Evaluating Roadway Lighting Systems Using Unit Power · PPT file · Web...

Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056

EvaluatingEvaluatingRoadway Lighting Roadway Lighting

SystemsSystemsUsingUsing

Unit Power DensityUnit Power DensityBy

David M. Keith

Street and Area Lighting Committee Conference 2001


What is Unit Power What is Unit Power Density?Density?

• Unit Power Density (UPD) is

the energy for lighting

-------------------------------- divided by

the area of the roadway

• units: Watts / square foot or Watts / square meter

(W/ft2) (W/m2)


UPD CalculationUPD Calculation• UPD =

#Luminaire * (1.15*Watts/luminaire) -----------------------------------------------------(LumCycle * #Lanes * Width of each lane)

• #Luminaire = 2 for staggered arrangement• 1.15 factor to match previous work in

IESNA publication LEM-6-1987• LumCycle is twice the “spacing” for staggered


Why use Unit Power Why use Unit Power Density?Density?

• more appropriate than using spacing– spacing definition differs with layout– spacing is inversely proportional while UPD

is directly proportional– includes ballast losses, reflects

technological opportunities– more universal, useful for different

comparisons



• more appropriate than using money– UPD is a less complex, more stable

evaluation – focuses on the lighting system

• does not reflect specific utility costs• does not reflect “the cost of money”

– UPD is less specific, more generally useful to public



• applies to roadway lighting systems (not luminaires!)

• corresponds to relative costs in– energy & pollution– installation & equipment– operation & maintenance

• evaluation of relative performance and savings through comparisons

• less valid comparing different wattages or sources• does not address: aesthetics, light trespass, and

many other important lighting issues


What are the components What are the components of a of a

Roadway Lighting Roadway Lighting System?System?

• “Roadway Lighting System” includes:– luminaire and lamp (source and wattage) – roadway dimensions and surface– geometry of layout, height & overhang

(setback)– operation and maintenance characteristics– design criteria


Why Roadway Lighting Why Roadway Lighting Systems?Systems?

• overall performance reflects trade-offs– wattage, mounting height, overhang &

spacing– maintenance program– cutoff classifications– source types– design methods

• value in comparisons of related cases– directly proportional changes– some comparisons are more valid than others


Why Roadway Lighting Why Roadway Lighting Systems?Systems?

• NOT limited to evaluating a luminaire's physical or photometric characteristics– shape or materials– photometric distributions or cutoff categories

• allows comparative evaluation of– luminaire and lamp – geometry of layout, height & overhang (setback)– operation and maintenance characteristics– design criteria


Design CriteriaDesign Criteria• ANSI/IESNA RP-8-00

American National Standard Practice forRoadway Lighting

• Revised in 2000• three separate design methods

– Illuminance– Luminance– Small Target Visibility (STV)


Design Methods: Design Methods: IlluminanceIlluminance

• Illuminance method– classical - 1928– lighting system alone

• lamp, luminaire and photometry• system geometry

– one uniformity criterion: average to minimum• no constraint on Emax

– now includes veiling luminance criterion• constrains Lvmax, from luminance calculation


Design Methods: Design Methods: LuminanceLuminance

• Luminance method – recent - 1983– roadway and lighting system interaction

• lamp, luminaire and photometry• system geometry• roadway surface

– two uniformity criteria• average to minimum, maximum to minimum

– ”moving observer” & glare calculations


Design Methods: STVDesign Methods: STV• Small Target Visibility method (STV)

– brand new in 2000 document– unfamiliar and complex metric VL

• uses luminance, both horizontal and vertical• contrast weighted over entire roadway• veiling luminance included

– extension of luminance calculations– radically different design techniques

• not suitable for optimization


Roadway Lighting CriteriaRoadway Lighting Criteria Classifications Eavg Eavg / Lavg Lavg / Lmax /

Lveil /Roadway Area R3 Emin Lmin Lmin Lavg

(lux) (cd/m2) Major Med 13.0 3.0 0.90 3.00 5.0 0.3 Collector Med 9.0 4.0 0.60 3.50 6.0 0.4 Local Med 7.0 6.0 0.50 6.00 10.0 0.4Source: ANSI/IESNA RP-8-00

• All system calculations meet entire set(s) of criteria – averages, uniformities & glare


SourcesSources• high pressure sodium (HPS) or metal halide (MH)• difference in Light Loss Factor (LLF) - at end of life!

