CLD-AP132 rev 0E
Application Note
Cree® XLamp® XT-E LED
Streetlight Reference Design
Table of Contents
Introduction
Introduction..................................................................................... 1
Municipalities from Beijing, China, to Los Angeles, California, to
Design approach/objectives.......................................................... 3
Apecchio, Italy, have implemented projects to replace traditional
The 6-step methodology................................................................. 3
streetlights
with
energy‑saving
LED
streetlights.
Local
1.Define lighting requirements.................................................. 3
governments, universities and utility companies world-wide are
2.Define design goals................................................................. 7
taking advantage of the energy savings and lower maintenance
3.Estimate efficiencies of the optical, thermal & electrical
costs provided by LED-based streetlights and walkway lights.
systems.................................................................................... 7
4.Calculate the number of LEDs ............................................. 10
5.Consider all design possibilities........................................... 10
6.Complete the final steps: implementation and analysis..... 10
Conclusions................................................................................... 16
Special thanks............................................................................... 16
Bill of materials............................................................................. 16
This application note details the design of a prototype streetlight
using Cree’s XLamp® XT‑E LED to produce a Type III intensity
distribution. Built on the SC³ Technology® next‑generation
LED platform, the XLamp XT‑E LED brings high performance
and quality of light to this outdoor application. Streetlights
incorporating the XLamp XT-E LED offer numerous benefits
compared to traditional fixtures including energy efficiency,
better illumination and longer lifetime. The highly efficient XT-E
www.cree.com/Xlamp
LED makes using this LED in a streetlight a viable alternative to
an incumbent‑technology streetlight.
Reliance on any of the information provided in this Application Note is at the user’s sole risk. Cree and its affiliates make no warranties or representations about, nor assume
any liability with respect to, the information in this document or any LED-based lamp or luminaire made in accordance with this reference design, including without limitation
that the lamps or luminaires will not infringe the intellectual property rights of Cree or a third party. Luminaire manufacturers who base product designs in whole or part on
any Cree Application Note or Reference Design are solely responsible for the compliance of their products with all applicable laws and industry requirements.
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3
Technology® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental
Protection Agency. Other trademarks, product, and company names are the property of their respective owners and do not imply specific product and/
or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty
information, please contact Cree Sales at [email protected].
Cree, Inc.
4600 Silicon Drive
Durham, NC 27703
USA Tel: +1.919.313.5300
XLamp ® XT-E LED Streetlight Reference Design
An XT-E streetlight has multiple advantages over traditional high-pressure sodium (HPS) and metal halide (MH) lamps.
•
Lower energy usage
•
No warm-up time
•
No humming or flickering
•
No mercury
•
Longer lifetime
•
Better color rendering
•
No re-lamping cost, which can be a significant expense in streetlight applications
Figure 1: LED streetlight installations
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
2
XLamp ® XT-E LED Streetlight Reference Design
Design approach/objectives
The Cree “LED Luminaire Design Guide” advocates a six‑step framework for creating LED luminaires and lamps. We used this framework,
with the design guide’s summary table reproduced in Table 1.
Table 1: Cree 6-step framework
Step
Explanation
1. Define lighting requirements
•
The design goals can be based either on an existing fixture or on the application’s lighting requirements.
2. Define design goals
•
•
Specify design goals, which will be based on the application’s lighting requirements.
Specify any other goals that will influence the design, such as special optical or environmental requirements.
•
•
•
Design goals will place constraints on the optical, thermal and electrical systems.
Good estimations of efficiencies of each system can be made based on these constraints.
The combination of lighting goals and system efficiencies will drive the number of LEDs needed in the
luminaire.
•
Based on the design goals and estimated losses, the designer can calculate the number of LEDs to meet the
design goals.
5. Consider all design possibilities and choose
the best
•
•
With any design, there are many ways to achieve the goals.
LED lighting is a new field; assumptions that work for conventional lighting sources may not apply.
6. Complete final steps
•
•
•
•
•
Complete circuit board layout.
Test design choices by building a prototype luminaire.
Make sure the design achieves all the design goals.
Use the prototype to further refine the luminaire design.
Record observations and ideas for improvement.
