Page 81 - Analysis and Design of Energy Geostructures

Energy geostructures 51

Figure 2.17 Monthly energy balance for the energy pile system at Zürich Airport. Redrawn after
Pahud, D., Hubbuch, M., 2007b. Performances mesurées des pieux énergétiques. Bull. Soc. Suisse
Géotherm. 42(17), 13 14.

This amount of energy was covered by simultaneous heating requirements
(370 MWh, 32%), geocooling (620 MWh, 53%) and by the heat pump used as a cool-
ing machine (180 MWh, 15%). The electrical energy for the circulation pumps and
the cooling machine was measured to be 90 MWh. The annual geocooling efficiency,
that is the ratio between the injected energy in the piles and the electrical energy used
to transfer the cooling energy from the distribution system to the piles, was 61. The
annual cooling machine efficiency, that is the ratio between the cooling energy
extracted at the evaporator and the electrical energy absorbed by the compressor, was
measured to be 2.7. This value was decreased by the electric consumption of the cir-
culation pumps. The overall cooling efficiency, that is the ratio between the delivered
cooling energy and the electrical energy used to operate the system for the cooling
production, was estimated to be of 13.
Fig. 2.17 summarises the monthly energy balance for heating and cooling based on
the previously presented results, from October 2005 to September 2006. Fig. 2.18
shows the monthly extracted and injected energy as well as the inflow and outflow
temperatures associated with energy extraction and injection for the energy pile