Everything around us contains thermal energy – or heat. Heat naturally flows from a warmer place to a colder place. To use the heat energy in a home when outdoor temperatures are colder, we need heat to flow in the other direction – from a colder place to a warmer place. But how does it do it?
When the pressure of a fluid increases, the temperature of the fluid increases. When the pressure decreases, the temperature decreases. This relationship between pressure and temperature is the key to how a heat pump works.
The fluid is typically referred to as a refrigerant. The heat pump uses electricity to compress this fluid, increasing the pressure and therefore the temperature.
As the fluid’s heat is transferred to your home, it cools down a little. The fluid is then allowed to expand so that it cools even further. It’s now cold enough to absorb more heat from outside and begin the process again.
The heat can then be used in your home’s central heating system (in an air-to-water or ground-to-water heat pump) or passed into hot air blowers (in an air-to-air heat pump).