PV arrays can be mounted on the ground, rooftops and other structures that provide adequate protection, support and solar access. The site conditions usually dictate the best mounting system location and approach to use. Below are some PV Array Mounting Methods.
Rooftop PV Array Mounting Methods
Rooftops are very popular locations for installing PV arrays. Because they are elevated, roof mounts offer some physical protection and limited access to the array for safety, and usually provide better sun exposure.
Rooftop PV installations also do not occupy space on the ground that might be needed for other purposes. Rooftop and other building mounted PV arrays must be structurally secured and any attachments and penetrations must be properly weather sealed.
Available rooftop areas for mounting PV arrays may be limited by any number of factors, including required spaces about the array for installation and service, pathways and ventilation access for fire codes, wind load setbacks, and spaces for other equipment.
Sloped roofs also present a significant fall hazard, and require appropriate fall protection systems and/or personal fall arrest systems (PFAS) for installers and maintenance workers.
Ground PV Array Mounting Methods
Ground-mounted PV arrays are commonly used for larger systems, or where rooftop installations are not possible or practical. Ground-mounts can use a variety of racks, poles and other foundations to support the arrays.
Ground-mounted arrays are generally more susceptible to damage than roof-mounted arrays, although their location and orientation is less constrained than for rooftop installations. If an array is mounted at ground level, NEC 690.31(A) requires that the wiring be protected from ready access.
Several options may be possible to meet this requirement, including protecting the wiring with non conductive screening like PVC, limiting access with security fencing, or by elevating the array. Elevating arrays also provides physical protection, and usually helps avoid shading concerns that may exist at lower heights.
Other PV Array Mounting Methods
Integral mounting systems are where modules are integrated into the roofing or building exterior. These systems are sometimes referred to as building-integrated PV or BIPV.
Standoff mounting, referred to by some as flush mounting, uses standoffs attached to the roof to support rails on which PV modules are attached. This is the most common method for residential installations.
Ballasted mounting systems are often used in large-scale flat roof commercial projects. These mounting systems require engineering for roof structural loading and ballast requirements. Often roof tethers augment the ballast for seismic concerns or excessive wind requirements.
Rack mounting is typically used for non-tracking systems at ground level and on flat rooftops. This method is typical on large commercial or utility-scale arrays.
Pole mounting, is typically used with manufactured racks mounted on top or attached to the side of a steel pole. Pole-top arrays are common for off-grid residential PV systems since the weight of the array is balanced over the pole, allowing easy seasonal adjustment.
Side-of-pole mounts are most common in small one- or two module applications where the entire system, such as remote telemetry application, is mounted on a single pole.
Tracking mounting systems are systems that follow the sun on a daily or seasonal basis. Tracking may increase summer gain by 30% or more, but winter gain may be 15% or less. Tracking may be two-axis for maximum performance or single-axis for simplicity and reliability.