Hey HN! I'm part of the team behind this device. It can keep vaccines cold indefinitely without electricity—you only need to move the device in and out of the vaccines container and maybe lay it in the sun once in a while. This is a link to our design contest submission page.
It's an absorption heat-pump that uses osmosis and exo-/endothermic salts. There's a cooling phase (absorbing heat) and heating phase (releasing it) and it switches b/w them when it crosses a temp threshold (73°F). See diagrams in URL.
How to use it:
Put vaccines in an insulated box (maybe cooled earlier w/ the device). Put the pack into a stream (or already cold box), which lowers the pack's temp below 73°F and starts the runaway cooling. The pack gets cold (~40°F) in a matter of seconds. It absorbs heat from the box and stores it as chemical potential energy in the form of dissolved NaNO3 and crystalized CaCl2. After hours or days, remove the pack. If outside air is above 73°F, it automatically triggers the heating phase when it warms up to room temp. If not, manually warm it up (lay in the sun or on the stove) to bring it above 73. Then in just minutes it gets hot (~105°F) as the salts release all their stored heat. When heating finishes and the pack returns to room temp, store it or put it back in the box to start cooling again.
Principle is similar to other systems, e.g. A/C in RVs (wikipedia.org/wiki/Absorption_refrigerator).
But A) it's driven by small temp changes you apply, so it's easier to do w/out electricity, and B) it uses safe cheap materials.
Cooling per kg (of salt+water) is around 90% of melting ice. (ie, approx the same weight of ice in the cooler for same amount of cooling)
--
Big impact where spotty electricity makes storing vaccines difficult: long electricity outages spoil vaccines, which have to be thrown away.
Another monetization: sell as electricity-free heating to backpackers.
This is part of an engineering competition. If you want to support it please vote for us!
It's an absorption heat-pump that uses osmosis and exo-/endothermic salts. There's a cooling phase (absorbing heat) and heating phase (releasing it) and it switches b/w them when it crosses a temp threshold (73°F). See diagrams in URL.
How to use it:
Put vaccines in an insulated box (maybe cooled earlier w/ the device). Put the pack into a stream (or already cold box), which lowers the pack's temp below 73°F and starts the runaway cooling. The pack gets cold (~40°F) in a matter of seconds. It absorbs heat from the box and stores it as chemical potential energy in the form of dissolved NaNO3 and crystalized CaCl2. After hours or days, remove the pack. If outside air is above 73°F, it automatically triggers the heating phase when it warms up to room temp. If not, manually warm it up (lay in the sun or on the stove) to bring it above 73. Then in just minutes it gets hot (~105°F) as the salts release all their stored heat. When heating finishes and the pack returns to room temp, store it or put it back in the box to start cooling again.
Principle is similar to other systems, e.g. A/C in RVs (wikipedia.org/wiki/Absorption_refrigerator). But A) it's driven by small temp changes you apply, so it's easier to do w/out electricity, and B) it uses safe cheap materials.
Cooling per kg (of salt+water) is around 90% of melting ice. (ie, approx the same weight of ice in the cooler for same amount of cooling)
--
Big impact where spotty electricity makes storing vaccines difficult: long electricity outages spoil vaccines, which have to be thrown away.
Another monetization: sell as electricity-free heating to backpackers.
This is part of an engineering competition. If you want to support it please vote for us!