3. Estimate efficiencies of the optical, thermal &
electrical systems
4. Calculate the number of LEDs needed
The 6-step methodology
The major goal for this project was to create a high-efficiency XLamp XT-E LED-based 120‑watt streetlight capable of producing a Type III
beam pattern. Luminous flux and light distribution patterns for commercially available high‑intensity discharge (HID) streetlight systems
vary greatly by supplier, luminaire model, and ballast type. The 120-watt design goal for this LED luminaire is meant to approximate the
photometric performance of a typical 250- to 400‑watt HID system.
1. Define lighting requirements
Table 2 shows a ranked list of desirable characteristics for a streetlight.
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
3
XLamp ® XT-E LED Streetlight Reference Design
Table 2: Ranked design criteria for a high-bay luminaire
Importance
Critical
Important
Characteristics
Units
Illuminance distribution
footcandles (fc)/lux (lx)
Electrical power
watts (W)
Lifetime
hours
Payback
months
Luminous flux
lumens (lm)
Efficacy
lm/W
Operating temperatures
°C
Operating humidity
% RH
Correlated color temperature (CCT)
K
Color rendering index (CRI)
100-point scale
Ease of installation
Figure 2, Figure 3 and Figure 4 show the advantages of directional XLamp XT-E LEDs in this application. Omnidirectional HPS and MH
lamps do not transmit all their light toward the target area to be illuminated, resulting in losses within the fixture. The directional XT-E LED
transmits all its light toward the target area, with minimal to no losses within the fixture. As a result of this difference, a lumens-for-lumens
match between an XT-E LED and an HPS or MH lamp is only partially relevant.
Figure 6
Figure 2: Typical metal halide light distribution
Figure 3: Light distribution of typical metal halide streetlight
Figure 4: Typical high-power LED light distribution
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
4
XLamp ® XT-E LED Streetlight Reference Design
The Illuminating Engineering Society (IES) defines both an intensity distribution
classification and a luminaire classification system (LCS) for outdoor luminaires. The
intensity distributions range from Type I, a “narrow, symmetric illuminance pattern,”
to Type VS, a “symmetrical, nearly square illuminance pattern.” The IES defines a
Figure 5: Type III intensity distribution
Type III intensity distribution as a “wide, asymmetric illuminance pattern” with the
“highest intensity between 25° and 35° from nadir,” as shown in Figure 5. This is a
Specifier Bulle
for Da
useful distribution for a streetlight that is to illuminate not only a roadway but also a
pedestrian walkway beside the roadway.
The LCS divides a luminaire or lamp’s lumen distribution into three solid angles, with each angle divided into secondary solid angles. The
amount of light in each secondary solid angle allows luminaires to be compared and evaluated for a particular situation.
volume 2: issue 1 : 2009 — International Dark-Sky As
Figure 6 shows these secondary solid angles.1 Backlight
(B) components indicate light trespass onto adjacent sites,
opposite the area intended to be illuminated. Uplight (U)
components produce artificial sky glow. Glare (G), shown as
forward (F) components in the figure, can impair vision. At a
low level it is merely annoying but at a high level it prevents
clear vision and is a large liability.
Key
BVH
BH
BM
BL
The BUG System—A New Way To C
Light from Outdoor Luminaires
Backlight Very High
UH Uplight High
Backlight High
UL Uplight Low
Backlight Medium
Backlight Low
FVH
FH
FM
FL
Forward Light Very High
Forward Light High
Forward Light Medium
Forward Light Low
Figure 6: LCS solid angles
B
UG stands for “Backlig
describes the types of str
in defining standards for outdoor lighting related to light trespass, sky glow, and glare.2 The MLO uses the backlight, uplight and glare
luminaire. “B” stands for
The MLO
(BUG) classification of outdoor lighting fixtures defined by the IES in The Lighting Handbook Tenth Edition and inthe
IES mounting
TM-15-11.3 pole.
“U” stands
defines limits for the amount of light that should be applied to each of five lighting zones. The lighting zoneshorizontal
are described
inTable
plane
of the3,luminaire
light emitted from the luminaire
excerpted from the MLO.4
It is expected that BUG val
turers so lighting specifiers, desi
well a certain luminaire controls s
under consideration for an instal
1 Joint IDA - IES Model Lighting Ordinance (MLO) with User Guide, June 15, 2011
2Ibid.
