Air Source heat pumpsAir source heat pumps make use of the limitless supply of renewable energy found in the outside air. Air source heat pumps provide safe, reliable and pollution free heating and cooling for houses, bungalows, flats and large commercial buildings. A brief explanation about how an air source heat pump worksStep 1 – Turning heat from the air into heat for your home An air source heat pump positioned in a suitable location outside your home draws air through it. The air is drawn in through the front or side of the unit and expelled through the back or opposite side. As the air travels through the unit it passes over heat exchange coils that absorb heat energy from the air that will be used to provide heating for your home. The Evaporator – Flowing through the inside of the heat exchange coils is a liquid refrigerant. In liquid form the refrigerant will have a temperature below -40°C, making these coils very cold. Heat from the warm air is absorbed by the coils and transferred to the refrigerant. The refrigerant has a boiling point of about -40°C so as it absorbs heat and increases in temperature it boils and evaporates, turning from a liquid into a vapour. The Compressor – The vapour is then drawn into a compressor. Compression causes the vapour’s temperature to rise to over 100°C. The Heat Exchanger – After leaving the compressor the vapour enters a heat exchanger. Heat from the vapour is absorbed by air or water that is then used to provide heating and domestic hot water for the house. As heat is absorbed the temperature of the vapour reduces and it condenses back to a liquid. This process releases a considerable amount of additional heat energy into the heat exchanger, which is also absorbed by the air or water and used for house and hot water heating. The Expansion Valve – The refrigerant leaves the heat exchanger as a very cold liquid at high pressure and enters the expansion valve. Here the pressure of the liquid refrigerant is reduced before it is sent back to the evaporator to repeat the whole process again. Diagram Heat Pump 1 Step 2 – Distributing heat around the home There are three main types of air source heat pump that are popular for use in the home: 1. Air to water systems At the heat exchange stage water is heated or cooled which is then circulated around the home providing hot or cold water to underfloor heating and radiators. Heating for the domestic hot water can also be provided.
2. Air to air systems At the heat exchange stage air is heated or cooled and then circulated around the home by the use of air ducts and fans.
3. Small air to air units Smaller units are available that can be used to provide heating or cooling for one or two rooms. These systems are divided into two parts. The first part is an outside unit to collect heat from the outside air when heating is required and to transfer heat to the outside when cooling is required. The second part is inside the room, usually wall or ceiling mounted, that warms or cools the air around the room by drawing air through it before passing it through a heat exchanger.
Air source heat pumps for coolingSome air source heat pumps can provide cooling for your home on hot days. When the heat pump is operating in cooling mode it is basically working in reverse. In cooling mode cold air or water is supplied to the heating system in place of hot. The extent of cooling that can be achieved can however be limited when using radiators and underfloor heating due to the problem of condensation forming on cold surfaces. Condensation will form on the surface of the radiators, the floor and the walls if they become too cold. Condensation dripping off radiators and wet slippery floors is obviously undesirable. Therefore relative humidity censors are used to monitor the ambient dew point and regulate the temperature of the cooling water. This prevents the temperature of the cooling surfaces (radiators, walls and floors) from falling below the dew point temperature and avoids the formation of condensation.
Energy ConsumptionAn air source heat pump consumes heat energy from the air, which is totally renewable, free of charge and has no carbon emissions. It also consumes electricity! Because heat energy from the air is made use of, the heat energy generated by the heat pump is greater than the electrical energy it consumes. An air source heat pump can therefore bring you considerable savings on your heating bills and also reduce your carbon footprint. Buying your electricity from a renewable supplier will further reduce your carbon footprint. You could also generate your own renewable electricity through the addition of PV Solar panels, wind turbines or a hydroelectric system. When installing an air source heat pump buying your electricity from a renewable supplier may not be an option or you may choose not to, but it could always be a consideration for the future. Likewise you may not have any PV solar panels or a wind turbine, but you may decide to install methods or generating your own electricity in the future, in which case having a heating system that can run on these renewable sources is a great future benefit.
Considerations for having an air source heat pump
Advantages of air source heat pumps
more here
|