What’s a Thermal Response test?

On developments over 100kW where boreholes are planned, Kensa would recommend a thermal response test (TRT). The amount of energy that can be obtained from a borehole is never accurately known until the system is actually up and running and hence the number of boreholes required is generally over estimated to ensure that there is sufficient energy output for the system. While using rules of thumb maybe acceptable for small developments, for larger developments it could mean that the bore field is significantly oversized and costs are increased.

For sites where the heating load is over 100kW Kensa would recommend that a TRT is carried out. A TRT involves drilling a trial borehole that is representative of the boreholes planned for the site. Heat is then injected at a constant rate into the borehole and the inlet and outlet water temperatures are monitored over a period of time (minimum 72 hours to overcome any thermal storage in the U tube and borehole). The results are then plotted and can be used to estimate the thermal conductivity of the borehole and hence the amount of energy that can be obtained.

A borefield specialist can then advise on the number and layout of the boreholes for the development.

Kensa operate one of the few TRT rigs in the UK and can provide the contact details of a Borefield Consultant to help design a suitable borehole layout.

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