Chapter One - Photovoltaics

The process of converting light into electricity was perfected as a product of the space industry. Satellites needed a source of power while in orbit or traveling among the planets, and the logical solution was to deploy large panels of photovoltaic modules. Toady, this technology is available to ordinary citizens of Earth to provide clean, renewable energy for everyday use.

Terrestrial use of PV's is becoming quite popular in the recreational vehicle industry, as PV power frees RV'ers from the use of noisy and polluting gasoline generators. Our discussions will be directed at those of you who dwell in a house bus or truck, but is applicable to all forms of habitation.

Most commercially available PV modules are composed of 36 series-connected PV cells wired internally to provide 12 volt DC electric power. Modules are rated in Watts, which is a product of the module's operating voltage multiplied by the output current. 12 volts times 4 amps = 48 watts, etc. This will allow the user to specify modules of a size and quantity to satisfy expected power requirements of the home power system. It also allows the user to have a benchmark by which to measure the panels performance against itself and others of similar output.

Multiple modules can be wired in series to increase voltage, parallel to increase current, or series and parallel to increase both. It is possible to construct very large arrays of modules, capable of outputting a virtually unlimited amount of power.

Orientation of the modules to the sun is critical to the successful operation of a PV system. Ideally, the modules will be at a 90° angle to the sun's rays at all times. In practice, this is not always practical. Tracking mounts are available which will automatically reposition the modules continuously throughout the day, although they are quite expensive, and installed only on large arrays. Most systems are installed on a fixed-azimuth mount, which is adjustable seasonally for elevation. This means that the modules are pointed due south (Northern Hemisphere) or north (Southern Hemisphere), and the angle to the horizon adjusted several times a year as needed to keep the modules best aligned with the sun's rays. The result is slightly lower output power during the morning and evening, but results also in a much lower installed price. Even small areas of shade on a module will decrease the output dramatically, so location is an important consideration during installation.

PV modules, once installed, require no maintenance whatsoever, except for occasional cleaning to remove dust, bird droppings, etc.

The real beauty of PV's is that it is possible to add modules to a system at any time without compromising the efficiency of either the existing system, or of the new modules. Panels do not have to be of the same manufacturer, wattage or even construction type, as long as the voltage of each module matches the others. This allows one to begin constructing a solar power system with a very small panel and add to it as finances allow, with no penalty.

If powering your home with solar power appeals to you, I urge you to investigate purchasing a small photovoltaic panel and power even one small lamp with it. Solar powered radios and flashlights are available and are great tools for learning more about this exciting and non-polluting power source.