Geothermal Cooling - Low Energy Cooling for Sustainable Buildings - page 97

Figure 4.14 Operating hours of ventilation system in SIC building with manual user control (grey =
ON, black = OFF) in the year 2005

is an undersized heat exchanger in the ventilation system, which did not allow the
supply air temperature to be raised (see Figure 4.15).
Due to the infrequent use of the seminar room ventilation system, the floor cooling
system was operating very often for 2289 hours in 2005 and 2922 hours in 2006 (see
Figures 4.16 and 4.17).
The measured average soil temperature is close to 16 ◦ C during the summer. The
brine temperature rises steadily as soon as the pump is turned on, reaching a spread of
nearly 3 K during the day. However, the soil recovers quickly during the night when
the pump is shut off. Still, a rising trend in the soil temperature is clearly visible from
below 15 ◦ C to almost 17 ◦ C within a week. Supply air temperatures during operation
were between 18 and 22 ◦ C (see Figure 4.18). Again, the COPs are excellent due to
the low pressure drop across the heat exchanger and the low power consumption of
the geothermal heat exchanger pump of 170W. The average COP is 21.6 for cooling
and 18.8 for heating.
The heat delivery to or from the ground varies between a maximum of about 15W
per metre of tube in winter and 25Wm − 1 in summer. The maximumpower withdrawal

Table 4.1 Electricity savings for automatic night switch-
off of the ventilation system for 10, 8 or 6 hours daily during
the months of January to March

Savings Savings

Night switch-off / kWh / %

21:00-7:00 840 42

22:00-6:00 672 34

23:00-5:00 503 25