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Streetlights |
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External lighting is often an art in itself - an art which more often than
not goes unnoticed. And yet if we look more carefully, we can discover a
wide range of outdoor decorative lighting. It comes in all shapes and sizes,
antique and modern, in different materials such as cast iron, steel and cast
aluminium. Some lamps have cross-arms, some are on brackets and some have
multiple lamps. Styles vary and include acorns, spheres, square lanterns,
octagonal lanterns, hexagonal lanterns to name but a few. The variety is so
vast that streetlights can be matched to any architectural style. Methods of lighting have changed considerably over the decades and gas lights have long been replaced by electric lights. Lighting technology has also continued to make great strides over the years. Sodium vapour lamps, which can turn one watt of power into 200 lumens, are about 16 times more efficient than incandescent bulbs. A sodium vapour lamp works on the principle of a gas-discharge tube. The process takes place in a tube with a small amount of sodium-neon-argon (SOX lamp) or mercury-sodium amalgam (SON lamp). Not only are these lamps very efficient, but they also have a life span of around 20,000 hours, 20 times longer than an incandescent bulb. Another advantage is their yellow colour, which helps to increase vision in misty conditions, thus making the lamps ideal for road lighting. Because of their long life, sodium vapour lamps are considered to be environmentally friendly, however, because they contain mercury, they require careful disposal. Great advances have also been made in lighting using LED (Light Emitting Diode) technology. A LED is a semiconductor diode that emits light when an electric current is applied from the anode to the cathode. The colour of the light can vary. In the past, LEDs were mainly used for indicators on household appliances and such like. Today however, LED technology is used extensively in lighting, whether home or office block, TV screen or cinema. Because of the long life span, considered to be twice that of sodium vapour lamps, the use of LED lighting is on the increase. As LEDs do not contain mercury, their disposal is also far less complicated. We are continually being told to save energy, especially electricity, and yet every night, towns and cities seem to be lit up in overabundance. Street lighting for the safety of the community is one thing, but isn’t illumination being used to excess when the night sky can be seen to glow from miles away? |
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