Exergy-Based and Economic Evaluation of Liquefaction Processes for Cryogenics Energy Storage

• Main Authors: Sarah Hamdy, Francisco Moser, Tatiana Morosuk, George Tsatsaronis
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Energies
• Subjects: cryogenic energy storage; air liquefaction; exergy analysis; economic analysis; exergoeconomic analysis
• Online Access: https://www.mdpi.com/1996-1073/12/3/493

Cryogenics-based energy storage (CES) is a thermo-electric bulk-energy storage technology, which stores electricity in the form of a liquefied gas at cryogenic temperatures. The charging process is an energy-intensive gas liquefaction process and the limiting factor to CES round trip efficiency (RTE). During discharge, the liquefied gas is pressurized, evaporated and then super-heated to drive a gas turbine. The cold released during evaporation can be stored and supplied to the subsequent charging process. In this research, exergy-based methods are applied to quantify the effect of cold storage on the thermodynamic performance of six liquefaction processes and to identify the most cost-efficient process. For all liquefaction processes assessed, the integration of cold storage was shown to multiply the liquid yield, reduce the specific power requirement by 50&#8315;70% and increase the exergetic efficiency by 30&#8315;100%. The Claude-based liquefaction processes reached the highest exergetic efficiencies (76&#8315;82%). The processes reached their maximum efficiency at different liquefaction pressures. The Heylandt process reaches the highest RTE (50%) and the lowest specific power requirement (1021 kJ/kg). The lowest production cost of liquid air (18.4 &#8364;/ton) and the lowest specific investment cost (&lt;700 &#8364;/kW<i>_char</i>) were achieved by the Kapitza process.