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The Space Thermoacoustic Refrigerator (STAR) was designed and built by a team at the Naval Postgraduate School led by Steve Garrett. It has the ability to move about 5 Watts of heat and exhibited a peak coefficient of performance relative to Carnot (COPR) across the stack of about 20%. A good paper about the STAR project is "Thermoacoustic Refrigerator for Space Applications."
See Refrigeration Systems