Reflected Street lighting question

bcbeaver

Newly Enlightened
Joined
Mar 12, 2015
Messages
1
If I illuminate a section of road with 3 - 100w led luminaires spaced to give me a design light level, or I have the same section illuminated with twice as many 50w luinaires which scenario will produce the most light reflected off the road into the night sky? Assuming dark sky fixtures of the same type. The fewer luminaires will create less desirable lighting but will it reflect more into space? I'm wondering if more lumens in a small area will reflect a larger percentage than fewer lumens in a small area.
 

MeMeMe

Banned
Joined
Aug 27, 2018
Messages
125
If I illuminate a section of road with 3 - 100w led luminaires spaced to give me a design light level, or I have the same section illuminated with twice as many 50w luinaires which scenario will produce the most light reflected off the road into the night sky? Assuming dark sky fixtures of the same type. The fewer luminaires will create less desirable lighting but will it reflect more into space? I'm wondering if more lumens in a small area will reflect a larger percentage than fewer lumens in a small area.


If you have twice the number of fixtures, odds are those fixtures could be less than 1/2 the power, IF they are well chosen w.r.t. beam pattern for your target street design, including road, sidewalk if needed, etc. I am assuming if using twice the fixtures, they have a much different beam pattern.

As you have described, from a basic level, both will put about the same amount of light into the sky. Practically, farther spaced fixtures will have a wider beam pattern and lower angle reflections, hence more of the reflected light may be absorbed by surrounding trees and structures. Conversely, it will also pass through more sky close to the ground (due to the angle) and hence has more ability to create sky glow.

Generally more fixtures allows for optimization of light placement allowing less total light (and spill), hence has a low contribution. Close spaced fixtures need a much different distribution than wide spaced fixtures.

Then again, this is complicated by the design method used, luminance or illuminance as one can create a bias for high angle or low angle distribution based on pavement type.
 

angerdan

Enlightened
Joined
Feb 12, 2015
Messages
290
Location
Europe
The fewer luminaires will create less desirable lighting but will it reflect more into space?
I'm wondering if more lumens in a small area will reflect a larger percentage than fewer lumens in a small area.
Depends on the illuminance in lux (lm / m²) and the incoming angle of light distribution.

Then again, this is complicated by the design method used, luminance or illuminance as one can create a bias for high angle or low angle distribution based on pavement type.
When the light source is aligned horizontal, lowest grade of light pollution (reflection from light source over street surface towards sky) will be reached.
Example lights for this:
lumitronix.com/en_gb/philips-mygarden-outdoor-light-stock-6w-43264.html
lumitronix.com/en_gb/philips-mygarden-outdoor-light-arbour-6w-43261.html
lumitronix.com/en_gb/philips-hue-led-pedestal-light-turaco-anthracite-hue-white-33701.html
lumitronix.com/en_gb/philips-hue-led-path-light-turaco-anthracite-hue-white-33700.html
 

MeMeMe

Banned
Joined
Aug 27, 2018
Messages
125
Depends on the illuminance in lux (lm / m²) and the incoming angle of light distribution.


When the light source is aligned horizontal, lowest grade of light pollution (reflection from light source over street surface towards sky) will be reached.
Example lights for this:
lumitronix.com/en_gb/philips-mygarden-outdoor-light-stock-6w-43264.html
lumitronix.com/en_gb/philips-mygarden-outdoor-light-arbour-6w-43261.html
lumitronix.com/en_gb/philips-hue-led-pedestal-light-turaco-anthracite-hue-white-33701.html
lumitronix.com/en_gb/philips-hue-led-path-light-turaco-anthracite-hue-white-33700.html


We this a reply or an advertisement? Did you read the title of the post. STREETLIGHT? Why are you posting links to residential bollards?

Virtually everything product posted break one rule of reduced sky glow ... it must be a full cutoff fixture, which none of these are.

Your statement about horizontal alignment is a generalization that just cannot be made, not to mention in a streetlight environment, means more glare.
 
Top