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7/31/2019 Digest Outdoor May2012
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sponsored by:
editorial digest
s :sv w
Outdoor street and area lighting remains the
hottest segment o the LED lighting industry
as solid-state lighting (SSL) provides incredible
energy savings in applications where lights
burn throughout the night. Moreover
adaptive-control technology can be combined
with inherently-controllable LED sources to
compound energy savings via dimming and
powering lights o when not needed. LEDs
urther oer better light quality than HID
sources and eliminate light pollution. Fully
understand the outdoor lighting segment by
investigating control technologies, evaluating
deployment strategies, and considering the
delicate balance between sae lighting levels
and minimal energy usage.
2 Seattle condctsLED street ligttesting and osts
smposim
14LEDs eadline atSALC, speakerspredict signifcant
efcienc gains
27 Raleig LED ligtinprojects demonstrdrabilit and
savings
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2
LEDs Magazine :: EDITORIAL DIGEST
Seattle conducts LED street light
testing and hosts symposium
Outdoor lighting experts gathered in Seattle, WA or
a ull-day symposium on LED street light technology
ollowed by a three-night demonstration and test session
ocused on determining sae roadway lighting levels.
by MAuRy WRIGhT
in seattle, Wa, the Virginia Tech
Transportation Institute (VTTI) and
lighting consultancy Clanton &
Associates recently led a LED street
light symposium and conducted three
nights o solid-state lighting (SSL) roadway
tests ocused on the balance o dimming
lights and saety. The symposium included
lessons learned rom LED lighting case
studies, a review o previous VTTI tests o
light levels and sae object/pedestrian detection
distances, and an explanation o the goals o the Seattle
testing. Participants in the testing program provided
both qualitative and quantitative data to the projectteam that will build on a growing knowledge base
ocused on energy eciency and saety.
The Northwest Energy Eciency Alliance (NEEA) hosted the symposium and
test session, and Continuum Industries helped organize the tests. The actual
demonstration and tests took place in Seattles Ballard neighborhood on the
nights o March 6-8, 2012 along a closed stretch o 15th Ave. The Seattle City Light
Fig. 1. The BUG classifcation
system is now used in luminairespecifcation.
100
90
80
60
60
30
0
G
G
U
B
B - Backlight/trespass
U - Uplight/skyglow
G - Glare/offensive light
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Seattle conducts LED street light testing and hosts symposium
LEDs Magazine :: EDITORIAL DIGEST
utility assisted in the site selection and arranging or the road closure.
The symposium kicked o with a brie presentation rom Mark Rehley, emerging
technology operations manager at NEEA. Rehley said that the goal o the Seattle
test was to help establish national and regional standards that dictate Whats the
right amount o light to put on the roadway.
The issue o course is that lower light levels equate to less energy used and thats
important even in the case o inherently-ecient LED lighting. We think that
SSL alone is not the answer, said Rehley.
The biggest value comes when you
combine [SSL] with advanced controls.The advanced controls provide the value
o being able to turn the lights on and o
at very precise periods instead o relying
on a photo sensor that gets dirty and
perhaps ails more readily than the SSL.
Rehley also discussed the added
implications o smart street lights
making the analogy o having a
smartphone and apps on light poles. He suggested that networked street lights
in the uture will strobe to guide emergency workers to an accident. And he said
such lights could indicate detour routes in the case o a
natural disaster.
Qu cv wm
Nancy Clanton, president o Clanton & Associates, took the podium to start the
technical presentations and immediately issued a challenge to the audience. Aboutstreet lighting she asked, Are we doing it the right way? And specically she was
reerring to deploying street lights with LEDs as a revolutionary light source.
We take this LED light and stick it on a pole because thats how we have
always done street lighting. said Clanton. LEDs are great at grazing. Maybe we
should have more layered lighting like we do in interior design with an ambient
and a task.
Fig. 2. Street lights that light the sidewalk but
not the building adjacent to the sidewalk may
be ideal.
7/31/2019 Digest Outdoor May2012
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Seattle conducts LED street light testing and hosts symposium
LEDs Magazine :: EDITORIAL DIGEST
Clanton suggested that just
putting light down on a
road isnt sucient. She said
eective lighting requires
contrast o suraces along
with the ability to optimize
color contrast. Indeed she
was oreshadowing some
o the concepts that VTTI
is researching through LED
street light tests.
Clanton certainly doesnt
ignore more commonly
discussed attributes o LED
sources including inherent eciency, compatibility with dimming controls to
urther increase eciency, and the ability to eectively control beam patterns.
Dimming lights when trac is reduced late at night is part o the eciency
equation. Clanton suggested that we need a nighttime level that is more subdued
and just bright enough so that a driver knows a pedestrian is crossing the road.
