Solar electric panel arrays for stand-alone systems are installed in many unique and innovative ways. However, there are common issues involved in any installation, whether the array is fixed or tracking, mounted at ground level, or on a pole or building.
Solar electric panel arrays for stand-alone systems are installed in many unique and innovative ways. However, there are common issues involved in any installation, whether the array is fixed or tracking, mounted at ground level, or on a pole or building. The array orientation and tilt angle considerations are discussed in the article Solar Panels (Photovoltaic Panels): Overview.
The objective is a solidly mounted solar panel array that will last for many years and withstand all kinds of weather. Regardless of whether you buy or build the mounting structure make sure it is anchored and the modules are restrained. Several manufacturers make mounting structures designed to work with almost any solar panel model. This hardware is intended for multiple applications and different mounting techniques and considerations like wind loading have been included in the design. Using this mounting hardware is the simplest and often the most cost effective. Customized array mounting structures can be expensive. Consider the characteristics of various mounting materials:
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 and the tilt angle. Ask a local contractor how to anchor your array to withstand the wind expected in your area.
Changing the tilt angle of an array to account for seasonal changes in sun altitude is 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 solar panel array is desired, the recommended trackers are single-axis units that require little control or power. One kind of passive tracker is driven by a closed Freon system that causes the tracker to follow the sun with adequate accuracy for flat-plate PV modules, such as the Zomeworks. In high wind areas a powered tracker may be preferred. Pole mounted trackers that support 4 to 12 PV modules are available and often used for small stand-alone systems, particularly water pumping applications. The tracker manufacturer will provide all the array mounting hardware and instructions for securely installing the tracker. The amount and type of foundation for the pole-mounted tracker depends on the size of the array being supported. Reinforced concrete with anchor bolts is recommended. The foundation and frame should be designed to withstand the worst case wind expected in the area. The movement of the array should be checked to make sure the path is clear of obstructions.
In general, roof mounting of solar panels 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. 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.
If a roof mount is required, be sure to allow a clear air flow path up the roof under the array. The array will operate cooler and produce more energy if it stands off the roof at least 3 inches. Flush mounting solar panels 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.