Continue Your Green Education Today With Solar PV 104 – Racking

Throughout this series of articles on solar PV, we have compared an array to the human body. Keeping with the analogy, this article covers the skeleton of the system: Racking. The least animate of all parts of the solar array, its stability is what makes racking a key component of an efficient solar array.

Before we get into the more common uses of racking, consider that panels do not necessarily have to be mounted to your roof. Perhaps you have a driveway, but no garage; a patio, and no awning; a pool, with no shaded areas. These locations are becoming very popular places to install solar arrays for both their form and the function — electricity production aside, these structures offer a sexy look while protecting you and your property from the elements – and are made possible by racking.

The primary purpose of racking, however, is to attach a system of panels to your roof. There are two ways in which this is accomplished. For flat roofs, a ballasted system may be used; this system often uses concrete blocks to weigh down the array such that a strong gust of wind will not blow it away. For pitched roofs, racking must be fastened to the structure of your roof. On the bright side, panels are mounted to the racking, not directly to your roof, greatly reducing the number of roof penetrations required to mount the array. (Rest assured that each of the few connection points that are required, are “flashed,” or weatherized, such that rainwater will not leak into your home).

The use of racking also allows integrators to play with the position of panels which may often greatly increase panel efficiency. Previously in the Solar PV series, we mentioned that panels have an optimal tilt and orientation; with the racking securely fastened to the roof, panels may now be tilted such that they face the sun more directly. Also mentioned previously, shade is a solar killer. For homes with chimneys or exhaust fans on the roof, racking can help raise the system to be even with these obstacles such that their shadows become less of an issue (this is more often seen on flat roofs). Additionally, heat and electronics tend not to play nicely together. Raising the panels off the roof, even slightly, allows air to flow on all sides of the panels cooling them down. Each of these advantages leads to more efficient panels and greater efficiency means fewer panels are needed to power your home (translation: it is cheaper!).

The last feature of racking to discuss involves installation, protection, and maintenance. Panels are much easier to adhere to racking than to your roof, hence, once the racking is fastened to the roof, installation moves very quickly. Racking also provides a nice channel in which the extremely high voltage of a lightning strike may travel into the ground, and away from your array and your home. Lastly, in the event of some violent act of nature where one of your panels is damaged, racking allows for simple removal and replacement of panels, without harm to your roof.

Despite being completely inanimate, with no moving parts, no electronics, and no flow of electricity, the racking system goes a long way in improving performance and appearance, decreasing installation and maintenance time, and protecting the array and your home. That is quite a lot for a few pieces of aluminum.

This concludes our introductory program on the components of a solar array. Be sure to keep an eye out for the next series of articles discussing ways in which to afford solar.