Ground Source Heating & Cooling

Ground Source HeatingGround source systems have actually been around in North America, Scandinavia and Mainland Europe for a lot longer than they have in the UK. It’s taken a while for the UK industry to progress but the growth is here now. It needs to be understood however, that coupling a building to the ground to extract or reject energy takes experience and know-how.

On larger schemes, buildings tend to be best served by either closed loop or open loop borehole systems. Vertically drilled closed loop systems use a network of plastic pipes installed into boreholes to allow heat to be exchanged with the ground.  Typically, borehole depths range from 50m to 200m and thermal transfer fluid is circulated through the pipes either absorbing heat (heating) or rejecting heat (cooling). The bore field is sized on the magnitude of the heating / cooling loads that the ground is expected to deal with. The larger the load, the more the overall length of loop in the ground must be.

These systems can generally be installed on any site in the UK but some geological conditions are more demanding and complex to drill than others. Unlike Open Loop systems, closed loop systems are not subject to Environment Agency ( EA ) regulatory procedures but there are strict protocols in place to ensure that groundwater sources ( aquifers ) are protected from potential pollution.

Ground Source Heating

Open Loop systems see groundwater abstracted at ambient temperature from a water bearing sub-strata known as an aquifer. The groundwater is pumped up from the well or borehole, passed through a plate heat exchanger before being re-injected back into the ground usually from the same horizon from which it was originally sourced.

For buildings with heating/cooling demands of 100-200 kW or more (e.g. a large office building), open-loop systems can be more economic than closed-loop systems. They can also offer what is known as free-cooling where the naturally low temperature of the groundwater ( 10-14°C )

In order to consider an open loop borehole scheme, the presence of an aquifer of sufficient productivity and water quality must be beneath the target site. If the chosen site is close or adjacent to a river or lake then there is the potential to use this as the energy source or sink but surface water systems have annual temperature profiles that closely follow the air temperature so drawing water from it during a cold winter snap can have undesirable consequences and this needs to be considered in the UK. Closed loop surface water systems operate satisfactorily regardless of surface water temperature.

Contact us to learn more about which system may be best suited to your project.

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