An air drying system includes a first air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below, a second air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below, and a valve coupled to and selectively switching between output from the air dryers to provide exceptionally dry air, where one of the first and second air dryers is automatically regenerated while the valve switches to provide exceptionally dry air from an other one of the first and second air dryers. The air dryers may remove moisture from ambient air by cooling the ambient air to approximately −57° C. Each of the air dryers may include a heat sink section, a cooling section (possibly with cooling elements), and an air flow section.