An Australian guy hacked a freezer into a super-efficient refrigerator:
Nearly every household on Earth has a fridge that totally wastes at least 30 kwh of energy every month. Most of the energy is wasted every time you open the door. Cold air is heavier and falls out on the floor every time you open your fridge and warm air rises to fill the space it left. But with a top opening fridge; even if you leave the door wide open, gravity effortlessly leaves the heavy cold air inside. [...]
His home-made fridge uses much energy in 24 hours as a 100W light bulb gets through in just an hour.
Not only is it energy efficient; but it’s absolutely silent too. The thing is only running for a minute or two every hour. At all other times it is perfectly quiet and consumes no power whatsoever.
(via Atom Jack)
I can see why this hasn’t taken off – space constraints. It wouldn’t fit in my kitchen, or in the kitchens of any of the apartments I’ve ever lived in. This may cause a problem for mass production. Still, it’s a smart solution.