Energy Performance of CFA Piles used as Heat Exchangers in a GSHP System

Decarbonising heating and cooling represents a significant challenge in meeting the UK’s Net Zero target by 2050. One approach to this challenge involves significant increases in the adoption of ground source heat pump (GSHP) systems. These have traditionally been constructed using borehole heat exchangers to access the ground source, but the last decade has seen an increase in the use of pile ground heat exchangers instead. This paper investigates a building utilising both pile heat exchangers and boreholes connected to a GSHP system to provide heating and cooling all year round. Data has been collected from the Building Energy Management System (BEMS) and temperature sensors on a single pile over a six year period. Initial analysis shows that the GSHP system appears to have been operating in recovery mode for large periods of time. The use of this system has resulted in carbon emissions savings estimated to be around 167 tCO2 for the heating alone. The pile heat exchangers have seen a slight increase in temperature over the period of their operation, but this may now have plateaued. An initial investigation into the performance of the system shows a peak seasonal performance factor of 3.2.