Potential of geothermal heat exchangers for office building climatisation

Low depth geothermal energy can be efficiently used as a heat sink for building energy produced during summer.In the current work, several geometries of geothermalheat exchangers implemented in office building climatisationprojects are evaluated for their energetic performance.For all geometries, simulation models were developed and validated using the experimental data, so that parameter studies could be carried out.A main result of the performance analysis is that the ground coupled heat exchangers have excellent coefficientsof performance ranging from 20 50 as average annual ratios of cold produced to electricity used. Best performance is reached, if the ground cooling system is used to cool down high temperature ambient air. The maximum heat dissipation per meter of ground heat exchangermeasured is often lower than assumed in the planning phase. In the projects evaluated, the heat dissipationvaried between 8W per meter for the low depth horizontal heat exchangers up to 25 W per meter for the vertical heat exchangers. The power dissipation varies by plus/minus 30% depending on the soil conductivity. The heat conductivity of vertical tube filling material is very important, as the power dissipation changes by plus/minus 30% for different materials.As a result of the work, planning and operation recommendationsfor the optimal choice of ground coupled heat exchangers for office building cooling can be given.