Geothermal Heat Pumps

How does a geothermal or ground source heat pump work?

Ground source heat pumps used for geothermal heating can be used efficiently to heat a house by drawing heat from the ground, condensing it and delivering it to the building. Systems use the heat pump and a compressor to remove heat from one side of the circuit and eject heat to the other side.

A geothermal heat pump moves heat into or out of the earth using either water wells or a network of high-density polyethylene pipes buried in vertical boreholes.

The pipes carry a water and antifreeze solution, which is pumped through the pipes buried in the ground. The heat transfer fluid extracts heat (heating mode) from the earth surrounding the ground loop system.

The geothermal heat pump increases the heat, which is then distributed throughout the building by the chosen heating system. The heat pump also has the capacity to work in reverse and provide a cooling system (heat pump dependant). More information on ground source heat pumps.

Geothermal heatpumpsa geothermal heat pump’s main components

The Evaporator

(e.g. The squiggly thing in the cold part of your fridge) takes the heat from the water in the ground loop.

The Compressor

(This is what makes the noise in a fridge) moves the refrigerant round the heat pump and compresses the gaseous refrigerant to the temperature needed for the heat distribution circuit.

The Condenser

(The hot part at the back of your fridge) gives up heat to a hot water tank that feeds the distribution system.

What advantages do geothermal heat pump systems offer?

  • A 25 to 40 percent reduction in heating and cooling costs
  • Standard, simple controls
  • No need for a highly specialized chiller technician or boiler operator
  • Highly durable piping (the life expectancy is between 30 and 50 years)
  • No high-maintenance, freezing-prone cooling tower
  • No boiler to clean or maintain
  • No air conditioning equipment on roof to cause leaks
  • No harmful chemicals
  • No danger of fire, asphyxiation, or explosion from coal, gas, or oil
  • Nothing outside to vandalize or steal
  • No central system to fail or shut down the entire building
  • Boreholes and Ground Source Heating Principles

Underneath the frost line, the ground stays at a constant temperature of about 57 degrees Fahrenheit. That happens to be an extremely efficient operating temperature for heat pumps. Geothermal heat pump systems circulate water between an underground water loop, called an earth heat exchanger, and water-to-air heat pumps located throughout a large building.

There are little or no disadvantages with Geothermal Heat Pump Systems.

What to keep in mind when considering a ground source heat pump;

  • The type of heat distribution system. GSHPs can be combined with radiators but under-floor heating is better as it works at a lower temperature.
  • Is there space to get the rig in to install the ground loop?
  • What fuel is being replaced? If it’s electricity, oil, LPG or any other conventional fossil fuel the payback will be more favourable. Heat pumps are a good option where gas is unavailable.
  • Is there also a cooling requirement?
  • Is the system for a new building development? Combining the installation with other building works can reduce costs.
  • Can you incorporate insulation measures? Wall, floor and loft insulation will lower your heat demand.

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