TECH-TALK AND FAQ
General Considerations for Various PV Mounting Approaches
Fixed Ground Mounting
Energy harvest is typically 25%-40% less than a tracked array of the same capacity. Ground mounting is best suited to well secured sites where unobstructed sun exposure is available without having to place the panels at a significant height. It is also the most susceptible to tampering and/or vandalism. This mounting method can also be adapted to a flat or low pitch roof.
Fixed Roof Mounting
Fixed roof mounting has all the advantages of fixed ground mounting but with reduced ease of maintenance traded off against immunity to tampering and/or vandalism. One additional issue is the possible need for roof penetrations to accommodate mounting hardware.
There are a number of ballasted mounting systems available that make it possible to avoid roof penetrations or at least keep them to a minimum. Ballasted systems typically use concrete blocks to keep the modules and racking in place.
Modules can also be attached securely to metal roofing. Metal roof penetrations can be repaired more easily than tar and gravel, or membrane roofs. There are several vendors now producing mounting hardware specific to corrugated metal roofing that minimizes or avoids penetrations altogether.
PV composite film products are also available intended for direct mounting to metal roofing, walls, and other relatively smooth surfaces. These products are best used with south facing surfaces to maximize harvest.
Wall Mounting
South facing building walls can be taken advantage of as module mounting surfaces. Modules arrays can be parallel to the wall, tilted away from the wall, or configured as an overhanging canopy.
Tracked Mounting
Using a tracker can increase array energy harvest 25% - 40% over fixed mounting. Trackers can be ground or roof mounted. When ground mounted, the tracking hardware can add 15% - 20% to the cost of a project over fixed mounting hardware. Since roof top installations require more engineering and labor to complete, the system cost differential between tracked and fixed related to mounting method alone will be smaller still.
Strategic ground mounting locations, could allow trackers to serve a secondary role in providing useful shade for site users.
Top of Pole Mounts
Top of pole mounting is another fixed array mounting method. Arrays remain stationary even through the arrangement looks similar to a tracker. This approach can be used for roof or ground mounting.
