Solid-State Lighting Applications


Solid-state lighting (SSL) is a new technology, not simply a refinement of an existing one. New materials and technologies are not only offering substantial improvements in efficiency compared with conventional incandescent lighting, but also opportunities to put light in new and sometimes startling places and modes that are only beginning to emerge in a rapidly changing field. But it also presents significant challenges to end users, designers, the lighting industry, and regulating authorities as they try to cope with the implications of this change in a very basic service.

Incorporating SSL products in a home or office is not always simply a matter of unscrewing one lamp and screwing in another, because they are significantly different in form and function, as described in Chapter 4. At the current stage of development, these new light sources (currently comprising light-emitting diodes (LEDs) and organic LEDs (OLEDs)) have been highly successful for some applications, show promise in many more, and have serious problems that need addressing before they can be used in yet other applications.

SSL is becoming more popular with end users and designers. The general public’s perception is that LEDs are more energy efficient and “advanced.” Users’ expectations are that the SSL quality will be as good as standard lighting products. They also expect that SSL can be applied to existing electrical distribution systems with no problems, which is not always the case.

Advantages of SSL include the following: small size, ease of control, uni-directional distribution, cool beam and color rendering that can be very high and comparable to high fluorescent lamps with high color rendering index (CRI), lower energy use compared to incandescent lamps, high performance in cold environments, long life, and new form factors. Current challenges with SSLs include cost, system and controls compatibility, heat management, power quality, the failure process, color consistency, and glare issues.

Whereas SSL lamps have relatively low lumen output (approximately equivalent to a 60 W incandescent) and the majority produce a unidirectional beam, the best applications currently are those in which the light source is close to the task, lower lumen output is sufficient, and directionality is important. Examples of these best applications are task, undercabinet, track, wall washing, surface grazing, step lights, semi-recess, lower light output street and area lighting, and color changing theatrical lighting.

Challenging applications include omni-directional lighting (e.g., such as those applications for the linear fluorescent lamps) and high output. Examples of these are fluorescent lamp replacements and high output downlights. Street and area lighting is improving dramatically, but high light output and glare are still an issue with poorer quality luminaires.

At this stage of development, the challenges outweigh the advantages for many applications. Of course, what is a challenge in one application can be an advantage in another. However, product development is very active, and the trends are toward decreased cost, better glare control, and better color rendering and color consistency. Standards, guidelines, and better designer/user education are needed to help make SSL ready for successful applications in large-scale markets. The outdoor and residential markets currently offer the greatest opportunities for large-scale deployment because commercial and industrial applications already have low cost and relatively efficient fluorescent and high-intensity discharge (HID) lamps.

This chapter outlines the types of applications where SSLs have been incorporated and evaluates their current status.



Residential lighting typically consists of recessed downlights, wall sconces, pendants or chandeliers, track lighting,

