LED street light
Encyclopedia
The LED street light is an integrated light-emitting diode
(LED) light fixture that is used for street light
ing. LED street lights can reduce the cost of keeping streets well-lit when dark.
. These are considered integrated lights because, in most cases, the luminaire and the fixture
are not separate parts (except LEDGine-based luminaires). New in manufacturing, the LED light cluster is sealed on a panel and then assembled to the LED panel with a heat sink
to become an integrated lighting fixture.
Different designs have been created that incorporate various types of LEDs into a light fixture. The current trend is to use high power 1 watt LEDs, but some companies use low power LEDs in their products, including several low power LEDs packed together to perform the same purpose as a single high power LED. The shape of the LED street light depends on several factors, including LED configuration, the heat sink used with the LEDs, and aesthetic design preference.
Heat sinks for LED street lights are similar in design to heat sinks used to cool other electronics such as computer
s. Heat sinks tend to have as many grooves as possible to facilitate the flow of hot air away from the LEDs. The area of heat exchange will directly affect the lifespan of the LED street light.
The lifespan of an LED street light is determined by its light output compared to its original design specification. Once its brightness decreases by 70 percent, an LED street light is considered to be at the end of its life.
Most LED street lights have a lens on the LED panel, which is designed to cast its light in a rectangular pattern, an advantage compared to traditional street lights, which typically have a reflector on the back side of a high-pressure sodium lamp. In this case much of the luminance of the light is lost and produces light pollution
in the air and surrounding environment. Such street lights can also cause glare for drivers and pedestrians.
A drawback of LED focus panels is that most light is directed to the road, and less light to the footpaths and other areas. This can be addressed by the use of specialised lens design and adjustable mounting spigots.
An LED street light based on a 901 milliwatt output LED can normally produce the same amount of (or higher) luminance as a traditional light, but requires only half of the power consumption.
As the LED lighting fixtures normally produce less lumen/Watt illumination it is very crucial to have a well distributed illumination pattern in order to do the same job as higher lumen/Watt conventional fixtures. So a good design of LED street lights is to point different LEDs in one fixture to different target points.
has available a number of reports on the results of many pilot projects for municipal outdoor lighting. Cities that have announced their intention to install LED street lights include Boston
, Worcester
, and Cleveland
.
Cities that have installed at least some LED street lights include:
Warren, Michigan
Warren, Michigan
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
(LED) light fixture that is used for street light
Street light
A street light, lamppost, street lamp, light standard, or lamp standard is a raised source of light on the edge of a road or walkway, which is turned on or lit at a certain time every night. Modern lamps may also have light-sensitive photocells to turn them on at dusk, off at dawn, or activate...
ing. LED street lights can reduce the cost of keeping streets well-lit when dark.
Design and style
An LED street light is an integrated light that uses LEDs as its light sourceLight
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
. These are considered integrated lights because, in most cases, the luminaire and the fixture
Light fixture
A light fixture, light fitting, or luminaire is an electrical device used to create artificial light and/or illumination, by use of an electric lamp...
are not separate parts (except LEDGine-based luminaires). New in manufacturing, the LED light cluster is sealed on a panel and then assembled to the LED panel with a heat sink
Heat sink
A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...
to become an integrated lighting fixture.
Different designs have been created that incorporate various types of LEDs into a light fixture. The current trend is to use high power 1 watt LEDs, but some companies use low power LEDs in their products, including several low power LEDs packed together to perform the same purpose as a single high power LED. The shape of the LED street light depends on several factors, including LED configuration, the heat sink used with the LEDs, and aesthetic design preference.
Heat sinks for LED street lights are similar in design to heat sinks used to cool other electronics such as computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s. Heat sinks tend to have as many grooves as possible to facilitate the flow of hot air away from the LEDs. The area of heat exchange will directly affect the lifespan of the LED street light.
The lifespan of an LED street light is determined by its light output compared to its original design specification. Once its brightness decreases by 70 percent, an LED street light is considered to be at the end of its life.
