The two major types of "green" street lights are induction and light emitting diodes. Both offer significant advantages over traditional high-intensity or gas-discharge lighting, such as substantial reduction in energy use, long life, reduced maintenance and little to no mercury. However, green street lighting is an emerging market; its primary disadvantages revolve around cost and product standardisation.
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Both induction and LED street lighting incur higher upfront costs, as put forth by the New Jersey State League of Municipalities. While induction lighting is typically three times the cost of traditional high-intensity discharge lamps, light-emitting-diode street lights can cost 10 times as much to install. In contrast to the £195 per fixture cost of conventional street lighting, an LED street light comes to approximately £1,300 per fixture as of 2009, according to the American Daily Review.
Lamps for induction lighting lack standardisation, so size will vary depending on the manufacturer, according to the International Municipal Signal Association. Although new lamp sizes are being introduced into the U.S. market, the selection of ready-to-use lighting units currently in the market is still limited. Induction lights tend to be larger and heavier than high intensity discharge lamps and are therefore only suitable for large fixtures. Because the induction lamps are hard-wired in, they can be difficult to replace. However, their long lamp life may offset the wiring issue. New manufacturers are flooding into the promising LED street light market, but many do not have requisite expertise in the lighting field, reports LEDs Magazine. Hence, the quality of LED street lamps can be erratic.
While LED lights offer directional light control or more focused light, some applications, such as storefronts, require spill light. In contrast to halogen lamps, in which efficiency depends on more heat, LED lamps are heat-sensitive. If the temperature of the LED exceeds 75 degrees C, its efficiency decreases, according to LEDs Magazine. In addition, regulations typically require a uniformity of lighting for roads as well as ratings for the amount of glare. In order to meet these specifications, more street lights may need to be installed for LED street lighting in order to avoid a zebra pattern. Induction lighting has the opposite problem. An induction light source acts more like a flood light than a point source, and is challenging to direct or control. Induction lamps are best used for large area lighting, says the International Municipal Signal Association.
LED lights can only be installed or retrofitted into a limited number of fixtures; induction lighting may require special fixtures. Neither type is easily installed in existing street lamps, according to the New Jersey State League of Municipalities.
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- International Municipal Signal Association: Street Lighting Maintenance -- Use of Induction Lighting
- LEDs Magazine: LED Street Light Design Technology
- American Daily Review: Green Street Lights
- Illinois Department of Transportation: Energy Efficient Roadway Lighting Applications
- New Jersey State League of Municipalities: Green Street Lighting, Fact Vs. Fiction