Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056 Evaluating Evaluating Roadway Lighting Roadway Lighting Systems Systems Using Using Unit Power Density Unit Power Density By David M. Keith Street and Area Lighting Committee Conference 2001
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Evaluating Roadway Lighting Systems Using Unit Power · PPT file · Web viewEvaluating Roadway Lighting Systems Using Unit Power Density By David M. Keith Street and Area Lighting
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Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
• 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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
UPD vs Avg Luminance:UPD vs Avg Luminance:Collector 2 Lanes 250W Collector 2 Lanes 250W
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
Average Pavement Luminance (cd/m 2)
Uni
t Pow
er D
ensi
ty (W
/m2 )
FCCOSCNC
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
• 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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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)
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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)
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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?
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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
Average Pavement Luminance (cd/m 2)
Uni
t Pow
er D
ensi
ty (W
/m2 )
FCCOSCNC
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
Comparing UPD and UUDComparing UPD and UUD Base UPD Base UUD(W/m2) (lms/m2)
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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?
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
% Increase (any Wattage) % Increase (any Wattage) in Base UPD for “Full in Base UPD for “Full
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
% 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
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056
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.
Marshall Design, Inc. 1534 Marshall Road Boulder, CO 80305 303-499-2056