Clanton, however, explored a more subtle concept with controllable LED lighting
that could have a big impact in slashing power usage. She said that in the case o
legacy sources such as high-pressure sodium (HPS) lamps, there is little chance
to select the light level needed or an application. I a 150W HPS lamp alls just
short o meeting the requisite level or a given application, the only recourse has
always been to go to a 250W lamp. But with LEDs you can step up to the brighter
source but dim it down to where it just meets the required level and pocket the
energy savings.
bm bUg
Control o the beam pattern both saves energy by eciently using the produced
light and eliminating light pollution. Clanton was very involved in developing
the Model Lighting Ordinance (MLO) thats being recommended or area lighting,
and has been involved with ways to speciy beam control or roadway lighting
working with the Illuminating Engineering Society o North America (IESNA).
Fig. 3. Philips Lumec Roadstar luminaires in a prior installation.
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Seattle conducts LED street light testing and hosts symposium
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LEDs Magazine :: EDITORIAL DIGEST
Clanton described the new backlight, uplight, and glare (BUG) approach to
dening beam control or luminaires (Fig. 1). Specically, lighting standards can
set maximum ratings or uplight or light pollution, glare that might adversely
impact a driver, or backlight that might trespass on the side o a building or into
someones second
story window. The
light levels are
specied based on
the angles shown in
the gure.
Ironically, perhaps,Clanton said that
some LED xtures
control light too
rigidly. She is a dark
sky advocate and
was not suggesting
any tolerance or
light pollution. But
she said many people
preer a uzzy cuto.
Fig. 2 provides an example o the concept. Clanton dened the example as well-
designed lighting because it does illuminate the sidewalk although it only allows
backlight on the base o the building. That perormance is superior according to
Clanton to either a light that only illuminates the street, or one that casts a lot o
backlight on the building.
s led A presentation o several LED street light case studies was among the most
inormation-packed elements o the symposium. Edward Smalley presented
Seattles experience to date with LEDs. Smalley works or Seattle City Light,
although he has spent the bulk o his time in the past two years on his duties
as director o the US Department o Energy (DOE) Municipal Solid-State Street
Lighting Consortium. But Smalley led Seattles oray into LEDs.
Fig. 4. Street lights with an asymmetrical beam pattern let periodic
dark areas on the roadway.
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Seattle conducts LED street light testing and hosts symposium
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LEDs Magazine :: EDITORIAL DIGEST
Smalley said Seattle City Light is the 10th largest municipally-owned utility in
the US and has an inventory o around 84,000 street lights. In 2008 when they
started experimenting with LEDs, the annual energy cost or street lights was $5.3
million. Including maintenance and other expenses such as debt service, the total
cost was $11.5 million. And Smalley said they aced a 17% rate hike in 2009.
The cost issues led the city to consider LEDs, and a chie concern was cost o the
luminaires. Smalley said he
was asked in 2008, What
will it take or Seattle to pull
the trigger on LED street
lights? implying a majordeployment. Smalley said
at the time the luminaire
they were considering or
residential streets was
selling or more than $400.
He said $350 was their target
trigger point.
Fast orward to today, and
Seattle has converted somewhere between 18,000 and 21,000 lights they have
products in inventory to reach the higher number. They have realized $1 million
per year in savings. The expenditures to date are in the $8 million range. Smalley
said the projected payback is 7.6 years.
The economic picture gets even brighter looking orward. Smalley said that Seattle
is paying around $240 per luminaire today. He said, Prices are going to drop and
thats a good thing. He attributed the expected declines to the semiconductorindustry that is behind both LED components and the driver electronics. Smalley
projects that the price will ultimately bottom out in the $175 range.
C s led xc
The experience o Colorado Springs, CO with LEDs is at a much earlier level
than Seattle, but the lessons learned there may be equally valuable. City trac
engineer David Krauth described the dilemma the city aced three years ago with
Fig. 5. The HPS lights on the right create signifcant light trespass on
the buildings while the LED lights on the let only light the sidewalk.
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LEDs Magazine :: EDITORIAL DIGEST
municipal budget cuts and the cost o operating street lights. Krauth said, Our
answer was were going to turn o one third o the lights.
Ultimately the city did turn o 3500 lights on hand-picked arterial roads out o a
total inventory o 25,805 lights. They continued to operate all lights in residential
areas. Krauth said that the process o evaluating the arterial streets revealed that
the city was lit extremely inconsistently and in many cases was wasting energy
on lights that were too bright.
Krauth said when he started work or the city, 400W HPS lights were common
on arterials and that the city also had a number o high-mast lights that had six
1000W lamps per pole. He said turning three poles o saved $16,000 per year.
Krauth detailed some o the common issues with over-lighting a city. He said One
bright spot begats a bigger bright spot. Ater people go through an over-lit area,
Krauth said a correctly-lit area appears to be under lit. That inconsistency can
lead a municipality to brighter and brighter lights.
In Colorado Springs ater the selected lights were extinguished, Krauth said the
city received over 1000 complaint calls. But the complaints werent just about sae
lighting on streets. Krauth said, Its amazing the number o people that want
their backyards lit by street lights, and the number o people that dont. That was
a recurring theme at the symposium in that some citizens like light spill onto
their property. It led Frauth to rhetorically ask, How do you run a system that
does both?
