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How to choose the best led street light Solutions?

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How to choose the best led street light solutions?


 What is the best and suitable led street light for your roadway lighting?



1: The purpose of the street lighting:


Roadway lighting or street lighting plays an important role for the drivers or pedestrians in the darkness, considering the situation of the roadway or a street is not always simple but complicated, only based on the lighting provided by a car or a truck is not enough for safety reason. According to CIE investigation report,  for those roadways or streets with suitable lighting in the darkness could reduce the city traffic accident less than 30%, the country traffic accident less than 45%, high speed traffic accident less than 30%. Roadway or street lighting provides the pedestrians and vehicles with a safety environment and the same time that make the city more beautiful.


2: About  street light types used for roadway or streets:


High pressure sodium lamps (HPS) have been widely used for roadway or street lighting due to its high lumen output  around 120lm per watt, with an average life time for 24,000hrs. HPS lamps  with accommodated fixtures could provide good performance for the street or roadway lights so that they have been the 1st option for those applications  before the application of Led lights.


However, as we know,  with the development of led lights,  with the appearance of more lumen efficient  above 120lm led light  used for street or roadway lighting , HPS has lost its dominant position for these applications,  led has better  CRI over 70 compared with  the CRI of HPS from 20-30, long life time over 50,000hrs, these are obvious advantages over HPS lamps, more and more street or roadway lighting now applies with led lighting.


We will just  ignore the various reasons why the led light is better than HPS light for the street or roadway lighting, most of these points are now very obvious to us, in this article, we will go straight to the point when you are considering  about “ How  I  could choose a better or best or suitable led street light  for the roadway or street light application”


3: Important key points for a better led street light:


Before we decide to purchase or consider a led street light, firstly we shall have a basic understanding  about  the roadway or street illumination standard, this is simply that without the standard, we do not have the real way to check if  a led street light is suitable or not. The below is an example of the illumination standard based on EU roadway lighting standard for an example:


EU Roadway Lighting Luminance Standard-Dry Roadway Surface luminance-ME series


Roadway

Lav [cd/m²]

U0

UI

TI [%]

SR

Class

Min.

(min.)

(min.)

Max.

Min.

ME1

2.0

0.4

0.7

10

0.5

ME2

1.5

0.4

0.7

10

0.5

ME3a

1.0

0.4

0.7

15

0.5

ME3b

1.0

0.4

0.6

15

0.5

ME3c

1.0

0.4

0.5

15

0.5

ME4a

0.75

0.4

0.6

15

0.5

ME4b

0.75

0.4

0.5

15

0.5

ME5

0.5

0.35

0.4

15

0.5

ME6

0.3

0.35

0.4

15

not request



Based on the chart  above, we could find 6 key indicators related with a street lighting application as the following aspects: 



Six (6) key indicators   for a standard street lighting application-ME series

Roadway Class

Lav [cd/m²] min.

U0 Min.

Ul Min.

TI [%] Max.

SR Min.

ME-Series

average road surface luminance

overall uniformity of the luminance

longitudinal uniformity of the luminance

threshold increment 

surround ratio


The above are the very important 6 key indicators when to evaluate a qualified street lighting application when a led street light is installed, following are the conception about how to understand these  6 indicators



What is  a Roadway class?


For example here, the ME classes  are designed for drivers of motorized vehicles for user on traffic routes, including residential roads, from medium to high driving speeds, which designed for EU roadway lighting application. There are also other classes like CIE, IESNA classes etc for different areas or countries roadway lighting class.


What is average road surface luminance-Lav [cd/m²] min.?


illuminance of the road surface averaged over the carriageway, candelas per square meter


What is the overall uniformity of the luminance U0 Min.?


illuminance on a road area, ratio of the lowest to the average value


What is the longitudinal uniformity of the luminance Ul Min?


The lowest of the longitudinal uniformities of the driving lanes of the carriageway


What is the threshold increment TI [%] Max.?


 The loss of visibility by the disability glare of the luminaries in road lighting


What is the surround ratio SR Min.?


Average illuminance on strips just outside the edges of carriageway in proportion to average illuminance on strips just inside the edges



4: Choose your best led street light for your roadway or street lighting application



Apart from a nice light fixture shape , several common key factors for a street light is like as follows:


1:Luminous efficacy-from the whole light fixture but not from the original led light source, like for a 80w led street light, chips lumen total reaches like 10400lm, but when installed into a led light fixture, the actual lumen output will be like more than 9400lm, the loss because the chips cover or tempered glass cover etc.


2:  Driver and led chips-like Philips/cree/osram/samsung led chips, meanwell, inventronics, philipsdriver etc, if you consider a well-known brand drivers or led chips, these brands are more popular in terms of the led street light, as these are branded chips and drivers have been verified its quality and performance in the lighting industry, however, there are also other brand drivers and chips with good quality that could be considered as well based on your different level of the budgets for your lighting application, choose the suitable option based on your situation is the best way.


3: Photometric pattern-or we call this ies files, this is one of the very important keys for the street light if it is suitable for your street lighting application, as even the point 1 and point 2 is qualified, with an unsuitable photometric file street light means actually nothing.


4:  led light fixture structure qualification like if it is strong enough above IK06 or IK08, IP level like above IP65


5: In terms of CRI, as most of the led street light is all above 70, so this point will be commonly qualified but also you need to have a check for this point as well.


6: other points not related or there is very special application like extremely worse application environment like ex-proof,  corrosive areas would be neglected in this article, we would mainly focus on the normal street lighting application in city or urban applications.


Let us suppose the following situation that you are considering the led street light for the below roadway situation:


The case is there is a part of the street-24 meters wide with 5 kilometers long, we will have a basic evaluation for this street situation. 


