Robert Stirling founded the idea and was awarded a patent for the first Stirling engine in 1816. From there, his invention was first used as a cooling tool in 1834 by astronomer John Herschel. This charted the way that has led us to produce the industry’s most energy-efficient ultra-low freezer. Various free-piston Stirling engine configurations were invented and developed in the 1960s. These machines required no mechanical linkages since the moving parts are either driven by internal gas pressure or a linear motor/alternator. Later developments included gas bearings where both the piston and displacer are supported on helium bearings, thus eliminating the need for any lubrication whatsoever. In 2017, Stirling Ultracold earned a 0.286 kWh/day/ft3 certification from ENERGY STAR®, the lowest energy use of any certified ULT freezer.