The BUG system was develo
3 Luminaire Classification System for Outdoor Luminaires, IES TM-15-11
(IES) to make comparing and e
4 Joint IDA - IES Model Lighting Ordinance (MLO) with User Guide, op. cit.
more complete than older system
Work on the BUG system
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree , XLamp and SC Technology are registered trademarks and the Cree logo
roadway
shielding
s
is a trademark of Cree, Inc. ENERGY STAR is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their
respective classification
owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
the ratings full cutoff, cutoff,
sem
contact Cree Sales at [email protected].
5
as a rating system solely for stree
The IES and the International Dark-Sky Association (IDA) have issued the Model Lighting Ordinance (MLO) to assist local governments
®
®
®
3
®
XLamp ® XT-E LED Streetlight Reference Design
Table 3: MLO-defined lighting zones
Zone
Recommended Uses or Areas
Zoning Considerations
Recommended default zone for wilderness areas, parks and preserves, and
undeveloped rural areas.
LZ-0
Lighting Zone 0 should be applied to areas in which permanent lighting is
not expected and when used, is limited in the amount of lighting and the
period of operation. LZ-0 typically includes undeveloped areas of open space,
wilderness parks and preserves, areas near astronomical observatories, or
any other area where the protection of a dark environment is critical. Special
review should be required for any permanent lighting in this zone. Some rural
communities may choose to adopt LZ-0 for residential areas
Recommended default zone for rural and low density residential areas.
LZ-1
Lighting Zone 1 pertains to areas that desire low ambient lighting levels. These
typically include single and two family residential communities, rural town
centers, business parks, and other commercial or industrial/ storage areas
typically with limited nighttime activity. May also include the developed areas
in parks and other natural settings.
Recommended default zone for light commercial business districts and high
density or mixed use residential districts.
LZ-2
Lighting Zone 2 pertains to areas with moderate ambient lighting levels. These
typically include multifamily residential uses, institutional residential uses,
schools, churches, hospitals, hotels/motels, commercial and/or businesses
areas with evening activities embedded in predominately residential areas,
neighborhood serving recreational and playing fields and/or mixed use
development with a predominance of residential uses. Can be used to
accommodate a district of outdoor sales or industry in an area otherwise
zoned LZ-1.
Recommended default zone for large cities’ business district.
LZ-3
Lighting Zone 3 pertains to areas with moderately high lighting levels. These
typically include commercial corridors, high intensity suburban commercial
areas, town centers, mixed use areas, industrial uses and shipping and rail
yards with high night time activity, high use recreational and playing fields,
regional shopping malls, car dealerships, gas stations, and other nighttime
active exterior retail areas.
Lighting zone 4 pertains to areas of very high ambient lighting levels. LZ-4
should only be used for special cases and is not appropriate for most cities.
LZ-4 may be used for extremely unusual installations such as high density
entertainment districts, and heavy industrial uses.
Not a default zone.
LZ-4
Includes protected wildlife areas and corridors.
Includes residential single or two family; agricultural zone districts; rural
residential zone districts; business parks; open space include preserves in
developed areas.
Includes neighborhood business districts; churches, schools and
neighborhood recreation facilities; and light industrial zoning with modest
nighttime uses or lighting requirements.
Includes business zone districts; commercial mixed use; and heavy industrial
and/or manufacturing zone districts.
Includes high intensity business or industrial zone districts.
The maximum lumen levels for each BUG component are shown in Table 4, Table 5 and Table 6.5
Table 4: Backlight ratings (maximum zone lumens)
Backlight/Trespass
Secondary Solid
Angle
B0
B1
B2
B3
B4
B5
BH
110
500
1,000
2,500
5,000
> 5,000
BM
220
1,000
2,500
5,000
8,500
> 8,500
BL
110
500
1,000
2,500
5,000
> 5,000
U3
U4
U5
Table 5: Uplight ratings (maximum zone lumens)
Secondary Solid
Angle
Uplight/Sky Glow
U0
U1
U2
UH
0
10
50
500
1,000
> 1,000
UL
0
10
50
500
1,000
> 1,000
G4
G5
Table 6: Glare ratings for Type III luminaire (maximum zone lumens)
Secondary Solid
Angle
Glare/Offensive Light
5
G0
G1
G2
G3
FVH
10
100
225
500
750
> 750
BVH
10
100
225
500
750
> 750
FH
660
1,800
5,000
7,500
12,000
> 12,000
BH
110
500
1,000
2,500
5,000
> 5,000
Luminaire Classification System for Outdoor Luminaires, Addendum A. op. cit.