Most LED street lights have a lens on the LED panel, which is designed to cast its light in a rectangular pattern, an advantage compared to traditional street lights, which typically have a reflector on the back side of a high-pressure sodium lamp. In this case much of the luminance of the light is lost and produces light pollution
Light pollution
Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.The International Dark-Sky Association defines light pollution as:...
in the air and surrounding environment. Such street lights can also cause glare for drivers and pedestrians.
A drawback of LED focus panels is that most light is directed to the road, and less light to the footpaths and other areas. This can be addressed by the use of specialised lens design and adjustable mounting spigots.
Energy efficiency
The primary appeal of LED street lighting is energy efficiency compared to incandescent bulbs of the same luminance. Research continues to improve the efficiency of newer models. One such advance can be found in a street light product created by Lighting Science Group. One model of LED street lights produced by this group is up to 60 percent more efficient than previous models, lasts for 12 years, and allows for cost recovery through energy savings in only three years.An LED street light based on a 901 milliwatt output LED can normally produce the same amount of (or higher) luminance as a traditional light, but requires only half of the power consumption.
As the LED lighting fixtures normally produce less lumen/Watt illumination it is very crucial to have a well distributed illumination pattern in order to do the same job as higher lumen/Watt conventional fixtures. So a good design of LED street lights is to point different LEDs in one fixture to different target points.
Advantages
Advantages of using LED lights:
Low power consumption and long and predictable life time
The lifetime of Led Street lights is usually 10 to 15 years which is three times the life of current technologies adopted. The LED’s also have low maintenance cost which adds to the benefit.
- Dimming
LED’s can be dimmned at times when the use of the street lights is less like late nights and early mornings.
- Small package size
- High color rendering
The color rendering index is the ability of a light source to correctly reproduce the colors of the objects in comparison to the normal light source.
- Quick turn on and off
Unlike flourescent bulbs which take time to heat up once switched on LED’s turn on instantly. LED’s don’t have problem with hot ignition
- RoHS complaint free
LED’s dont contain Hg/Pb and dont emit poisonous gases
- Less attraction to nocturnal insects
Insects are sensitive to the UV-blue and green region of the light spectrum. Nocturnal insects are attracted to the emission of UV-blue and green light from conventional light sources. White LEDs, however, emit light in a small peak in the blue range and smaller in the green range, so nocturnal insects are less attracted to such light sources.
- Easy to design non glare lighting equipment
Most LED street lights have a lens on the LED panel, which is designed to cast its light in a rectangular pattern, an advantage compared to traditional street lights, which typically have a reflector on the back side of a high-pressure sodium lamp. In this case much of the luminance of the light is lost and produces light pollution in the air and surrounding environment. Such street lights can also cause glare for drivers and pedestrians.
- Higher light input even at low temperatures
Notable installations
LED street lights have been installed or announced for installation in several large cities as well as smaller cities throughout the world. The United States Department of EnergyUnited States Department of Energy
The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
has available a number of reports on the results of many pilot projects for municipal outdoor lighting. Cities that have announced their intention to install LED street lights include Boston
Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...
, Worcester
Worcester, Massachusetts
Worcester is a city and the county seat of Worcester County, Massachusetts, United States. Named after Worcester, England, as of the 2010 Census the city's population is 181,045, making it the second largest city in New England after Boston....
, and Cleveland
Cleveland, Ohio
Cleveland is a city in the U.S. state of Ohio and is the county seat of Cuyahoga County, the most populous county in the state. The city is located in northeastern Ohio on the southern shore of Lake Erie, approximately west of the Pennsylvania border...
.
Cities that have installed at least some LED street lights include:
- Woodland, CaliforniaWoodland, CaliforniaWoodland is the county seat of Yolo County, California, located approximately northwest of Sacramento, and is a part of the Sacramento - Arden-Arcade - Roseville Metropolitan Statistical Area. The population was 55,468 at the 2010 census.Woodland's origins trace back to 1850 when California...
