24 June 2014
This paper describes field tests on ten different vertical-bore ground heat
exchangers (GHXs). The field tests consist of both short-term thermal response tests on the boreholes and full-year performance measurements on the associated ground source heat
pump (GSHP) systems. While providing space conditioning to nearly identical homes, the energy consumptions of these GSHP systems varied significantly—not only due to the
various fluid temperatures supplied by each of the GHXs, but also the room temperature set points (especially in winter), and the internal heat gains in the buildings. The measured data
were used to verify computer simulations, which later estimated required borehole depths of
different GHXs when supplying the same fluid temperature in response to the same building loads. Both the field tests and the computer simulations indicated that the tested alternative
GHXs require 14-30% less borehole depth than the conventional single U-tube GHX while delivering the same performance.