analysis of the influences of solar radiation and façade glazing ...

3.5 Optimization of a solar domestic hot water system 97
Fig. 3.48: Dependence of accumulated solar energy on the storage tank volume.
Fig. 3.49 depicts the average daily water temperature inside the storage tank with a volume
of 2 m 3 (solid line) and of 6 m 3 (dashed line). We can clearly observe that the increase in
system thermal capacity leads to the prolonging of the storage tanks operating period with
raised output temperatures. As shown in Fig. 3.49, the simulation results can be
approximated by the second order polynomial function of temperature versus time.
Storage tank temperatute [ 0 C]
60
50
40
30
20
10
0
Energy [kWh]
01/01
12 000
10 000
8 000
6 000
4 000
2 000
01/21
0
02/10
Auxiliary energy demand
Solar energy
0 1 2 3 4 5 6 7 8 9 10 11 12
Storage tank volume [m 3 ]
03/02
03/22
04/11
Fig. 3.49: Average daily storage tank temperature for a volume of 2 m 3 and of 6 m 3 .
05/01
05/21
2 m3
6 m3
Approx. 2 m3
Approx. 6 m3
06/10
Eq. (3.7) represents temperature profile for 2 m 3 tank volume and Eq. (3.8) fit the
numerical data for 6 m 3 tank volume.
06/30
07/20
08/09
08/29
09/18
10/08
10/28
11/17
12/07
12/27