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 roof mounted, mounted at ground level, or on a pole or building. The array orientation and tilt angle considerations are discussed in the article.
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 solar panel 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:
- Aluminum – lightweight, strong, and resistant to corrosion. Aluminum angle is an easy material to work with, holes can be drilled with commonly available tools, and the material is compatible with many PV module frames. Aluminum is not easy to weld.
- Angle Iron – easy to work with but corrodes rapidly. Galvanizing will slow corrosion but mounting brackets and bolts will still rust, particularly in a wet environment. The material is readily available and brackets can be welded easily.
- Stainless Steel – expensive and difficult to work with but will last for decades. May be a good investment in salt spray environments.
- Wood – inexpensive, available, and easy to work with but may not withstand the weather for many years – even if treated with preservative. Attaching modules to a wooden frame requires battens or clips to hold them in place.
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.
In general, roof mounting 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. IronRidge roof mounts use a handy Design Assistant tool to guide you through the list of components you’ll need based on your location, wind/snow loads, type of solar panel etc.
Some pole mounts from companies like MT Solar allow you to assemble at waist level, wire the solar panels at eye level, chain hoist your array up to the top, and adjust your tilt angle from the ground. No more heavy equipment, cranes, scaffolding, or large ladders needed!