Simon Keel of Daikin Airconditioning explains how air source heat pumps can warm your home in a green-friendly manner
AIR source (air to water) heat pumps are now recognised as renewable technology in the drive to reduce CO2 emissions.
They use heat stored in the air, concentrate it and move it indoors. This means all types and sizes of homes can be heated, and supplied with hot water without undue damage to the environment.
The pumps do use some
electricity to concentrate the heat and move it around but modern, efficient, heat pumps are able to convert electricity into extra heat.
This means that for every one kilowatt of electricity used, up to 4kW of heat is transferred to
the building.
This begs the question: 'Why doesn't everyone replace the old gas boiler with one of these new heat pumps.'
The answer is simple - there is a big difference in the temperature of water that can be produced. A normal boiler is set to produce water at 70˚C, but an efficient heat pump pushes it out at 45˚C. This means householders wishing to renew an old boiler cannot make a direct replacement.
Restricts use
The lower-temperature water can only be used effectively when the indoor heating system has been specifically designed for it, which restricts the use of heat pumps to new builds or comprehensive refurbishments.
Three types of heating can be used - underfloor heating, special radiators and fan coils.
Underfloor heating is the
preferred method and is now recognised as the most
comfortable, and least wasteful, form of heating.
Special radiators and fan heaters must be carefully sized in order to maximise usefulness. New building regulations stipulate high standards to prevent heat loss.
This means much smaller boilers/heat pumps are needed - domestic air-source heat pumps on the market typically range between 5kW and 16kW.
At the heart of a heat pump is a compressor, which takes heat from the outside air and transfers it to a water circuit inside the building.
In spring and early autumn, the heat needed to get the house up to temperature will obviously be less than in deep winter.
The latest heat pumps
modulate the speed of the
compressor so that it exactly matches the heating required at any time. And this is achieved via inverter control - a technology that has been used in
commercial-building heat pumps for many years.
The main benefit of this feature is that the heated space does not suffer from wide swings in
temperature.
If the weather starts to warm up, the system will recognise that the level of heat needed will be less, so it will throttle back the
compressor and reduce water
temperature.
Modern heat pumps also look after the domestic hot-water requirements throughout the year.
Summer months
This is a particularly economic consideration in summer months where the heat to be collected from the air is plentiful.
Even in the winter, however, heat pumps like Daikin's Altherma can perform at temperatures well below zero. Units installed in Norway regularly work at -15˚C to -20˚C.
The system package features an external unit and an indoor section which looks like a wall boiler and a hot-water tank.