Solar Coverage; Orientation, Inclination And Shading Of The Receiver Surface; Inclination Of The Receiver Surface; Orientation Of The Receiver Surface - Viessmann VITOSOL 100-F SV Technical Manual

Principles
(cont.)

Solar coverage

100
1
90
80
70
A
60
50
40
30
20
10
300 350
Energy (yield) in kWh/(m²/p.a.)
A Conventional sizing for DHW systems in detached houses
B Conventional sizing for large solar thermal systems

1.3 Orientation, inclination and shading of the receiver surface

Inclination of the receiver surface

The yield of a solar thermal system varies depending on the inclination
and orientation of the collector area. If the receiver surface is angled,
the angle of incidence changes, as does the irradiance, and conse-
quently the amount of energy. This is greatest when the radiation hits
the receiver surface at right angles. In our latitudes, this case never
arises relative to the horizontal. Consequently, the inclination of the
receiver surface can optimise the yield. In Germany, a receiver surface
angled 35° receives approx. 12 % more energy when oriented towards
the south (compared with a horizontal position).

Orientation of the receiver surface

An additional factor for calculating the amount of energy that can be
expected is the orientation of the receiver surface. In the northern
hemisphere, an orientation towards south is ideal. The following figure
shows the interaction of orientation and inclination. Relative to the
horizontal, greater or lesser yields result. A range for optimum yield of
a solar thermal system can be defined between south-east and south-
west and at angles of inclination between 25 and 70°. Greater devia-
tions, for example, for installation on walls, can be compensated for by
a correspondingly larger collector area.
±0%
-15%
+5%
-40%
-25%
West
South-west

Avoiding shading of the receiver surface

Looking at the installation of a collector facing south, we recommend
that the area between south-east and south-west is kept free of shad-
ing (at an angle towards the horizon of up to 20°). It should be remem-
bered that the system is to operate for longer than 20 years, and that
during this time, for example, trees would grow substantially.
VIESMANN
10
B
400 450 500 550
+10% +10%
-20% -20%
South South
The solar coverage rate indicates what percentage of the energy
required annually for DHW applications can be covered by the solar
thermal system.
Designing a solar thermal system always entails finding a good com-
promise between yield and solar coverage. The higher the selected
solar coverage, the more conventional energy is saved.
However, this is linked to an excess of heat in summer. This means a
lower average collector efficiency and consequently lower yields
(energy in kWh) per m
600
±0%
-15%
+5%
-40%
-25%
East
South-east
2 absorber area.
VITOSOL