– probably have one or two luminaires contributing to point– 0.7 for HPS– 0.5 for MH– “both should be even lower”

• difference in lamp life and in maintenance• does represent pulse start MH (vertical lamps)

– better rated lumens but same LLF (mean @ 40% of life)


Lamp and Luminaire DataLamp and Luminaire DataLamp Wattage Rated Lumens Input Watts

LLF HPS 150 16,000 166 0.70

250 27,500 295 0.70 400 50,000 460 0.70

MHP 175 17,500 210 0.50

250 21,500 295 0.50 400 44,000 455 0.50


Cutoff ClassificationsCutoff Classifications• relative to lamp lumen rating• combination of intensity limits in two

separate zones– both just below and anywhere above horizontal

FC CO SC


Photometric FilesPhotometric FilesLamp Wattage All FC CO SC NC

HPS 150 67 17 21 14 15 250 70 30 19 14 7 400 97 28 36 21 12 All 234 32% 32% 21% 15%

MH 175 59 25 6 15 13 250 47 27 4 9 7 400 47 20 16 4 7 All 153 47% 17% 18% 18%

All 387 38% 26% 20% 16%


Roadway and Lamp Roadway and Lamp WattageWattage

Roadway Class

--------------------------------------------------------------Width Lanes Local Collector Major (m) 4 1 150/175 & 250 150/175, 250 & 400

250 & 400 7 2 150/175 & 250 150/175, 250 & 400

250 & 400 10 3 150/175, 250 & 400 250 & 400 13 4 250 & 400 17 5 250 & 400 20 6 250 & 400


OptimizationOptimization• For each combination of

“photometry & roadway”– Find the geometry with max. luminaire

cycle– Over a range of mounting heights and

over a range of setbacks/overhangs– Meeting entire set of appropriate criteria– Result is “best” for combination – but may

be impractical (too high or out over road)


UPD vs Avg Luminance:UPD vs Avg Luminance:Collector 2 Lanes 250W Collector 2 Lanes 250W

HPSHPS

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.4 0.6 0.8 1.0 1.2

Average Pavement Luminance (cd/m 2)

Uni

t Pow

er D

ensi

ty (W

/m2 )

FCCOSCNC


Comparing Cutoff Comparing Cutoff ClassificationsClassifications

• for 250W HPS, photometric file distribution is Lamp Wattage All FC CO SC NCHPS 250 70 30 19 14 743% 27% 20% 10%

• Best (lowest) UPD values mostly SC or NC– in “Best 5”, all SC or NC– in “Best 10”, one is CO and all others SC or NC– best FC is tied for 13th best UPD value



MHPMHP

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.4 0.6 0.8 1.0 1.2


Uni

t Pow

er D

ensi

ty (W

/m2 )

FCCOSCNC


Comparing Cutoff Comparing Cutoff ClassificationsClassifications

• for 250W MH, photometric file distribution is Lamp Wattage All FC CO SC NCMH 250 47 27 4 9 757% 9% 19% 15%

• Best (lowest) UPD values mostly SC or NC– in “Best 5”, all SC or NC– in “Best 10”, one is FC, others all SC or NC– best FC is 9th best UPD value



HPSHPS

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.4 0.6 0.8 1.0 1.2


Uni

t Pow

er D

ensi

ty (W

/m2 )

FCCOSCNC



MHPMHP

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.4 0.6 0.8 1.0 1.2


Uni

t Pow

er D

ensi

ty (W

/m2 )

FCCOSCNC


Comparing Sources: HPS Comparing Sources: HPS vs MHPvs MHP

UPD (W/m2) #Averaged HPS MHP %Incr

to MHP

Best 1 0.56 0.8551%Best 3 0.57 0.8650%Best 5 0.58 0.8650%Best 10 0.59 0.9154%


Comparing Design Comparing Design MethodsMethods

• Base calculations meet criteria for BOTHilluminance and luminance methods– this is the most conservative approach