The city has installed around 500 LED street lights including a mix o cobrahead-
and acorn-style xtures. But the city is struggling with consistency even with the
LED lights. Krauth said that in the case o the acorn xtures, the city maintainedthe same pole spacing that it has used with HPS lights, but the LEDs are brighter.
He said, We have one street that goes into the airport that Im amazed an
airplane hasnt landed on it yet. It is bright. Krauth is planning a new set o
consistent standards developed rom the ground up.
Ultimately the move to LEDs is ocused on operating cost. Krauth said the city
wants to make sure we can pay or the system and keep operating it. He did point
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Seattle conducts LED street light testing and hosts symposium
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LEDs Magazine :: EDITORIAL DIGEST
out a surprising place where SSL is adding to the savings. He said the city had 450
lights incapacitated by copper wire thet totaling almost a quarter million eet o
wire. He said lower-power LED xtures do allow or smaller, lower-cost wire.
b
At the end o the symposium, the bulk o the attendees made their way to the
test site in the Ballard area, where some brie presentations (www.ledsmagazine.
com/news/9/3/4), including one by Seattle mayor Mike McGinn, were ollowed
by a walking tour o the test site. The symposium attendees went through the
qualitative lighting evaluation process just as public volunteers would over the
course o three nights.
The evaluation was based
on a survey orm that had to
be completed or each o the
six roadway segments that
had dierent lights installed.
As documented in the above
link, one segment was lit by
the 400W HPS legacy lights
or the roadway, a second
segment was lit by 250W HPS
lights, and LED lights lit our
segments. All o the LED-lit
segments used 105W Philips
Lumec Roadstar luminaires
(Fig. 3). Three o the segments
used standard Type II
beam patterns with the dierence being correlated color temperature (CCT) 3500K, 4000K, and 5000K (see, www.ledsmagazine.com/eatures/7/9/8 or more
inormation about beam pattern).
The nal segment used a custom asymmetrical beam pattern that directed all light
in the direction o trac with no glare in evidence or drivers (Fig. 4). The roadway is
three lanes in each direction with a center turn lane. The lights or the southbound
lanes only projected light south, and vice versa or the northbound lanes.
Fig. 6. A data acquisition system in the VTTI test vehicle links to
cameras, sensors, a GPS receiver, and the pushbuttons used by
testers.
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LEDs Magazine :: EDITORIAL DIGEST
The survey was primarily based on 12 statements or which the respondents had
to choose among ve choices ranging rom strongly disagree to strongly agree.
Examples include there is too much light on the street, the light sources are
glaring, and I like the color o the light. There are also numerous questions
involving how sae a respondent eels walking in the area. Down the road, we will
see those results tabulated.
evu
Here, I will summarize my own observations o the lighting. Upon rst
impression, the 400W HPS sources provided ar better pedestrian visibility than
any o the other lights tested. But without question that test area was over lit.
Consider Fig. 5. Those side-by side images are o completely dierent buildingsyet you can easily see the dierences in backlight. In the HPS example on the
right, there is substantial light on the wall and window on the second foor o
the house on the ar right. In the image on the let with LED lighting there is
virtually no light cast on the walls o the one-story building, yet you can see that
the sidewalk is lit.
While the 400W HPS sources produced what seem to be more than plentiul light,
the lights did not render colors well. Watching other participants in the walking
tour with various colors o clothing, you could see how color contrast might come
into play allowing better object detection even at lower light levels.
I was very surprised that I couldnt really discern the dierences in CCT with
the three sets o LEDs that used a standard beam pattern. Those three lights
generated uniorm light levels on the roadway and sidewalk, and also rendered
colors very well.
The road segment with an asymmetric pattern was immediately recognizable.You could see that the light on the roadway got dimmer arther rom the pole.
And there was no light rom the next pole helping to ll in and make the light
level appear uniorm. Essentially you could see periodic dark sections on the road.
Ultimately, that may or may not be a problem, as it could enable superior contrast
thats among the reasons the team chose to test the asymmetric xture.
We were also aorded the opportunity to view the LED lights dimmed to 50%
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LEDs Magazine :: EDITORIAL DIGEST
and 25% o ull light output. One o the project team members used an iPad to
change the light levels o individual luminaires and groups o luminaires. While
you could see the dimming happening by ocusing on the light projected on the
road, it was dicult to discern any dierence in visibility once the luminaires
were stable at 50%. There was noticeably less light at 25%, although Im not sure I
would have elt unsae walking in that light.
Quv
Ultimately its the quantitative testing that will determine how well drivers might
see objects or pedestrians under the lights including tests conducted at the 25%
and 50% dim levels or the LEDs. We wont see that data or several month. But I
did have a chance to participate in one o the tests.
VTTI equipped an SUV with a data acquisition system used or the tests (Fig.
