Presentation on theme: "LEDs: WADING THROUGH THE HYPE TO GET GREAT RESULTS Naomi Miller, FIES, FIALD, LC Pacific Northwest National Laboratory Better Buildings."— Presentation transcript:
LEDs: WADING THROUGH THE HYPE TO GET GREAT RESULTS Naomi Miller, FIES, FIALD, LC Pacific Northwest National Laboratory Better Buildings by Design 2011 Burlington VT
Efficiency Vermont is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Learning Objectives By the end of this program, participants will be able to: Apply LEDs to architectural applications successfully Understand and use tools and metrics to help with applying LEDs to projects Understand a process to follow that helps reduce risks when using LED technology Discuss flicker and dimming issues with LEDs Know more about lumens, candelas, CBCP, beam spread, and other light output metrics Understand how to use the DOE CALiPer website to evaluate LED products
Course Evaluations In order to maintain high-quality learning experiences, please access the evaluation for this course by logging into CES Discovery and clicking on the Course Evaluation link on the left side of the page.
The Potential of LEDs is Amazing!
Learn the Lingo of LEDs
But, the industry is awash in snake oil... LED Technology Strategy to increase your chances of success: Learn the LED Lingo Be skeptical Assume product literature is more hype than fact Learn to read photometric reports and color data
IES LM-79 Approved method describing procedures and precautions in performing reproducible measurements of LEDs: –total flux, –electrical power, –efficacy (lm/watt), and –Chromaticity Absolute photometry, not relative photometry Electrical and Photometric Measurements of Solid-State Lighting Products
LM-79 Report Full photometric testing - Compare to photometric report on similar luminaire or lamp
LM-79 Report Sphere testing only – Good for color data and light output, but no spatial distribution data Lumens important (not just Lumens-per- Watt [LPW]) Input power for system (not just LED chip).
Lamp Beam Angle
15 | Solid-State Lighting Program Beam Angle Field Angle 40 ° FLOOD LIGHT Field Angle Beam Angle Beam Angle at 50% of CBCP (2500 cd) Beam angle at 50% of CBCP (2500 cd) Field angle at 10% of CBCP (500 cd) 5000 cd CBCP Field angle at 10% of CBCP (500 cd) Beam Angle at 50%of CBCP (2500 cd) Beam Angle at 50% of CBCP (2500 cd) Field angle at 10% of CBCP (500cd) 5000 cd CBCP Field angle at 10% of CBCP (500 cd) 60 ° FLOOD LIGHT Beam angle
Color The Problem Current color metrics are inadequate for communicating appearance and color rendering of white light to the lighting designer, architect, engineer, and consumer Two sources with same CCT can look very different The u-v color coordinates track back to the black body locus to determine CCT, even if its very green or very pink Duv tells the designer whether its green (>0.006) or pink (<-0.006)
Color The Problem Long red wavelengths (630 – 700 nm) and saturated colors are under-represented in Color Rendering Index (CRI, or R a ) metric LEDs look better than their CRI value suggests Without better metrics, manufacturers will make high efficacy light sources with poor color, slowing the adoption of LED lighting by the designer and consumer
Color Quality Metrics Color Quality Scale (CQS) Color rendering metric with a nod to color preferences Uses a set of standard colors more equally positioned in color space Weights red colors more heavily than CRI does Doesnt penalize slight increase in saturation (color contrast) Rewards slight pink shifts, not green shifts Produces more intuitive color quality values, esp. for LED Single metric easier to comprehend and use
Color Quality Metrics Improved CRI (CIECAM06UCS) Color fidelity metric with no enhancements for preference Uses traditional set of CRI pastel colors Does not weight red colors more heavily than CRI Penalizes any perceived increase in saturation Calculates values that vary slightly from conventional CRI Values are not more intuitive for designer unless combined with a special R 9 (red) value (i.e. two metrics)
Color Applications where Color Rendering/Preference matters: Retail clothing/ Furnishings Homes Retail (produce)
Color Applications where Color Rendering/Preference matters: Face-to-face communication, schools Hospitality (hotel/spa/restaurant)
Color Applications where Color Rendering/Preference matters: Anywhere food is served Anywhere faces are important
Color Applications where Color Fidelity matters: Industrial color matching, interior design selections Food inspection Healthcare (jaundice, redness, cyanosis)
Color Conclusions Color metrics for the Professional Designer/Color Specialist: SPD CCT and Duv CQS for single-number color rendering/preference Improved CRI (R a ) with Special R 9 value, for fidelity
Color Conclusions Color metrics for the Engineer/Architect/Consumer: CCT communicated through graphical scale CQS for single-number color rendering/preference
Color Conclusions Energy efficiency standards should include minimum targets for color rendering using Improved CRI with R 9 and/or CQS Standardized luminaire photometry should include color metrics of SPD, CQS, Improved CRI with R9, and CCT with Duv
Flicker Flicker factors for both Visible and Invisible Flicker Modulation Frequency Modulation Amplitude DC Component Duty Cycle
Light Source Waveforms
Flicker What makes flicker worse: Duration of exposure (longer is worse) Area of the retina receiving stimulation (greater is worse) Location in visual field (central is worse because it projects to a greater area of the visual cortex, even though flicker is less noticeable) Brightness of the flash (higher luminances are worse; scotopic luminances produce low risk, high mesopic and photopic luminances produce higher risk) Contrast of the flash with the surround luminance (higher is worse) Color contrast of flash (deep red is worse)
Flicker Implications of flicker: Headaches (see Wilkins et al) Neurological problems including epileptic seizure Distraction Hazard from strobe effect stopping or slowing apparent motion of machinery Impaired visual performance (Veitch et al)
Flicker Applications where flicker matters: Offices Classrooms Industrial spaces Hospitals/clinics General lighting Task lighting
Flicker Applications where flicker is less important: Accent lighting on artwork Roadways and parking lots Sports and industrial lighting on 3-phase electrical system
Flicker Products more likely to flicker: AC LEDs DC LEDs with poor drivers LEDs dimmed with phase-cut (Triac) dimmers LEDs dimmed with Pulse Width Modulation (PWM) dimmers
Flicker Conclusions: Keep an eye out for reliable predictive flicker metrics (Flicker Index and Percent Flicker are both inadequate) Be aware of applications where flicker might be a health or distraction issue Check the products you are specifying for flicker, and for interactions between dimmer, driver, and LED product that may produce flicker
Check CALiPER website for a report on the product and a Benchmark comparable technology product. (http://www1.eere.e nergy.gov/buildings/ ssl/caliper.html ) Do the marketing claims match the performance testing? Reducing the risk of icky products…..
