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Light Spread in LED compared to Mercury vapor and High pressure sodium street lights

Posted by NaBa Green Energy Labels: , , ,

As discussed in my previous articles LED technology is growing leaps and bounds, we will compare the light throw of street lights. It has many advantages compared to other light technologies such as
  • Even distribution of light from LED street light creates a better environment.
  • Due to even distribution the visibility improves tremendously.
We will compare LED light beam spread and Lux levels with that of high pressure sodium, mercury vapor lamps.

Mercury vapor street lights
              Mercury vapor lamp is a gas discharge lamp that uses mercury in an excited state to produce light. For sake of comparison we will use a 60 watts mercury vapor street light, with following features
  • Life span 16,000-24000 Hrs
  • Power consumption -60 watts 
  •  Required Beam angle-360, considering pole height of 10 feet,
To calculate beam spread, Beam width = angle x. 018  x distance      =64.8 feet rectangle
In the above scenario, 90 degree beam angle is wasted. We can calculate for 270 degree beam spread only.
Mercury vapor lamp gives 30 lumens per watt, totally flux-1800 lumens
Lux =  foot candle x 10.76(for 10 feet pole height 1fc=100 lumens) =(18 x 10.76) 193.68
Lux/watt = 3.2


High Pressure Sodium street  lights 
As we all know sodium vapor lamps cause little light pollution than mercury lamps. It is a high intensity discharge lamp that uses sodium high pressure as the primary light producing element. We will compare 60 watts high pressure sodium vapor street light with following specification

  • Better Life span is 20,000-30,000 hrs compared than mercury lamps
  • Power consumption -60 watts
  • Required Beam angle -360,considering pole height of 10 feet

To calculate beam spread, Beam width = angle x. 018  x distance=64.8 feet rectangle
Based on the 270 degree beam spread as discussed above. 60 lumens per watts, totally flux=3600 lumens

Lux =  foot candle x 10.76(for 10 feet pole height 1fc=100 lumens) =(36 x 10.76) 387.36
Lux/watt =6.4

LED street lights                                   
                       Coming to led street light,  We all know it can produce more light with less wattage. Below is the calculation. 60 watts led street light is used as replacement of 120 watts high pressure sodium vapor lamp. we will use same 60 watts led street light with following specification



  • Excellent Life span is 60000 hrs 
  • Very low  Power consumption -60 watts
  • Beam angle -120 degree 
To calculate beam spread, Beam width = angle x. 018 x distance =21.6 feet rectangle
Full beam spread is used in this scenario, because LED gives only light at 120 degrees.
Based on120 lumens per watts, totally flux-7200 lumens.
Lux =  foot candle x 10.76(for 10 feet pole height 1fc=100 lumens)=(72 x 10.76) 774.14
Lux/watt = 12.90





Features
Mercury vapor lamp
High pressure sodium lamp
Led lamp
Power consumption
60 watts
60 watts
60 watts
System efficacy(lumens/watt)
30
60
120
Flux(total lumens)
1800
3600
7200
Lux
193.68
387.36
774.14
Lux/watt
3.2
6.4
12.09
Life span
16000-24000 hrs
20000-30000 hrs
60000 hrs

This calculation clearly shows led lamp lux value is twice than high pressure sodium lamp and four times than that of mercury vapor lamp. Mercury vapor lamp puts out bluish light , because it contain some amount of toxic mercury content.  High-pressure sodium lamps produce light from the yellow, red and orange spectrums.The LED based efficient lighting puts out white light because consists of various colors, which undergo varying degrees of refraction and diffusion.



This led light used to avoid the hot spots and wasted light I mean beam spread of the light. Visit us at link to learn more about the LED street lights



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