6). That system links to a number o light sensors, cameras, a GPS receiver or
precise location, and a push button that test subjects use to signal when they
spot an object. The VTTI team located 7x7-in objects o various colors along the
test site. And VTTI drivers navigated the roadway at a constant 35 MPH while test
subjects looked or the objects and responded with the push button with the GPS
logging the location o each depression o the button.
I really cant pass judgment as to whether I saw objects more easily under one
light type or another. Its simply too much eort to concentrate on looking or the
objects and trying to know which light type you are under. What I do know, and a
ellow tester agreed, is that you regularly spot some objects that are urther away
beore you spot one that is nearer. That could be due to object color or perhaps
the light at any given spot.
I asked Ron Gibbons o VTTI how the system accurately detected an instanceo two button pushes when the test subject may have seen the urther object
rst. Gibbons said the orward-looking mono and binocular cameras mounted in
the SUV mimic the human visual system and would see the objects in similar
order to testers. Evidently the system uses that camera data to correlate the data
generated by the volunteers.
What will come out o the test is likely to be similar to the results we have
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Seattle conducts LED street light testing and hosts symposium
2
LEDs Magazine :: EDITORIAL DIGEST
seen rom Gibbons and his team beore. Gibbons uses the reerence source and
compares the other test sources in terms o object detection distance. In prior
tests, or example, LEDs have provided detection distance 66-78% as great as the
reerence source while generating only 9-18% o the illuminance, and o course
the LEDs use ar less energy.
During the symposium, Gibbons said, Lighting level has very little to do with
detection. Gibbons said the human body responds to sensory things like lighting
on a logarithmic scale. He added, Foot candles are meaningless. Its all about
detection distance.
We will cover the results once released and the nding will surely be interesting.Gibbons said in similar previous tests, the team had not been able to reduce the
light level o the LEDs low enough to render the tested lights unsuitable in terms
o detection distance. We will see i the 25% level in Seattle does so, and what
impact the asymmetric pattern may have had on detection distance.
MAuRy WRIGhT is Editor-in-Chie with LEDs Magazine.
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4
LEDs headline at SALC,
speakers predict signifcantefciency gains
SSL technology dominated both the sessions and exhibits
at the annual Street & Area Lighting Conerence,
reports MAURY WRIGHT, and LED-based lighting
that is already succeeding based on efcacy will
soon deliver signifcant additional power savings.
by MAuRy WRIGhT
the annUal ies (Illuminating Engineering Society) Street & Area
Lighting Conerence (SALC) took place Sept 19-21 in New Orleans, LA
and the rst speaker, Entergy Services business systems manager
Bob Olsonoski, said Were not
against LEDs. We just dont know what
to do with them. We dont know how to
price them yet. Olsonoski likely elt like
the Lone Ranger through the remainder
o the event because LEDs were central
to virtually every other presentation,
and dominated the exhibit hall. Despitehigher upront costs, LED-based solid-
state lighting (SSL) is winning in outdoor
applications based on energy eciency
and the inherent controllability o the
technology. The prevailing theme o the
conerence was that energy savings will escalate signicantly through more
ecient LEDs, better lighting that can be operated at lower levels, and standards
Exhibit hall at SALC (courtesy o the Illuminating
Engineering Society o North America; Bob Horner,
photographer).
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LEDs headline at SALC, speakers predict signifcant efciency gains
5
LEDs Magazine :: EDITORIAL DIGEST
and technologies that minimize over-lighting.
The IES limits the exhibit area to 50 booths and around ten companies took
dual booths so there were even ewer companies displaying products. One booth
included induction street lights and one had high-pressure sodium (HPS) street
lights. More than 20 eatured LED street and area lights. Even exhibitors such as
Philips Lighting, Osram
Sylvania, Acuity, and
Cooper that sell legacy
lighting products only
exhibited SSL.
Why the ocus on
SSL? Edward Smalley,
the director o the US
Department o Energy
(DOE) Municipal Solid-
State Street Lighting
Consortium (MSSLC) and
the manager o street
light engineering at
Seattle City Light, pinpointed the reason. Smalley showed a graph rom the DOEs
latest SSL Multi-Year Program Plan (MYPP) that charts luminous ecacy against
time or various light sources (Fig. 1). While ecacy is slowly increasing or HID
and fuorescent sources and has been or 70 years, SSL (both LED and OLED) is on
a steep ramp.
Today HPS and low-pressure sodium (LPS) sources are still more ecient than SSL.
But that advantage wont last long. Moreover, adaptive controls and dimming candeliver energy savings or SSL relative to HPS and LPS sources. And as well discuss
shortly, broad-spectrum LED light is simply a better match or the physiology o the
eye than are HPS and LPS sources. These were all prevailing themes at SALC.
O course SSL still has to overcome steep upront cost, although that premium
is certainly dropping rapidly. John Curran, president o LED Transormations,
presented a graphic that precisely describes the LED value proposition (Fig. 2). Its
FIG. 1. LED system efcacy is on a steep ramp (courtesy o US
DOE).
