DOE Predicts LED Use and Energy Savings

In September the DOE issued, Energy Savings Forecast of Solid-State Lighting in General Illumination Applications (PDF, 116 pages), the latest edition of a biannual report which models the adoption of LEDs in the U.S. general-lighting market, along with associated energy savings, based on the full potential DOE has determined to be technically feasible over time. The new report projects that energy savings from LED lighting will top 5 quadrillion Btus (quads) annually by 2035. Among the key findings:

By 2035, LED lamps and luminaires are anticipated to occupy the majority of lighting installations for each of the niches examined, comprising 86% of installed stock across all categories (compared to only 6% in 2015).
Annual savings from LED lighting will be 5.1 quads in 2035, nearly equivalent to the total annual energy consumed by 45 million U.S. homes today, and representing a 75% reduction in energy consumption versus a no-LED scenario.
Most of the 5.1 quads of projected energy savings by 2035 will be attributable to two commercial lighting applications (linear and low/high-bay), one residential application (A-type), and one that crosses both residential and commercial (directional). Connected lighting and other control technologies will be essential in achieving these savings, accounting for almost 2.3 quads of the total.
From 2015 to 2035, a total cumulative energy savings of 62 quads – equivalent to nearly $630 billion in avoided energy costs – is possible if the DOE SSL Program goals for LED efficacy and connected lighting are achieved.

Don’t have time for the full report? Download the report summary.

Measuring and Reporting LED Life

I’m putting the finishing touches on a lighting design and as I look at cut sheets I continue to be disappointed that many fixture manufacturers still don’t seem to understand the proper methods of measuring and reporting LED life. For example, an Edison Price cut sheet says that lamp life is “rated 50,000 hours based on L70/B50 criteria. LM80 report by the LED manufacturer furnished upon request,” a USAI cut sheet says that life is “Based on IESNA LM80-2008 50,000 hours at 70% lumen maintenance (L70),” and a Lighting Services Inc. cut sheet just says “Tested to LM79 and LM80 Protocols” and then gives a life of 50,000 hours. Unfortunately, these statements don’t mean what the manufacturers suggest they mean. Let’s take a look.

Back in the early days of LEDs of lighting (say around 2005!) it was the wild west in terms of manufacturers reporting product life. The rated life of traditional lamps is the amount of time that passes until one-half of a sample set has burned out. LEDs don’t burn out, they just get dimmer and dimmer over time, so many LED manufacturers estimated the amount of time until an LED’s output had fallen to one-half and called that the LED’s life. This led to reported lifetimes of over 100,000 hours, which sounds great until you realize that at 100,000 hours the space you’re lighting is only half as bright as it was at the first hour. How many of our designs provide twice as much light on day one so that we can lose 50% of the light and still provide an acceptable light level? None! Clearly the industry needed another method of calculating life.

Somehow (sorry, I don’t know the history of this) the industry settled on a loss of 30% of output as the lifetime of an LED. This is in line with the Lamp Lumen Depreciation (LLD) factor applied to many CFL and HID lamps in illuminance calculations. The lifetime to 70% of initial light output is often abbreviated as L70. Many lighting designers have pointed out that a 30% loss of light is pretty poor performance and some manufacturers have responded by providing L80, and even L90, data (that is, the life until the LED has lost 10% of its initial brightness). All of this was a step in the right direction, but there was no standard method for taking the measurements to determine L70.

In 2008 the Illuminating Engineering Society stepped up to clarify things with LM-80-08 Approved Method: Measuring Lumen Maintenance of LED Light Sources. LM-80 (LM stands for Lumen Maintenance) specifies the test conditions and methods to be used to measure and report the lumen maintenance of an LED package. Data is collected every 1,000 hours for a minimum of 6,000 hours. Even accurately collected LM-80 data isn’t ideal, though. LM-80 is used to evaluate LED packages, not entire fixtures, so the conditions of the test (temperature, electrical characteristics of the driver, etc.) may, or may not, be similar to those in the assembled and installed fixture.

