Ground Source Heat Pumps
GSHPs utilise the heat energy stored in the ground to heat water that can then be distributed to the taps, appliances and heating system within a building. The GSHP works by passing the low energy heat captured from the ground through a refrigerant cycle that converts it into higher temperatures for use within the home. The heat is collected via means of a loop array that may either be placed in a trench (c.1.5-2m deep) or within a vertical or angled (radial) borehole. These are both closed loop arrays. Other forms such as open loop arrays can be used, but are more complex and generally not used in a residential situation. GSHPs can also be used for summer cooling.
Once installed, GSHPs offer a reliable and low cost form of heating requiring only relatively small amounts of electricity to drive the pumps. Heat pumps aim to supply a constant temperature to buildings. In this, they initially heat the building and then top-up any heat loss on a constant flow basis. They have many sensors that monitor the building, ground loops and outside temperatures. By monitoring outside temperatures they try and predict how much heat the house will require and start supplying that heat before the natural heat loss occurs.
The efficient design of GSHPs is critical to their good and long term performance, and an understanding of both the ground and groundwater conditions and available drilling techniques is crucial in this. In many situations a single deep borehole may not necessarily be the most cost effective solution as it may require more costly larger plant and equipment to drill. Furthermore, the use of larger plant precludes the use of vertical loops at many sites due to access restrictions.
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