Air Source Heat Pumps (Domestic Renewable Heat Incentive)
Air source heat pumps work on the same principle as refridgerators, but in reverse. Refridgerators and freezers extract heat energy from inside the unit and expel it to the outside air. Air source heat pumps extract heat energy from external air and expel it into a building. It's a simple, well understood process that has been in effective use for many years.
All matter, whether it be solid, liquid or gaseous, contains ambient energy, even below what we know as 'freezing' temperature, or 0°C. In fact, there is heat energy in matter all the way down to 'Absolute Zero', or −273.15°. However, we don't come anywhere near that low temperature anywhere on the planet, except in the lab. This means there is useful energy available, all around, which can be extracted by air source - and indeed ground source - heat pumps.
You can see a heat pump working anytime, comparing the temperatures of the icebox and the 'element' at the rear of your refridgerator or freezer. A freezer with an internal temperature of minus 18°C still has enough heat energy inside to warm the element, when the motor is running. (Please be careful not to burn yourself on the element when trying this.) However, the amount of energy that can be extracted from the inside a freezer is miniscule in comparison to what is available in the air, water and soil outside your property.
So, heat pumps 'produce' far more heat energy than they take from the electricity grid. Very efficient heat pumps can use 1 unit of electrical energy to produce 4 or 5 units of heat energy. The term used to descibe this efficiency is the 'Coefficient of Performance' or COP. The COP can be as much as 5. However the figure varies between around 3 - 4 in most appliances, or 3-4kW out for an input of 1kW.
|Technology||Savings per year*||RHI income per year**|
|Air source heat pump||£290 - £1845||£805 - £1280|
*depending on existing system
**depending on new system installed
Figures published by the Energy savings trust
For more information visit the Domestic Renewable Heat Incentive FAQ page