Solar powered lights are any lighting devices which rely on sunlight and solar cells to function. The power-generating solar cells are usually part of the device itself, or are attached nearby. Many solar-powered lights use sunlight to charge a battery during the day, which then powers the light after dark. Solar powered lights are especially suited to places where a regular power source is unavailable, such as outdoors, or in remote areas.
There are four main components used to build a basic solar powered light: the solar cell array, a high-efficiency lamp, a battery, and a charge controller. Out of these, the solar array is the most expensive. All the electrical components must also be sealed in a weatherproof housing.
The charge controller functions as the brain, so to speak, of the whole device. It protects the battery from being over-charged, as well as maximizing the electrical output of the solar array and the voltage with which the battery gets charged. It also controls when the light operates.
One of the most popular uses for solar powered lights is for the illumination of outdoor walkways and gardens. This is because they not only use free energy, but they can be placed or moved anywhere, without digging ditches for laying wires, or connecting them to an electrical grid. Outdoor ground lighting needs are also well-adapted to one of the main drawbacks of solar powered lights. Put simply, it is the fact that solar powered lights slowly diminish in light output during the night, and are strongest during the first few hours of operation. Since the earlier evening hours are when most outdoor lights are needed, solar powered lights are an ideal solution for outdoor lighting.
The operating conditions of solar powered lights fluctuate with weather conditions as well. For example, if the weather is rainy or overcast, the battery will charge much less than on a sunny day in summer. This fact, combined with the high cost of solar arrays and other problems already discussed, make it so that solar powered lights still have only limited applications.
The advances being made in the field of photovoltaics may one day make solar power much more abundant and cost-effective. A significant breakthrough has been made in the form of photovoltaic film, which is tough and versatile enough to be used in many more places than traditional solar panels. As the efficiency of solar arrays improves and their cost goes down, solar powered lighting will become more reliable and practical for widespread use.