Racking & Mounting Systems Solar power module manufacturers typically put a great deal of engineering effort into the modules and inverters. However, since racks and mounting systems are frequently assembled on site, it is easy to overlook these critical components. There are common issues involved in any installation, whether the array is fixed or tracking, mounted at ground level, on a pole or on a building. First, the solar energy array must be solidly and securely mounted so that it will last for 20+ years and withstand all kinds of weather, wind loads and corrosion. Many module manufacturers and distributors sell mounting hardware specifically designed for their modules. Use of this hardware can reduce on-site assembly costs and simplify system installation. Customized array mounting structures can be expensive. Design and construction of these customized racks must consider the characteristics of various mounting materials: Aluminum - lightweight, strong, resistant to corrosion and moderately expensive. Aluminum angle is an easy material to work with, holes can be drilled with commonly available tools, and the material is compatible with many solar electric module frames. Aluminum is not easy to weld. Overall, the best combination of price, durability and weight. Stainless Steel - expensive and difficult to work with but will last for decades. May be a good investment in salt spray environments. Galvanized Steel - easier to work with than stainless steel, and more affordable. Galvanized surface treatment resists corrosion for many years in all but marine environments. Wood - inexpensive, available, and easy to work with but will not withstand the weather for many years--even if treated with preservative. Not recommended for PV installations.  Tilt Up Aluminum Rack Mount System           Large Reverse Tilt Ground Rack -  For some sites it may be necessary to install the racks at a reverse tilt. Typically this happens when the best module location is on a north-facing roof or hillside. In order to optimize system performance we install a rack that is tilted up sufficiently so that it is actually facing south. Changing the tilt angle of an array to account for seasonal changes in sun altitude is generally not required. For mid-latitude locations, a tilt angle change every three months is estimated to increase energy production about 5 percent on an annual basis. For most applications, the additional labor and the added complexity of the array mount does not justify the small increase in energy produced. If tracking of the flat-plate array is desired, the recommended trackers are single-axis (following the daily motion of the sun from east to west) units that require little control or power. In high wind areas a powered tracker may be preferred. Pole mounted trackers that support 4 to 12 solar electric modules are available and often used for small stand-alone systems, particularly water pumping applications. The tracker manufacturer typically provides all the array mounting hardware and instructions for securely installing the tracker. Because of wind load problems and long term durability issues, Akeen Solar does not install residential tracker systems. The foundation for the array should be designed to meet the wind load requirements of the region. Wind load depends on the size of the array, elevation, surrounding obstructions and tilt angle. The amount and type of foundation for pole-mounted systems depends on the size of the array being supported. Concrete with heavy-duty galvanized support poles are recommended. The foundation and frame should be designed to withstand the worst-case wind expected in the area. Roof Mounted Solar Power Systems In general, roof mounting of solar power modules is more complex than either ground mounting or pole mounting. Roof mounts are more difficult to install and maintain, particularly if the roof orientation and angle are not compatible with the optimum solar array tilt angle. Penetrating the roof seal is inevitable and leaks may occur if the solar energy system is not installed properly. Also, it is important to achieve a firm and secure attachment of the array mounting brackets to the roof. Attaching the mounting brackets to the rafters will provide the best foundation, but this may be difficult because module size and rafter spacing are usually not compatible. If there is access to the underside of the roof, 2 x 6-inch blocks can be inserted between the rafters and the attachment made to the blocks. Attaching the array to the plywood sheathing of the roof may result in roof damage, particularly if high winds are likely. The brittle nature of tile and slate roofs makes these installations more complex than composite shingle or built up roofs -- special mounting hardware is necessary for a secure and leak-proof installation. If a roof mount is required, it is important to allow a clear air flow path up the roof under the array. The array will operate at a lower temperature and produce more energy if it stands off the roof at least 1.5 inches. Unless specially designed for this purpose, flush mounting PV modules to the roof of a building is not recommended. The modules are more difficult to test and replace, and the performance of the array is decreased because of the higher operating temperatures.