Introduction to Solar Electricity

How It Works

In very basic terms, a PV module is a device that will produce a flow of electricity under sunlight. This electricity can be used to charge batteries and, with the aid of an inverter, it can power normal household electrical devices, or "loads". PV modules can also be used in systems without batteries. Most panels (properly called "modules") are framed in aluminum, topped with tempered glass, and sealed by a waterproof backing. Sandwiched between the glass and backing layers are the photo-reactive cells themselves, often made of silicon. On the back of the module is a Junction Box that may or may not have two cables coming out of it. If the junction box has no cables, it can be opened to access the electrical terminals where wires can be attached to conduct the generated electricity away from the module. If there are cables already in place, the junction box is usually sealed and not user-accessible. Sealed junction boxes are more common.

Portable power

There are lots of ways to make use of solar electricity. One of the simplest is to charge small electronic devices, like cell phones and music players, with lightweight, portable PV modules. These small battery-charging panels are even being integrated into backpacks and clothing for maximum convenience. Solar panels can be used individually or wired together to form a solar array. For larger electrical loads, there are two main types of systems for providing electrical power to homes, cabins and offices, etc: Grid-interactive systems and Off-grid systems. You’ll want to decide which system is best for your needs by reading more about both.

Cell Technology

There are several technologies used to make solar cells, the building blocks of panels. The main types currently on the market are: monocrystalline, polycrystalline (aka multicrystalline), string ribbon, amorphous (aka thin-film) and CIGS. The first three technologies are silicon-based while CIGS panels use other elements. Monocrystalline panels are often the most expensive due to the manufacturing process, which uses large amounts of highly purified silicon and a great deal of energy. Monocrystalline solar cells are about 13-16% efficient at converting sunlight to electricity. Polycrystalline cell efficiencies range between 11-14% and tend to produce panels slightly less expensive than monocrystalline ones on a price-per-Watt basis. String ribbon is a proprietary technology similar to polycrystalline. It uses less silicon in the cell manufacturing process than the other crystalline types and achieves efficiencies in the 12-14% range. Amorphous (or thin-film amorphous silicon, A-si) panels are not constructed from individual cells, but are made by depositing a photo-sensitive compound onto a substrate. While these panels have lower efficiencies, (usually 7-10%), they offer certain advantages. They can often be used in hotter climates since they suffer less power loss than other types under hot conditions. Additionally, the amorphous technology does not use the typical “glass sandwich” construction, allowing for the creation of flexible and very durable panels. The CIGS technology, or Copper Indium Gallium di-Selenide, uses no silicon at all, and can be made into panels with or without discrete cells. There are also “hybrid” panels which use both crystalline and thin-film technologies to increase energy capture; these modules boast efficiencies up to 19%. Researchers are still working on lower-cost, higher-efficiency alternatives, but for the foreseeable future, these five types represent what is commercially available.