30 May 2005

SEASONAL SYSTEM PERFORMANCES FOR VERTICAL GROUNDCOUPLED HEAT EXCHANGERS AND COMPARISON WITH AIR-TO-WATER HEAT PUMP SYSTEMS


To make a global assessment of a Ground Coupled Heat Exchanger (GCHE) it is not only important
to understand the behaviour of the GCHE, but also to consider the system in which it will operate: its
loads and utilization factors (as a function of climate conditions and application), efficiency (which also
depends on the heat pump) and other system parameters, such as pumping requirements, long term soil
heat imbalance, etc.
In the frame of the European project GEOCOOL, this paper shows the results of applying a
methodology developed for the comparative study between a system combining a water-to-water
reversible heat pump of commercial size with a vertical GCHE and an equivalent air-to-water heat pump
system in typical conditions of the European Mediterranean rim (of great importance for Cooling). For
this purpose, the seasonal system performance factors for heating and cooling, and the temperature
profiles of the water in the GCHE for a 25 years period were calculated for different backfill materials. In
addition, an extensive study of relevant climatological parameters of Valencia-Spain was made. These
results were transformed in bin-hour data which are used for calculating the seasonal system performance
factors for heating and cooling for the air-to-water heat pump system. The heat pump properties have
been calculated using the IMST Group’s ART software.
Finally, a comparison was made between GCHE-system and air-to-water heat pump showing the
efficiency improvement obtained for various grouting materials.