7/28/2019 Street Lighting 2011_kauffman
1/36
Calculating Light Loss Factors
for LED Street Lighting Systems
Rick Kauffman
Kauffman Consulting, LLC
7/28/2019 Street Lighting 2011_kauffman
2/36
Contents
Why worry about LLF?Factors Affecting Light Loss
Discussion of Major FactorsRecommended ProcedureMinimum RequirementsReferences
Q&A
2
7/28/2019 Street Lighting 2011_kauffman
3/36
Global Deaths Caused by Injuries for 2008
3Source: World Health Organization
7/28/2019 Street Lighting 2011_kauffman
4/36
4
7/28/2019 Street Lighting 2011_kauffman
5/36
5
Red is highest number
Blue is lowest number
Vehicle occupant deaths 1987-2003, FARS
7/28/2019 Street Lighting 2011_kauffman
6/36
6
Red is highest number
Blue is lowest number
Pedestrian deaths 1987-2003, FARS
7/28/2019 Street Lighting 2011_kauffman
7/36
Why use LLF?
Luminaires age, and unlike fine wine they dont getbetter with time
RP-8 & AASHTO specify Minimum Maintained Averagelighting levels
SafetySecurity
Commercial interestsCommunity pride
7
7/28/2019 Street Lighting 2011_kauffman
8/36
Factors Affecting LLF in SSL LuminairesLLF = LLD x LDD x LATF x HE x VF x BF x LCD
Maintenance Factors Equipment Factors
Lamp (Source) lumendepreciation LLD
Luminaire dirt depreciation LDD
System burnout or failureChanges in local conditions
Luminaire ambienttemperature effects LATF
Luminaire heat extraction -- HEVoltage (Power, Transients) -- VFBallast (PSU) & Lamp (LED)
Factors -- BFLuminaire component
depreciation -- LCD
8
7/28/2019 Street Lighting 2011_kauffman
9/36
Lumen Maintenance of Common Light Sources
9
SOURCE HPS PSMH CMH INDUCTION
RATED LIFE
(HRS)24,000
15,000-
20,000
15,000-
20,000100,000
LUMEN
MAINTENANCE75-80% 40-59% 70% 60%
MORTALITYRATE
35% 55% 50% 40%
7/28/2019 Street Lighting 2011_kauffman
10/36
LED Lumen Depreciation - LLDLumen Maintenance is a function of
Tj and Ta within the LED package.
L70 is commonly used to definethe useful life of an LED system,use LLD= 0.7, OR
Define useful system life and
determine LLD.
10
LM-80 & TM-21 data relate tothe LED package only but areuseful.
7/28/2019 Street Lighting 2011_kauffman
11/36
11
7/28/2019 Street Lighting 2011_kauffman
12/36
12
LM-80 Results for Cree XP-G
Note: TM-21 only projects life to 6x test period or 60,000
hours max., anything past that is based on trust.
7/28/2019 Street Lighting 2011_kauffman
13/36
13
Lumen Maintenance Methods
1. Define system life, calculate Lxx based on test
data
2. Use manufacturers recommended data
3. Use L70 as default at rated life
7/28/2019 Street Lighting 2011_kauffman
14/36
Luminaire Dirt Depreciation - LDD
14
7/28/2019 Street Lighting 2011_kauffman
15/36
Luminaire CleaningGet recommended cleaning procedures from luminaire
manufacturers to get them to like new condition.Evaluate location types as to degree of depreciation.
i.e. residential, commercial, industrial, construction, etc.Perform an economic analysis by type of location todetermine optimum cleaning frequency.
Establish cleaning schedules by location based onconditions and economic analysis.
Do periodic audits to verify the procedure is working.Caution: LED luminaires with exposed secondary optics
will experience light distribution pattern changes as theyget dirty, and may require special cleaning.
15
7/28/2019 Street Lighting 2011_kauffman
16/36
LDD Field Determination
Remove existing luminaire in retrofit area of knownlength of service since last cleaning. Test, clean,
and re-test to establish % LDD.Testing can be performed by a lab or by using a
homemade black box and light meter to establishrelative difference.
16
7/28/2019 Street Lighting 2011_kauffman
17/36
Changes in Local Conditions
Pavement condition and future street pavingConstruction
Trees and vegetationChanges in adjacent land useAtmospheric conditions, smog index, etc.
17
7/28/2019 Street Lighting 2011_kauffman
18/36
LDD ~ 3-5% per year over 1-2 year period. More studies
needed. Only 2 sites, very limited data & length of service.
