I'm puzzled by the fact that the CoP (Coefficient of Perfomance) of residential heat pumps is usually stated to be between 4 and 5, meaning that for every kWh of electricity used by the pump one gets between 4 to 5 kWh of heat transferred into the house. How's that even possible?
Here's my reasoning: the gaseous fluid in the power pump gets compressed inside the house, releasing heat into the residence. Fine. The compressed liquid fluid is moved to the outside where it is allowed to expand, and in the process will cool down even more. The compressed gas then absorbs energy from the environment outside the house to become a gas again. The expanded gas is then moved inside the house and compressed (thus heated up again), closing the circle.
- I can see that (discarding losses) one can put in 1 kWh to compress gas inside the house to release 1 kWh of heat. So far so good, so how can manufacturers state that the CoP (Coefficient of Performance) is 3 to 5?
- Also, the expanded gas coming from outside the house will be at outside ambient temperature, so we are actually introducing a cold substance into the house which would mean that the CoP would be even less.
Can somebody care to elaborate? It seems that I'm missing something vital in my reasoning. Thanks!