Where should the Array be Mounted
A PV array consists of several PV modules that are roof-mounted, ground-mounted, or building-integrated. Most roof-mounted modules are installed on aluminium racks attached to the metal or tile roof sub-structure. These racks are best installed on an unshaded, South-facing roof (Northern hemisphere) parallel to the roof line, with an intervening air space of 3 to 4 inches. The air space under the array helps lower PV module temperatures; cooler modules produce more electricity than hotter modules. Ideally the PV array is tilted at an angle close to the latitude of the installed location to maximise the electricity production between summer and winter as the angle of the sun varies. Maximum PV production usually occurs on clear sunny days with low ambient temperatures.
Roof-mounted arrays dominate the PV retrofit market, but they aren’t the only option. Installing a ground-mounted array avoids having to remove modules for roof restorations, and can overcome limitations on roof space suitable for solar power. It’s usually easier to remove snow and dust from a ground-mounted array compared to on the roof and is better for maintenance of larger systems.
Ground-mounted arrays require a site without any nearby trees or buildings that would block the sunlight. Such an array can be installed at a fixed angle or on a tracking system that automatically adjusts the array’s angle as the sun moves across the sky. This is usually only economical for larger commercial scale installations to offset the capital cost of trackers, and the additional power consumption and maintenance required.
Building-integrated PV arrays are not as common and are often more expensive to install. In this case the panels are installed onto the roof framework in place of roof sheets or tiles. This requires additional water-proofing and is more commonly installed on new buildings.