Islanded, renewably powered microgrids require energy storage or emergency generation to overcome intermittency. Batteries and fossil fuel generators have traditionally filled these roles. However, liquid air energy storage (LAES) is a promising alternative. Using power in excess of immediate demand, a LAES system can liquefy and cryogenically store ambient air. When renewable generation abates, the liquid air can be expanded through a turbine to provide power to the microgrid. This study explores energy recovery from a dual Stirling cycle LAES system. Liquid air is generated by a commercial Stirling cryocooler and stored in a vacuum dewar. A second Stirling engine utilizes the temperature difference between the liquid air and surroundings to run a small electric generator. This paper focuses on energy recovery from the cryogenic liquid air through the Stirling engine using a series of experiments. Liquid air volume as a function of time and power for varying loads were measured and used to quantify the energy recovered from the stored liquid air. Energy efficiency is calculated and recommendations for design improvements are presented. Follow-on work will include design and operation of an updated dual-Stirling LAES system. This work is part of a larger effort to determine the feasibility of different energy storage methods for small, mobile applications as well as fixed infrastructure energy storage systems.

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