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Solar power: Not just for rooftops any more

Bill Sepmeier and Matthew Charles
Vail, CO, Colorado

One of the first things we hear from people interested in adding solar power systems to their homes generally has to do with their roof.

“I’ve got a big, south-facing roof,” people say, or, “I’d love to put up solar power but I don’t have a south-facing roof.” Frankly, it doesn’t matter any more. The average homeowner who wants to offset half of the monthly electric bill is going to need 12 to 16 photovoltaic solar modules, and the best place for this size system generally isn’t on a roof, it’s on a free-standing pole mount.

Over the years we have placed panels on rooftops, on ground mounts and atop poles using mounts that bear striking resemblance to systems used in old satellite TV systems. Of the many ways tohave your solar panels produce the most power, pole mounts are proving to be the best option for most installations.

Solar electric panels produce the most power when they are directly perpendicular to the sun’s rays, or “looking” directly at the sun. In this area of Colorado, the sun’s angle above the ground varies by about 40 degrees throughout the four seasons. If solar panels are mounted “flush” on a typical 6:12 roof, they are only tilted up from horizontal by 22.5 degrees. This means that, while they’ll make a lot of power in the summer when the solar day is some three times longer than it is during the winter and the sun is much higher in the sky and shining more directly on the panels, their performance in the winter months will be significantly reduced due to the sun’s lower angle in the horizon.

Another caveat; solar panels work best when they’re cool, and a rooftop can easily reach 120 degrees in the summer. Panels flush-mounted on a roof will suffer power losses at these temperatures because of their sensitivity to heat, reducing output by up to 10 percent.

Then there’s the problem with snow accumulation. If even a portion of most solar electric modules become covered with a little snow the result is like pulling a bulb out of a Christmas tree light string ” power production is cut from 30 percent to 100 percent. In this area, solar modules should be mounted at a minimum of 40 degrees from horizontal ” and even at that angle snow still has a chance to accumulate on the face of the modules.

With our climate’s regular freezing and thawing cycles, a metal mounting frame for the solar array will expand and contract daily. Since the frame is typically bolted through the roof deck to underlying studs, this daily expansion and contraction can induce stresses into the roof that, over time, can cause leakage and require maintenance.

Solar pole mounts don’t have these problems. Between two and 18 panels can be mounted atop a single pole easily and attractively. Since the array is free-standing, there is no problem with summertime heat buildup. Array angles can be adjusted on the equinoxes to maximize power production ” it takes less than 60 seconds to switch from summer to winter angles (35 degrees in the summer, 55 degrees in the winter). You can also fix the array at our latitude ” 40 degrees ” and forget it, although we’ve found that high country snow typically melts off and falls away from an array oriented to 55 degrees elevation after one sunny day.

Our friends who’ve insisted on flush rooftop mounts can see snow on their array all winter if it isn’t carefully removed. And “carefully” means just that ” those modules won’t hold up to a shovel, so snow must be removed with nothing more substantial than a stiff broom.

If you’re thinking about adding solar power, don’t worry about which way the house and roof were pointed when it was built. Think ground or pole mounts, and ask your solar pro to show you the latest innovations in solar mounting systems. Then relax and enjoy years of maintenance-free energy.

Bill Sepmeier is Chief Technical Officer and Matthew Charles is the marketing director for Grid Feeders, based in Eagle-Vail. For more information, go to http://www.gridfeeders.com.


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