| dc.description.abstract | i
n the search for new renewable energy sources, photovoltaic systems and solar thermal collectors have become more common
in buildings. With increased efficiency and demand for energy, solar power has also become exploitable at higher latitudes
where snow is a major load on buildings. For flat roofs, one usually expects approximately 80% of the snow to be eroded off
the roof surface.
i
nstalling solar panels would change this since the flow pattern and wind conditions on the roof are affected
by their presence.
t
his study shows the erosion of sand particles from underneath solar panels of various configurations associ
-
ated with different wind velocities. The pattern of erosion is used to determine the relative friction velocity,
u
*
rel
, of the wind
on the roof.
t
his value is the friction velocity on the roof relative to the friction velocity on a flat roof without solar panels.
t
he
experiments, conducted in a wind tunnel, show that the area where
u
*
rel
is 0 and where it is expected that sand and snow will
accumulate in case of an upwind particle source and decrease with increasing distances between roof and solar panel.
i
t is also
shown that a larger gap between the solar panel and roof surface creates larger erosion zones, where
u
*
rel
> 1 for both wind
directions.
s
ince the erosion is closely linked to the air flow under the solar panels, and that higher air velocity increases the
erosion, it is likely that a larger solar panel, extending higher into the free air flow would be desirable to avoid snow accumula
-
tion on a flat roof with solar panels.
i
f the solar panel has large enough dimensions, the solar panels can be used as a
deflector
to decrease snow accumulation on flat roofs. With solar panels of the size in the current experiments, a building with a length
smaller than the equivalent of
x/L
= 0.3 would have
u
*
rel
> 1 on most of the roof surface and would thus likely have a lower
snow load than an equivalent float roof without solar panels. | nb_NO |
