Solar Outdoor Lighting: Breakthrough in Technology, Simplicity of Design

By Bruce Dennis

The guts of solar lighting: A small controller board and battery compartment?EUR??,,????'??+NiMH rechargeable batteries are recommended over the NiCAD type. A photoresistor cell; (Right) An LED light source.

Roughly 20% of residential landscape contractors install outdoor lighting. Why not more? Many contractors don?EUR??,,????'???t understand the nuances of low-voltage lighting (cable, transformers).

Some don?EUR??,,????'???t or can?EUR??,,????'???t educate their crews in lighting procedures. Others don?EUR??,,????'???t want to bring in power, nor have the costly headache of the ?EUR??,,????'??call back?EUR??,,????'?? of improperly installed lighting.

Photovoltaic energy (solar, renewable power) allows light to be placed almost anywhere in the landscape: no transformers, wire, cable, conduit, or voltage drop concerns. Bringing light to remote areas where power is hard to come by is as easy as digging a hole (for a ground spike) or mounting a bracket with a pair of screws. Solar lighting is produced for landscape, posts, columns, walls, patio and decks, and is ideal for path lighting. The cost savings over 12v and 120v lighting installations are tremendous.

Understanding Solar Powered Lighting

Advanced LED (light emitting diodes) lamps draw a minimum of current yet provide intense illumination. Most solar lights are equipped with a built-in photo cell powered by rechargeable batteries (NiCad or NiMH). Expect to change batteries at least once a year for best performance. Although LEDs last for many years some may degrade and lose overall intensity over time. I recommend solar products that have replaceable LED lamps. Fully charged batteries (4-5 hours of direct sunlight) can provide up to 10-12 hours of good accent light, with light projection up to 20 feet. Solar can?EUR??,,????'???t compete with the conventional energy guzzling lighting, but it can be perfect where regular power is unavailable and where accent lighting is appropriate.

Professional solar lighting has super bright, efficient LED lamps that produce an intense cool white glow that has often been referred to as a ?EUR??,,????'??moonlight effect.?EUR??,,????'?? Solar lights are strongest in the first few hours of operation and then slowly diminish in output as the battery source is spent. The batteries will recharge when again exposed to sunlight.

Solar Technology Overview

Photovoltaic cells are primarily made of semiconductors and silicon cells. When sunlight strikes the semiconductor it is absorbed into the material. The energy created from ?EUR??,,????'??the strike?EUR??,,????'?? allows the electrons (current) to flow, sending energy to the battery and energizing the LED. The efficiency (or light output) is based upon several factors?EUR??,,????'??+cell capacity, lamp source, battery type and the PC board design.

The key elements of solar lighting products are battery and lamp type. Most solar lights are equipped with rechargeable NiCAD (nickel cadmium) batteries, very common but they don?EUR??,,????'???t have good ?EUR??,,????'??memory,?EUR??,,????'?? are not environmentally friendly and must be carefully disposed or recycled. A better choice is NiMH (nickel metal hydride).

The most popular solar lamp bulb, the LED, is used in everything from automotive brake lights to city traffic signals. LEDs come in a variety of colors, the most intense being super white. LED lamp intensity is measured in milli-candles (mcd) as opposed to watts and lumens, milli-amps (ma) rather than amps, and beam spreads are measured in viewing angles (20-60 degree avg.).

Granted, there is so much more to photovoltaic science and LED technology than can be said is this short space. Solar power is now part of everyday products, including calculators, clocks, water pumps and irrigation controllers. Solar lighting provides new solutions and alternatives to conventional lighting products that until recently were not possible.