Nadarajah Narendran, Ph.D. Jean Paul Freyssinier, i M.S. Lighting Research Center Rensselaer Polytechnic Institute Troy, New York 12180, U.S.A.

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1 LED What to Look for Today and in the Future presented by Nadarajah Narendran, Ph.D. Jean Paul Freyssinier, i M.S. Lighting Research Center Rensselaer Polytechnic Institute Troy, New York 1218, U.S.A.

2 Acknowledgments 2 Organizers of NALMCO Annual Convention and Tradeshow 21 Sponsors of ASSIST Program LRC faculty, staff, and students

3 SSL Target? 3 Solid-state light sources including LED and OLED hold the promise for revolutionizing lighting 15 lm/w Energy savings 9 lm/w 12 lm/w 15 lm/w Lower maintenance cost 1 hrs 2, hrs 3, hrs 1, hrs Picture credits: GE, OSRAM Sylvania, OSRAM Opto, Philips Lumileds, Nichia, Cree

4 Where are we now? 4 25 U.S. Efficacy Target for LEDs R&D Efficacy 2 ma m/w) 2 R&D Efficacy 35 ma Perform mance (l Commercial 35 ma Cree XLamp LED 12 lm/w 1 lm/w 6 lm/w Year lm/w

5 Commercial White LED Performance From manufacturers data sheets, August 21 Commercial white LEDs are approaching 14 lm/w in cool white and 1 lm/w in warm white Cool White 14 Warm White Lum minous efficacy (lm/w) Lum minous efficacy (lm/w) Luminous flux (lm) Luminous flux (lm)

6 LED Lighting System Performance 6 LED system efficiency: 6% at best Optics 85% Driver 85% Thermal 85% LED Optical Thermal Electrical Lighting Research Center 6

Product Development Challenges 7 Secondary optic LED

temperature (Ts) Heat sink LEDs and secondary optics

efficiency LED PCB Heat sink size weight T j Light

7 Product Development Challenges 7 Secondary optic LED Driver Driver case temperature (Td) LED board temperature (Ts) Heat sink LEDs and secondary optics Optic holder Life Power Forward voltage Driver efficiency LED PCB Heat sink size weight T j Light output Forward current Efficacy Drawing adapted from Cree Optics Cost

8 Heat & Current Affect Life 8 Lig ght Output 1% Rough Rule 9% 8% Increasing heat 1 deg. C increase in pin temperature the life halves 7% Hours 5 4 R 2 =.96 Life (hrs) Thermocouple T-point Temperature (deg C)

9 Failure methods 9 Catastrophic Abrupt and complete cessation Device related System related Degradation Continuous deterioration over time Time-dependent light loss Time-dependent color shift Taipei

10 LED driver life 1 An LED lighting system s reliability depends on the weakest component of the system. Electrolytic tic capacitors used in drivers have the highest probability of failure Each 1 C increase results in half the life rating Type Rated Temperature (Tn) Rated Life Electrolytic 85 C 4, h Electrolytic 15 C 15, h Electrolytic 18 C 5 h % of Failure 8% 7% 6% 5% 4% 3% 2% 1% % LED Driver Heat sink Distribution tion of Failure for Each Power Component 53%51% Electro olytic capac citor 3% LED Driver 1 LED Driver 2 1% 13% 9% 11% 6% 8% 3% 5% 1% MOS SFET Transfo ormer Opto- cou upler Sam mpling resi istor Diode

11 Luminaire Life 11 Basing luminaire life using LM8 data for LEDs is incorrect. There are many components and several failure modes in a system LED Circuit boards with LED array - interconnections Driver Optics Thermal interface materials etc

12 Energy Star Qualified LED Downlights 12 From Energy Star Website, Oct Recessed downlights (Commercial) 1 Recessed downlights (Residential) Lum inaire effic cacy (lume ns/watt) Lumi inaire effic cacy (lumen ns/watt) Lumens Lumens

13 Program 13 Established: 22 Goal: To support the development e e and widespread ead application of LEDs for general illumination Identify and reduce the major technical hurdles currently facing solid- state lighting Activities: iti Industry collaboration, research, demonstration, ti and education

