Solar PV modules can be installed on almost all kinds of rooftops. The complexities involved in installing a PV module may differ with different rooftops, type of roof construction and roof strength. Therefore there are different PV module mounting structures for metal roofs and flat concrete roofs. Some of the examples of commonly used mounting structures based on the roof type are mentioned below.
Flat concrete roofs (example RCC)
Concrete roofs are in general the easiest way to install a solar power plant as the access for installation and later operations and maintenance if very easy. Depending on the roof design and shadow-free area the common type of module mounting structures for concrete roofs are highlighted below:
1. Low elevation ballast structures
This type of structures are designed for flat roofs with limited load capacity and where there are no shadow issues. The design of the system includes a windshield (sloped wind deflector) that seals the system and reduces the suction force of the wind on the PV modules making the installation stable under high wind load and prevents the frame from overturning/lifting. Typically such mounting structures have a tilt angle of not more than 15 degrees.
2. Elevated ballast structure
This type of structures are advised for flat RCC roofs which have shading issues. These structures can be designed for high ground clearance and can easily combat heavy wind loads. These structures are also designed for installation with penetration to the roof; however, it is not recommended. Instead ballast-based elevated structures can be preferred which do not penetrate the roof and concrete ballast are used as a counterweight for the installation.
Metal roofs (example galvanised iron)
Metal roofs are also relatively easy to install a solar power plant however need more attention towards study of their strength, lifespan, access for installation and later operations and maintenance. Commonly used mounting structures for metal roofs are highlighted below:
1. Rail-type mounting structures
Such mounting structures include metal “L” brackets that are attached to existing roof screw points, and rails are then attached to the L brackets. The PV modules are mounted onto the rails using special clamps i.e. end clamp and mid clamp. It is important that the “L” brackets do not touch the metal roof and have a long-lasting rubber spacer/insulation below them in order to avoid premature rusting of the roof.
2. Clamp-type mounting structures
Clamps are attached to the roofs structure by using aluminium grip rivets as a substitute to roof purlins. This is preferable due to their ease of installation with less number of components and very less lead time for manufacturing.