• recalculate for meeting criteria of eitherilluminance method OR luminance method– different criteria, same optimization procedure

• compare each luminaire’s performance undereach single method to Base (BOTH methods)


UPD by Design Method:UPD by Design Method:Collector 2 Lanes 250W Collector 2 Lanes 250W

HPSHPS

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

S C S S N S S S S C C S N N C S F S C C N N C C F F F F F F F F F

Uni

t Pow

er D

ensi

ty (W

/m2 )

BothIllumLumin


Comparing Design Comparing Design Methods: HPSMethods: HPS

UPD (W/m2)#Avgd Base Illum Lum %Decr

to Lum

Best 1 0.56 0.56 0.40 -29%Best 3 0.57 0.57 0.41 -28%Best 5 0.58 0.57 0.43 -24%Best 10 0.59 0.59 0.46 -23%


UPD by Design Method:UPD by Design Method:Collector 2 Lanes 250W Collector 2 Lanes 250W

MHMH

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

S S N N N N S S N F N N F S S F F F F S F F F C F C C C

Uni

t Pow

er D

ensi

ty (W

/m2 )

BothIllumLumin


Comparing Design Comparing Design Methods: MHMethods: MH

UPD (W/m2)#Avgd Base Illum Lum %Decr

to Lum

Best 1 0.85 0.85 0.46 -46%Best 3 0.86 0.86 0.55 -36%Best 5 0.86 0.86 0.60 -31%Best 10 0.91 0.89 0.66 -27%


Comparing Lamp OutputComparing Lamp Output• corresponds to the product of:

– Light Loss Factor (dependent on maintenance)– Rated Lumens (dependent on lamp technology)

• for one lane roads with HPS luminaires, makeseparate calculations for LLF of 0.50 or 0.70– 40% LLF increase ~ 16% UPD decrease (3:1)

• for all MH, replace standard with Pulse-Start– each 2% lumen increase ~ 1% UPD decrease

(2:1)


Comparing Overhang Comparing Overhang LimitsLimits

• overhang may be restricted by utility or jurisdiction (it’s a maintenance safety issue)

• recalculate all 250W HPS and MHP for overhang <= zero (Oh<=0)– allow setbacks, but no luminaires over roadway

• typically no effect or increase UPD up to 15%– may change which files have lowest UPD values

• increase greater for wider roadways


What are the What are the characteristics of acharacteristics of aRoadway Lighting Roadway Lighting

System?System?• “Roadway Lighting System” includes:– luminaire and lamp (source and wattage) – roadway dimensions and surface– geometry of layout, height & overhang

(setback)– operation and maintenance characteristics– design criteria– uplight (like skyglow but more specific

to lighting)


What is Unit Uplight What is Unit Uplight Density?Density?

• Unit Uplight Density (UUD) is

the uplight from lighting

-------------------------------- divided by

the area of the roadway

• units: lumens / square foot or lumens / square meter

(lms/ft2) (lms/m2)


UUD CalculationUUD Calculation• UUD =

Uplight + ReflfromRoad + ReflfromOffRoad ---------------------------------------------------------(LumCycle * #Lanes * Width of each lane)

• Uplight: all “up lumens” (2 luminaires for staggered)

• ReflfromRoad: 0.07 * lumens onto the roadway• ReflfromOffRoad: 0.18 * “down lumens” not on road


Comparing UplightComparing Uplight• with the “best six” luminaires

– from 400W MHP on 4 lane Major road– two FC, two CO and two NC– all have full spherical photometric data

• evaluate Unit Power Density (UPD) and Unit Uplight Density (UUD) for each luminaire– does more cutoff correspond to less uplight?– does system efficiency (UPD) correspond to

uplight?