- VarnaVarnaVarna is the largest city and seaside resort on the Bulgarian Black Sea Coast and third-largest in Bulgaria after Sofia and Plovdiv, with a population of 334,870 inhabitants according to Census 2011...
, Bulgaria, A2 Highway - TorontoTorontoToronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...
- Dallas, TexasDallas, TexasDallas is the third-largest city in Texas and the ninth-largest in the United States. The Dallas-Fort Worth Metroplex is the largest metropolitan area in the South and fourth-largest metropolitan area in the United States...
- Richmond, BC
- Reno, NevadaReno, NevadaReno is the county seat of Washoe County, Nevada, United States. The city has a population of about 220,500 and is the most populous Nevada city outside of the Las Vegas metropolitan area...
- BudapestBudapestBudapest is the capital of Hungary. As the largest city of Hungary, it is the country's principal political, cultural, commercial, industrial, and transportation centre. In 2011, Budapest had 1,733,685 inhabitants, down from its 1989 peak of 2,113,645 due to suburbanization. The Budapest Commuter...
- New York CityNew York CityNew York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
- Washington, D.C.Washington, D.C.Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
- Baltimore, Maryland
- Mesa, ArizonaMesa, ArizonaAccording to the 2010 Census, the racial composition of Mesa was as follows:* White: 77.1% * Hispanic or Latino : 26.54%* Black or African American: 3.5%* Two or more races: 3.4%* Native American: 2.4%...
- Adelaide, South Australia
- MiriMiriMiri is a city in northern Sarawak, Malaysia, on the island of Borneo. It is the second largest city in Sarawak, with a population of about 300,000, and the government administrative centre of Miri District in Miri Division....
, Subang JayaSubang JayaSubang Jaya is a suburban city in the Klang Valley, Selangor, Malaysia. It comprises the southern third of the district of Petaling, and is home to a third of the district population of 1.78 million. Subang Jaya comprises , Bandar Sunway, UEP Subang Jaya, Putra Heights and Batu Tiga...
, PontianPontian, JohorPontian is a district in southwest Johor. It is located 62km from Johor Bahru, the state capital of Johor. It is also located at Miles 37 from Johor Bahru. The name Pontian is also used in the names of two towns in the district, Pontian Besar and Pontian Kechil, of which the latter serves as its...
, Kuala Lumpur - Karak Expressway in Malaysia - Hanscom Air Force Base, Massachusetts
- Cebu City, Philippines
- St. John's, Newfoundland and LabradorSt. John's, Newfoundland and LabradorSt. John's is the capital and largest city in Newfoundland and Labrador, and is the oldest English-founded city in North America. It is located on the eastern tip of the Avalon Peninsula on the island of Newfoundland. With a population of 192,326 as of July 1, 2010, the St...
- HalifaxHalifax Regional Municipality, Nova ScotiaHalifax Regional Municipality is the capital of the province of Nova Scotia, Canada. The Regional Municipality had a 2006 census population of 372,679, while the metropolitan area had a 2010 estimated population of 403,188, and the urban area of Halifax had a population of 282,924...
, Amherst, Annapolis Royal, Wolfville, Halifax International AirportHalifax International AirportHalifax/Robert L. Stanfield International Airport, or Halifax Stanfield International Airport is an airport in Enfield, Nova Scotia and in Halifax Regional Municipality, Canada...
, Truro, Antigonish, and many other smaller towns in Nova ScotiaNova ScotiaNova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
have installed fixtures manufactured and designed by a company in that province. - Seattle, WashingtonSeattle, WashingtonSeattle is the county seat of King County, Washington. With 608,660 residents as of the 2010 Census, Seattle is the largest city in the Northwestern United States. The Seattle metropolitan area of about 3.4 million inhabitants is the 15th largest metropolitan area in the country...
http://powerlines.seattle.gov/tag/led-street-lights/
Warren, Michigan
Warren, Michigan
External links
- U.S. Department of Energy reports on municipal LED lighting pilot projects: Solid-State Lighting GATEWAY Demonstration Results
- New Streetlights – LED streetlight news and analysis