14 LED Lighting Institute 14 3-day workshop about LED lighting system and application requirements Twice a year since 21 Hands-on workshop Technology Thermal Electrical Optical Fixture design and evaluation Sponsor: ASSIST

recommends 15 A series of publications that provides useful information to end users Application guides Recommendations for using LED light fixtures in applications General guide to

15 recommends 15 A series of publications that provides useful information to end users Application guides Recommendations for using LED light fixtures in applications General guide to applications Guide to selecting LED luminaires Recommendations for testing and evaluating LED luminaires Proposed test methods Technology-independent Consider application environment

asp 16 ASSIST recommends Outdoor Lighting

Luminaires ASSIST recommends Freezer Case

Light Engines ASSIST recommends Light Source

16 ASSIST Publications 16 ASSIST recommends Outdoor Lighting Luminaires ASSIST recommends Directional Luminaires ASSIST recommends Freezer Case Lighting Luminaires ASSIST recommends LED Light Engines ASSIST recommends Light Source Color for Retail Lighting ASSIST recommends Under-cabinet Lighting Luminaires

17 Testing LED Downlights 17 ASSIST recommends Three environmental conditions to test fixtures: Open air: Light source and driver have plenty of ventilation Semi-ventilated: Light source and driver have limited ventilation (similar to Non-IC) Enclosed: Light source and driver have almost no ventilation (similar to IC)

18 27 Downlights 18 Relative Flu ux 12% 1% 8% 6% 4% 2% % Fixture B (25 W; Aug 27) Open air Non IC IC Relative Flu ux 12% 1% 8% 6% 4% 2% % Fixture C (12 W; Oct. 27) Open air Non IC IC Relative Flu ux 12% 1% 8% 6% 4% 2% % Fixture D (3 W; Oct. 27) Open air Non IC IC C) T pin (deg B (24 W) C) T pin (deg C (12 W) 51.8 C) D (3 W) Open air Non IC IC Open air Non IC IC Open air Non IC IC 6.5 T pin (deg. 9.6

19 27 Downlights 19 11% Fixture B (25 W; Aug 27) 11% Fixture C (12 W; Oct. 27) 11% Fixture D (3 W; Oct. 27) ative Light Output Rel 1% 9% 8% 7% Rela ative Light Output 1% 9% 8% t Re elative Light Outpu 1% 9% 8% 6% Time (hrs) Open air Semi-ventilated Enclosed 7% Time (hrs) 1 Open air Semi-ventilated Enclosed 7% Time (hrs) 1 Open air Semi-ventilated llipses McAdam E Fixture B Time (hrs) McAdam Ellipses Fixture C Time (hrs) McAdam Ellipses Fixture D Time (hrs) Open air Semi-ventilated Enclosed Open air Semi-ventilated Enclosed Open air Semi-ventilated

20 29 Downlights 2 Relative Flux 12% 1% 8% 6% 4% 2% % Fixture F (14 W; March 29) Open air Non IC IC Relative Flux 12% 1% 8% 6% 4% 2% % Fixture G (15 W; June 29) Open air Non IC IC Relative Flux 12% 1% 8% 6% 4% 2% % Fixture H (12 W; Oct. 29) Open air Non IC IC T pin (deg g. C) F (14 W) Open air Non IC IC T pin (deg g. C) G (15 W) Open air Non IC IC T pin (deg g. C) H (12 W) Open air Non IC IC F G H 14 W 15 W 12 W Lumens % T pin (deg C) lm/w Lumens % T pin (deg C lm/w Lumens % T pin (deg C) Open air Non IC IC

21 29 Downlights 21 Relativ ve Light Output Fixture F 11% (14 W; March 29) 1% 9% 8% 7% Time (hrs) Open air Semi-ventilated Enclosed Relati ive Light Output Fixture G 12% (15 W; June 29) 11% 1% 9% 8% 7% Time (hrs) Open air Semi-ventilated Enclosed Relat tive Light Output Fixture H 11% (12 W; Oct. 29) 1% 9% 8% 7% Time (hrs) Open air Semi-ventilated Enclosed McAd dam Ellipses Fixture F Time (hrs) Open air Semi-ventilated Enclosed McAda am Ellipses Fixture G Time (hrs) Open air Semi-ventilated Enclosed McAda am Ellipses Fixture H Time (hrs) Open air Semi-ventilated Enclosed

