LED TECHNOLOGY is growing leaps and bounds, we will compare the light
throw STREET LIGHTS. It has many advantages compared to other light
technologies such as
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Even distribution of light from LED STREET LIGHTS 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
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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
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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 LIGHTS, We all know it can produce more light with less
wattage. Below is the calculation. 60 watts LED STREET LIGHTS is used as replacement of 120
watts high pressure sodium vapor lamp. we will use same 60 watts LED STREET LIGHTS with
following specification
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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
LED LAMP
60 watts
30
High pressure
sodium lamp
60 watts
60
Power consumption
System
efficacy(lumens/watt)
Flux(total lumens)
Lux
Lux/watt
Life span
1800
193.68
3.2
16000-24000 hrs
3600
387.36
6.4
20000-30000 hrs
7200
774.14
12.09
60000 hrs
60 watts
120
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.