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5 Solid-State Lighting Applications INTRODUCTION Whereas SSL lamps have relatively low lumen output (approximately equivalent to a 60 W incandescent) and the Solid-state lighting (SSL) is a new technology, not simply majority produce a unidirectional beam, the best applica- a refinement of an existing one. New materials and technolo- tions currently are those in which the light source is close to gies are not only offering substantial improvements in effi- the task, lower lumen output is sufficient, and directionality ciency compared with conventional incandescent lighting, is important. Examples of these best applications are task, but also opportunities to put light in new and sometimes undercabinet, track, wall washing, surface grazing, step startling places and modes that are only beginning to emerge lights, semi-recess, lower light output street and area light- in a rapidly changing field. But it also presents significant ing, and color changing theatrical lighting. challenges to end users, designers, the lighting industry, and Challenging applications include omni-directional light- regulating authorities as they try to cope with the implica- ing (e.g., such as those applications for the linear fluo- tions of this change in a very basic service. rescent lamps) and high output. Examples of these are Incorporating SSL products in a home or office is not fluorescent lamp replacements and high output downlights. always simply a matter of unscrewing one lamp and screw- Street and area lighting is improving dramatically, but high ing in another, because they are significantly different in light output and glare are still an issue with poorer quality form and function, as described in Chapter 4. At the current luminaires. stage of development, these new light sources (currently At this stage of development, the challenges outweigh comprising light-emitting diodes (LEDs) and organic LEDs the advantages for many applications. Of course, what is a (OLEDs)) have been highly successful for some applications, challenge in one application can be an advantage in another. show promise in many more, and have serious problems However, product development is very active, and the trends that need addressing before they can be used in yet other are toward decreased cost, better glare control, and better applications. color rendering and color consistency. Standards, guidelines, SSL is becoming more popular with end users and and better designer/user education are needed to help make d ­ esigners. The general public’s perception is that LEDs are SSL ready for successful applications in large-scale ­markets. more energy efficient and “advanced.” Users’ expectations The outdoor and residential markets currently offer the are that the SSL quality will be as good as standard lighting greatest opportunities for large-scale deployment because products. They also expect that SSL can be applied to exist- commercial and industrial applications already have low ing electrical distribution systems with no problems, which cost and relatively efficient fluorescent and high-intensity is not always the case. discharge (HID) lamps. Advantages of SSL include the following: small size, This chapter outlines the types of applications where SSLs ease of control, uni-directional distribution, cool beam and have been incorporated and evaluates their current status. color rendering that can be very high and comparable to high fluorescent lamps with high color rendering index (CRI), lower energy use compared to incandescent lamps, high OVERVIEW OF APPLICATION TYPES performance in cold environments, long life, and new form factors. Current challenges with SSLs include cost, system Residential and controls compatibility, heat management, power quality, Residential lighting typically consists of recessed down- the failure process, color consistency, and glare issues. lights, wall sconces, pendants or chandeliers, track lighting, 72

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SSL APPLICATIONS 73 table and floor lamps, and undercabinet and task lighting. mounted with direct/indirect distribution.1 All of these pro- Lighting levels are lower than in commercial or industrial vide uniform omni-directional light distribution, creating applications. Color, brightness, dimming capability, and uniform ambient lighting. appearance are extremely important. Accent lighting adds visual interest to an area and is Residential users expect SSL to look and act just like their frequently implemented with track lighting supplied with incandescent counterparts. Such attributes as smooth dim- tungsten halogen or ceramic metal halide lamps. Ceramic ming with existing residential dimmers, absence of flicker, metal halide track lighting is used in many grocery stores absence of radio interference, great color rendition, and equal because of the higher light output. light output and similar brightness to incumbent lighting Task lighting offers higher lighting levels for specific technologies will all be imperative for the successful SSL areas and has been traditionally supplied with tungsten halo- introduction into the residential market. Users also expect gen or CFLs. Task lighting is used primarily in office areas in to be able to use the new lamps without having to replace the form of under-shelf or free-standing desktop luminaires. existing luminaires (i.e., fixtures using screw-in lamps). In most commercial applications, the lighting system is SSL is easily controlled in principle. Dimming is readily expected to last for many years, requiring very little main- available, but flicker, so called “pop-on” effects and lower tenance with easy accessibility. Occupants expect controls end drop-out are still apparent in some products. Pop on to perform daylight dimming, occupancy/vacancy sensing, occurs in two ways: (1) when a preset dimming control is scene controls, and manual dimming. used and lights do not turn on to their pre-set dimming level, SSL is becoming more common in commercial applica- but first come on (near) full and then dim down automatically tions, especially for use with surface grazing (wall washing, to the preset level and (2) when a slide (or rotary) dimmer white board lighting, and cove lighting). SSL is ideal for is used, lights do not turn on at the low end, but require the task or personalized lighting and for accent or track lighting. slider to be raised to a relatively high level to start the lamp, The more difficult applications are general omni-directional before dimming to a lower level can be achieved. Lower end ambient lighting now supplied by fluorescent luminaires. drop-out occurs when lights are dimmed but turn off before The one exception is lower light output, semi-recessed indi- reaching the desired low level. All of these are symptoms of rect luminaires, which are becoming popular for ambient incompatibility between the LED lamp driver electronics and lighting. incandescent dimmers and can be mitigated when the ­drivers are designed for better compatibility using an industry stan- FINDING: The best LED applications take advantage of dard such those of the National Electrical Manufacturers the directional light put out by LEDs, such as downlights, Association (NEMA) on SSL 6 (see Chapter 4). Alterna- wall washers, and grazing and accent lighting. tively, the dimmer can be replaced with a new-generation device that is being designed to operate LED lamps. Existing FINDING: Omni-directional LED lamps are not as incandescent dimmers may not work with LED replacement efficient as linear fluorescent lamps. In order to become a lamps (even though the LED lamps are labeled “dimmable”). viable replacement alternative for linear fluorescent lamps, In some cases, the dimmers may have to be replaced. SSL products need to improve efficacy, become more omni- directional, and reduce initial cost in order to compete with FINDING: Replacing incandescent or fluorescent lamps fluorescent lamps. with LED lamps provides an opportunity to greatly reduce power load and increase lamp life. They can also turn on Total harmonic distortion (THD) of the line current and instantly and are able to dim. The market for these lamps the power factor (PF) of the LED lamps are serious con- will only expand as the light and color quality improve and cerns. Most existing commercial buildings have 120/208 the costs are reduced. or 277/480 volt three-phase electrical distribution systems, where three phases share a neutral. If the THD is too high, If SSL meets the above performance criteria, then long the neutral conductor may be overloaded, especially in exist- life and low energy use will attract users. If SSL does not ing buildings with older electrical distribution systems. In meet the criteria, then disappointment and frustration will new construction, the most recent National Electrical Code damage the market, as happened with compact fluorescent recommends separate neutrals for each circuit to avoid this lamps (CFLs) (see Chapter 2). Appropriate policies, regula- problem. This issue is discussed in more detail in Chapter 4, tions, and educational campaigns can help avoid this result. 1 A troffer is “a long, recessed luminaire installed with the opening flush Commercial with the ceiling.” A pendant is “a luminaire that is hung from the ceiling by supports.” A parabolic is “a luminaire with the light source at or near the Ambient lighting in commercial sites has been tradition- focus of a parabolic reflector producing near-parallel rays of light.” Both ally supplied with linear fluorescents in either recessed troffers and parabolics are installed as recessed luminaires. Indirect lighting involves “luminaires that distribute 90 to 100 percent of the emitted light troffers, recess parabolics, semi-recess indirect, or pendant upward” (ANSI/IES, 2010).

