advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...

+110
+100
West
+80
+120
+70
+60
+130
+50
+140
+40
+150
+30
+160
+20
+170
+10
Advanced Building Skins
North
-170
-10°
-160
-20°
-150
-30°
-140
-40°
-130
-50°
- 7 -
-120
0° 10°20°30°40°50°60°70°80°90°
South
-60°
-110
-100
-80°
-70°
East
annual irradiation Tilt angle
30%
40%
50%
60%
70%
80%
90%
95%
100%
© Christof Erban
Figure 9: Annual total irradiation for different orientations and tilt angles in Central Europe relative to the
maximum achievable value
Figure 10 introduces the topology and the orientation of the roof. It can be derived that the topology
has a much larger influence on the energy yield per m² ground area than the orientation of the roof.
When both parameters are combined, the deviation from the minimum to the maximum is 3.88.
Thus the range of electricity generation on a 100 m² building ranges from 3640 kWh (type 2 building
in Scandinavia - appr. 4.3 kWp) to 28288 kWh (type 4 building in Southern Spain - appr. 15 kWp).
tilt angle
rel. area covered 1
energy yield 2
energy yield 3
0°
30°
30° 30° 15°
active roof area
inactive roof area
inactive wall area
30° N
100%
30% 58% 115% 104%
115%
100% 118% 118% 118% 100%
92%
100% 35% 68% 136% 104%
106
Figure 10: Energy yield for different roof topology and roof orientation
1 2 3
active roof area/ ground area, in comparison to GHI as in Fig. 7, eq. 1 * 2
In Europe, the installed power of photovoltaic arrays on residential roofs typically ranges from 3-5
kWp. They are oriented – more or less – due south and provide enough electricity over the whole year
to compensate for all electricity demands in the building if the building is not heated or cooled by
electricity. If the topology and orientation of the roof is chosen properly, this holds true even in
Scandinavia. The surplus in summer is fed into the grid and sold.
On an annually averaged basis, photovoltaics in Central Europe can even contribute a significant share
of electricity for heating using a heat pump. This requires building designs with a high electricity yield
per m² ground ratio.
Buildings like this – incorporating photovoltaic systems as described before - thus would meet the
demands of the European directive for an annual net zero energy balance, but as figure 11 shows, there
is a mismatch between the time when photovoltaics supplies electricity – in summer – and the time
when the electricity is required by the heat pump – in winter.
10°
20°
30°
40°
50°
60°
70°
80°
90°
S
E
W