UPD vs Avg Luminance:UPD vs Avg Luminance:Major 4 Lanes 400W Major 4 Lanes 400W

MHPMHP

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.4 0.6 0.8 1.0 1.2


Uni

t Pow

er D

ensi

ty (W

/m2 )

FCCOSCNC


Comparing UPD and UUDComparing UPD and UUD Base UPD Base UUD(W/m2) (lms/m2)

FC 0.78 3.8FC 0.78 4.9CO 0.73 5.2CO 0.74 4.2NC 0.74 4.0NC 0.73 3.9


Comparing UplightComparing Uplight• with the “best six” luminaires• evaluate UPD and UUD for each luminaire• revise conditions

– for overhang <= 0 (luminaire not over roadway)– for Luminance design method– for Small Target Visibility (STV) design method

• compare trends and UPD-UUD relationship across different conditions


Comparing Uplight: UPDComparing Uplight: UPD

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

FC FC CO CO NC NC

Uni

t Pow

er D

ensi

ty (W

/m2)

Oh <=0BaseLumSTV


Comparing Uplight: UUDComparing Uplight: UUD

0.0

1.0

2.0

3.0

4.0

5.0

6.0

FC FC CO CO NC NC

Uni

t Upl

ight

Den

sity

(lum

ens/

m2)

Oh <=0BaseLumSTV


Comparing UplightComparing Uplight• more stringent cutoff (FC or CO) does not

necessarily correspond to less uplight• as UPD increases, UUD increases• as UPD decreases, UUD decreases• changes in UUD are nearly (but not

always) proportional to changes in UPD• more efficient lighting system (lower

UPD) does correspond to less uplight


Summary of UPD Summary of UPD ComparisonsComparisons

• deltaUPD corresponds strongly to deltaUUD• deltaUPD is ~ 1/2 to 1/3 of deltaLampOutput• UPD drops up to 25% for Luminance method• UPD drops up to 35% for STV method• systems with lowest UPD values typically

have distributions with less stringent cutoff– When full cutoff distributions are

required,what is the increase in UPD?


% Increase (any Wattage) % Increase (any Wattage) in Base UPD for “Full in Base UPD for “Full

Cutoff Required”Cutoff Required”Road Local Collector Major#Lanes 1L 2L 1L 2L 3L 1L 2L

3L

HPSBest 5 20% 17% 15% 17% 18% 12% 14% 15% Best 10 30% 28% 27% 28% 18% 17% 18% 16%

MHBest 5 19% 19% 18% 22% 20% 13% 14% 12%Best 10 21% 22% 20% 22% 24% 16% 15% 13%


% Increase in UPD for Full % Increase in UPD for Full CutoffCutoff

0%

10%

20%

30%

40%

50%

60%

70%

150L1

150L2

150C1

150C2

150C3

250L1

250L2

250C1

250C2

250C3

250M1

250M2

250M3

250M4

250M5

250M6

400C1

400C2

400C3

400M1

400M2

400M3

400M4

400M5

400M6

Wattage, Roadway and #Lanes

Perc

ent I

ncre

ase

in U

PD

from

"A

llow

Any

Cut

off"

to "

Req

uire

Ful

l Cut

off"

HPS Base MHP Base HPS Oh<=0 MHP Oh<=0 HPS Lumin MH Lumin


Conclusions of UPD Conclusions of UPD EvaluationsEvaluations

• There is a substantial potential for reductions in equipment, costs, energy use & uplight which correspond to lower Unit Power Density values for roadway lighting systems.

• Comparing systems can lead to results which may be counterintuitive (FC ~ less efficiency).

• The best use of this work may be for comparisons with specific UPD values developed from proposed roadway lighting systems with similar characteristics.


EvaluatingEvaluatingRoadway Lighting Roadway Lighting

SystemsSystemsUsingUsing

Unit Power Density Unit Power Density By David M. Keith

for a copy of this presentation:resodance.com/mdi/SALC2001.html

for questions or more information:[email protected]

Date post:	15-Mar-2018
Category:	Documents
Upload:	dothuy
View:	215 times
Download:	3 times

Evaluating Roadway Lighting Systems Using Unit Power · PPT file · Web...

Documents