The Advantages of Outdoor LED Street Lights
Outdoor led street lights consist of led street light module, driver power, heat dissipation device, optical system and lamp shell. Compared to the traditional street lamps, LED street lamp has many advantages.
①High light efficiency and luminaries light efficiency, low energy consumption. The lighting effect of high pressure sodium lamp is dominant due to its ability to reach 120lm/W. And at present, the luminous efficacy of LED can reach 100 ~ 150lm/w. At the beginning of 2009, Cree and Osram announced that the luminous efficiency of high-power white leds reached the laboratory level of 160lm/w. According to the United States department of energy (DOE), the luminescent efficiency of high-power leds could reach 165 lm/w by 2020, the laboratory sample can reach 230 lm/W. For the time being, LED lighting has exceeded most traditional sources, the high-pressure sodium lamp's monopoly position is in jeopardy.
Traditional light sources such as high pressure sodium lamp generally shine through the whole space while road lighting needs to illuminate only the road. Therefore, in order to make the light uniformly and centrally projected onto the road surface, it is usually necessary to use a curved reflector to collect the light to the desired direction. In the process of light transmission, the luminous efficiency of the lamp is only 65% ~ 70% because of the loss caused by the absorption of the light source and the reflector.
Because LED street lamp has good direction, the luminaire efficiency will reach about 80% in the use of a secondary optical lens. Through three times optical designs, the lighting efficiency can be reached about 90%.
The following table shows the comparison between the efficiency of a 400W high pressure sodium lamp and a 250W LED lamp luminaire efficiency and pavement utilization.
|Types of Lights||Power(W)||Light Efficacy(lm/W)||
Total Luminous Flux
High Pressure Sodium
|LED Street Lights||250||90||80||90%||16000|
It can also meet the standard requirements of average illumination while using 100W outdoor led street lights with reasonable light distribution replace the street lamps with 250W high pressure sodium lamps on some secondary roads.
In addition, outdoor led street light can achieve 0~100% dimming. The light output can be adjusted according to ambient lighting and traffic conditions, reduce unnecessary energy consumption while ensuring the lighting demand. LED street light, generally can only achieves a small range of dimming control. Large-scale LED street lighting is beneficial to energy conservation and emission reduction for road lighting that accounts for 15%~20% of total lighting consumption.
② Long lifespan. The lifetime of outdoor LED street lamps directly affects the maintenance costs of whole road lighting. The life expectancy of high-pressure sodium lamps is about 20,000 hours, the life of high-pressure sodium road lamps is generally only about 5,000 hours. But LED has a life expectancy of 50,000 hours, some 70,000 hours, and the lowest one still has 30,000 hours.
Of course, the lifetime of LED is not the lifetime of outdoor led street lights, the light’s lifespan is much lower than that of LED light source. However, the life of outdoor led street light is bound to be much longer than that of traditional street lamp as long as the reliability of the cooling and driving circuit of outdoor LED street lamps is solved.
③ High color rendering index. CRI of traditional sodium lamps can only reach about 20. The color index of LED can reach 70~80 and It's more reflective of the real color of the object itself. High CRI helps drivers and pedestrians identify targets exactly, and provides better travel conditions under the same brightness.
④ Quick start. The gas discharge street lights will take tens of seconds or even dozens of minutes to switch from power to stable light output and the hot start time lasts 3 ~ 6 minutes after extinguishing. The LED street lights don’t have the waiting time to start again, the start-up time is only a few tens of nanoseconds, it can work normally in a continuous switch.
⑤ Convenient optical design. The LEDs should be considered as point light sources when designing because of its small volume and directional light on the half plane. It is very suitable to use lens or reflective cup for optical design to obtain the ideal match light and higher lamp efficiency.
⑥ Strong plastic molding and sturdy construction. Outdoor led street lights can be designed to reflect decorative and local cultural features, adding value added to aesthetic and urban imagery. LED is a solid source of light, without glass, filament and other vulnerable parts. LED module, drive circuit, the radiator and light learn parts of outdoor led street light, through reasonable design the structure can be very strong.
⑦ Low-carbon environment, especially suitable for solar photovoltaic technology. Street lights made by the gas discharge light source contains mercury and other harmful substances, which can cause serious pollution to the environment and water source. And the elements that can replace mercury have not been found. LED contains no harmful substances such as lead and mercury and is easy to meet the EU RoHS directive requirements.
Besides, LED is especially suitable to apply solar photovoltaic technology to outdoor led street lighting for its characteristic that can be driven by DC current. We can realize the real energy conservation and environmental protection lighting by the combination of LED and solar technology and landscape complementary technology.
⑧ Advantages of potential total costs. LED street lights are now about the same price as high pressure sodium street lamps. A 240w led street light is about the same brightness and price as a 400w high pressure sodium street lamp, but Leds use only half the power of traditional streetlamps and the energy and maintenance costs of outdoor led street lights will soon become apparent.