Geo-Thermal and Air Source Heat Pumps

In Brief

Heat pumps use the same principle of work that a fridge uses. In simple terms a fridge takes the warm air from inside and pumps it out leaving the inside cold. A highly insulated food chamber and quality door seals prevent further heat gain until the door is opened once again.
An Air Source heat pump takes the warmth from outside air and pumps it into a building. A Ground Source heat pump does the same only it uses the temperatures found below the soil.

Minor Correction of Public Perception

Geo-Thermal heat pumps are often given to be the same as ground source heat pumps but in fact they are not. By right in Ireland we should only be using the term ground source as it reflects the origin of heat from the ground. Studies show this heat to be stored heat from the sun. By comparison Geo-Thermal is a title given to heat drawn from the ground in areas where geological activity results in massive temperature increases e.g. parts of Iceland that experience geysers and other volcanic activity.

Other Info

A ground source pump can draw heat from below the ground either with a vertical or a horizontal loop. A vertical loop is normally placed in a shaft and then covered/filled so only a small footprint or surface is required. A horizontal loop could take take up a large portion of your garden but it would be buried below the winter frost line. In Ireland the ground in some places froze 43 inches / 110 cms below the surface during the snow of winter 2010/2011. The deeper under ground you go the more consistent the temperature. Some people with very large ponds will use this as the location for their horizontal loop. The loop, by the way is a strong pipe system filled with refrigerant and does not suffer at the high or low temperatures it may experience.

Air Source

An air source hear pump system can be fitted very simply by comparison. Systems vary in size, style and ability. They are widely used in residential and commercial properties. One nursing home in Cavan recently had a full air source system fitted to provide all of its ambient heating requirements.

How a heat pump works

  1. Depending on the system heat is absorbed from the ground or air into the external loop(outside the building).
  2. This results in the refrigerant taking on enough heat to convert it to a gaseous state.
  3. The warm gas refrigerant is compressed as it comes to the inner loop in the house.
  4. At this point the refrigerant is hot due to being pressurised by the compressor and it is still in a gas state.
  5. It travels into a condenser where the gas condenses – it gives its heat to the house at this point.
  6. Now having condensed to a liquid it travels to an expansion valve to decompress before starting all over again

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