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LEDs headline at SALC, speakers predict signifcant efciency gains
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LEDs Magazine :: EDITORIAL DIGEST
the combination o long
lie and energy eciency
that provides the LED
value proposition.
imv led uc
Mark McClear, global
director o applications
engineering at Cree,
discussed the state-
o-the-art in LED
components and thenear-term outlook or
improvements. Cool-
white LEDs at 6000K
CCT (correlated color
temperature) are readily available with an ecacy o 160 lm/W. McClear said that
a luminaire design typically suers a 10% loss due to thermal issues, a 10% loss
due to optics such as lenses, and a 15% loss due to driver eciency. So cool-white
luminaire system ecacy is a bit over 100 lm/W.
At the other end o the LED CCT spectrum, 2700K warm-white LED ecacy is 115
lm/W, resulting in a system ecacy o around 75 lm/W. McClear said, I really
like the 4300K and 4100K LEDs. At 4100K system ecacy is 93 lm/W and that
CCT is preerable or many people relative to the 6000K LEDs that have more
blue energy in the spectral distribution. McClear said the cooler temperatures
work better rom an economic perspective because you can use ewer LEDs in a
luminaire design.
McClear and others including the DOE expect a continued increase in ecacy.
McClear pointed out that the rst DOE MYPP projected an ecacy plateau at
around 150 lm/W. That plateau has been moved to 250 lm/W in the latest MYPP
update issued earlier this year.
McClear said that LED luminaire ecacy has improved rom 50 to 90 lm/W,
at maximum drive current, over the last six years (Fig. 3). He projected system
FIG. 2. Long lie and energy savings justiy SSL deployments
(courtesy o LED Transormations).
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LEDs headline at SALC, speakers predict signifcant efciency gains
7
LEDs Magazine :: EDITORIAL DIGEST
ecacy or sources in the 4100K CCT range to hit 120 lm/W within the next two
to three years. He added, LEDs will be the most ecient light source available.
Its also noteworthy to mention that prices are dropping at the same time that
LED components are improving and volumes are increasing a recurring trend
in the semiconductor industry. McClear said, The semiconductor industry has
always been a massive solution looking or a problem. The message is that the
same juggernaut that delivered cheap PCs and cell phones will drive lighting
going orward, and the escalation in LED manuacturing has begun. McClear said
that more MOCVD (metal-organic chemical vapor deposition) reactors, used or
epitaxial growth in LED manuacturing, have been installed in the past two years
than existed previously.
The act is that LED cost has already diminished signicantly in terms o the
bill-o-materials (BOM) cost in luminaires. According to McClear, LED cost
accounted or around 70% o the BOM in 2008 and has dropped typically toaround 25%. The driver is now the biggest part o the BOM, but McClear said,
The driver community is now just as engaged [in SSL] as the LED community.
And the drivers are largely comprised o semiconductors so prices should drop as
eciencies increase.
CCt -cum
While McClear had noted the economic advantages o cooler CCTs, other speakers
FIG. 3. LED luminaires drop in price while efcacy improves (courtesy o Cree).
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LEDs Magazine :: EDITORIAL DIGEST
described the benets o white light with a broad spectral distribution typical
o todays LED sources. Ron Gibbons o the Virginia Tech Transportation Institute,
said, White broad-spectrum light may provide equivalent task perormance at
lower illuminances than a less-broad source. Gibbons presented a graph that
depicted the luminosity unction o the human eye both or bright photopic and
dark scotopic conditions. And he showed the energy peak o a LPS light that alls
almost completely outside the spectrum o scotopic response by the eye at night.
Across CCTs that range rom 3500K to 5000K Gibbons showed that LED sources
have signicant spectral content in both the photopic and scotopic bands.
Gibbons said, The physiology o the eye lends itsel to broad-spectrum sources.
The ultimate goal o Gibbons research is to determine whether white light sources
can be operated at lower levels than have been conventionally required, and still
provide driver and pedestrian saety. Indeed many people believe the world issignicantly over-lit and reducing light levels would provide direct energy savings.
O course there are both scientic and emotional challenges to white-light in
general and a move to lower levels. Many people including several questioners in
the SALC audience insist that driving under yellow- and orange-tinted HPS and
LPS lights is more relaxing than driving under white lights. Gibbons, however,
insisted that every study conducted nds that people like white light better
FIG. 4. LEDs oer superior lumen maintenance (courtesy o Kauman Consulting).
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LEDs headline at SALC, speakers predict signifcant efciency gains
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LEDs Magazine :: EDITORIAL DIGEST
although they may not realize it until going through a controlled experiment.
Gibbons also said that white lights render colors
better. And color contrast is important in enabling
the eye to detect objects, especially in the peripheral
vision, he said.
lv c
Gibbons and Rick Kauman, o Kauman Consulting
and the chairman o the IES committee working
on the latest update to the ANSI RP-8 standard or
roadway lighting, both discussed how the research onlower light levels will be applied in the near term. The
RP-8 update due imminently will allow or lower light
levels in some cases in mesopic conditions (relatively
low light levels where the eye combines photopic and
scotopic response).
