The History of the Technology
The history of the technology.
A heat pump is an energy efficient heating system that takes free, renewable heat energy from the ground, water or air. For 1 unit of electricity required to run it, the heat pump delivers up to 5 units* of heat to the heating system. In other words 500% efficient. Compare this to oil and gas boilers which are somewhere between 75% and 90% efficient.
The story started in Scotland with renowned physicist Lord Kelvin who, in the 1850s, discovered the Joule-Kelvin Effect which is the science behind how systems with refrigerants work. But it was across the North Sea in Sweden where the heat pump came into its own as a response to the energy crises in the 1970s. It has since been developed and refined to the point where it is now a mainstream household product, tried and tested over 30 years in the rigours of the Nordic climate. Annual installations in Sweden are currently running at 70,000.
* In accordance with EN 255 for heat source entry at 0° C / hot water flow at 35° C.
Types of Heat Pumps
Ground Source Heat Pump
Heat is collected in a similar way to the surface ground collector except the u-shaped collector piping is sunk into a borehole. The total borehole depth is again dependant on the size of heat pump and can be achieved across a number of separate boreholes which should be 15 metres apart. Typically the depth required can be between 70 and 190 metres. Drilling a borehole needs to be carried out by a specialist contractor and may require permissions depending on local conditions e.g. mine workings, tunnels etc. It tends to be more expensive than the surface ground collector. A borehole requires little ground area and is suited to smaller plots and where a heat pump is replacing an existing fossil fuel boiler.
Outdoor Air Heat Pump
An outdoor air heat pump doesn't need any borehole of ground collector. Instead it uses warmth in the air even when the air temperature is below freezing. An outdoor unit collects the heat required to vaporise the refrigerant. The heat pump connects to the water based heating system inside and delivers both heating and domestic hot water. The fan in the heat pump can be heard and therefore consideration is required about where to site the outdoor unit. It is effective down to - 15° C but the efficiency reduces at colder temperatures. The advantage of this type of heat pump is that there is no collector pipe required and it is ideal where space and access is limited.
Exhaust Air Heat Pump
Ventilation is a basic requirement for living in a healthy house. Controlled domestic ventilation with heat recovery reuses the energy from the exhaust air. Not only that, the additional heat generated internally from lighting, people and domestic appliances is also utilised by the heat pump. Designed for airtight and well insulated homes, the heat recovery heat pump is the ideal solution for new apartments and houses up to 200 m2. It delivers domestic hot water, heating via water based systems (under floor and / or radiators) and controlled ventilation. An immersion heater in the integrated hot water tank provides back-up if required making it a complete solution. 90% of new homes in Sweden have a heat recovery heat pump installed. Ventilation ducting is built into the building design. As with all heating systems, efficiency increases the higher the level of insulation.