Introduction to Solar Electricity

Location and Orientation of the Array

Location of the PV panels is critical to their energy output. A panel installed in Florida will produce more energy over the course of a year than an identical panel installed in North Dakota. Places closer to the equator will get more sunlight (also referred to as irradiance) throughout the year than places further north or south. The more irradiance striking a PV panel, the more electrical energy it will produce.

Another factor that will affect the electrical output of your array is the directional orientation of the modules. When choosing a location for your garden, you know that a southern exposure will increase yield. So with solar panels: they perform best when facing due south to get maximum exposure as the sun travels from East to West. If you are using a compass to find south, make sure to adjust for magnetic declination, which varies with location. The tilt angle of the array will also affect power output. In the Northern Hemisphere, a tilt angle equal to your latitude will yield the best year-round production. A tilt angle equal to your latitude minus 15 degrees will favor summer production, while an angle equal to your latitude plus 15 degrees will favor winter production.

Shading – Don’t let it happen to you!

One of the biggest environmental factors affecting solar electricity production is shading. PV modules are very sensitive to shade. For example, if shaded by as much as a leafless tree branch, a PV module could lose up to 80% of its output. When selecting a site for your installation, choose one with the least possible shade during the hours between 9 AM and 3 PM. Consider things that may possibly shade the array during different times of the year as the sun travels higher or lower in the sky. A location that, in June, doesn’t get any shading, may be shaded for a significant part of the day in December. A Solar Pathfinder is a useful tool for determining the optimal location for solar production. Plan on your PV panels producing power for more than 20 years. Young trees might not be an issue today, but as they grow they may become a source of shade.

Knowledge is Power

PV modules are only one component in a solar electric system. Check out some of our other articles to find out more about the other components you’ll need for your system. Remember that electricity is dangerous and can be lethal. Review the National Electric Code Section 690 for information on installing a code-compliant system. Read over John Wiles’s Photovoltaic Power Systems and the 2005 National Electrical Code: Suggested Practices. If you’re designing a large system, make sure to contact your local electrical inspector prior to the installation.