Want to add lighting to your yard without having to dig up your landscaping or pay an electrician? Solar-powered lights are becoming an increasingly useful way to bring light into dark places.

Solar lighting is powered by photovoltaic (PV) cells, which convert light energy into electrical energy. The energy of the light absorbed by certain materials is transferred to electrons in the atoms of the PV cell. An electrical current s a flow of electrons, and the newly energized electrons flow into the PV circuit, usually to charge some type of battery.

The first PV device was introduced by Bell Labs in 1954, and by 1958 solar cells were being used for things like the space program and supplying power to remote switches and monitoring devices.

Today, solar cells provide power for many small appliances such as calculators, flashlights and radios. Photovoltaic systems power road and traffic signs; railroad signals; monitoring devices; and the like in areas where it would be very expensive to run electrical wires.

Outdoor solar lights have improved dramatically in the last few years, both because of improvements in PV efficiency and because of the use of high-tech bright LED (light-emitting diode), fluorescent and halogen bulbs.

The most common home use of solar lighting is yard lights. They're available to stick in the ground to mark a path or illuminate landscape features, and some styles can be mounted on a post or wall. Solar spotlights are available to highlight landscape features. Since these lights require no wiring, lights can be added to your landscape almost instantly. Commercial solar lighting applications include lighting signs, flagpoles and remote lights.

You can make your house number visible to visitors and emergency personnel with solar-powered street-number lights. These charge during the day and can be seen from more than a 100 feet away at night.

Solar security lights usually respond to motion by turning on a bright halogen bulb. They have a higher demand for power than decorative yard lights and usually use a small separate solar panel for power. This means that the light can be placed under a roof overhang while the attached charging unit is placed in full sun on the roof.

Other available solar lighting includes solar-powered lanterns, good for camping and power outages; solar "candles" that add a warm light to nighttime on your deck or patio; solar-powered holiday lights; floating pond lights; and novelty yard decorations such as plastic turtles that light up at night.

Solar lights are generally made with a photocell that turns them on when it gets dark. How long the light stays on depends on how much sun the PV cells took in during the day. Performance can be affected by shade, cloudy weather and dirt.

Solar lighting can also improve the lives of people who live in locations remote from an electricity grid or can be used in the case of natural disasters. For example, non-profit organizations such as the Light Up The World Foundation (www.lightuptheworld.org) and the Solar Electric Light Fund (www.self.org) supply solar-powered lights to poor rural families around the world, replacing lighting from dangerous and expensive kerosene lanterns and candles. Several companies and the Department of Energy's National Renewable Energy Laboratory and the Florida Solar Energy Center provided solar lights and solar electric charging stations to areas devastated by Hurricane Katrina.

Solar Lighting Resources

Solar lighting is available at hardware, lighting and discount retailers including The Home Depot, Lowe's, Sears, Target and Wal-Mart, as well as through many mail order and online companies.

Online resources for solar lighting include:

Brinkmann Corporation (manufacturer):
www.brinkmann.net

Buy-Solar.com (retailer):
www.buy-solar.com

Intermatic Malibu Solar Lighting (manufacturer):
www.intermatic.com

Solardyne (manufacturer):
www.solardyne.com

Silicon Solar (retailer and manufacturer):
www.siliconsolar.com