PV panel mounting systems have to firmly and safely attach PV panels to a rigidly fixed system, eg, ground, a façade, or a roof. In case a horizontal or near horizontal surface is available. Attachment can be penetration type, i.e., nut-bolt, anchoring in the ground, etc., or it can be non-penetrating. Now the panels can offer a substantial area, and wind loading can be huge particularly during a storm or hurricane.
The mounting system must be such that it can withstand both aerodynamic lift and torque (tendency to turn over). Non-penetration mounting system, therefore, have to be ballasted.
A ballast is a heavy weight which will try to hold it in place because of gravitation effect. The weight distribution of the structure itself may act as the ballast, or trays may be designed in to receive concrete blocks. Instead of concrete ballast masses in the trays, it is also possible to ballast the feet of these structures with steel or concrete.
Ballasted solar mounting systems should be wind tunnel tested for aerodynamic forces expected to act on them and must remain stable against aerodynamic lift and overturning forces. In all cases of ballast distribution EPDM rubber padding must be provided between the feet and the roof. Non-compliance may invalidate the roof insurance.
EPDM stands for ethylene propylene diene terpolymer which is a tough and extremely durable synthetic rubber. It is used worldwide as a roofing membrane in such applications.
To cater for unevenness of the surface on which the mount is to be placed, some sort of leg adjustment is available so that the platform sits stable on the roof. Also some designs may provide a small local adjustment to tilt angle.
All designs of prebuilt ballasted mounts are stackable horizontally, and may have arrangements for wire connecting or bolting together. In all cases arrangements will be provided for electrical grounding. UL 467 applies to grounding of ballasted solar mounting systems.