The heat pump explained
What is a heat pump?
A heat pump generates heat through the process of compression. The principal is the same as a bicycle pump warming up through the action of inflating a tyre. A fridge uses the same principal to generate cold air but in reverse.
Within the heat pump there are three circuits; the heating circuit which has the traditional elements of a hot water tank and radiators; the heat source circuit which has the boreholes or ground loop or air source linked to it; and thirdly the heat pump circuit itself.
How does a heat pump deliver the benefits?
A heat pump concentrates the heat collected from the heat source (ground or air) through the employment of two heat exchangers and a compression pump. It is through this simple process that we are able to gather free energy from the ground or atmosphere and convert it via a heat exchanger to keep your home warm and your water piping hot.
The extraction of the heat/energy from the heat source uses freely available carbon free energy. A typical new condensing boiler has efficiencies of about 80-95%, a ground source heat pump has efficiencies of more than 430%, i.e. for every unit of energy expended on electricity more than 4 units of heat are generated and for air source the figure is about 275%.
The impact on carbon footprint is very positive, firstly due to the use of free energy from the heat source and secondly because it uses electricity which is the most carbon clean of the everyday energy sources that we use.
How does a heat pump work?
Within the heat pump circuit there are four key stages:
- Heat is gathered from the energy source (e.g. ground loop) by the refrigerant passing over a heat exchanger.
- The refrigerant is compressed to generate heat. At this stage it liquefies.
- The heat is passed to the heating hot water circuit by passage over a heat exchanger.
- The cooler refrigerant is decompressed and further cooled.