Importantly, LM-80 does not provide a method of extrapolating the 6,000 hours of data to predict future performance. As a result, any cut sheet saying that a 50,000 hour life is calculated according to LM-80 is misstating things unless the manufacturer has actually had the same LED packages under test. 50,000 hours translates to nearly six years, to that’s unlikely. LM-80 was revised in 2015 and is now the ANSI standard ANSI/IES LM-80-15 IES Approved Method: Measuring Luminous Flux and Color Maintenance of LED Packages, Arrays and Modules.

How do manufacturers calculate an LED’s life? They (should) use IES TM-21-11 Projecting Long Term Lumen Maintenance of LED Light Sources. TM-21 (TM stands for Technical Memorandum) describes a method for projecting the lumen maintenance of LEDs using the data collected during LM-80 testing. So, a cut sheet should say something like, “L70 life of 50,000 hours based on LM-80 testing data according to TM-21 protocol.”

The statements I quoted at the beginning leave wiggle room for the manufacturers to provide lifetimes that may, or may not, be calculated according to TM-21. TM-21 is the only standard we have that allows us to compare apples to apples, so omitting a statement about using TM-21 as the basis of lifetime calculation should make you suspicious about the reported life. It’s also important to understand that LM-80 is a testing procedure, and TM-21 is a calculation procedure. They are not tests. There’s no such thing as an LED that “passes” LM-80 or TM-21 (as some reps have tried to tell me). LM-80 and TM-21 produce information about the life of an LED that the designer uses to assess the appropriateness of a fixture.

Specifiers need to tell reps and manufacturers that LED life must be calculated according to TM-21. It’s the only way to be sure that the lifetimes of various fixtures are all calculated the same way so that we can make reasonable comparisons. They should also urge the IES to develop a procedure that tests a complete fixture: housing, power supply, and LEDs. That’s going to be the best estimate of the true life of an LED fixture. Yes it will take time, but we need accurate information that is calculated the same way across all manufacturers.

Who Needs A Lighting Designer? Museums and Galleries!

A few weeks ago I gave a three-hour seminar on lighting museums and galleries to the graduate students in an art curating program at a university here in New York. Condensing everything I’d like to say into less than three hours was tough. The two big questions were what to include and what to leave out. I started with a quick overview of how to think about light and lighting before moving on to basic vocabulary and some common lighting techniques. Then, since LEDs are clearly the future, even when lighting art, I moved on to an overview of both color temperature and color rendering. I talked about reference materials such as the IES Lighting Handbook, intensity and brightness ratios, and other considerations before we moved into their gallery space to use their track light system for some demonstrations.

After the whole affair a faculty member, who sat in on most of the seminar, said he had hoped I would have spent much more time talking about how to use track lights and less time on unimportant issues like design, color temperature, and color rendering (!). I was respectful, but stunned. Focusing track lights is so complex that it requires extensive demonstrations? Understanding that with LEDs the color qualities of the light vary widely, and can only be properly selected when they are understood is unimportant information? Uhh…NO. Or, as my 20 month old niece says, “no no no no.”

Yes, five or ten years ago the default light source in museums was an incandescent or halogen lamp. The color temperature difference was minor and the color rendering of both was excellent. That’s not true today. Look at the cut sheet for any museum grade track light and you’ll see that you have a choice of several color temperatures and CRI values. If ANYONE needs to understand the qualities of light that must be selected when using LED fixtures, if anyone needs to understand the affect that color temperature and CRI have on how colors are perceived, it’s certainly people involved in displaying and lighting art. To me, that means the curators of exhibits and the lighting designers they hire.

As I’ve discussed earlier, changing the color temperature of the light changes the color appearance of objects, as shown below.

