Solar PV - Solar PV Orientation - Photovoltaics
Where a Solar PV array is to be mounted on an existing pitched roof, it is likely that the orientation of the building and the angle of tilt of the roof are already established
Solar PV Orientation
In order to produce the most electricity, the Solar PV array should be orientated between south-east and south-west. It is not absolutely necessary for the array to face due south. There will be only a small percentage power loss, as a result of moving a few degrees east or west of south.
In trials, high annual yield values have been recorded for systems up to 30 degrees off south. It is much more important to keep all system losses low than to optimise the orientation. More substantial output reductions are recorded where the orientation is more than 40 degrees off south (i.e. east of south-east or west of south-west.
Solar PV Orientation - Compromise Roof Tilt
There is some flexibility with the angle of tilt and Solar PV arrays can be tilted at an angle as low as 12 degrees. At this angle the system efficiency is only reduced by around 5 per cent and the angle is still steep enough to stop dirt building up on the Solar PV panels.
Solar PV Orientation - Angle of Tilt
In many cases, the proposed Solar PV array orientation and tilt are determined by the design and location of the building. In the UK, a conventional roof pitch of 30 to 40 degrees positions the Solar PV panels at a favourable angle to the incoming solar radiation. In the summer, the angle of the sun is 50 to 60 degrees so, with a 30 to 40 degree roof, it will result in a combined angle of 90 degrees. This angle is ideal for the maximum intensity of solar radiation.
Solar PV Orientation - Location on a Flat Roof
When planning to install a Solar PV system, the roof of the building is usually the most suitable place. This solution is effective where the roof is south facing or where the roof is flat and panels can be fitted using angled mountings. An alternative is to mount Solar PV panels on a wall. This can work well with longer, slimmer panels that can be mounted at an angle without protruding too far from the wall itself.
In addition to roofs, solar equipment may also be mounted on frames sitting on the ground or on the roofs of sheds, carports, or other outbuildings. In these cases the same rules apply for site evaluation.
Solar PV Orientation and Tilt Calculator
Orientation and tilt are probably the most important factors affecting Solar PV system efficiency. The Orientation and Tilt Chart shows that maximum efficiencies are achieved at a tilt of about 35 degrees with an orientation due south.
Solar PV Orientation - East and West Facing Roofs
If a south facing roof is not available, or the total Solar PV array is larger than the area of a south facing roof, an east or west facing surface is the next best option. It is important to remember that the solar power output decreases proportionally with a horizontal angle greater that 15 per cent from due south.
Solar PV Orientation - Positioning Solar PV Panels
The most productive part of the roof for Solar PV arrays is the slope facing south. Although this position is the best, there is plenty of latitude for both the tilt and orientation of the Solar PV arrays. Tilt and orientation angles can be varied over a considerable range without substantially reducing the amount of solar radiation.
Solar PV Orientation - Producing Power for Peak Demand
Conventional electricity generating companies may prefer the Solar PV arrays to be situated towards the west in order to gather more late afternoon sun to match their peak demand. When due south is not an option, it is possible that at least one elevation of the building will receive adequate solar energy to justify a Solar PV array.
Solar PV panels can be fitted on or integral with pitched roofs, on an angled framework on flat roofs, on the ground or vertically on walls. They all should work efficiently as long as no part of the Solar PV panel is shaded from the sun
About Solar PV - Orientation and Tilt - Solar PV Arrays