18
7/28/2019 Street Lighting 2011_kauffman
19/36
Luminaire Ambient Temperature Effects - LATFLM-79 and LM-80 testing performed in 25oC ambient
~0.224% per C
Light reduction
19
7/28/2019 Street Lighting 2011_kauffman
20/36
Drive Current vs. Forward Voltage
20
7/28/2019 Street Lighting 2011_kauffman
21/36
Ambient Temperature Effects
21
7/28/2019 Street Lighting 2011_kauffman
22/36
Luminaire Thermal Capacitance andT Effects
As Tj increases,Vfdecreases and
input powerdecreases
Internal and externalambient changes can
affect Tj and Vf
Values in this chart are not significant. This data
is only given to show that a relationship exists.
Courtesy of Mike Stevens, Georgia Power
22
7/28/2019 Street Lighting 2011_kauffman
23/36
Small decrease in illumination (E) over 2-month period.
One location had low output due to failing power supply.
23
7/28/2019 Street Lighting 2011_kauffman
24/36
Ambient Temperature Effects
April avg. = 14CJ une avg. = 26C
T = 12C E ~ 3%
www.weather.com 24
7/28/2019 Street Lighting 2011_kauffman
25/36
Voltage (Power, Transient) EffectsMost PSUs operate between 120V and 277V, however
efficiency varies with input voltage, get the facts!480V is a more expensive option, 480V PSUs are more
expensive and less reliable. Step down transformers addcost and reduce system efficiency.
25
7/28/2019 Street Lighting 2011_kauffman
26/36
Ballast (PSU) and Lamp (LED) FactorsGenerally this is 0.95 for HID systems and often assumed
to be 1.0Most drivers are constant current DC to the LEDSome drivers supply AC to the LED to increase system
efficiency (beware of flicker)Some drivers have fixed drive currents and some are
adjustable
Dimming circuits vary in design and operationManufacturing tolerances varyGet the variables from the manufacturer and determine
if they are significant for your environment
26
7/28/2019 Street Lighting 2011_kauffman
27/36
LED Driver De-rating Curve
27
7/28/2019 Street Lighting 2011_kauffman
28/36
Example LED Driver Efficiency vs. Load
28
7/28/2019 Street Lighting 2011_kauffman
29/36
LED Driver Dimming Curve
29
7/28/2019 Street Lighting 2011_kauffman
30/36
LED Driver Power Factor
30
7/28/2019 Street Lighting 2011_kauffman
31/36
LED Driver Life vs. Tcase
31
7/28/2019 Street Lighting 2011_kauffman
32/36
Luminaire Component Depreciation - LCD
Environmental effects such as (acid) rain, exhaust fumes(hydrocarbons), UV exposure, humidity, vibration, salt spray
from ice and snow treatments, coastal conditions, etc. affectthe surfaces of optical components, conductors, fasteners, etc.(DHMO is the worst)
Thermal cycling and aging affects plastic materials, rubbergaskets and wire insulation.
Require manufacturers to furnish test results to quantify theseand determine if it is significant for the given system.
32
7/28/2019 Street Lighting 2011_kauffman
33/36
LLF Calculation Procedure
Use the LLF checklist provided or develop your own.Determine if factors are significant or not. Document,
be prepared to defend your reasoning.All factors are 1.0. (The only exception to this is ifyour maximum operating external ambient temperatureis significantly below 25C or you have consistentlyheavy winds.)
Multiply them together to get LLF.Ex. LLF = LLD x LDD x LATF x LCD
Use this LLF in your lighting calculations and planning.
33
7/28/2019 Street Lighting 2011_kauffman
34/36
Recommended Default Depreciation
LLD = 0.70, for L70 lifetime ratingLDD = 0.9, for very clean environments
LLF = 0.70 x 0.9 = 0.63
34
7/28/2019 Street Lighting 2011_kauffman
35/36
ReferencesWorld Health OrganizationNational Highway Transportation Safety AdministrationRoadway Lighting Update-Research, Carl Andersen, FHWA
SALC 2007ANSI/IES RP-8-2000, American National Standard
Practice for Roadway LightingIESNA Lighting Handbook, 10th ed.Philips Lamp Data SheetsCree Data SheetsLEDs in the Real World, Bruce Kinzey, PNNL, DOE SSL
R&D Workshop 2010, Raleigh, NC
35
7/28/2019 Street Lighting 2011_kauffman
36/36
Rick Kauffman
Kauffman Consulting, LLC
Tel. (901) 219-6979
36