How do heat pumps work?

In basic terms a heat pump moves heat from one source to another. The area where the heat is taken from is always hotter than the area the heat is being delivered to. Heat can be sourced from a number of locations such as the air, ground or water. For this reason there are several types of heat pumps, including air source heat pumps and ground source heat pumps. As the heat is derived from a natural source using a heat pump is highly efficient.

The heat pump uses a refrigeration cycle which consists of two principle heat exchangers; one that absorbs heat (the source), and the other that rejects it (the destination).

Heat is absorbed and transported through a system via pipes. These pipes contain water and a cooling fluid like antifreeze. As the water is directed into a building it is turned into gas by a heat exchanger. How the heat is released into the property depends on the system e.g. underfloor heating. The gas in the pipes is thus cooled into a liquid and continues back on its cycle to the original source where it is once again used to absorb heat.

To summarise

A heat pump system can be broken down into three parts:

1) Ground loop – This is the network of pipes filled with water to absorb heat from a source such as the earth.

2) Heat pump – A device which physically moves the water around a loop.

3) Heat distribution system – This is used to extract the heat and then releases it into a building such as a house.

How much heat is provided?

A heat pump is a good way to save money on energy bills as it can be used to preheat water. However, it cannot be depended on as a sole source of heat in the home. For example it will not provide a hot enough water temperature for bathing or washing alone.

A heat pump’s efficiency is measured in CoP (Coefficient of Performance). A CoP of three means that for every kilowatt of electricity put in, you get three kilowatts of energy in the form of warm water.

The temperature of the warm water is somewhere between 35^oC – 45^oC which is much lower than that achieved by a standard domestic boiler. The units are capable of generating higher temperatures but it should be kept to a minimum so the CoP is not compromised.

Heat pumps are best suited for underfloor heating for this reason.

What are the advantages of heat pumps?

As mentioned, heat pump systems are highly efficient and because they use renewable energy some forms qualify for the upcoming Renewable Heat Incentive (e.g. ground source heat pumps).

Heat pumps can be used throughout the entire year – in the winter to heat a home and in the summer to cool it when the operation is run in reverse. In addition, a heat pump is very low maintenance.