As energy prices continue to rise and the use of fossil fuels is increasingly shunned, people are searching for cheaper and more sustainable forms of heating. Chief among these is the use of heat pumps, but the way they work is a mystery to most people because they literally seem to extract heat from thin air. So do heat pumps work?
Heat pumps aren’t a completely sustainable form of heating because they do need some electricity to make them work. However, they are a low-carbon alternative, as heat pumps considerably use less than conventional electric heating methods, so they can be much better for the environment, especially if the electricity is from renewable sources.
How do Heat Pumps Work, and Types Available?
Different types of heat pumps extract heat from the ground, water or air and are known as the following, ground source heat pump, water source heat pump and air source heat pump.
As the name suggests, Ground source heat pumps work by absorbing heat form the land. They, therefore, require a lot of land for the installation either across or down with a borehole, they are mainly installed in agricultural settings, and. not so much for flats or apartments, while water source heat pumps work by absorbing heat from a lake or well.
Air source heat pumps extract heat from the air and are suitable for most property types, even apartments at high levels. They are also typically half the price of other types to install and so are the most popular.
A heat pump works in a similar way to a domestic refrigerator by using a system of compression and evaporation. However, while a refrigerator creates a cold temperature to keep food fresh, a heat pump works in reverse to create heating and, in some cases, hot water. Heat pumps can be categorised as either air-to-air, generally referred to as air conditioning, or air-to-water.
The aim of a heat pump is to transfer thermal energy from one place to another. Heat will naturally move from a high temperature to a lower one and a heat pump uses this principle by extracting energy from the ambient air and transferring it inside a building as a heat source.
A heat pump unit contains a refrigerant cycle that moves through several stages:
- An evaporator is a heat exchanger outside the building with refrigerant passing through it. Outside air is drawn across the heat exchanger using a fan or impeller and the refrigerant in the heat exchanger absorbs the heat and evaporates as it gains energy.
- A compressor compresses the refrigerant and increases its pressure and temperature significantly.
- A condenser where the high temperature, high pressure refrigerant transfers its energy to the heating system and condenses back into liquid. This energy can be used to heat water being used to supply emitters such as suitable radiators or underfloor heating as well as potable hot water. It terms of air conditioning, it can also be used to warm the air up in a room.
- An expansion valve decreases the pressure of the refrigerant, lowering its temperature and preparing it to an optimal state to enter the evaporator starting the cycle again.
Will it Work?
Heat pumps are needed most in the depths of winter when the weather is at its coldest. Many people will therefore question whether a system can work effectively when the outside air is so cold. In reality, heat pumps work well in the UK, even if temperatures dip as low as -20⁰ Celsius.
These systems work best in modern homes that are well insulated reducing heat loss. In these circumstances they are usually cheaper to run than gas or oil-based equivalents, are extremely efficient and are good for the environment because they don’t depend on fossil fuels. They are, in effect, the future of heating for homes and businesses.