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Now That’s Cool: Fridge Runs for 10 Days Without Power

Sure Chill fridge technology works just like a frozen lake in the winter.

An illustrated fridge interior with vaccines in it. Credit:

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Efficiency is perhaps the most overlooked consideration consumers make when buying a fridge. And who can blame them? The difference in yearly savings between a super-efficient fridge and a more wasteful machine is relatively small—especially in the U.S., where energy is dirt cheap.

But when you consider how many fridges are running 24/7 in this country, appliance efficiency becomes a much bigger deal. That's precisely why efficiency standards are set and enforced by the government, and why fridges are getting more efficient with each successive generation.

But what if you could make a fridge that was so efficient you didn’t even need power to run it?

Sure Chill consumer fridge being monitored by Ian Tansley, Sure Chill Chief Technical Officer

Ian Tansley, Chief Technical Officer, monitors the Sure Chill consumer fridge. [Image credit: Sure Chill]

Sure Chill builds fridges that are about as efficient as it gets. Some are able to maintain appropriate temperatures—even without any electrical connection—for up to two weeks. How do they do it? In short, by circulating water in a compartment around the fridge cavity.

Sure Chill builds fridges that are about as efficient as the category gets.

Sure Chill’s inventor Ian Tansley came up with the idea while studying frozen lakes near his home. Water circulation, it turns out, is what allows the surface of a lake to freeze over while the water below remains liquid. Tansley correctly surmised that the same property could keep a fridge cold.

To understand precisely how a Sure Chill works, you need to grasp a basic rule of physics: that water is heaviest at 39°F (4°C).

When the Sure Chill fridge is turned on, a layer of ice forms near the top of the machine—just like a frozen lake. This is the initial draw of energy required to run the fridge. If the power goes out, or if you simply unplug the machine, the water climbs up above that 39°F threshold and rises to the top of the fridge, where it is again cooled and descends to the bottom. This causes a continuous cycle that maintains a consistent fridge temperature for 10 days or more.

While huge energy savings are certainly appealing, the real potential for this technology is in medical storage. Right now, Sure Chill technology is being used to deliver vaccines to rural areas with limited access to power. If vaccines can be preserved without power, they can reach more patients who need them.

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If vaccines can be preserved without power, they can reach more patients who need them.

“At the moment, one day a month someone comes with a box of vaccines,” Tansley tells Fast Company, describing the current state of vaccine distribution. “If they're lucky, people will then turn up and get the vaccinations done. But they probably miss a lot of people by doing that because the people are not necessarily in the village that day.” He hopes Sure Chill fridge technology will solve this conundrum, and make life-saving medicine more readily available.

Sure Chill fridges have been deployed to the Philippines, where UNICEF and the Bill and Melinda Gates Foundation used them to deliver important drugs. In all, the Welsh company has built more than 1,500 fridges with this technology.

A graph showing Sure Chill's temperature retention over time.

Hero image: Sure Chill

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