What is a Heat Pump?
A heat pump does what it suggests. Pumps heat from a low temperature source and forces that heat, using a compressor, to a higher temperature where it can be used to provide a total heating and hot water solution for a property. The low temperature source can either be the ground or the air, in which case you would either use a Ground Source Heat Pump (GSHP) or an Air Source Heat Pump (ASHP) respectively. As the renewable energy extracted is free, the only cost incurred when collecting energy for heat pumps is the electricity required to run them.
The lifespan of a heat pump varies for different types and brands, but in general an air/water (Air Source) or liquid/water (Ground Source) heat pump from a good manufacturer should last between 20 and 30 years.
A major advantage with a heat pump is that it requires minimal maintenance and attention. If it is installed correctly you can almost forget that you have one. It should work every day, all year, making your home warm and comfortable.
The EU has classified heat pumps as a renewable energy source because the output of solar energy greatly exceeds the input of energy needed to run it.
How do Air Source heat pumps work?
Heat from the air is absorbed at low temperature into a fluid. This fluid then passes through a compressor where its temperature is increased. This new generated heat can be used to heat radiators, under floor heating systems and provide hot water in your home.
- Collecting the heat
The air source pump uses a fan to force air over a heat exchanger (simply a copper coil filled with refrigerant) to extract heat from the air.
- The Evaporator
The purpose of the Evaporator within the Air Source Heat Pump is to take the air source heat obtained by the heat exchanger and boil the refrigerant (which boils at approximately -10˚C). The act of boiling turns the refrigerant into a vapour which is then transferred to the Compressor.
- The Compressor
The Compressor does exactly what its name suggests; vapour is compressed in volume and as its volume reduces, its temperature increases to levels between 75˚C and 125˚C. The gas is then fed through a heat exchanger within the heating pump.
- The Heat Exchanger
Forcing the hot gas across the cold water from the central heating system condenses the refrigerant back into a liquid. As it condenses its heat is passed into the heat exchanger which supplies the domestic hot water and powers the central heating system using the air source heat extracted originally.
- The Expansion Valve
To complete the closed circuit of the Air Source Heat Pump, the only thing which needs to be done is reduce the pressure of the condensed liquid. This is achieved via the expansion valve.
How do Ground Source heat pumps work?
Ground source heat pumps use pipes to extract heat from the ground. The heat pump circulates a mixture of water and antifreeze around a loop of pipe, called a ground loop, which is buried in your garden. Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump.
While Ground Source Heat Pumps offer greater efficiencies over Air Source Heat Pumps, the ground source solution is not for everyone often due to space considerations or the required ground works. Air Source Heat Pumps can save you hundreds of pounds on your annual running costs with minimal installation disruption.