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
6
XLamp ® XT-E LED Streetlight Reference Design
The MLO defines two systems for evaluating outdoor lighting installations. One method prescribes a lumen limit for the site to be
illuminated. The second method prescribes B, U and G values for each lighting zone for various installation parameters. This is to allow
luminaires with different BUG ratings to be evaluated depending on the lighting zone of the area being illuminated. For example, whether
a streetlight is mounted close to or far from the property line determines whether a higher or lower B rating is desirable.
There are currently no ENERGY STAR® requirements for streetlights, however the DesignLights Consortium® provides requirements for
outdoor pole/arm‑mounted luminaires, given in Table 7.6
Table 7: DesignLights Consortium high-bay luminaire requirements
Application
Characteristic
Outdoor Pole/Arm-Mounted Area and Roadway
Luminaires
Outdoor Pole/Arm-Mounted Decorative Luminaires
Minimum light output
1,000 lm
1,000 lm
Zonal lumen density
100%: 0–90°,
< 10%: 80–90°
65%: 0–90°
Minimum luminaire efficacy
70 lm/W
60 lm/W
Allowable CCTs (ANSI C78.377-2008)
≤ 5700 K
≤ 5700 K
Minimum CRI
L70 lumen maintenance
Minimum luminaire warranty
65
65
50,000 hours
50,000 hours
5 years
5 years
2. Define design goals
The design goals for this project are given in Table 8. The luminaire efficacy goal was established to demonstrate the performance of the
XLamp XT-E LED in this application. The power goal was established to reflect the tendency in the industry to offer 120‑W LED streetlights
as replacements for 250‑ to 400‑W HPS and MH streetlights. The lumen output goal is the product of these two goals.
Table 8: Design goals
Characteristic
Unit
Illuminance distribution
Minimum Goal
Target Goal
IES Type III
IES Type III
W
120
< 120
lm/W
90
> 90
Light output
lm
10,800
> 10,800
CCT
K
5700
5700
Power
Luminaire efficacy
CRI
75
> 75
Power factor
0.9
> 0.9
This reference design is not being developed for a specific lighting zone or installation location and we have not established a specific
BUG rating design goal.
3. Estimate efficiencies of the optical, thermal & electrical systems
We used Cree’s Product Characterization Tool (PCT) tool to determine the drive current for the design. For the 10,800‑lm target, we
estimated 90% optical efficiency and 90% driver efficiency. We also estimated a solder‑point temperature (TSP) of 50 °C.
6
Technical Requirements Table v2.0
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
7
XLamp ® XT-E LED Streetlight Reference Design
The PCT output highlighted in Figure 7 shows the options considered for this reference design. For either the R3 or R4 flux code, 56‑70
LED System Comparison Report
XT-E LEDs at 500‑650 mA provide sufficient light output to meet the design goals. In an effort to use the minimum number of LEDs to meet
the design goals, we1used 56 XT-E LEDs operating at 650 mA.
System:
10,800
Target Lumens :
90%
Optical Efficiency:
LED 1
LED 2
Price
SYS lm tot SYS # LED SYS lm/W
0.350
0.400
0.450
0.500
0.550
0.600
0.650
0.700
0.750
0.800
11554.6
11099.5
12250.9
11133.3
12023.7
12881.7
10966.9
11602.1
12217.3
12808.1
Flux
Model
Cree XLamp XT-E {AWT} x14
Current (A)
Model
Tsp (ºC)
R3 [122]
$
98
84
84
70
70
70
56
56
56
56
Electrical Efficien
50
-
103.7
100.6
97.7
95
92.5
90.1
87.9
85.7
83.6
81.7
Flux
SYS W
Tsp (ºC)
R4 [130]
Price
SYS lm tot SYS # LED SYS lm/W
$
111.475
110.342
125.351
117.134
129.961
142.93
124.824
135.392
146.063
156.811
12312.3
11827.3
10878.5
11863.3
12812.1
10981.1
11686
12362.9
13018.5
13648
Model
Cree XLamp XT-E {AWT} x14
98
84
70
70
70
56
56
56
56
56
50
110.4
107.2
104.1
101.3
98.6
96
93.6
91.3
89.1
87
Flux
Price
-
(non
$
SYS W
111.475
110.342
104.459
117.134
129.961
114.344
124.824
135.392
146.063
156.811
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
#N/A
Figure 7: PCT output for number of LEDs and drive current
Design Concept
This streetlight design uses an existing LED streetlight housing and heat sinks. The XT-E streetlight is a modular design in which fourteen
XLamp XT‑E LEDs are mounted on a rectangular heat sink to form a module. The number of modules and the number of LEDs per module
can be adjusted to achieve various light output levels. Secondary optics are used to achieve the desired beam pattern. An o-ring between
the secondary optics and the heat sink provides environmental protection. The driver is located inside the stainless steel streetlight
housing, away from the heat sinks.