Illuminated with Warm White Fluorescent Lamp — Illuminated with 3000 K light

Illuminated with Cool White Fluorescent Lamp — Illuminated with 4000 K light

The phenomenon of color consistency means that the shift in color appearance isn’t as great as one might expect or as these photos suggest, but the shifts are real. If you’ve ever bought a black garment only to discover later that it was actually dark blue you’ve experienced this shift. A similar thing happens when we compare a high CRI light source and a low CRI light source. If your work involves color perception this is basic and critical information.

Curators can be forgiven for not knowing much about this, but if they know nothing how can they collaborate with their lighting designer to show the art as they intend? Administrators and curators of museums and galleries – educate yourselves, then hire a lighting designer!

Use of LED Lamps To Improve Health

Today’s New York Times has an article on several manufacturers’ new LED products that are intended to improve wakefulness, sleep, focus, and other aspects of daily life and health. The article appears on both the business and technology pages, but not on the health page, and I think that’s appropriate. Although there are testimonials by the consumers of some of these products, there’s no discussion about any peer reviewed science behind them. In fact, about two-thirds of the way through the article the author finally gets to the fact that, “Researchers are still determining how spectrum and intensity of light affect the brain.” So, the article is an uncritical look at new LED products that make health claims. We shouldn’t rely only on the claims of the manufacturers, though – remember the claims of 100,000 hour lifetimes for LED lamps?

I’m not saying that we know nothing about how light affects us, because we know quite a bit. The question is, “Do we know enough to properly and safely integrate that information into our design practice?” and there things become uncertain. So, before accepting the claims of manufacturers, or making the same claims to clients, it’s important for designers to be up to date on the current state of research and to understand the strength of the findings, as well as how (and if) those findings can be folded into a design.

There are a few web sites that I find useful for keeping up to date. The first is the Health and Vision page of the Lighting Research Center’s web site, which has links to many of their recently published research papers. The second is the Research page of USAI Lighting’s web site. This page provides links to a mix of newspaper articles and scholarly publications on a variety of topics connected to LED lighting. The third is the Research page of the IES web site. Finally, members if the IES can download copies of Leucos, and non-members can purchase copies.

LEDs continue to revolutionize the lighting industry. Most manufacturers have ended research and development for incandescent and fluorescent products. OLEDs are increasing in efficacy and prices are dropping, while new technologies (such as light emitting plasma and quantum dots) are on the horizon or already here. To preserve their client’s money, the occupant’s health and safety, and their own reputations, designers need to make sure that they don’t get swept up in the possibilities that are marketed to them before the facts are in.

OLEDs Are Ready For Their Closeup

Last week I attended a webinar on the history, future, and application of OLEDs presented by Dietmar Thomas of Philips. It was an interesting and informative hour that has just been posted online. Perhaps the most surprising thing is that Philips sees commercial lighting fixtures lamped almost exclusively with LEDs and OLEDs as soon as 2020! The webinar is worth the time. Take a look.

New LED Performance Measurements

The Illuminating Engineering Society (IES) has published two new documents related to measuring the performance of Light Emitting Diodes (LEDs). The titles, as well as the aspects that are included and excluded, reveal the complexity of LEDs.

The basic problem is that LEDs typically do not fail the way other lamps do. Instead of a failure that results in the end of light output, LED output fades over time. The result is that at some point, although the LED is still producing light, it is no longer producing enough light for the application so we would say that it has reached the end of its useful life. LEDs have very long lives and relatively short development cycles so it is entirely possible that by the time testing of an LED is complete a newer product has already replaced it. This is compounded by the sensitivity LEDs have to temperature, voltage, and other factors that can mean lab measurements differ greatly from real world measurements. This gives rise to the need for clearly defined testing procedures that reproduce conditions found in typical installations so that designers can rely on the information from the manufacturers.

The first document is LM-84-14 IES Approved Method for Measuring Luminous Flux and Color Maintenance of LED Lamps, Light Engines, and Luminaires. (In the IES naming system LM stands for lumen maintenance, 84 is the document number, and 14 is the year it was issued or updated.) It describes the procedures to be followed in obtaining luminous flux (light output) and color maintenance measurements under standard operating conditions. However, it does not provide information on sampling, or extrapolation of the data for longer time frames.