22 Energy Star Qualified LED Downlights 22 1 Recessed downlights (Commercial) 1 Recessed downlights (Residential) Lum inaire effic cacy (lume ns/watt) Lumi inaire effic cacy (lumen ns/watt) Lumens Lumens

23 Energy Star 23 Luminaire life estimation: Greater than 91.8% lumen maintenance at 6 hrs - 25, hrs life (Residential) Greater than 94.1% lumen maintenance at 6 hrs - 35, hrs life (Commercial) Relative Light Output 11% 1% 9% 8% 7% Fixture G (15 W; June 29) Time (hrs) Open air Semi-ventilated Enclosed

24 A-Lamp Replacements 24 1 W 2 W 6 W LED CFL Incandescent

25 Late 29 Commercial LED A-lamps 25 Power: 5 to 11 W Flux: 18 to 57 lumens Efficacy: 22 to 65 lm/w Price $2 to $6 Powe er (W) Flu ux (lm) fficacy (lm/w) Ef Lamp Lamp Lamp

warm up time for many products A few products have shown

26 Late 29 Commercial LED A-lamps 26 In the first 4 hours, 7 out of 22 lamps have completely failed High lumen depreciation during warm up time for many products A few products have shown reasonable lumen maintenance after an initial 1% drop during warm up period

27 Light source efficacy and energy savings 27 Energy use depends on the connected load and time of use Watt-hours MYTH: High efficacy light sources always save more energy than low efficacy light sources. Spatial light not reaching the application area is wasted light (energy) Temporal light beyond the required time is wasted light (energy)

Forms of Luminous Efficacy 28 Light source efficacy: Total lumens out of the light source divided by the total input power Measured at 25 C ambient temperature Luminaire i efficacy: Total lumens

28 Forms of Luminous Efficacy 28 Light source efficacy: Total lumens out of the light source divided by the total input power Measured at 25 C ambient temperature Luminaire i efficacy: Total lumens exiting the luminaire divided by the total input power Measured at 25 C ambient temperature Application efficacy: Total lumens reaching a task area and meeting the application s lighting requirements divided by the total input power Measured in the application environment More appropriate to evaluate energy savings

29 Application Efficacy Spatial and Temporal 29 Spatial Illuminating the picture on the wall Wasted lumens: Lumens beyond the area of the picture Wasted lumens Application lumens Time of use Not switching off the light at times not needed wastes energy

Outdoor area lighting luminaires 3 LED is

30 Outdoor area lighting luminaires 3 LED is becoming a potential light source for street and parking lot lighting applications. Many commercial products Claims of One-to-one one replacement of traditional light sources Short payback time High efficacy Long life How to screen for good-quality products? Street lamp with OSRAM's Golden DRAGON with lens

31 ASSIST metric 31 Application Efficacy: Considers how effectively light is delivered to the task How much light on task area How much of the light meets the application s needs Minimum i light levels l and uniformity it ratios How large is the coverage of the beam in terms of luminaire classification types Larger coverage means smaller number of luminaires Good correlation with application s power density Useful lumens Visual Efficacy: Accounts for how effectively the light source caters to nighttime vision Peripheral vision is more important under low light levels Field demos have shown up to 3% energy savings Extracted from

Outdoor Lighting 32 Outdoor Lighting Outdoor Lighting: A Short Guide to Applications, Objectives and Considerations Vol. 6 Issue 1 Visual Efficacy Mesopic vision Vol.

32 Outdoor Lighting 32 Outdoor Lighting Outdoor Lighting: A Short Guide to Applications, Objectives and Considerations Vol. 6 Issue 1 Visual Efficacy Mesopic vision Vol. 6 Issue 2 Parking Lot Lighting Starlight Scotopic Moonlight Mesopic Radiant Energy Dim interiors Application-specific ASSIST recommends Online Calculator Office lighting Photopic Daylight Test and Evaluation Methods Vol. 7 Issue 3 Pole Height Overhang distance

Sample Calculation 3 mounting height 15 W HPS, Type III S 15 W LED, Type III S 15 W MH, Type III S 33 Luminous flux in grid cells meeting criteria i (white cells inside id red rectangle) 764 lm 4745

