Ground Source Heat Pumps

How they work

                   

 

Ground source heat pumps draw geothermal heat out of the ground by circulating a solution of water and anti-freeze through virtually indestructible plastic tubing, placed in the subsoil. This tubing is inserted either vertically or horizontally into the ground, literally "tapping" into the geothermal energy contained within. This heat energy then flows back through a water-heat exchanger, where it is absorbed by a refrigerant.

 

The refrigerant is then compressed, increasing its temperature to 65-71°C, and an air-heat exchanger circulates it throughout the building. Air is circulated through ducts & water is circulated in radiators or flooring panels.

By simply reversing the process, ambient heat can be removed back in the ground or water, resulting in a cool, dehumidified interior.

 

 Geological Factors influencing Ground Source Heat Pumps

  • The UK has an extremely varied solid geology with an extensive Quaternary cover.
  • Rock thermal conductivity ranges from about 1.5-3.5 Wm-1K-1 and has a strong influence on the heat exchange potential of the external loop.
  • The geological prognosis of the site and rock geotechnical properties will influence the drilling methods and system costs.
  • Other important aspects are the predicted subsurface temperatures, the thermal properties of the strata, the water saturation level and the natural or induced hydraulic flow.
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    Advantages

  • High Efficiency

  • A reduction in cost & consumption of purchased heat energy

  • Simultaneously heat & cool different parts of the same building, as can be set up in multiple zones, with each zone having an individual room control

  • Provide humidity control and water heating

  • Minimal noise, possible to install anywhere in the building

  • Greater freedoms in building design due to 50-80% less mechanical room space

  • No outside equipment, eliminating vandalism and roof top units

  • Low life cycle costs - pipes have about 50-year life expectancy and ground heat exchanger is maintenance free and should last 40-50 years

  • All electric, which eliminates multiple utility services

  • Do not require boiler, fuel tank or cooling tower

  • Not being connected to the national energy grid, they can operate 24-7, with no dysfunction as a result of an interruption in power supply.

  • They reduce dependency on foreign and domestic oil supplies.

  • Highly efficient for buildings with high demand for heating, cooling & long hours of usage, i.e. hotels, hospitals.

  • Heat pumps produce some CO2 from compressors, but are still lower than conventional boilers. Other integrative renewable technologies can be applied to power the heat pumps.

  • Do not require transportation of fuels

 

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      Disadvantages  

  • •Initial installation costs are higher than conventional heating systems.

  • •Heat pumps require access to sufficient areas of ground surrounding the development or to suitable bodies of water & groundwater.