By marking public roads and sidewalks in many communities, street lights help keep streets safe and prevent drivers and pedestrians from having an accident. Older street lamps use conventional light bulbs, while newer street lamps use energy-saving light-emitting diode (LED) technology. In both cases, street lights must be durable enough to withstand these elements while continuing to provide light.
Street lamps come in many styles and sizes. Most conventional street lamps use halogen bulbs, which are similar in function and appearance to household incandescent bulbs. These bulbs are composed of a vacuum tube with a filament inside and an inert gas (such as halogen). The inert gas can re-collect the burning part of the filament on the filament, thereby extending the life of the bulb. Metal halide bulbs use similar technology, but consume less energy and produce more light.
Fluorescent street light bulbs are fluorescent tubes that contain gas that reacts to current to produce lighting. Fluorescent street lights use less energy than other bulbs and emit green light, while halogen bulbs emit warm orange light. Finally, light-emitting diodes or LEDs are the most effective type of street light. LEDs are semiconductors that produce intense lighting and have a much longer lifespan than light bulbs.
For all types of street lamps, one of the common components is a pillar that rises from the bottom of the ground and supports the lighting elements above. The lamppost contains wires that connect the wires directly to the grid. Some positions also include an access door for access to the control unit of the street light and maintenance or adjustment from the ground.
The lamppost must be able to withstand ice, wind and rain. Rust-proof metals or protective paint coatings can help keep the columns free of element corrosion, and metals are by far the most common materials for strength and rigidity. Some lampposts, such as those in historic areas, may be decorative, while others are simple gray shafts.
LEDs and traditional street lamps have curved lenses, which are usually made of heavy glass or plastic. The role of the street light lens is to amplify the influence of internal light. They also direct light down the street for maximum efficiency. Finally, the street light lens can protect the delicate lighting elements inside. Foggy, scratched or damaged lenses are easier to replace and more cost-effective than the entire lighting element.
The LED street lamp includes a heat exchanger for temperature adjustment. These devices can regulate the heat generated when the LED is powered. The heat exchanger uses air through a series of fins to keep the lighting elements cool and to ensure that the LED can produce uniform light without dark areas or otherwise "hot spots" that may occur.