Theoretical analysis on performance enhancement of stand-alone liquid air energy storage from perspective of energy storage and heat transfer

Abstract

Liquid air energy storage (LAES) is a powerful technology for balancing power supply and demand for a low carbon network. However, its round trip efficiency is relatively lower compared with other large-scale energy storage technologies. In this paper, a stand-alone LAES is studied to provide guidelines for improving its round trip efficiency, from the perspective of energy storage and heat transfer. Storage exergy efficiencies of tanks (ηst) and heat transfer thermal efficiencies of heat exchangers (ηHE) are considered. Simulation results show that, among the storage tanks, the liquid air tank plays the most important role: when ηst increases from 0.7 to 1, ηRTE increases dramatically from 0.18 to 0.51; the M-cold tank determines if the stand-alone LAES could work. To improve ηst, first, good thermal insulation materials should cover the tanks; second, measures need to be taken to mitigate the mix of energy with different grades in the tanks, such as multi-stage energy storage; thirdly, reducing the number of tanks by looking for a liquid that has large temperature scales from -190 to 20 °C. For the heat exchangers, ηHE of HE #2 has the most significant effect on ηRTE; for Cooler or Heater, ηHE does not affect ηRTE as ηHE is above 0.65, which indicates that almost 35% of the stored air compression heat is excess, which could be used for other purposes to improve the round trip efficiency.