Thermal Requirements
Proper thermal management is a key component of any successful LED-based lamp or luminaire design. As with most LED-based luminaire
designs, this streetlight design requires a heat sink to dissipate the thermal load. The heat sink in this design, shown in Figure 8, is made
of extruded aluminum, machined on one side with a flat surface for good thermal contact with a custom metal ‑core printed circuit board
(MCPCB). A groove near the edge of the flat surface permits the installation of a silicone o-ring. The o-ring provides environmental sealing
and prevents the LEDs from coming in contact with contaminants.
Figure 8: XT-E streetlight heat sink
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
8
#N/
#N/
#N/
#N/
#N/
#N/
#N/
#N/
#N/
#N/
XLamp ® XT-E LED Streetlight Reference Design
This prototype streetlight design incorporates not only the heat sinks, but also the streetlight housing into the heat dissipation path. This
helps to maximize the thermal transfer to the ambient environment. In addition, the streetlight housing has vents in both the top and
bottom that allow airflow past the heat sinks. The heat sinks are located apart from each other in the housing to allow air to flow between
them. Such vents would probably not be present in the top of a production streetlight. One alternative is to design the top of the housing
to allow airflow while providing protection from debris.
Cree performed thermal simulation to verify the thermal performance of this design. Figure 9 shows a thermal simulation of a cross
section of a module at steady state in a 25 °C ambient operating environment. The simulated solder‑point temperature was 46 °C.
Figure 9: XT-E streetlight module thermal simulation
Secondary Optics
To meet the Type III beam pattern requirement, we worked with LEDLink Optics Inc. to develop a custom secondary optic for this design.
Shown in Figure 10, the optic for each individual LED is 90% efficient. Fourteen individual optics were molded into an rectangular optic
module that is attached to the heat sink. The optic module positions the optics in a 7 X 2 pattern and locates each optic above an LED.
Figure 10: 2 views of XT-E streetlight optic
Figure 11: XT-E streetlight optic module
Drive Electronics
For this streetlight design, Cree chose a constant‑current, universal‑input‑voltage driver, shown in Figure 12. The driver has an ingress
protection (IP) rating of IP65. The driver is located within the streetlight housing away from the heat sinks.
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
9
XLamp ® XT-E LED Streetlight Reference Design
Figure 12: XT-E streetlight driver
4. Calculate the number of LEDs
The PCT output showed that 56 XLamp XT-E LEDs can provide sufficient light output to meet the design goals. We selected a Cool White
LED for this reference design, shown highlighted in yellow in Table 9, to give the best efficacy while still meeting the DLC requirements.
The directionality of the XT-E LED source, with a 125° beam spread, directs more flux toward the fixture opening than the spherical
illuminance profile of an HPS or MH lamp. By choosing an LED from a mid-level flux bin, we ensured that the design uses LEDs that are
readily available.
