Air source heat pumps (ASHPs) operate using the same process as water or ground source heat pumps, simply, by extracting heat from one location and transferring it to another. In this case, the heat is collected from air outside the home and transferred to the internal spaces. ASHPs require electricity to operate but generate about 3 times the energy they use, making them a great renewable heating option.
Air Source Heat Pumps – How They Work
The system comprises of three parts:
1. Outdoor Heat Exchanger
Refrigerant is pumped around an evaporator coil which extracts heat from the outside air. Remarkably, they can operate at very low temperatures and the Heat Pump Association state that they can continue to operate in temperatures as low as -15 degC. That’s right… minus 15!
2. The Heat Pump
Removes and concentrates the heat from the refrigerant and transfers it to the distribution system. The cooled refrigerant is returned to the coil to collect more heat.
3. The Distribution System
Supplies the collected heat throughout the house through an air or water based system. Due to the low temperatures of the heat generated, air source heat pumps work most effectively when coupled with a heating system that only requires a low operating temperature. Under floor heating and warm air systems are well suited to the job.
Efficiency is measured using the coefficient of performance (CoP) which defines the ratio of electrical input with the units of heat generated. ASHPs generate 3-4 times the energy they require to function. (DECC)
Electrical input is required to power the pumps and compressors in the system. By incorporating photovoltaic panels, a wind turbine or signing up to a green energy supplier to provide the electricity, the overall environmental efficiency can be vastly improved.
The Energy Saving Trust estimates that the costs for providing and installing an air source heat pump suitable for a detached home is between £6,000 and £8,000. This is in addition to any costs for your distribution system.
Air source heat pumps are primarily used for space heating although if you live somewhere where it gets hot enough, they can also be used to cool your home by reversing the direction of heat transfer.
They can be used for water heating but due to the lower output temperatures they are really only suitable for preheating and additional heaters are required to fully heat domestic water.
Design and Installation
Design and installation should be completed by an MCS registered company. They will be able to advise on the best installation to meet your needs.
As a self builder you are in an ideal position to integrate microgeneration into your new home whilst maximising insulation and air tightness, reducing energy use, costs and improving the sustainability of your home.
If you are interested in incorporating air source heat pumps, speak to your designer. If you fancy installing several microgeneration systems, discuss with them whether it’s worth contacting a specialist mechanical and electrical engineer to achieve the most efficient system possible.
ASHPs are another of the few microgeneration systems that fall outside any permitted development rights and as such you’ll need planning permission to have one. If you are self building, then you can discuss with the planners what details to include in your full planning application.
If you want to add one to your existing home, contact your Local Authority planning department for direction.
More information on air source heat pumps is available from the usual suspects:
- The Department for Energy and Climate Change.
- Energy Saving Trust.
- The Microgeneration Certification Scheme (MCS) – For manufacturers and installers.
- The Heat Pump Association.
Don’t forget to return to our Eco Homes section for other ideas on how to make your home more sustainable and have a look through the rest of our site for more information on building your own home.
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