The new standard will speciy calculations called
Eective Luminance Factor (ELF) and Eective
Luminance Multiplier (ELM) that rely on photopic
and scotopic luminance values: these are presented
in a table relative to various light sources. The math
is beyond our scope here, but Kauman presented
a relatively simple example in a case where a light
source has a scotopic to photopic ratio o 2 and photopic luminance o 0.3 cd/m2.
In such a case the required minimum light level could be reduced by 16.6%.
There is a caveat to the change to RP-8. For now the standard prescribes that thelower light levels can only be used on streets where the speed limit is 25 mph or
less. At such speeds, drivers dont even need street lights according to Gibbons
because the headlights illuminate a distance greater than the stopping distance
o the car. Street lights in such cases are primarily intended or pedestrian saety.
Gibbons has begun another research project that will determine i lower light
levels are also sae at higher speeds.
Rick Kauman o Kauman
Consulting (courtesy o
Illuminating Engineering Society
o North America; Bob Horner,
photographer).
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LEDs headline at SALC, speakers predict signifcant efciency gains
20
LEDs Magazine :: EDITORIAL DIGEST
Mm v-
In addition to discussing the ability to reduce light levels, Kauman addressed
the larger issue o over-lighting and wasting energy. We routinely install lights
that operate at higher light levels than necessary to compensate or light loss.
Lighting speciers typically calculate a light-loss actor (LLF) when planning a
project. The calculation can be quite complicated, said Kauman, and includes
accounting or thermal issues, driver or ballast issues, and even ambient
temperature at an
installation. But
primary actors are
lumen depreciation
and luminairedepreciation caused
by dirt.
The RP-8 standard
includes a graph or
dirt depreciation
actors. For very
clean environments
the actor can be as
high as 0.9 over 8
years. In very dirty
areas the actor can be in the 0.8 to 0.9 range or one year but as low as 0.3 over
8 years. Kauman described DOE tests that have measured dirt depreciation o
3.7% to 5.3% per year but said more testing is needed.
Lumen depreciation is a well-known phenomenon and has been documented or
a number o light sources. Ironically many have questioned LED perormanceover time, but LEDs actually provide superior lumen maintenance to most other
sources with only HPS matching SSL. The graph in Fig. 4 depicts the typical
advantage LEDs oer in terms o uniormity over time.
The specier will oten utilize a lumen depreciation actor o 0.7 or LEDs
essentially tied to the widely-accepted denition o the L70 LED lietime that
describes how long a light will maintain 70% o the initial lumen output. Multiply
FIG. 5. Constant light output eliminates over-lighting (courtesy o PhilipsRoadway Lighting).
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LEDs Magazine :: EDITORIAL DIGEST
lumen depreciation o 0.7 by dirt depreciation o 0.9 and you get 0.63 as the
LLF. This is used to de-rate lumen output. A 100-lm source would be used in an
application requiring 63 lm.
LEDs, however, oer our best chance yet o minimizing over-lighting. Some
companies are designing luminaires that slowly increase drive current over time
in a way that matches the projected
lumen depreciation curve. And it turns
out that L70 may not be the right lumen-
depreciation actor with LEDs getting
better and the new IES TM-21 standard
available to project LED lie.
C uu
David Baum, director o sales and
marketing at Philips Roadway Lighting,
addressed constant light output relative
to the companys Fortimo linear LED
module. Baum compared the Fortimo
light with a legacy source and a typical
LED source (Fig. 5). The legacy light
provides signicantly too much light
each time it is relamped over time. The legacy LED source provides too much light
initially and gradually degrades over time.
The Fortimo design gradually increases drive current over time thereby
maintaining the target lumen output although that also means the power
consumption gradually increases as well. Baum showed an example where
luminaire system power increased rom 26W to 31W over 50,000 hours. But hesaid a conventional source with comparable light output would require 38W.
In the case o TM-21, meanwhile, a solution to reduce over-lighting may be an
unintended consequence. TM-21 was in the works or a long time as we covered
in a eature earlier this year. The idea behind the standard was development o a
mathematical model that allows accurate projection o LED lietime. LEDs rarely
ail over time but rather degrade to the point o being ineective. That led to
Ron Gibbons, Virginia Tech Transportation
Institute (courtesy o Illuminating Engineering
Society o North America; Bob Horner,photographer).
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LEDs Magazine :: EDITORIAL DIGEST
concepts such as L70 lie. TM-21
provides a way to take the reams
o data that are produced in LM-
80 LED component testing and
produce projections across a range
o scenarios.
The details o TM-21 are beyond
our scope here, but lets examine
the basics. TM-21 utilizes data
rom a 5000-hour window o LM-
80 testing. I a particular LEDmodel has been tested or the
requisite 6000-hour minimum
required by LM-80, then TM-21
uses data collected rom the 1000-
hour mark orward. I an LED has been tested or 10,000 hours, then TM-21 data
uses data collected rom the 5000-hour mark orward.
tM-21 v-
TM-21 results are reported in hours alongside a descriptor in the orm Lxx(Yk)
where Lxx is the level o lumen maintenance and Y is the number o hours tested.
