First a bit of physics:

A refrigerator is one of the biggest electricity consumers at home.
It works with refrigerant-generally Freon gas. When the refrigerant is liquid condition, it sucks heat so that the fridge does cooling. But it emits heat when gas condition. While refrigerant repeats gas-liquid condition, the compressor and condenser(long and thin copper/aluminum pipes at back of fridges) are heated up because gas has to evaporate this heat. To blow this heat, a refrigerator has to be placed 5-10 cm apart from the wall in the kitchen.

The idea of Hot Fridge is based on an experimental use of waste heat from a refrigerator and is inspired by Gudul (Ondol), the traditional under-floor Korean heating system.

By having its structure and condenser redesigned, the fridge is able to store not only cold food but also warm food. The condenser is on top of the fridge so that you can put and keep left-over food warm until next meal. Plastic shelves in door are changed to fabric net pocket bags that help cool air circulation and allow easy storing. Hot Fridge is easy to move so you can pull it to bring warm dishes on the dinner table. If you cannot finish all your pizza at lunch, put the pizza plate up on the fridge. The afternnon bite will be warm!

By designer Hae-jin Kim.