Solar Photovoltaic systems and Shading

Document Sample
Solar Photovoltaic systems and Shading Powered By Docstoc
					?Solar Photovoltaic (Solar PV) systems are significantly impacted by shading as it can
reduce the output of the PV array. Ideally the Solar PV systems should be located in a
shade-free area. However most grid-connected systems are often located on-roofs in
built locations, where shading is largely inevitable. There are many forms of
temporary shading that can affect the performance of the Solar Panels including: snow,
fallen leaves and general dirt. Nonetheless generally this loss of efficiency amounts to
between 2 per cent and 5 per cent and can be overcome by paying careful attention to
the arrangement and angle of the panels. A tilt of 12 degrees or more allows for the
solar panel to self-clean, as greater tilts increase the flow of rain and thus helps to get
rid of any potential shading blockages. By arranging the Solar PV modules
horizontally this enables losses made by the shading to be reduced by half (in
comparison to if it was positioned vertically).

The snow on Solar PV arrays melts faster than the surrounding snow so the temporary
shading effect should not last for a long period of time. Generally the shading arising
from shading factors such as: air pollution, fallen leaves and dirt can be managed by
regular cleaning; this can significantly improve the effects of shading on the solar
yield. A good cleaning method is to simply clean the Soar PV array with water,
avoiding powerful detergents and cleaning tools that could scratch and damage the PV

The most common forms shading can derive from the location of the Solar PV array,
the building itself, self-shadings from the Solar Panels and Direct Shading. Shading
resulting from the location can be caused by the buildings surroundings. This can
range from tall trees to neighbouring buildings. Shading resulting from the building
should be strongly considered, special attention could be paid to satellite dishes and
offset building structures. One you have identified if there are any obstructions,
shading can be avoided by moving these obstacles. However if this is not possible the
shading effect can be minimised if taken into account during the initial stage of
deciding the type of system being installed (stand-alone and grid-connected systems).
When installing a rack-mounting system potential self-shading can arise from the
rows of Solar Panels in front of each other. A good Solar PV system will minimise
this effect by optimizing the tilt and distance between the panels, in the design process
of the system. In instances of direct shading, it can cause high losses of energy
although the intensity of the energy loss is largely dependent on how close the she
shadow is from the obstructing object to the Solar PV array. The larger the distance to
the shadow- casting object from the Solar PV system, the brighter the shadow is and
the more shading losses are reduced.

EvoEnergy are Solar PV Installers they design and install PV Solar Systems for both
residential and commercial properties.