Check the CALiPER data
Once you have the numbers and it LOOKS OK on paper… See it yourself, more than one sample Check color rendering on your own skin, familiar fabrics Check for flicker Try dimming it, using the recommended dimmer and the specified transformer Check for flicker in dimmed state if you plan to dim it Reducing the risk of icky products…..
Check on the life of the product: What is the life of the chip? Is it replaceable in 3 years? What is the life of the power supply and driver? Are they replaceable in 3 years? How does the client get replacement parts? What does the client do with the old parts? Does the luminaire stay clean over life of LED? If you can, specify the LED product as a system Put tough performance metrics in your specification to ensure its not substituted with an inferior product (Use CALiPER metrics as a good start for these performance specs) Reducing the Risk….
When doing lighting calculations Use LLFs based on light output at 40% of useful life LLF = LLD x LDD x RSDD x BF For linear fluorescent, LLD (at 40% mean life) = What about LEDs? Old LEDs never die…they just fade away. Reducing the Risk….
LLF = LLD x LDD x RSDD x BF (or PSF) For fluorescent, LLD (at 40% mean life) = For LEDs, LLD (at 40% mean life) = anybodys guess Educated guess for better LEDs is LLD = 0.70 – 0.90 Reducing the Risk
Reducing the Risks Beware: T8 Replacement Lamps, but know that they are getting better with time….
Reducing the Risks….. Performance of the bare lamp…. –Manufacturer literature claims 15W / 1500lm / 100 lm/W Replaces 32 – 45W fluorescent –CALiPER measurements for bare lamp LED 16W /~1100lm / 69 lm/W Fluorescent 32W / 3250lm / 101 lm/W And then when its in the fixture…. –LED T8 CALiPER measurements 32W /~1800lm / 56 lm/W –Fluorescent T8 CALiPER measurements 69W /~4800lm / 69 lm/W Bypassing ballast –Safety? –Shunted sockets? Rewired sockets? –Cost of labor? –Irreversibility?
In summary See it before you specify it. See two or three. Do mockups with the LED equipment Use LM-79 testing for best information on performance Evaluate lumens and LPW and candela distribution Check CALiPER for test data. Compare to mfgs claims. Consider maintained light output and dirt accumulation in calculations Dimming LEDs can be problematic. Reliable dimming requires extra homework on your product specification. Specify products from companies you know or whom you trust, or that have a documented support history Get a written warranty that includes light output and color variation Reducing the Risks
Getting great results And the good news is…. LEDs CAN do a visually terrific job AND save energy! InterContinental Hotel Lobby, Howard St. San Francisco. GATEWAY Project demonstration by DOE/PNNL and PG&E and InterContinental Hotel Group.
InterContinental Hotel, Howard St. San Francisco (GATEWAY Demonstration) Registration Desk Area of Lobby LED lamp replacements: –(217) 20W Halogen MR16 lamps* in wall grazing, with 6W LED MR16s by CRS Electronics –(7) 30W Halogen IR MR16 lamps* in downlight task ltg, with 6W LED MR16s by CRS Electronics –(6) 75W Halogen Par30 shortneck lamps* for floor lighting, with 11W LED Par30 lamps by Philips * All halogen lamps were originally dimmed from 35% to 85% of full output by the dimming system, depending on time of day.
InterContinental Hotel, Howard St. San Francisco (GATEWAY Demonstration) Payback assumptions: 24/7 operation $50 labor cost to change a lamp $0.13/kWh melded rate $60 to $65 LED lamp cost 25,000+ hours LED lamp life Analysis over 3 years Preliminary simple payback is 1.1 years.
InterContinental Hotel, Howard St. San Francisco (GATEWAY Demonstration) The full GATEWAY demonstration report, includes other hotel spaces
If you want to know more… Main DOE website: DOEs Commercially Available LED Product Evaluation and Reporting program (CALiPER): Look for the Lighting Facts: ENERGY STAR ® : IESNA Standards and Guidelines:
Thats all folks! Any pesky questions?? LED TECHNOLOGY AND HOW TO TELL THE GOOD FROM THE ICKY