Ballasted mounting structures have traditionally been used on flat commercial-style roofs, where penetrating the roof surface is undesirable or impossible. Instead, a heavy ballast, often concrete blocks, sits in trays attached to the mount to firmly hold the array in place. Ballast weight is based on the site’s design wind speed and other factors that affect the wind loading and pressure on the system. The building also must be structurally sound to support the added ballast and system weight.
Ballasted mounts are now being used on the ground, too. In places like brownfields that have contaminated soil, or landfill sites that have been capped, a ballasted system can be the only way to secure an array without penetrating the soil—turning a previously unusable site into a clean energy generation plant! Ballasted systems also work well in places where the soil is extremely rocky. For environmentally sensitive sites, a ballasted system can be more easily moved. Even abandoned parking lots can accommodate ballasted PV arrays without needing to tear up the paving. Ballasted ground mounts do not accommodate sites with more than a 5% slope.
Concrete pavers or other blocks can be used to keep a ground-mounted array from being lifted by wind.
The ballast used for ground-mounted arrays is locally sourced, and can be sand bags, paver blocks, or a precast concrete form specifically designed for the mount. Depending on the ballast racking system used, the site may not require heavy machinery or concrete pouring, and may require only minimal surface prep during installation.