Table 9: XT-E LED order codes
XLamp XT-E LED Standard Kit Codes - White
Chromaticity
Kit
CCT
Minimum Luminous
Flux (lm) @ 350 mA*
Order Codes
Code
Flux (lm)
No Minimum CRI
70 CRI Minimum
80 CRI Minimum
R5
139
XTEAWT-00-0000-000000H51
XTEAWT-00-0000-00000BH51
R4
130
XTEAWT-00-0000-000000G51
XTEAWT-00-0000-00000BG51
R3
122
XTEAWT-00-0000-000000F51
XTEAWT-00-0000-00000BF51
R2
114
R5
139
XTEAWT-00-0000-000000H53
XTEAWT-00-0000-00000BH53
R4
130
XTEAWT-00-0000-000000G53
XTEAWT-00-0000-00000BG53
R3
122
XTEAWT-00-0000-000000F53
XTEAWT-00-0000-00000BF53
R2
114
R5
139
XTEAWT-00-0000-000000H50
XTEAWT-00-0000-00000BH50
R4
130
XTEAWT-00-0000-000000G50
XTEAWT-00-0000-00000BG50
XTEAWT-00-0000-00000HG50
R3
122
XTEAWT-00-0000-000000F50
XTEAWT-00-0000-00000BF50
XTEAWT-00-0000-00000HF50
R2
114
ANSI Cool White (5000 K – 8300 K)
51
53
50
6200 K
6000 K
6200 K
XTEAWT-00-0000-00000HG51
XTEAWT-00-0000-00000HF51
XTEAWT-00-0000-00000HE51
XTEAWT-00-0000-00000HG53
XTEAWT-00-0000-00000HF53
XTEAWT-00-0000-00000HE53
XTEAWT-00-0000-00000HE50
5. Consider all design possibilities
As can be seen in the numerous LED streetlight projects world-wide, there are an almost limitless number of ways to design an LED-based
streetlight. This reference design shows one way to design an excellent streetlight based on XLamp XT-E LEDs. Contemporary, traditional
and decorative streetlight designs are possible.
6. Complete the final steps: implementation and analysis
This section illustrates the techniques Cree used to create a prototype streetlight using the Cree XLamp XT-E LED and reviews the optical
and electrical results.
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
10
XLamp ® XT-E LED Streetlight Reference Design
Prototyping Details
The essence of this prototype design is to assemble four LED modules, each with fourteen XLamp XT-E LEDs, and assemble the modules
with the driver to create an LED-based streetlight with a Type III beam pattern. The prototyping steps are detailed below.
1. We verified the component dimensions to ensure a correct fit.
2. Following the XLamp XT LED family recommendations,7 we reflow soldered fourteen XT-E LEDs onto each MCPCB, connected in
series, with an appropriate solder paste and reflow profile.
3. We cleaned the flux residue with isopropyl alcohol.
4. We applied a thin layer of thermal conductive compound to the back of the MCPCB and secured the MCPCB to the heat sink with
screws. Consult Cree’s Chemical Compatibility Application Note for compounds safe for use with XLamp LEDs.
5. We fed the driver DC output wires through the through-hole in each heat sink and soldered them to the terminal pads on the MCPCB.
Figure 13 shows a module after this step. The four modules are connected in parallel.
Figure 13: LEDs and MCPCB attached to heat sink
6. We tested the connections by applying power to the LEDs and verified they illuminated.
7. Because of a streetlight’s outdoor operating environment, the LEDs could be exposed to substances that are harmful. To prevent this,
we installed a silicone o-ring in a groove in each heat sink. This prevents contaminants from entering between the LED MCPCB and
the optic module. As with the thermal conductive compound, the silicone o-ring is compatible for use with XLamp LEDs.
8. We positioned an optic module on each heat sink and secured it with screws, as shown in Figure 14.
7
Cree XLamp XT LED Family LEDs Soldering and Handling Application Note
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
11
XLamp ® XT-E LED Streetlight Reference Design
Figure 14: LED module attached to heat sink
9. We attached the modules to the housing with screws.
10. We attached the driver to the housing with screws.
11. We closed the housing and secured it with the clips provided.
12. We performed final testing.
Results
Thermal Results
To verify the thermal dissipation performance of the heat sink, we used a thermocouple to measure a steady‑state solder‑point temperature
of 46 °C. This thermal performance exactly matches the thermal simulation.
Based on the measured solder‑point temperature, the junction temperature (TJ) can be calculated as follows.
TJ = TSP + (LED power * LED thermal resistance)
TJ = 46 °C + (1.95 W)/ * 5 °C/W)
TJ = 56 °C
Estimated LED Lifetime
We used the Environmental Protection Agency (EPA) TM-21 Calculator to determine the calculated and reported lifetimes for the XLamp
XT-E LED at a 1-A input current and a 46 °C case temperature. The duration of Cree’s XT-E LM-80 data set is 6,048 hours at 55 °C, 85 °C
and 105 °C. The TM-21 methodology limits the projection to six times the duration of the LM-80 data set.