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74 ASSESSMENT OF ADVANCED SOLID-STATE LIGHTING where recommendations are made for SSL devices. It should Outdoor Lighting also be noted that when replacement dimmable LED lamps Roadway and area lighting appear to be one of the fastest are installed in existing luminaires, many of the existing growing application markets for SSL. The requirements in incandescent dimmers may cause lamp flickering (this issue such applications for lower light levels (compared to interior is also discussed in detail in Chapter 4). Pop-on dimming applications); larger luminaires with non-confined mounting, effects are very similar to those in residential applications mostly open to air, which enhances heat dissipation; perfor- and have been discussed above. mance at cold temperatures; and long life have made SSLs attractive to this rapidly growing market. Traditional outdoor FINDING: SSL must have power quality standards to luminaires have used HID lamps, mostly high-pressure mitigate against high THD, low PF, and repetitive peak cur- sodium (HPS), where the lamp is located inside the luminaire rent issues. reflector. This configuration has the advantage that the arc tube brightness is typically not viewed by motorists or pedes- FINDING: New dimmers must be able to operate LED trians. HPS luminaires have a narrow spectral distribution, luminaires and lamps smoothly without perceptible flicker which provides poorer color rendering properties than white and should be available to dim from 100 percent power to light sources such as metal halide, induction, and SSL. HID 1 percent power. life is mid-range, requiring lamp replacement approximately every 2 to 3 years. Industrial SSL luminaires are uni-directional, unlike HID lumi- naires, which are more omni-directional. The advantage of Industrial applications typically use a combination of high using omni-directional HID luminaires is they offer glare bay luminaires (directional downlights) or low bay lumi- control and a soft gradient edge. The disadvantage is that naires (omni-directional downlights). Task lighting is also the light from an HID luminaire is harder to control, provid- used for specific applications where higher light levels are ing higher lighting levels directly below the luminaire and required, such as in manufacturing facilities. Long-lasting requiring a large reflector system to control light spillage. light sources are required for reliability and safety, espe- The uni-­ irectional properties of SSL mean it can direct d cially in 24-hour facilities. Controls have typically not been light exactly where it is required without unwanted higher expected in industrial sites but are becoming more popular, light levels below the luminaire while having more light especially in applications where daylight can supplement in-between luminaires, which improves overall uniformity. the light level, allowing energy reduction by dimming the But glare can be greater with the SSL luminaires if the light interior lights. sources are not shielded with a lens or redirected and diffused Traditionally, high ceilings and harder access has lead by a reflector. many industrial sites to higher-wattage, standard HID lumi- The American Medical Association has issued a policy naires. Standard HID luminaires provide higher light output that states, “Many older citizens are significantly affected by than fluorescents, but do not last as long (having roughly glare as the eye ages, leading to unsafe driving conditions; two-thirds the life). Also, HID lamps have a slow start, and glare light is also light trespass and is intrusive and requiring several minutes to achieve full light output, making unwanted in households and dwellings; and light trespass them harder to control with occupancy sensing or daylight has been implicated in disruption of the human and animal on/off switching. circadian rhythm, and strongly suspected as an etiology of SSL applications are more difficult for industrial appli- suppressed melatonin production, depressed immune sys- cations because of high light level requirements. Also, heat tems, and increase in cancer rates such as breast cancers” management is difficult in high ceilings where ambient (Motta, 2009). temperatures are higher. In some settings, the failure process may be an issue, because SSLs gradually lose luminous flux FINDING: Discomfort or disability glare can be an rather than burn out. If these issues can be solved, then SSL issue with directional LED luminaires. Luminaires must be could provide lower maintenance costs and controllability. designed so as not to increase glare potential compared to Power quality issues are similar to the commercial their HID counterparts. applications. Heat still needs to be managed, especially if the lumi- FINDING: Industrial applications of SSL products will naires are left on during the day because of a malfunctioning require higher light output for ambient lighting because of photocell. However, the superior performance of SSLs at their use in high ceiling applications. cooler temperatures is an advantage for some applications, such as roadway lighting and signals. Currently, white LED modules always include a blue LED, which raises environmental concerns similar to those

