Environmental Engineering Reference
In-Depth Information
In this context, energy losses due to excessive temperature rise attributable to
sub-optimal installation must be considered (e.g. /6-31/). For instance, a photo-
voltaic module mounted at a distance of only 10 cm from a slanting roof generates
additional losses due to heating between 1.5 and 2.5 % of the annual energy yield
compared to a completely detached solar generator of the same size and orienta-
tion. If the modules are fully integrated into the roof without rear ventilation,
losses are between 4 and 5 % compared to a completely detached system; for a
fully facade incorporated generator the losses amount to 7 to 10 % assuming Cen-
tral European weather conditions.
Mounting and installations systems must be adapted to the respective site con-
ditions concerning material (hot-galvanized steel, wood etc.) and soil conditions
in case of free-standing installation (concrete foundations, ground anchors, pile-
driven profiles, foundation-less installation etc.). Regarding roof and facade in-
stallation special mounting systems are available. In case of roof installation rack
systems may be installed at a certain distance to the roof cladding; however, also
integration into the roof is technically possible. The latter option is often preferred
for architectural and esthetical reasons and does not require any conventional roof
cover. However, it makes convective cooling of modules more difficult and thus
leads to increased energy losses as mentioned above.
In terms of stationary systems module orientation towards the south allows to
maximise energy yields. Deviations of below 30° to the east or to the west are in
most cases of negligible effect since they only decrease the energy yield by less
than 5 % /6-32/. Optimal inclination of solar modules is primarily determined by
the latitude. If an inclination angle is selected vertical to the mean midday solar
altitude this corresponds exactly to the latitude of the respective site. If the maxi-
mum annual energy yield is to be achieved, in summertime, due to higher solar
radiation during this time of the year, solar modules are to be installed with a
lower inclination angle. For Central European latitudes, inclination angles be-
tween 25 and 45° allow for the highest energy yields in terms of grid-connected
modules.
Yet, it is more difficult to determine the optimal inclination of stand-alone
modules. Systems lacking of an additional power generator (e.g. Diesel genera-
tor), and that are to provide about the same energy quantity over the whole year,
should be set to a much steeper angle of about 60°. While the energy yield needs
to be optimised within such systems in wintertime, in summer excess energy usu-
ally cannot be utilised. For stand-alone photovoltaic systems provided with addi-
tional generators supplying 20 % or more of the annual energy demand inclination
angles between 35 and 45° are most suitable for Central European conditions.
Seasonal tracking of the inclination is also technically feasible and requires only
little effort (summer: flat angle; winter: steep angle).
Tracking of solar modules to the actual solar altitude increases the energy
yield. The following tracking systems are distinguished
single-axis tracking around the horizontal rotation axis,
single-axis tracking around the polar axis,
Search WWH ::




Custom Search