ColdSafe™ Technology

Most ice-lined vaccine refrigerators use direct contact between ice or evaporator coils to cool the vaccine chamber, exposing the vaccines to temperature swings and freezing temperatures. The MetaFridge keeps vaccines separated from dangerously low temperatures, using a thermosyphon coupled to an insulated block of ice to create a passive feedback system that maintains the perfect safe temperature range for vaccines, even during extended power outages.

Thermosyphon cooling diagram

MetaFridge uses an integrated thermosyphon coupled to an ice block to cool the vaccine chamber.

Heat moves, cold doesn't

The patented ColdSafe technology works by pulling heat out of the vaccine chamber into a precisely engineered thermosyphon, which moves the heat up to the ice block. During a power outage, this system continues cooling the vaccines while gradually melting the ice block, without using any moving parts or electricity.  ColdSafe technology has been shown to keep vaccines cold through outages lasting 5 days or more, even with door openings, allowing health workers to continue to use the MetaFridge and access vaccines normally. The MetaFridge automatically creates more holdover whenever power is available, operating so efficiently that it can maintain full holdover capability with just 3 hours of power each day.

The ColdSafe thermosyphon contains a mix of liquid and vapor. The bottom of the syphon surrounds the vaccine chamber. Any excess heat in the vaccine chamber is transferred to the liquid inside the syphon. The liquid absorbs the heat, turns into vapor, and rises to the top of the thermosyphon. As the vapor rises, it is cooled by the ice block bonded to the top of the thermosyphon. The vapor condenses back into a liquid, releasing its absorbed heat to melt the ice, and the liquid falls back down towards the vaccine chamber to repeat the cycle.

ColdSafe technology mimics the Earth’s own water cycle, where water evaporates from a warm ocean to form clouds of vapor at colder elevations, which condense as they cool and fall back down to the ground as rain.

Coldsafe Holdover

8 Days intermittent power showing MetaFridge holdover
8 Days intermittent power showing ambient and refrigerator temperatures

MetaFridge ColdSafe technology maintains safe vaccine temperatures at an East African clinic through 8 days without power followed by additional multi-day outages. The refrigerator was used normally with daily door openings throughout the outages. When technicians visited the site they found a faulty power outlet that was creating the problem.