Residential Solar Panels: Consider All The Factors

We have all seen residential solar panels on roofs and might not have realized that there are countless factors which go into the design and installation of a home solar power system. An incorrect calculation of a single factor can drastically drop the power generation capacity of a system.

When installing PhotoVoltaic (PV) panels on the roof of a house or on a pole mounted array, a variety of factors need to be considered. One of the most vital is shading. Since PV panels consist of various cells connected together in series, if even one cell is shaded it can not only shutdown an entire series of cells around it (even though the others are receiving full sun), but can really turn out to be a current drain on the entire system!

The amount of luminosity the PV panels are exposed to is also a major factor. It’s obvious that latitude and prevailing cloudiness are the most significant factors. Two solar power arrays installed at exactly the same latitude, say Seattle and Spokane WA will provide vastly different amounts of electrical energy. Spokane’s semi-desert sun will trump perennially cloudy Seattle.

Tilt angle is very vital as well, as many residential roofs lack the proper angle to fully capture the sun’s rays from season to season. The angle should be approximately the same as the latitude of the site and must face no more than 15 degrees off from due south (in the Northern Hemisphere). If you wish to maximize summer performance angle the PV panels 15 degrees less than your latitude and for maximum winter generation tilt the panels 15 degrees more than your latitude.

Of course the best system is the one that tracks the sun throughout its journeys, and the pole mounted arrays do just that. These PV panels go via computer-controlled motors while different kinds of trackers go via the imbalance of fluid flowing through copper tubing heated by the sun. This motion of the panels acts to keep the surface exactly perpendicular to the sun at all times to maximize the sun’s energy that falls on them. Various forms of trackers can increase the production of energy by 25% or more over static systems.

What comes as a complete surprise to many residential solar energy neophytes is that the magnetic declination must also be taken into consideration. The difference between the magnetic poles of south and the right solar south has to be added or subtracted from your proper angle. While Minneapolis has a close to zero declination adjustment, Seattle’s is close to 19 degrees. Check one of the declination maps to find out how to adjust your array in your location.

The relative performance of PV panels varies widely, so it is best to read all of the manufacturer’s specification sheets as well as seek out independent reviews and evaluations. Although a truly effective residential solar power system can cost so much it may never be fully amortized in net electricity savings, home solar energy generation is certainly here to stay.

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