8.2 Heat gains from heat pumps
The difference between a heat pump’s heat output and its electricity input is known as the heat gain.
Under the 2009 European Union Renewable Energy Directive (CEC, 2009) the heat gains from heat pumps are classified as renewable energy, but there are several classifications, which can be a source of confusion:
- aerothermal gains – heat gains from air-source heat pumps
- hydrothermal gains – heat gains from rivers or lakes
- geothermal gains – gains from energy stored in the form of heat beneath the surface of solid earth – although here the source of energy is normally fairly near the surface and essentially solar in origin, not geothermal heat from deep inside the Earth.
Heat gains from heat pumps are beginning to feature in national renewable energy statistics and may be classified together with solar gains, although they do not directly depend on solar radiation for their performance.
For the UK energy statistics the heat gains from all heat pumps (ground source and air source) are classified together with heat from deep geothermal wells. Together in 2015 they supplied an estimated 7.1 PJ of heat (BEIS, 2016). This was roughly 1% of the UK’s total renewable energy supply for that year.
You’ll now move on to look at solar thermal electricity generation.