The second document is LM-85-14 IES Approved Method for Electrical and Photometric Measurements of High Power LEDs, which describes the procedures to be followed in performing accurate measurements of light output of white and colored high-power LEDs. The procedures do not cover LED arrays or modules, AC driven LEDs, among other things.

These two documents join several others that describe the testing and measuring of LEDs. The first is LM-79-08 Approved Method: Photometric Measurements of Solid State Lighting Products, which describes the procedures for testing and reporting of: total flux (light output); color temperature; color rendering index, electrical power characteristics; efficacy (in lumens/watt). LM-79 requires testing of a complete lighting fixture. It does not apply to bare LED packages. LM-79 does not measure the distribution, only the total light output. As a result, it does not provide us with complete photometric performance of the fixture tested.

The next standard is LM-80-08 Approved Method: Measuring Lumen Maintenance of LED Light Sources, which is intended to measure only the LED package, not a complete fixture. LM-80 does not define the end of life for an LED package. It is simply method for determining the light output degradation. LM-80 outlines the testing conditions and the measurement methods that are to be used to measure, track and report the lumen maintenance of an LED package over the course of 6,000 hours. it does not provide a means of estimating life expectancy or light output beyond 6,000 hours.

TM-21-11 Projecting Long Term Lumen Maintenance of LED Light Sources picks up where LM-80 leaves off. (TM stands for Technical Memorandum) It recommends a method for projecting the lumen maintenance of LEDs using the data obtained from LM-80 testing. TM-21 is used to derive L70, which is the number of hours, or life, before the LED package is emitting 70% of the initial lumens. L70 is the number most frequently used by manufacturers as the life, or the useful life, of their LEDs.

DOE Suspends PAR38 L-Prize Competition

On June 13, 2014 the U.S. Department of Energy (DOE) suspended the L-Prize PAR38 Competition. The LED PAR38 products currently on the market fall far short of reaching the rigorous L -rize targets, making it unlikely the DOE will receive a qualifying entry in a reasonable amount of time. The DOE cannot lower the efficacy target because it was set by Congress. The DOE will continue to monitor the PAR38 market for performance and price improvements, to consider reopening the competition at a later date. The graph below illustrates the market vs the L-Prize goals as of November 2013.

More information is available on the DOE web site.

Basking in a New Glow

The New York times has an “I Heart LEDs” article in today’s paper that leaves out some important information about evaluating them. Here are some additional thoughts.

The government hasn’t done a very good job of publicizing or explaining that the Energy Independence and Security Act of 2007 (EISA) set minimum efficiency requirements for general use light bulbs (the act excluded decorative and colored products). The incandescent lamp that’s been around for over 100 years doesn’t meet the energy efficiency standard. Rather than re-engineer incandescent lamps, the lamp manufacturers have focused on expanding and emphasizing compact fluorescent (CFL) and light emitting diode (LED) technologies. Again, you can still purchase 40 – 100 watt decorative incandescent lamps but not A-lamps, the most common shape in use.

The easiest substitution, one that requires no thinking about rewiring, dimming, etc., is the halogen lamp. Halogen lamps are an improvement on standard incandescent lamps, and many of them meet the EISA energy efficiency requirements.

If you’re looking for higher energy efficiency, and are willing to pay a higher price up front to get it, CFL and LED lamps are available in a wide range of wattages and shapes. However, they need to be approached with caution. Both technologies can be difficult to dim, especially with older dimmers that were designed with incandescent lamps in mind, so your existing dimmers may need to be replaced. They can also produce unsatisfactory tints of white light. LEDs are especially notorious for not matching the information provided on the packaging, as demonstrated through the Department of Energy’s CALiPER program.

Here’s what to look for. Every light bulb package should have a Lighting Facts Label that looks like this.

