Liquid air energy storage (LAES): a review on technology state-of-the-art, integration pathways and future perspectives

Energy system decarbonisation pathways rely, to a considerable extent, on electricity storage to mitigate the volatility of renewables and ensure high levels of flexibility to future power grids. In this context, liquid air energy storage (LAES) has recently emerged as feasible solution to provide 10-100s MW power output and a storage capacity of GWhs. High energy density and ease of deployment are only two of the many favourable features of LAES, when compared to incumbent storage technologies, which are driving LAES transition from the concept proposed in 1977 to a real-life option. Two plants (350 kW and 5 MW) have been successfully built and demonstrated by Highview Power, and a 50 MW/250 MWh commercial plant is now under construction. Besides the commercial deployment, an ever-increasing body of literature on the topic proves the academic interest on LAES. However, literature heterogeneity in terms of the investigated concepts and plant layouts, working methodologies and study scope currently complicates the interpretation of outcomes. Few literature surveys have attempted to rationalise this landscape, yet leaving some key areas such as LAES integration practically unaddressed. The present article aims at filling these gaps and providing a holistic review of the LAES development. Uniquely in this review: i) we propose a new methodology for cross comparing the results from the literature and use it to harmonise techno-economic findings, ii) we review works where LAES operation in the energy system is considered and iii) we highlight promising LAES integration pathways and future research directions. More than 120 references on LAES have been processed according to the methodology. The results include once for all the state-of-the-art techno-economic performance of LAES, across all the concepts proposed, and propose necessary steps to further advance the LAES research. The need for more realistic LAES models for integration studies and a broader focus on LAES capabilities beyond electricity output, specifically for hybrid concepts, are highlighted.