IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration
Subtask A Report, Date:…
4.4 Analysis of the absorption chiller and the reject heat loop
Figure 4 shows the capacity of the chiller and the heat rejection loop during the course of a
typical summer day. The absorption chiller provides about 11 kW chilled water by means of
14.5 kW driving heat from 10 a.m. to 5 p.m. Until 9 p.m. chiller operation is continued with
surplus driving heat from the buffer tank, gained during daytime. The chiller’s reject heat is
primarily dissipated by the dry cooler. Although auxiliary energy saving has not been the
major focus of this first pilot installation, the electrical COP (chilled water capacity per driving
electric input) is about 7 to 10. The daily electrical COP comprises also the pumping energy
during regeneration of the latent heat storage during night time and reaches values between
4.5 and 8 depending on the stored heat in the latent heat storage and the ambient
temperature.
capacitiy / kW
20
18
16
14
12
10
8
6
4
2
Absorption chiller
COP electrical / -
20
chiller in operation
hot water / kW
COP electrical / -
chilled water / kW
total electricity consumption / kW
time / hh:mm
0
0
9:00 11:00 13:00 15:00 17:00 19:00 21:00
18
16
14
12
10
8
6
4
2
24
20
16
12
8
4
0
-4
-8
Dry cooler and latent heat store
capacitiy / kW
chiller reject heat
heat dissipation
by dry cooler
stored heat in
latent heat storage
chiller in
unloading
the latent
heat
storage
dry
cooler
latent
heat
storage
operation
time / hh:mm
-12
9:00 12:00 15:00 18:00 21:00 0:00 3:00 6:00 9:00
Fig. 4. Operational data of the solar cooling system during the course of a typical day
During hot ambient conditions (10 a.m. to 8 p.m.) the latent heat storage supports the dry
cooler with maximum cooling water temperature about 33°C. The discharging of the latent
heat storage is controlled with regard to the actual heat content (here from 0 to 6 a.m.).
Temperature / °C
38
36
34
32
latent heat storage OUT
dry air cooler OUT
-> latent heat storage IN
30
28
26
24
ambient temperature
22
20
18
16
unloading the latent
14
chiller in operation
heat storage time / hh:mm
9:00 11:00 13:00 15:00 17:00 19:00 21:00 23:00 1:00 3:00 5:00 7:00 9:00