How to Design efficient Street lighting-(Part-6)

(3) Light trespass:

  • Light trespass is condition when spill (Unwanted or Unneeded) light from a streetlight or floodlight enters a window and illuminates an indoor area.

 How to Reduce Trespass

  • Select luminaries, locations, and orientations to minimize spill light onto adjacent properties.
  • Use well-shielded luminaries.
  • Keep floodlight aiming angles low so that the entire beam falls within the intended lighted area.

 Difference between full cutoffs and fully shielded:

  • The full cutoff has is luminaries that have no direct up light (no light emitted above horizontal) and 10% of light intensity between 80° and 90°.
  • The term full cutoff is often substituted for the term fully shielded.
  • The both terms are not equivalent. Fully shielded luminaires emit no direct up light, but have no limitation on the intensity in the region between 80° and 90°
  • Luminaires that are full cutoff, cutoff, semi cutoff, and non cutoff , may also qualify as fully shielded.

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  • There is also a confusing assumption that a luminaire with a flat lens qualifies as a full cutoff luminaries. While this may be true or not in some Lighting Fixtures case.

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  • Fully shielded means, a lighting fixture constructed in such a manner that the bulb should be fully recessed into Fixture so that all light is directed downward below the horizontal.
  • The fixture is angled so the lamp is not visible below the barrier (no light visible below the horizontal angle).

(G) Selection of Luminas:

(1) Types of Lighting Source

  • Street Lights are mostly Low-pressure sodium (LPS), High-pressure sodium (HPS), Metal halide and Light emitting diodes (LED).
  • LPS is very energy efficient but emits only a narrow spectrum of pumpkin-colored light that some find to be undesirable.
  • LPS is an excellent choice for lighting near astronomical observatories and in some environmentally sensitive areas.
  • HPS is commonly used for street lighting in many cities. Although it still emits an orange-colored light, its coloring is more “true to life” than that of LPS.
  • Where it’s necessary to use white light, there are metal halide and LEDs.

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  • High-pressure sodium lamps should be used for expressways, main roads, secondary roads and branch roads.
  • Low-power metal halide lamps should be used in mixed traffic roads for motor vehicles and pedestrians in residential areas.
  • Metal halide lamps can be used for motor vehicle traffic, such as city centers and commercial centers, which require high color identification.
  • Metal halide lamps, CFL lamps are used at Pedestrian streets in industrial areas, sidewalks in residential areas, and sidewalks on both sides of motorway traffic.
  • LED streetlights are more durable, longer lasting, efficiency, dimmable capacity and cost effective than traditional lights.
  • LED also enhances public safety by delivering superior visible light while providing the environmental advantage of using less energy.

 (2) Color Rendering Index (CRI):

  • CRI Measures the ability of the artificial light to show or reproduce the colors of the road or objects on the road, relative to a natural light source.
  • The natural light source (the sun) has CRI of 100. The higher
  • This index the better the visibility will be. For all types of road CRI ≥ 70 is recommended.

(3) Efficacy

  • At the low end LED efficacy starts at 70 lumens per watt (lm/W) and reaches as high as 150 lm/W.
  • While the mean efficacy for outdoor area fixtures is slightly lower than common indoor fixtures such as troffers and linear lighting about 100 lm/W for area lights compared to about 110 lm/W for troffers and linear fixtures this difference is not significant. It may be the result of outdoor area lights requiring more precise luminous intensity distributions and other factors unique to outdoor lighting.

(4) Fixture Protection:

  • When using sealed road lighting, the protection level of the light source cavity should not be lower than IP54.
  • For roads and places with dangerous environmental pollution and heavy maintenance, the protection level of the light source cavity should not be lower than IP65.
  • The degree of protection of the lamp electrical appliance cavity should not be lesser than IP43.
  • Lamps with excellent corrosion resistance should be used in areas or places with high levels of corrosive gases such as acid and alkali in the air.

(H) Effective Road Lighting:

  • Sufficient illumination.
  • Good uniformity.
  • No Glare.
  • Low consumption.
  • No Color Temperature abnormalities
  • No Zebra effect
  • Shielded lighting to ensure light is pointed downwards
  •  Completely uniform illuminance.
  • No requirement for over lighting to obtain sufficient average illumination.
  • Absence of glare.
  • Absence of low angle radiation that causes sky glow.
  • Control of light trespass.
  • High redundancy.

 Effective Lightning

Features Benefits
Proper pole height & spacing  Provide uniform light distribution
Proper Luminaire aesthetics  Blends in with the surroundings
Good maintenance Reduce problems in lightning
High lamp efficiency  Minimize energy cost
Life of Luminaire Reduce lamp replacement cost
Good color rendering  Helps object appear more natural
Proper light distribution  Provide required light on roads
Cost effectiveness  Lowers operating cost
Minimizing light pollution & glare  Reduce energy use

 

Effective Energy-efficient Street Lighting Systems (NYSERDA, 2002)

Features Benefits
Proper pole height and spacing Provides uniform light distribution, which improves appearance for safety and security Meets recommended light levels Minimizes the number of poles, reducing energy and maintenance costs
Proper luminaire aesthetics Blends in with the surroundings
High lamp efficacy and Luminaire efficiency Minimizes Energy cost
Life of the luminaire and other components Reduces lamp replacement costs
Cost effectiveness Lowers operating cost
High Lumen Maintenance Reduces lamp replacement costs
Good color rendering Helps object appear more natural and pleasing to the public Allows better recognition of the environment, improves security
Short lamp Re strike Allows the lamp to quickly come back after a power interruption
Proper light distribution Provides required light on the roads and walkways
Proper Cutoff Provides adequate optical control to minimize light pollution
Minimizing light pollution and Glare Reduces energy use
Automatic Shutoff Saves energy and maintenance costs by turning lamps off when not needed

 

Minimum Value of Street Light Designing

Descriptions Min Value
Watt 400
Lumens Per Watt 80 To 140
Voltage 230Volt
Frequency 50 To 60Hz
Power Factor   More than 95
THD  < 20%
Life Hours 70,000 hours
Color Temperature 4000K  To  5000K
CRI More than 75
Beam Angle / Beam Pattern  Type 2,3,4,5
Operating Temperature (-)25°C To (+)50°C
Working Humidity 10% To 90% RH
IP Rating  IP67
Dimmable 0-10V
Optic Lens Material High Polycarbonate (PMMA)
Forward Current >600mA
Housing IP65 – Aluminum Alloy and PC Lens
Dimension  18.23″ X 13.58″ X 4.57″
Weight  15.30 lbs – 34.39 lbs
Warranty 10 Years

About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

2 Responses to How to Design efficient Street lighting-(Part-6)

  1. Sumon Myint says:

    Dear Sir, Thanks for your knowledge sharing! I had read these articles about effective street lighting. Besides, I would like to know about ground grid design for substation and grounding system of a building after these articles. Thanks for your important time!

  2. Rohit says:

    Hey Amazing article, totally appreciate your work!

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