This month I’m going to continue with an article I began in December 2007. This multipart article tracks my family’s solar electric system (photovoltaic or PV system) through our decision-making processes to the completed installation. My previous article addressed the basics of PV systems. This month I’ll address the topic of siting and mounting the solar panels.

We purchased 12 Evergreen Solar 180 watt panels to give us 2160 watts total for our solar array. This will be adequate to offset 100 percent of our electricity needs. There are many utilities available online to assist you in this calculation and any installer you work will assist you to. One beauty of grid-intertied systems is that sizing is much less critical since you aren’t relying on your solar panels to provide all of your electricity.

Solar panels can be mounted in many ways. We opted to mount our panels on tilt legs since the outbuilding we mounted them on is close to flat. Two basic principles in mounting panels are that they need to be oriented as close to true south as possible and output can be increased if they can be seasonally adjusted to capture the lower sun in winter and higher sun in summer. It used to be believed that if your panels weren’t facing due south then they weren’t going to produce well. Several years ago, Home Power magazine (www.homepower.com, Issue #93) published an article that looked at this specifically and the gist of the story is that facing within 30 degrees of south can make as little as 5-10 percent difference in yearly output. Also the tilt angle of the panels to the horizon isn’t as critical as once thought. The reason I mention this is that I don’t want people to think that if their house isn’t oriented to true south or their roof pitch isn’t perfect that they throw in the towel regarding PV systems.

The biggest concern with any array is shading; that will kill your output more than any orientation issue. There are several devices made to help you estimate shading over the course of the year. Some are fancy and electronic while others are elegant geometric devices. I used the latter called a Solar Pathfinder to estimate the shading for our site and situated the panels where they would receive no shading during any point of the year. The basic principle that the devices use is to look at the horizon and overlay the sun’s path in the sky over the course of the year. This step is very critical and unless you have a completely unobstructed view of the south from NE to NW, it should not be overlooked. It is surprising what will shade your completely summer sun drenched house during the winter. If you hire an installer they will be able to do this site analysis for you or if you do it yourself the $200+ is well worth it.

Once our site was selected, a friend and I installed the hanger bolts and brackets to the roof and rafters. Our roof was complicated in that it required some fabrication of bolts since the rafters didn’t run perpendicular to the panels. The tilt legs were installed onto the brackets and on the rainiest day of fall, I opted to install the solar panels. The tilt legs allow me to adjust the panels to capture to most energy as possible. A rough rule-of-thumb is that you want to be able to tilt your panels at your latitude +/-15 degrees for winter/summer respectively. If you get close to this you’ll be fine and if your panels are going to be fixed to the roof then as close to your latitude is best.

The panels installed easily on the legs and once they were installed I braced them additionally for the winter storms and set them at their winter angle of 62 degrees. I haven’t been able to get on the roof to finish the wiring of the panels since the snow is 1-2 feet deep on the roof.