Stirling Engine running in reverse creates a cooling effect.
FROM WIKIPEDIA
Portable refrigeration
The Free Piston Stirling Cooler (FPSC) is an elegant, completely sealed heat transfer system that has only two moving parts (a piston and a displacer), and which can use helium as the working fluid without concern about seal leakage. The piston is typically driven by an oscillating magnetic field that is the source of the power needed to drive the refrigeration cycle. The magnetic drive allows the piston to be
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