With a reported L70(6k) lifetime greater than 36,000 hours and a calculated L70(6k) lifetime of 2,518,000 hours for the XT-E LED, we
expect the XT-E streetlight, with each LED operating at 650 mA, to easily exceed an L70 lifetime of 50,000 hours.
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
12
XLamp ® XT-E LED Streetlight Reference Design
Optical Results
We obtained the results in Table 10 and following by testing the prototype streetlight at steady state after a 60-minute stabilization time.8
The streetlight provides the desired IES Type III illuminance distribution very efficiently. The wide chromaticity range provided by the
XLamp XT-E LED enables differing local municipality requirements to be met by making the correct XT-E LED binning selection.
Table 10: XT-E streetlight steady-state results
Characteristic
Unit
Illuminance distribution
Power
Luminaire efficacy
Result
IES Type III
W
119
lm/W
97
Light output
lm
11,541
CCT
K
5700
CRI
80
Power factor
0.97
The goniometric polar plot in Figure 15 shows a consistent beam shape and IES Type III light distribution for the XT-E streetlight.
Figure 15: Goniometric polar plot of XT-E streetlight (units - maximum candelas)
We used DIALux software to simulate the illumination produced by the XT-E streetlight in a roadway installation.9 Figure 16 shows the
mounting position of the streetlights in the simulation. The legend shows the various dimensions for the mounting position. The simulated
distance between streetlights was thirty meters. Figure 17 shows the simulation roadway dimensions.
8
9
Testing was performed using a 1.5‑meter integrating sphere and a Type A goniophotometer at Cree’s Shanghai Technology Center. An IES file for the streetlight is
available.
DIALux 4.9, DIAL GmbH
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
13
XLamp ® XT-E LED Streetlight Reference Design
21.00 m
Legend
(1) 10.0 m
(2) 1.3 m
(3) 0°
(4) 1.5 m
0.00
0.00
Figure 16: XT-E streetlight simulation mounting position
30.00 m
Figure 17: XT-E streetlight simulation roadway dimensions
Figure 18 shows the simulated illumination of a stretch of roadway illuminated by twelve XT-E streetlights, six on each side of the roadway,
directly across from each other.
Legend
Color
fc
lx
0
0
0.35
3.75
0.70
7.5
1.05
11.25
1.39
15
1.74
18.75
2.09
22.5
2.44
26.25
2.79
30
Figure 18: DIALux simulation of XT-E streetlight
The American National Standard Practice for Roadway Lighting10 recommends several methods for evaluating roadway lighting. The
illuminance method evaluates the amount of light reaching the roadway surface and makes recommendations based on the type and
surface of the roadway and the amount of pedestrian traffic. Table 11 shows the illuminance method recommendations and XT-E streetlight
results related to the illuminance method. The recommended values are for an expressway composed of dark asphalt paving having high
pedestrian traffic. The uniformity ratio measures the evenness of the roadway illumination by comparing the average illumination value
to the minimum value. The veiling luminance ratio indicates glare that inhibits drivers’ visibility. The recommendation for both ratios is a
maximum allowed value.
10 American National Standard Practice for Roadway Lighting, ANSI/IESNA RP-8-2000
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
14
XLamp ® XT-E LED Streetlight Reference Design
Table 11: XT-E streetlight evaluation by illuminance method
Minimum
Illuminance
Uniformity Ratio
Eavg/Emin
Veiling Luminance Ratio
Lvmax/Lavg
RP-8-2000 recommendation
14 lx
3.0
0.3
XT-E streetlight result
20 lx
1.7
0.1
The luminance method evaluates how “bright” a road is by determining the amount of light reflected from the pavement in the direction
of a driver and makes recommendations based on the type and surface of the roadway and the amount of pedestrian traffic. Table 12
shows the luminance method recommendations and XT-E streetlight results related to the illuminance method. The recommended values
are for an expressway composed of dark asphalt paving having high pedestrian traffic. The uniformity ratio measures the evenness of the
roadway lamination by comparing the average lumination value to the minimum value. The recommendation for both ratios is a maximum
allowed value.
