Integrated techno-economic assessment of Liquid Air Energy Storage (LAES) under off-design conditions: Links between provision of market services and thermodynamic performance

This paper deals with Liquid Air Energy Storage (LAES) - one of the most promising thermo-mechanical technologies with the potential to provide bulk energy storage functionalities. More specifically, an integrated technical and economic assessment of the performance of LAES when providing multiple energy and frequency control ancillary services is carried out. To this end, an off-design thermodynamic model of LAES was developed and validated against experimental data from the literature to allow understanding the links between the specific requirements of the market services to provide and the performance of each component of the LAES plant, and from here the performance of whole LAES process. The model was then applied to assess how a stand-alone LAES plant performs when providing three specific assets in the UK electricity market: arbitrage, short term operating reserve (STOR), and fast reserve (FR). The results obtained clearly demonstrate that (a) a strong link between type of service and LAES off-design conditions exists and cannot be neglected; (b) roundtrip efficiency and liquid air consumption can vary by up to 30% during off-design operation, causing some 10 k pound/MW of missed revenue; (c) the effect of off-design conditions is unevenly distributed across LAES components, with low-pressure turbines affected the most; (d) a suitable regulation strategy can alleviate but not prevent off-design performance variations, improving roundtrip efficiency by up to 4 percentage points. The modelling developed is thus essential for a realistic assessment of the value and constraints for LAES to participate in electricity markets and support low-carbon power system operation and development.