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With the recent heatwave it is perhaps not the time to be thinking about heating, but what if your heating system could also provide comfort cooling? With a ground source heat pump it is possible to do both.

Water source and borehole collectors are particularly suitable for providing the required heat sink needed for cooling as both normally interface with ground water allowing high heat transfer rates.

In heating mode, a heat pump collects energy from the collector, borehole or water source, elevates the temperature and delivers it to the property via the heating system. With some clever design it is possible to reverse this process collecting energy from the property and dumping it to the collector effectively cooling the property.

There are two methods of providing cooling with a ground source heat pump; passive cooling or active cooling.

With passive cooling the brine is circulated through the collector in the bore hole or water source which cools the brine. This is then circulated through a heat exchanger which cools the system fluid on the other side of the heat exchanger providing a chilled water for circulation through cooling fan coils or in some circumstances, underfloor cooling pipe work. Care should be taken when using underfloor cooling as condensation can build up in the form of dew.

Passive cooling only requires a simple switch over arrangement to divert the brine flow making this a cost effective cooling arrangement. Passive cooling is limited by the temperature of the brine and can become ineffective if this becomes too warm.

Active cooling requires the circuits to the evaporator and condenser to be swapped so that heat energy is taken from the heating (now cooling) circuit and is rejected into the boreholes or water via the brine circuit. This usually requires a switch over arrangement either in the heat pump casing or as a separate unit. Active cooling is more effective than passive cooling as a set cooling temperature can be maintained by the heat pump. This form of cooling is the most similar to air conditioning.

Active cooling is usually limited by the minimum allowable temperature of the cooling circuit or the ability of the borehole or water source to disperse the heat.

If you are interested in finding out more on how a ground source heat pump system can provide cooling as well as heating, please get in touch.