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SSL APPLICATIONS 75 for the short wavelength components of metal halide and FINDING: Exterior lighting is a prime candidate for fluorescent lighting. These concerns include photobiological early adoption of SSL because of the lower lighting levels effects and increased skyglow2 (IDA, 2010; Wright, 2011). required in such applications and the optical control, long These effects are most pronounced when lighting is ener- life, and dimmability characteristics of SSL. gized all night long. SSL APPLICATION ADVANTAGES FINDING: LED white light products produce light in spectral regions that may create environmental and health While some of the advantages of SSL are immediately concerns. These concerns should be recognized in the design obvious, others are still only possibilities. As new technolo- and application of LED luminaires. gies and luminaires are developed, new applications will also emerge, leading to unexpected opportunities in lighting The long life promised by SSL luminaires has the poten- design. Current SSLs offer small size, ease of control, uni- tial to reduce maintenance, offering not only replacement directional light, cool beam, superior color, low energy use, savings, but also higher reliability. However, SSLs typically and long life. OLEDs promise entirely new form factors, a do not burn out, but only reduce their light output. So in some prospect that opens up a whole new realm of possible appli- applications there may be a liability risk if the SSL is func- cations. Also, because of control compatibility, SSL can tioning but not producing the expected luminosity. Reduced further reduce energy through dimming strategies. light output occurred in the past with mercury vapor lighting. Outdoor SSL luminaires may be dimmed if adaptive stan- Small Size dards were to be applied. Adaptive standards are the practice of reducing lighting levels during periods of low activity, The compact size of the SSL modules offers opportunities such as in the middle of the night when many establishments to put lighting in areas that previously had restricted lumi- are closed. This practice is very popular in Europe and is now naire size. But the challenge of managing the heat generated being introduced into North America through recommenda- by the LED has prevented a desired reduction in the size of tions of the Illuminating Engineering Society (IES) (IES the light source needed for high lumen output. As modules and IDA, 2011). Adoption of such practices would provide become more efficacious, the size can shrink even more. communities and property owners the flexibility to reduce Shrinking size will allow more opportunities for replacement lighting levels during periods of low activity, or during peak of additional types of lamps such as high-output MR-16 demand periods, thus saving energy. lamps (see Chapter 1). The MR-16 is an important lamp for Several cities, such as New York City, San Francisco, retail, hospitality, and residential applications. Oakland, San Jose, and others have performed extensive LED street lighting demonstration projects (DOE, 2012a) as Inherent Controllability part of the U.S. Department of Energy’s GATEWAY demon- stration program.3 In all of these projects, the predicted and SSL products have instant on and off operation without measured energy use and maintenance are lower than for the requirement for a warm-up time, an attribute that is in conventional lighting, but illuminance levels are also lower contrast to that of HID and CFLs. With a dimmable driver, compared to existing HPS street lighting. Additional added SSL products can be dimmed over a wide range of luminous benefits include reductions in sky glow and light spillage. flux in a smooth manner. Dimming below 10 percent is only Some cities, such as San Jose (Figure 5.1) and Anchorage, available with a select number of drivers but is desirable conducted controlled public surveys to obtain community (see Chapter 4). Smooth dimming is also available with feedback on the LED street lighting (Clanton and Associates some SSL screw-in incandescent replacement lamps. The and VTTI, 2009, 2010). The public preferred the warmer appropriate choice of dimmers and drivers for SSL will color temperature LED, even at lower lighting levels, com- enable control compatibility, which is critical for intelligent pared to the existing higher wattage low pressure sodium energy control systems. (LPS) and HPS street lighting (Gibbons and Clanton, 2011). Some control systems can change the color of light by varying the intensity of different colored LEDs in a red, green, blue system (i.e., one which produces white light by combining red-, green-, and blue-component LEDs). These 2 are currently used mainly in special effects lighting, but Skyglow is the result of blue light being absorbed or scattered in the atmosphere resulting in a loss of visibility of the night sky, which is of have the potential for applications in commercial and high- special concern to the astronomy community. end residential markets. For example, retail venues might 3 DOE GATEWAY demonstrations have the objective to showcase LED wish to vary the color of light in a display to emphasize a products for general illumination. DOE publishes detailed reports and briefs product’s features. on completed projects. The reports include analysis of data collected, pro- jected energy savings, payback analysis, and user feedback. Adapted from http://www1.eere.energy.gov/buildings/ssl/gatewaydemos.html.

