• While it may seem like a secondary concern, the hardware that supports the solar panels on your roof is an extremely important element of a home solar system. While most people may write it off as something that doesn’t affect the overall performance of the system, the quality and performance of the racking is critical in the performance of the solar system in the long run. After all, if the panels aren’t properly supported, how can they, properly produce power?

    What makes good solar racking “good?” Obviously, due to their exposure from being on rooftops, solar systems are exposed to a variety of harsh elements including high winds, rain, snow, various chemicals, etc. Solar racking, in order to last, must be able to withstand uplift, weight, and corrosion from the elements. So, let’s look at these factors to see how and why solar racking is designed to withstand them.

  • 1. Wind Resistance

    Solar panels are relatively thin, like an airplane wing so winds blowing over and under the panels will result in “lift” – a force that good racking systems have to resist. It doesn’t matter where you live, eventually, there will be enough wind to try and lift up a solar panel. The last thing you want is to have a solar panel come unwired and hang, or fly off your roof because of bad racking. Both can result in disaster with unforeseen consequences.

    The “Max Uplift” of solar racking is how much wind load the racking can resist. This is important because  the space between the panels and the roof that’s intended to provide ventilation and dissipate heat can also allow enough force to try to move the panels. So you’ll want to make sure that the Max Uplift is high enough to handle the maximum amount of wind you can expect in your area. 

    Let’s say you live in an area where there is a potential for hurricanes. After landfall, most hurricanes don’t exceed wind speeds of 100 mph, but just to be sure you’d want to have a Max Uplift that can handle a little more than that, let’s say 120 MPH. Max Uplift is measured in Pascals (pa), so if you convert Wind Speed in MPH to Pascals, which you can do here, you’ll see that for sustained 120MPH winds, you would need a racking system with a Max Uplift of over 2000 pa.

    So when you do your research into solar racking, make sure the company that manufactures it lists the Max Uplift of the racking in their racking datasheet or on their website. Make sure that it’s high enough such that even the maximum winds in your area won’t get anywhere near it. The SunPower Invisimount racking system, as an example, has a Max Uplift of 3,000 Pascals. That’s plenty of strength to resist the highest winds, more than hurricane force.

  • 2. Weight Resistance

    Another major element that can put solar panel racking to the test is load in the form of downforce. Whether it’s snow, hail, leaves, etc., solar panels can be put under a lot of stress based on where they are located. This downforce resistance is a critical element of good solar racking, particularly in climates where large amounts of heavy snow can build up, so having strong racking that can support substantial  weight is critical.

    Downforce, like uplift, is typically measured in Pascals. But since not many people use Pascals as a measurement, a better way to describe solar racking resistance to weight is in “pounds per square foot.” Let’s look at what kind of weight we would expect solar racking to be able to support in order to resist heavy snowfall and other elements it could potentially be exposed to. 

    It’s important to realize that solar panels themselves are relatively light but even their minimal weight is usually spread out quite a bit through the use of many “stanchions” or feet, which attach the solar racking the roof beams themselves (not the shingles or plywood).

    As the typical solar panel is around 40 pounds and around 6’x3’ in dimension, we can say that a solar panel is only about 2.2 lbs per square foot. 

    So how much weight would be adding to the downforce on the solar racking with some snowfall, let’s say? Well, it is generally known that snowfall adds around 1 pound per square foot for every 1.25 inches of snow depth. So from that, we can calculate how much, let’s say, 10 inches of snowfall would add in pounds per square foot:

    10-inch roof snow depth x 1.25 Ibs per inch = 12.5 Ibs per sq ft of roof snow load

    So that’s 12.5 lbs of snow load per square foot, adding to that 2.2 lbs that already exist from the weight of the panel, making it around 14.7 lbs weight per square foot. 

    SunPower’s Invisimount racking system is able to support an enormous amount of downforce, expressed on the data sheet in Pascals:  up to 6,000 Pascals of downforce. 

    6,000 Pascals of downforce, if we use a converter, comes out to around 125.31 pounds per square foot – so well within the tolerance of the snow load in our example, which is only 14.7 lbs per square foot.

  • 3. Corrosion Resistance

    Besides uplift and downforce, the other force, if you can call it that, that solar racking must resist, is corrosion. There are different types of corrosion, but the one that can most likely affect solar panel racking systems made from unprotected or inexpensive metal is known as general corrosion. General corrosion occurs as a result of rust, which happens when metal is exposed to water and the surface of it oxidizes. If it continues unabated, rust can erode away critical components of solar racking, which can cause it to weaken and fail under pressure.

    Adding salt to the equation can make corrosion occur even quicker. The presence of salt in water increases the conductivity of the water, which ultimately leads it to oxidize the metal faster. So for those homeowners that live near the ocean, which many Californians do, corrosion resistance of their solar racking should definitely be something they consider, and they should seek out solar racking that is proven to be corrosion resistant.

    So what makes solar racking corrosion resistant? There are two ways to make solar racking corrosion resistant. Either the racking has to have corrosion resistant coating, or the metal that makes up the racking has to corrosion resistant. The only metals that are corrosion resistant are stainless steel, aluminum metal, copper, and galvanized steel, so make sure that the solar company you choose uses solar racking that is made up of one of those metals.

    As far as corrosion resistant coating, anodizing is the typical method for making metals have increased corrosion resistance. In technical terms, it is a process used to make the natural oxide layer on the surface of metal parts thicker. So, as with the type of metals used for the racking, when homeowners are researching solar, they should make sure that the racking used has anodization.

    SunPower’s Invisimount racking system is made up of only corrosion resistant metals, with most of its components being anodized. Specifically, the rails and end clamps of the Invisimount racking system are both made of aluminum and have black anodization. The other components are made up of either stainless steel or aluminum alloy, and are coated as well.

  • So, as you can see, solar racking has to be able to resist several forces: uplift, downforce, and corrosion. As all three of these forces can lead to solar racking failing, and as a result your solar system either falling apart or not producing, it is extremely important to make sure that your solar racking is top quality such that it can resist these forces. SunPower’s Invisimount racking can stand up to these forces, even at their most intense, so when you’re looking at solar, be sure to include SunPower in your search.

  • About the Author

    Michael Powers

    http://www.terrawatts.com/

    Michael is one of the founding partners of SunPower by Stellar Solar. In 2001, he helped launch The Home Depot’s national solar energy program which is now offering home solar through hundreds of stores in nearly a dozen states. He is a writer and marketing professional with over 30 years’ experience in the fields of energy, market intelligence and leadership training. He currently serves as treasurer and board member of Global Energy Network Institute (GENI), a San Diego-based non-governmental organization that advocates linking renewable energy resources around the world using electricity transmission.