Liquid air energy storage (LAES) is promising for decarbonizing the power network. Fluids are popular as both cold recovery and storage media with the benefits of no additional heat exchangers and straightforward control strategy. Methanol and propane are required to work together as single fluid is not able to work in such a wide temperature range of 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 range 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. Therefore, a compact LAES configuration is proposed with pressurized propane (1 MPa) as an example for cold recovery and storage. A new concept of cold storage density is discussed for the first time to show how much cold energy is stored per unit. The Simulation results show that the proposed LAES system increases the volumetric cold storage density by ~52%, saves the capital cost of cold storage by 37%, and shortens the simple payback period of the system by 1.13-67.72%, compared with the traditional LAES system with fluids-based cold storage. This study will provide a feasible way to simplify the LAES system and improve the economic benefits.
Keywords liquid air energy storage, thermo-economic, thermal energy storage, cold storage, power plants