Sure Chill Vaccine Refrigerator
Sure Chill works on the principle that water is at its densest at 4˚C. Water, not ice, surrounds a Sure Chill refrigeration compartment. When power is supplied to the refrigerator, the water cools and ice is formed above the compartment leaving only water at 4˚C cooling the contents. When the power is switched off, the water warms and rises while the ice begins to melt. This keeps only water at a perfect 4˚C cooling the contents of the compartment. The system can operate like this, without any power whatsoever, for many days.