Case for  Street Profile-6 lanes street lighting based on Me4b class


Maintenance factor: 0.67-Roadway 1 (Width: 24.000 m, Number of lanes: 6, tarmac: R3, q0: 0.070)


Luminaire Arrangements-38 meters pole distance



Arrangement

Pole distance

Mounting height(1)

Overhang(2)

Boom Angle(3)

Boom length(4)

Double row, opposing

38.000 m

12.000 m

0.510 m

12 degree

1.000m



image.png

We firstly would take a 38 meters pole distance which is wider than 3 times of the pole height, meters, by this situation, we would see what will happen to the light performance. 


Valuation Field Roadway 1 / Results overview-38 meters width


Assigned Observer (6 Pieces):


No.

Observer

Position [m]

Lav[cd/m²]

U0

Ul

TI[%]

Result

1

Observer1

(-60.000,2.000,1.500)

0.85

0.57

0.84

6

Fufilled

2

Observer2

(-60.000,6.000,1.500)

0.87

0.59

0.86

6

Fufilled

3

Observer3

(-60.000,10.000,1.500)

0.87

0.62

0.84

5

Fufilled

4

Observer4

(-60.000,14.000,1.500)

0.88

0.68

0.84

5

Fufilled

5

Observer5

(-60.000,18.000,1.500)

0.87

0.69

0.76

4

Fufilled

6

Observer6

(-60.000,22.000,1.500)

0.87

0.66

0.70

4

Fulfilled

ME4b-Class

Lav [cd/m²]

U0

Ul

TI[%]

SR

Calculated values:

0.85

0.57

0.70

6

0.67

Required values according to   class:

0.75

≥0.4

≥0.5

≤15

≥0.5

Fulfilled/Not fulfilled:

image.pngimage.pngimage.pngimage.pngimage.png

image.png


Based on the above calculation, by the application of our led street light model HYL-QMSL-120W led street light could meet this roadway lighting application, and  the calculation result and the performance is qualified based this roadway situation, each of the lighting indicators like U0, UI, TI[%], Lav[cd/m²] are fulfilled . If this solution is taken, for a 5000 meter street  will need 258 pcs of 120w street lights.


To this step, whether we could find more better options for this street light case, for example, if we could enlarge the pole distance so that the overall qty of the led lights reduced, as the led light quantity is related with the project budget.


Here we would make the pole distance to 40 meters pole distance, and we get the following result:


Valuation Field Roadway 1 / Results overview-40 meters pole distance


image.png

  image.png


After making the pole distance to 40 meters, each lighting indicator still is qualified, but the overall qty for this street light application is 246 pcs, which is 12 pcs of qty less than the 1st 38 meter pole distance. Now we would try to make it further like 42 meters, 43 meters till 45 meters and we will see the following result:


Results overview-42 meters pole distance

image.png

Results overview-43 meters pole distance

image.png

Results overview-44 meters pole distance

image.png

Calculated from 42 meters to 44 meters, we find out that 44 meters distance pole with not qualified average road surface luminance, in this way we could not go further for the light pole distance, while 43 meters although meet the requirement, but the luminance is too close to the min. > 0.75,  overall,  the 42 meters pole distance is a comprised way and also a better option,  this option would make the total street light qty to  234 pcs.

As a result, from 38 meters with 258 pcs to 40 meters with 246 pcs,  till the qty become 234 pcs street lights after with 42 meters light pole distance, of which, we could see the 120W street light with 42 meters light pole distance is the best solution in this case.

 

Conclusion:


Apart from the basic features for a led street light such as lumen, driver, led chips, IK, IP etc, the most important is that if the  photometric file is properly designed, before you consider to purchase a led street light, firstly, it is very necessary to know about your roadway situation and classification, and secondly, the necessary action to take before the purchase is to ask your supplier for  the tested photometric file to have the basic evaluation if it is suitable for your roadway situation, if this step is not fulfilled, it is not worth your effort to consider this street light no matter how it is boasted with a lot of attractive advantages, the step that you may consider to do is keep looking for another supplier with the suitable led street light with proper designed photometric for your project.


About HYL-QMSL-120W led street light


Our QMSL led street light is designed based on module structure, with Philips 3030 led chips and meanwell led drivers, the fixture is with robust structure IK10 and IP66, from 80w to 300W application,  average luminous efficacy is over 140 lumen per wattage, photometric file is designed based on the lighting class indicator like Lav[cd/m²]-U0-Ul-TI-SR etc, when it is put into the real application, it could meet most requirement of the different street classes like ME class, MEW class, IESNA class, CIE class etc. 


for more information and specification, you could check our web product link:


https://www.hyspectrum.com/led-street-light/140lm-intelligent-led-street-light-80w-300w/


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About Lighting Class: ME4b


Parameter

Value

Typical speed of the main user

Medium (Between 30 and 60 km/h)

Main user

Motorized  traffic, Slowly driving vehicles, Bicyclists

Other permitted users

Pedestrians

Excluded users

/

Illuminance conditions

B2

Link to other streets

Simple Junctions

Interchange density [number per   km]

<3

Conflict Zone

No

Constructions measures for   traffic calming

No

Traffic flow of vehicles [number   per day]

Between 7000 and 15000

Traffic flow of bicyclists

Normal

Degree of Navigational Difficulty

Normal

Parked Vehicles

No

Complexity of Field of Vision

Normal

Luminance level of the   environment

Medium (City Environment)

Main Weather Type

Dry

Note: other lighting classes have similar style of the request for the parameters but are different based on the specific situation. Considering a suitable led street light shall comply with this road class level.

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Building No.3-5, No.118, Lane 3588, Qi Lian Shan Road, Shanghai , China

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