Table 12: XT-E streetlight evaluation by luminance method
Minimum Average
Luminance
Uniformity Ratio
Lavg/Lmin
Veiling Luminance Ratio
Lvmax/Lavg
RP-8-2000 recommendation
1.0 cd/m2
3.0
0.3
XT-E streetlight result
1.2 cd/m
1.5
0.1
2
The XT-E streetlight results, calculated as part of the DIALux simulation, show that the XT-E streetlight betters the recommended values
for both the illuminance and luminance methods.
The LCS graph in Figure 19 and the LCS values in Table 13 show how the XT-E streetlight achieves its B2-U3-G2 BUG rating.
Table 13: XT-E streetlight LCS values
Lumens
% Lumens
BL
LCS Zone
(0°-30°)
723.7
6.7
BM
(30°-60°)
1353.4
12.5
BH
(60°-80°)
616.0
5.7
BVH
(80°-90°)
39.0
0.4
UL
(90°-100°)
58.7
0.5
UH
(100°-180°)
110.7
1.0
FL
(0°-30°)
1080.0
10.0
FM
(30°-60°)
4123.2
38.2
FH
(60°-80°)
2445.5
22.7
FVH
(80°-90°)
245.4
2.3
Figure 19: XT-E streetlight LCS graph
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
15
XLamp ® XT-E LED Streetlight Reference Design
The appropriateness of any streetlight in a particular installation depends on the streetlight position within the lighting zone of the
application and the streetlight mounting height. As in any lighting application, a luminaire that is perfect in one installation can be less
than satisfactory in another. We recognize that there are situations that require a streetlight to produce no sky glow, i.e., a BUG rating
Uplight (U) value equal to zero. To achieve a U0 value with the prototype XT-E streetlight, the top of the housing could be modified to
include shielding that prevents light from being emitted upward while maintaining the streetlight’s thermal performance.
Conclusions
This reference design demonstrates integrating the Cree XLamp XT-E LED into a streetlight to replace traditional HPS and CH fixtures.
Compared to 250‑ to 400‑W HPS and MH streetlights, this prototype streetlight offers longer lifetime, and therefore lower maintenance
costs, while using 50% to 70% less energy. Though a CRI value as high as this streetlight’s value of 80 is not required in all situations,
the XLamp XT-E LED enables this when it is required or advantageous. This design shows the level of performance that can be achieved
by combining the XLamp XT-E LED with appropriate optics to produce a desired illuminance distribution. Certainly optical control is
important in a streetlight design and where light is not can be nearly as important as where light is, but a streetlight that does not
sufficiently illuminate the site in which it is installed is of little use. This reference design shows that the XLamp XT-E LED enables a
streetlight that very usefully illuminates the roadway, walkway or parking lot in which it is located.
Special thanks
Cree would like to acknowledge and thank LedLink Optics Inc. for their assistance in creating the secondary optics and optic module for
this prototype streetlight.
Bill of materials
Table 14: Bill of materials for XT-E streetlight
Component
Order Code/Model Number
Company
Web Link
Driver
HLG-120H-48A
Mean Well USA, Inc.
www.meanwellusa.com
LED
XTEAWT-00-0000-00000HF53
Cree, Inc.
XT-E product page
Optics
LL14CR-AOC65150202
LedLink Optics Inc.
www.ledlink-optics.com
Thermal epoxy
Silver Ice 710NS
Timtronics
www.timtronics.com/electricallyconductive.htm
Reliance on any of the information provided in this Application Note is at the user’s sole risk. Cree and its affiliates make no warranties or representations about, nor assume any
liability with respect to, the information in this document or any LED-based lamp or luminaire made in accordance with this reference design, including without limitation that
the lamps or luminaires will not infringe the intellectual property rights of Cree or a third party. Luminaire manufacturers who base product designs in whole or part on any Cree
Application Note or Reference Design are solely responsible for the compliance of their products with all applicable laws and industry requirements.
Copyright © 2013-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree®, XLamp® and SC3 Technology® are registered trademarks and the Cree logo
is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product, and company names are the property of their respective owners
and do not imply specific product and/or vendor endorsement, sponsorship or association. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please
contact Cree Sales at [email protected].
16