A rating described by L70(10k) would iner that the LED would maintain 70% o
its initial light output and was based on 10,000 hours o LM-80 testing. The TM-21
methodology delivers two results, one called calculated and one called reported.
The ormer is the calculated output o the TM-21 math. The latter is limited to the
lesser o the calculated lie or 6 times the number o LM-80 test hours. An LED
tested or the 6,000 hour minimum can have no greater reported lie spec than
36,000 hours.
You can calculate TM-21 results or any lumen maintenance value you desire.
For example, Crees McClear showed an actual example where an L70(10k) test
included a calculated lie o 290,000 hours. And while TM-21 will be broadly used
to project lie, heres how it comes into play in reducing over-lighting. The example
McClear showed also included a L80(10k) calculated lie o 186,000 hours and a
L90(10k) calculated lie o 94,200 hours. McClears point is that maybe we should
TABLE 1. Light levels are allowed to drop by hal as
pedestrian activity wanes at night.
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LEDs Magazine :: EDITORIAL DIGEST
use 0.9 as a lumen-depreciation, lie-loss actor rather than 0.7. McClear said
LEDs are unshackled rom L70 and the result can be additional energy savings.
O course the LEDs are only one part o the SSL system-lie puzzle. For example,
McClear mentioned things like gaskets and paint that may not last 100,000 hours
and o course the driver is an issue. Philips Baum said quality drivers have a
maximum lie o 100,000 hours. But he said that driver lie declines rapidly when
case temperatures exceed 65C.
av c mm
Not surprisingly, adaptive controls and dimming was a popular topic at SALC
since dimming lights during periods o low activity can compound energysavings. And LEDs are dimmable to a ne level o granularity with commensurate
energy savings whereas other light sources lack that attribute. The talks included
the need or standards, ongoing eld trials, and activity on controls within the
DOE MSSLC.
Lets start with the MSSLC, which launched a control task orce about one year
ago. Tod Rosinbum rom the city o Portland is a member o the task orce
and described a wish list that is being molded into a model specication that
municipalities and communities can utilize in speciying control systems. The
document will be very similar in concept to the Model Luminaires Specication
that the MSSLC released in drat orm earlier this year and that is due or nal
release imminently. The controls specication will be released in beta orm later
this year or review and a nal version is due next year.
Rosinbum said on/o, dimming, and scheduled-based control are widely desired
by consortium members. The members also want diagnostic capabilities, energy
measurement or billing purposes, and automation o the work-order process orrepairs. He also said that the membership is universal in wanting to own and
control the data in-house. The most complete controls solution on the market
today, by contrast, is the Acuity Roam system in which ees or maintaining the
system and managing the data are part o the Acuity business model.
Michael Poplawski, another controls task-orce member rom the Pacic
Northwest National Laboratory (PNNL), addressed some obstacles and lamented
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LEDs Magazine :: EDITORIAL DIGEST
the lack o network standards that can be used in a wireless network. He noted
that Zigbee is a possibility but as we covered last year, Zigbee doesnt include
the denition o a complete protocol stack or a layer specic to the lighting
application. Poplawski also noted that work needs to be done to ensure that
dierent luminaires operate similarly when dimmed. He showed a graph o the
perormance o three luminaires that revealed noticeable dierences in light level
and power consumption when set to the same level by a 0-10V controller. But he
said that operation could be normalized with standardization.
rw cfc
Laura Stuchinsky heads the controls task orce and is also managing a pilot
controls project in San Jose, CA where she serves as the sustainability ocer inthe citys Department o Transportation. San Jose has been a leader in trialing
control technology and dimming. Indeed the citys work has been seminal in
pushing the concept o reclassiying roads at night so that light levels can be
reduced. Table 1 shows an example where light-level is reduced by as much as
hal later at night when there is little pedestrian activity.
San Jose had previously worked with Pacic Gas & Electric (PG&E) to negotiate
a lower xed tari or LED lighting. The city subsequently asked or even lower
rates based on operating the lights at reduced levels during portions o the night.
PG&E didnt oer to lower the rate now but agreed to participate in a 3-year pilot
program.
The utility mandated that the luminaires include a power meter with 2%
accuracy. Moreover PG&E has insisted that the metering include the power
consumption o the control electronics not just street-light power. San Jose must
also monitor the power used by the wireless gateway that connects to a group
o lights. San Joses work is being used as a guideline in the development o theMSSLC controls specication.
The combination o controls and baseline LED eciency appear to be the right
match or broad deployment o SSL. And there are more savings coming through
better LEDs. There is also more potential or savings in system design. Earlier
this year, Tom Geist o the Electric Power Research Institute (EPRI) contributed
an article to our publication on LED street-light eld trials, and at SALC presented
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LEDs Magazine :: EDITORIAL DIGEST
some additional data. Geist said EPRI has documented energy savings in the
range o 25-70% in dierent trial installations. But he added that there is other
low-hanging ruit in terms o savings. He said driver-eciency improvements,
temperature compensation in xtures, and better quality control by xture
manuacturers could deliver more than 10% in additional savings.