The orange/yellow/white/blue color bar is where you’ll find information about the warmth or coolness of the light, both with an arrow on the color bar and with a number. The number is called the Color Temperature (actually the correlated color temperature) and measures the warmth or coolness in Kelvin. The important thing to know is that a lower number (2700 to 3000 K) is roughly equal to an incandescent light bulb. As the number gets higher the light gets cooler.

Warmth/coolness isn’t the only measurement of the quality of light. Another consideration is how well the light source allows us to see the colors of objects. This is called Color Rendering (Color Accuracy on the Lighting Facts Label) and is indicated by a Color Rendering Index number. Higher numbers (with a maximum of 100) indicate better color rendering, so a light with a Color Accuracy of 95 should be visibly better than one of 80.

The Color Rendering Index is not very specific, however, and is known to misrepresent LEDs. Therefore you are the best, final test of whether or not a given light bulb is appropriate. I recommend purchasing only one or two and trying them out for a few days before committing to changing over your entire house.

My other recommendation is to stick with the major manufacturers (GE, Philips, Sylvania) for most lamps that you test. These companies have a track record of product consistency and quality that many of the newer manufacturers don’t. I can almost guarantee that with an off-brand 5-pack of lamps for $10 you’ll get what you pay for and hate the results. It’s not the technology that you’ll hate, but the manufacturer’s poor execution of the technology.

I hope this helps.

A Challenge for LED Luminaires

Today I was at an LED “shootout” at the New York City office of Barbizon (special thanks to John Gebbe and Scott Hali). We were looking at products that might be used in a specific application – that of lighting an auditorium or theatre. The shootout was between 26 fixtures from 17 manufacturers, all installed at a height of 10′.

Architecturally, the designer is essentially lighting three conjoined rooms: the orchestra, where the ceiling can be 35′ high or more; the balcony, where the ceiling can range from 12′ to 25′ because of the steep slope of the seating; under the balcony, where the ceiling may range from 12′ to 18′, again because of the slope of the seating.

The first part of the challenge is to find a set of fixtures that can provide even illumination in these three spaces, each one of which has a sloped floor and therefore a varying throw distance. The second part of the challenge is for all of the fixtures to dim simultaneously. Unfortunately, I don’t think we saw success. Here’s what we saw.

First, only one manufacturer had a product line for all three possible mounting conditions – pendant, surface, and recessed. That manufacturer, though, didn’t have three beam spread and/or brightness options to meet the range of typical installation heights.

Second, LED manufacturing is maturing, but it’s not mature. That means we still don’t have strong, industry-wide standards for things like color. In many cases it was difficult to use fixtures from two or more manufacturers because the color of the light produced (visually evaluated, and measured in color temperature, peak wavelength and spectral content) clearly didn’t match.

Finally, getting fixtures from multiple manufacturers to dim simultaneously proved very difficult. Each set of installed fixtures would need its own (perhaps custom) dimming curve just to get a close match, and identical performance seemed impossible. The problem here is three-fold. First, multiple control protocols would be required. The fixtures demonstrated used line voltage dimming, three-wire dimming, 0-10v DC, and DMX protocols. That’s not a deal breaker, but it is an unfortunate complication. Second, some of the LED drivers produced unacceptable dips, flickering, or pulsing of the light as they dimmed. Third, some of the LED drivers couldn’t make a smooth transition from darkness or light, or light to darkness. We saw fixtures pop on and drop out, dim up nicely but not dim out well, and dim out well but pop on. Eventually this might be as easy as working with incandescent lamps, but not yet.

The easy lesson was that, for now, the safest choice for smooth dimming from darkness to full light is still incandescent. The color of the light from fixtures in all of the installation conditions will match, the dimming curves will be the same, and they’re easy to dim.

The complicated lesson was that it is absolutely essential to mock up the proposed lighting system, using the LEDs, drivers, control protocols, and dimming equipment that will be installed. It’s the only way to be certain that the start and end of a show, when the house lights dim down and then back up, isn’t a light show of its own.