Digest Outdoor May2012

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


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.


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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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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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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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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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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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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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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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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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13/32

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14/32LEDsMagazine :: EDITORIAL DIGEST

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


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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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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7


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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8


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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9


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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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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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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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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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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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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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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27/32LEDsMagazine :: EDITORIAL DIGEST

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

28


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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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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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

Documents

Digest Outdoor May2012