and reduces the system capital cost by ∼7%. Besides, the proposed LAES system shows an electrical round trip efficiency of ∼50% and a combined heat and power efficiency of 74.9–81%. This study provides a feasible way to improve energy storage density and economic benefits of the LAES system.