Solar PV installations require support structures, commonly referred to as racking, to secure the panels to the ground or building roof. For ground mounted structures racking may be mounted onto foundations that are driven (I beams, channels or posts), or screwed (helical piles and earth screws). Ground systems are either fixed tilt or track the movement of the sun, either in one axis or two axes. Roof top racking are either ballasted with concrete pavers resting on ballast trays, or attached with penetrations onto the roof of the building, or fastened to metal seams with clips. There are also hybrid systems which are principally ballasted but also have attachments to compensate for seismic issues or where roof pitch typically exceeds 5 degrees. The size of installation, available surface area, type of incentive and utility program, building type and ground conditions predicate which system will be used.
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