33 Sample Calculation 3 mounting height 15 W HPS, Type III S 15 W LED, Type III S 15 W MH, Type III S 33 Luminous flux in grid cells meeting criteria i (white cells inside id red rectangle) 764 lm 4745 lm 4918 lm Percentage of cells meeting criteria (.2 fc < E <.4 fc) (% of white cells inside rectangle) 74% 67% 62% Application luminous flux ( ) and average illuminance (fc) on task area 5213 lm (.66 fc) 3184 lm (.46 fc) 339 lm (.48 fc) Luminaire input power 188 W 146 W 185 W Luminaire application efficacy ( ) 27.7 lm/w 21.8 lm/w 16.4 lm/w

34 Retrofit Lamps for Outdoor 34 Challenges in retrofitting lamps Lamp size may not fit all fixtures Lamp weight Thermal management Moisture sealing Beam distribution may not match s.com/img/led-retrofi

35 35 Freezer Case Lighting Luminaires Project Sponsor: ASSIST

Background 36 21 LRC laboratory study Demonstrated the benefits of using LEDs in 21

published the results Field Test DELTA Snapshot 23 28 and beyond Market transformation Many

36 Background LRC laboratory study Demonstrated the benefits of using LEDs in 21 refrigerated display cases 23 LRC conducted a field study With NYSERDA funding 26 LRC published the results Field Test DELTA Snapshot and beyond Market transformation Many retailers are using LED lighting fixtures Number of commercial products are increasing 26 Fluorescent LED

37 recommends 37 In 29, ASSIST published a technology-independent method for testing and evaluating the performance of white light luminaires used in refrigerated display cases. Proposed method: Application efficacy = Total lumens on the task Total power Total lumens on the task Flux on the task area at application temperature Total power Fixture power + extra power demanded by the freezer at application temperature

38 Test Results Commercial Products 38 The results show significant performance differences between room and application temperature. For example, fixture B has better room temperature fixture efficacy y( (42 lm/w) than fixture C (28 lm/w). However, when both fixtures are compared under application conditions, fixture B s application efficacy is lower and requires 3% more power. m/w) Efficacy (l Power (W) A B C D E F Fixture Efficacy at 22 C (lm/w) Application Efficacy at -22 C (lm/w) A B C D E F Fixture Power at 22 C (W) Total system power at -22 C (W)

recommends: Retail Lighting 39 Retail lighting has several important goals: Attract

Light and Color in Retail Merchandising Vol.

Retail Merchandising Vol. 8 Issue 2 Fluor. Inc.

retail lighting the strengths and limitations of color rendering metrics, including

practical method to evaluate color rendering properties of light sources two metric

39 recommends: Retail Lighting 39 Retail lighting has several important goals: Attract attention, generate interest, create a comfortable atmosphere, integrate with store identity, be flexible, etc. Good color rendering is necessary to achieve these goals Retail Lighting Guide to Light and Color in Retail Merchandising Vol. 8 Issue 1 Recommendations for Specifying Color Properties of Light Sources in Retail Merchandising Vol. 8 Issue 2 Fluor. Inc. MH Daylight u Edison Price Lighting i HPS Addresses the color rendering needs of retail lighting the strengths and limitations of color rendering metrics, including color rendering index (CRI) and gamut area index (GAI) Describes a simple to use, practical method to evaluate color rendering properties of light sources two metric approach using CRI and GAI based on several LRC experiments* helpful to predict higher ratings of acceptability than with single metrics v *Rea et al. 24; Figueiro et al. 26; Rea and Freyssinier 27; Rea and Freyssinier 29.

40 Summary 4 LED technology has been steadily advancing and is in the process of transforming certain markets. Cost is expected to reduce over time All LED products are not created equal LM 8 is not a good indicator of system reliability Replacement consideration i Availability of the same product in the future if replacement is needed. Industry experts are predicting up to 25% of the sales from LED products by 215

41 More Information 41

Application Efficacy for Comparing Energy Demand in Lighting Applications

Application Efficacy for Comparing Energy Demand in Lighting Applications Nadarajah Narendran, Jean Paul Freyssinier, Jennifer Taylor, Tianming Dong, and Rosa Capó Lighting Research Center Rensselaer Polytechnic