We're thinking of getting a heat pump so I've been watching lots of videos about them. (SATURDAY NIGHT FUN!)
It struck me that, having watched quite a few, I still didn't understand how they work. Lots of the videos say things like 'it's like a refrigerator in reverse' which is only helpful if you know how a fridge works and possibly not even then. I'm not convinced I need to know, I buy tons of things I don't understand, but, well, I probably should.
Having watched a lot of them I'd say this is the best one, though I'm not sure the marbles really help.
So, having learned that the best way to understand something is to see if you can explain it I have tried to write down 'how heat pumps work'.
It's probably not as simple as it should be while simultaneously being too simple for many of you. But here it is. I'd be grateful if any actual experts out there could let me know what you think. (Alby?)
I must have gotten something wrong. What is it?
- Even on a very cold day there is still heat energy in the outside air. (It’s above absolute zero)
- The heat pump sucks that air in with its fan and passes it over some tubes which contain a fluid called a ‘refrigerant’. A refrigerant is a liquid that turns into a gas at a low temperature.
- The refrigerant is very cold - even colder than the outside air - so the heat energy in the air is drawn into that refrigerant and heats it up, boiling it into a gas. This is how heat energy from the outside is brought into the system, even the low amounts of heat energy on a cold day.
- That gas is then put into a ‘compressor’ and electricity is used to squeeze it. When you squeeze (or compress) a gas it gets very hot - as you might have experienced with something like a football pump.
- That very hot gas is then passed over the water pipes of the central heating system and that water heats the house, through radiators etc.
- The refrigerant gas having passed its heat to the water is then allowed to expand, which means it becomes very cold again, and we go back to step 2.
The electricity in the system is used to run the fan and to compress the refrigerant - moving energy from air into home. This is normally much more efficient than using electricity (or another fuel) to directly heat up the water or air in the home. That’s how heat pumps can transform 1 unit of electricity into 3 or 4 units of heat.