The technology − known as ’geo exchange’ − uses a series of closed-loop boreholes drilled 200m underground. The boreholes store heat captured from the refrigeration system that runs the chillers and freezers in the store, which can later be released to provide heating, hot water and cooling.
The thermal energy from the refrigeration system is carried by a vegetable-based glycol and water fluid in a set of pipes to the closed-loop boreholes where the heat is transferred, effectively using the earth as a natural storage radiator.
The boreholes are encased in steel to maximise the use of the thermal energy and have been drilled at specific angles to maximise the heat retrieved from the earth − a technique commonly used in the oil and gas industry.
The technology, developed by UK company Greenfield Energy, is expected to reduce the store’s overall energy consumption by around 30 per cent compared with a typical store.
The newly extended supermarket in Crayford, Kent, is now 2.5 times bigger, at 100,000ft2, but has the same carbon footprint as the smaller store because of the use of onsite renewable technology.
In addition to the geo-exchange system, the store will also use sun pipes to maximise use of natural light, rainwater harvesting to supply water for flushing the toilets and LED lighting for the car park.