Ground Source Heat Pumps: a gift from mother earth
Ground Source Heat Pumps (GSHP) are widely used to provide efficient heating, hot water and cooling to domestic and commercial properties.
Geothermal energy is the thermal energy available in the ground that can be extracted as heat. If the temperature level of this energy is less than 30 °C, Ground Source Heat Pumps can be used to extract ground heat for space heating and Domestic Hot Water (DHW) production. Moreover, GSHPs can also be used for active and passive cooling.
"As more people are conscious about energy conservation and efficiencies and are building better buildings, we're seeing a massive uptake in GSHPs."
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The ground source heat pump system
A ground source heat pump system consists of 3 main parts:
- Ground heat collector system: loop of pipes buried underground to transfer energy to and from the system.
- Heat pump: located inside the building
- Heating and cooling distribution system
The extraction of ground energy using heat pumps requires a collector system. Collector systems commonly used to extract heat from the ground are vertical borehole collectors, horizontal ground collectors and groundwater systems.
Heating and cooling systems with GSHPs consist of the ground heat collector system, the heat pump and the heat distribution system inside the building. Distribution systems commonly used are underfloor heating and radiant surfaces, fancoil units or low temperature radiators.
How do GSHPs work?
- The ground absorbs low-grade solar energy by means of direct sunlight and rain. This gives the ground a year round temperature of approximately 8 – 12 °C.
- A cold water antifreeze mix is pumped through the ground within a series of looped, energy absorbing pipes, or deep ground bore holes.
- As heat naturally flows from warmer to cooler places, the anti-freeze mix circulating around the array is constantly warmed by the grounds low-grade heat.
- The heated antifreeze mixture is fed into a heat exchanger called the ‘evaporator’. On the side of the evaporator there is a refrigerant, which acts as a heat transfer fluid.
- When the water antifreeze mixture enters the evaporator it begins to boil and turn into gas. This gas is then fed into a compressor, increasing the pressure, which makes the gas temperature rise.
- The hot refrigerant gas then flows into a similar, second heat exchanger called a ‘condenser’ with identical heat transfer plates. This condenser delivers water hot enough to serve space heating and hot water needs.
- Having transferred its heat, the refrigerant gas reverts to a liquid, which is passed through an expansion at the end of a cycle to reduce its pressure and temperature, ready to commence the cycle all over again.