Also its important to realize that LEDs are being held to a higher standard. A
couple o times during Q&A sessions at SALC audience members asked why there
is no standard such as LM-79 with which legacy lighting must comply. Smalley o
the MSSLC said, We are asking more out o LEDs than we ever have o HID.
MAuRy WRIGhT is Editor-in-Chie with LEDs Magazine.
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27
Raleigh LED lighting
projects demonstratedurability and savings
Beginning in 2007, Raleigh, North Carolina, was among
the frst cities to install LED-based lighting, and has
demonstrated energy and maintenance savings over along term with better-than-expected lumen maintenance.
by MAuRy WRIGhT
in leds Magazine, we write about LED-based lighting installations, and
projected energy and maintenance savings, every week, but its unusual to
have a case study in which solid-state
lighting (SSL) has been installed or
years. Raleigh, North Carolina completed
its rst outdoor SSL project in 2007, and
positive results, including excellent lumen-
maintenance perormance, continue to
accumulate. Moreover, Raleighs lengthy
experience also illustrates the pace o
progress in outdoor LED technology. The
citys earliest projects delivered goodresults while the latest projects show even
better results in terms o light quality,
energy savings, and payback.
Raleigh began talking with Cree about
LED projects back in 2006, according to Assistant City Manager Daniel Howe. The
discussion began with Crees VP o corporate marketing Greg Merritt about Cree
LED lights in the Carolina Pines park in
Raleigh, NC, survived a recent tornado.
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Raleigh LED lighting projects demonstrate durability and savings
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LEDs Magazine :: EDITORIAL DIGEST
The middle deck in a Raleigh municipal parking garage was the citys
frst LED project.
participating in a civic artwork project that had an LED-lighting element. Those
discussions led to a plan to jointly install and test LED lighting on a much broader
scale, and ultimately resulted in the launch o the Cree LED City program in
early 2007 (www.ledsmagazine.com/news/4/2/2). Subsequently the DOE assumed
guidance o the LED City program (www.ledsmagazine.com/news/7/9/30) but
Raleigh remains the standard bearer or LED lighting.
t led c
According to Howe, Raleigh has undertaken 30-35 individual SSL projects. In
aggregate, Howe says the city is saving $225,000 per year on its LED projects,
$175,000 o which is in energy savings. Mayor Charles Meeker has been a major
LED proponent. In a recent state-o-the-city address, he said, Our real challengenow is to take some
o these pilot projects
such as LED street
lights and make them
everyday applications.
The city has
undertaken both
indoor and outdoor
LED projects. Indoor
examples include
general and accent
lighting in the citys
perorming arts
center, and lighting
in the mayors oce.
However, there are ar more examples o outdoor lighting. The city has used SSLin parking garages, to illuminate streets, parks and reeway underpasses, and
as lighting or pedestrian bridges. LED up-lights and bollards have been used as
landscape lighting. And the city used LEDs in an architectural application to light
its convention center aade (www.ledsmagazine.com/news/5/8/27).
Raleighs rst major LED project was in a municipal parking deck and was
completed just prior to the launch o the LED City program. The city used
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Raleigh LED lighting projects demonstrate durability and savings
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LEDs Magazine :: EDITORIAL DIGEST
luminaires developed by Lighting Science Group. A total o 144 70-watt LED
xtures replaced existing 188W high-pressure-sodium (HPS) xtures.
ru m f jc
The energy and maintenance savings o the rst project have been well
documented over our years at this point. The city installed the LED lights on a
dedicated circuit so that it could precisely measure power usage. In energy and
maintenance, the LEDs have saved the city more than $13,000 per year.
Ater the initial installation, Raleigh also commissioned an independent public
saety and security
consultant toevaluate the lighting
perormance, and
a market-research
rm to study public
perception o the
lights. The city
published positive
results rom both
in a report that is
still available on its
website (http://1.usa.
gov/jkS3R5). Howe
remembers being
surprised when the public study revealed that the people said it was brighter and
saer even though the lights cast 11% ewer lumens.
The real benet now, however, o a project that has been lit or our years isthe opportunity to evaluate lumen-maintenance perormance. All light sources
degrade over time. But some naysayers have been especially critical o LED
lumen maintenance and how ast SSL products would degrade to L70 (70% o
initial light output) essentially the equivalent o a ailed lamp. LED proponents
oten champion an expected lietime in the 15-year range but realizing such
expectancy requires LED technology with a slow rate o decrease in light output.
LED lighting in the Raleigh convention-center parking structure.
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Raleigh LED lighting projects demonstrate durability and savings
0
LEDs Magazine :: EDITORIAL DIGEST
led jc
As with most LED projects, Raleigh projected the parking-garage light installation
energy savings and payback period based on luminaire specications including
lumen maintenance
and typical operating
scenarios. The city
e