Solar-supported heating networks in multi-storey residential buildings

Hot Water Consumption [Litre/day at 45°C]
3 000
2 800
2 600
2 400
2 200
2 000
1 800
1 600
1 400
1 200
1 000
0 30 60 90 120 150 180 210 240 270 300 330 360
Day of the Year
Figure 19: Annual consumption profile generated from the daily consumptions profile where
measurements and probability calculations (with a daily mean domestic hot water consumption of
2000 litres at 45 °C) are taken into account (Weiß, 2003).
The annual consumption profile depicted in Figure 19 consists of daily consumption profiles lined up
with due consideration to the seasonal fluctuations calculated from the measurements. The seasonal
distribution can be approximately depicted by a sinus curve. Accordingly, maximum consumption
occurs in the months of February/March and minimum consumption in the months of July/August.
These seasonal fluctuations (up to around 20% is common) can be explained in principle by the
holiday season and the lower hot water temperatures required in summer due to the high outside
temperatures.
These aspects now have to be taken into consideration both with regard to the design of the solar
thermal systems and the overall domestic hot water plants. Solar thermal systems are generally
designed so that in the summer months with higher irradiation and slightly reduced consumption no
surpluses are attained. In designing complete domestic hot water plants, on the other hand, the peak
load is given priority to guarantee security of supply. Details of the dimensioning can be found in
Section 8.
5.2
Determining heating requirements
Apart from domestic hot water, the second largest source of consumption in multi-storey residential
buildings is heating energy. As shown in Figure 14, heating is required in Austria in the months from
September to May (around 5,000 operating hours). If the period of solar radiation is compared with
this demand period then it is apparent that the two do not correspond. The months with the lowest
amount of sunshine have the highest heating demand.
Nevertheless, solar thermal systems in multi-storey residential buildings can make a considerable
contribution towards covering heating demand particularly in the transitional period. If solar thermal
systems in multi-storey residential buildings are also to be used to support the heating system then
the heating requirements of the building need to be known for dimensioning the system.
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