“If it weren’t for the fact that the TV set and the refrigerator are so far apart, some of us wouldn’t get any exercise at all.”

-Joey Adams, American comedian

A refrigerator is a device that takes heat from the inside of the refrigerator to the outside, such that the inside stays cold. A heat pump is designed to do the opposite, such that it transfers heat from the outside to the inside. In this lecture, the working principle of the heat pump is explained, the performance is discussed, and the role of the heat pump in the energy transition is analysed.