Blowing Hot and Cold: Heat Pumps and the Future of Heating

Home energy bills are going through the roof. Heat pumps are the hot topic, but what are they?

A heat pump is a device which transfers heat from one place to another. There are three types: (i) airto-air, (ii) air-to-water, (iii) ground source-to-water. In an air-to-air installation operating in the summer, for example, heat is transferred from the inside air to the outside air. Some models can give cooling right down to 16 °C but they can also heat your home in the winter.

You have questions? We’ll answer them below:

How does this work?
Think of your fridge. It’s cold inside but warm at the back. Why? It contains a compressor and sealed pipework circuit containing a refrigerant which boils at a very low temperature (-18 °C in some cases) and takes the heat away. The refrigerant (now a gas) is compressed and becomes hot. It then condenses to a liquid at the back of the fridge. This is the vapour
compression cycle, you can read more about it here.

A bicycle pump uses much the same process, but in this case, the system is powered by the person doing the pumping. You could power your fridge the same way but you’ll need a big pump and a lot of pumping.

Is an air-conditioning unit a heat pump?
In the UK and Europe, typically Yes. Depending on your installation, you could be using your air-conditioning unit to heat your home.

Tell me more?
An air-conditioning unit with a four-way valve can reverse the flow of the refrigerant. The process is just the same as above, but now, it’s running in the opposite direction. This time heat is transferred from the outside air to the inside air, providing heating to 30 °C. If it had a 4-way valve then you could use fridge to keep food warm!

So my air-conditioning can heat, as well as cool?
That’s right. Your heat pump air-conditioning can provide heat even when it’s freezing outside.

Yes, but I have central heating and underfloor heating; I don’t need more heating.
In heating mode your heat pump air-conditioning could be up to 75% more efficient than your central heating. And this could save you money in the long run by reducing winter heating costs.

Tell me some other advantages?
With heat pump air-conditioning, you can zone the temperatures in your home. Suppose you spend much of the day in the office. With standard heating systems you’ll likely heat the entire home when many rooms have nobody in them! Using a heat pump, you can heat only the rooms you need.

Is this the kind of thing I should tell my friends about?
Dave bought one, installed it, and told his daughter who went and bought herself one.