Ground source heat pump

 

Ground Source Heat Pumps (otherwise known as geothermal heat pumps or water source heat pumps) have been used since the 1940's.  GSHP are a system designed to heat water (or a glycol/water mix) for use in radiant heating systems such as under floor heating or radiators.

A ground source heat pump is a very efficient way to heat a large house or building. It requires a higher initial investment but has very low operating costs.

How geothermal heat pumps work

GSHP operate by using the constant temperature of the ground to provide heating in the colder months and in some instances cooling in the summer months.  Ground temperatures range from 7°C to 21°C depending on your latitude.  The ground temperature is warmer than the air above it during winter and cooler than the air in summer.  The GSHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger.

The geothermal heat pump consists of three components:

  •  The ground loop.  This comprises a length of pipe buried underground either vertically (in a bore hole) or horizontally (trenches).  If a ground loop is used the pipe is closed circuit and filled with a glycol and water fluid. An open loop system is another option if a suitably sized water source is available.
  • A heat exchanger (evaporator/compressor and condenser).
  • Heat distribution system – either radiators or under floor pipes (or a combination).

A ground source heat pump can be either a closed loop system or an open loop system (also known as a water source heat pump). The two systems operate in a similar manner with a closed loop system using the earths temperature through horizontal or vertical piping. An open loop system collects energy from a bore, river, lake or pond. The open loop system pumps water directly from the water source to the heat pump unit without the need for installation of the large pipe loops used in a closed loop system. The most suitable system for a particular site will depend on a number of conditions and water stratification.

There are minimal differences in efficiencies between a closed loop and open loop system.

Things to consider

You should consider the following when considering a ground source heat pump:

  • You will need a large area outside your house to install the piping system
  • The heating system – whether hydronic, under floor or radiators (or a combination of the two)
  • If you have a large area of water available (a lake, river or stream) then this may be able to be used
  • The capital cost of the system is generally higher than a conventional system as extensive civil works are required (although these can be combined with earthworks for the house itself).
  • The more stable ground temperatures mean that a GSHP will operate at a higher efficiency than conventional air-sourced heat pumps and fossil fuelled heating systems.
  • The lengths of pipe for a closed loop GSHP will need to be at least 1m deep for a trench and the loops between 1m and 2m apart.

How much will it cost?

The cost of the ground source heat pump  system will depend on the civil works required.  However, in general terms the cost of a geothermal heat pump system is higher than for a conventional heating system.

To find out more download our Fact Sheet: Heat Sources for Central Heating or to obtain a quote contact a Right House Sales Consultant.