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76 ASSESSMENT OF ADVANCED SOLID-STATE LIGHTING FIGURE 5.1  Subjective lighting survey used by the city of San Jose, California. SOURCE: Clanton and Associates and VTTI (2010). Directional Distribution in other heat sensitive applications. SSLs based on LEDs are currently used in museums (e.g., in Portland, Oregon) and SSL has unique uni-directional distribution character- in refrigerated display cases (e.g., Albertsons Grocery in istics, providing excellent beam control and allowing the Eugene, Oregon) (DOE, 2012a). Newer domestic refrigera- fabrication of luminaires that are ideal for long-distance light tors are also using LEDs for interior lights. distributions. For instance, an entire building façade can be grazed with luminaires located at one level. Accent lighting in retail stores can produce high-quality illumination with Color Characteristics little energy. SSL has the potential to put light where it is SSL has the potential for superior chromaticity and color needed with minimal light spillage, but without appropriate rendering. As discussed in Chapters 1 and 3, the spectral optics it can exhibit a sharp cutoff in illuminance with an output of SSL products can be tuned to create virtually any abrupt termination of the lighted area. For instance, with- desired chromaticity. This is required in all applications out appropriate optics roadway lighting may not light the where the users typically compare the lighting color to rec- adjacent sidewalks. This attribute of SSL emitters may also ognizable sources such as daylight or an incandescent lamp. make for difficulties in the development of omni­ irectional d In addition to achieving excellent color rendering, some lamps replacements for fluorescent and incandescent lamps. SSL sources can create desirable effects, such as increas- In the future this problem could be solved by proper optical ing the saturation of object colors. Opportunities exist to designs. select spectral distributions for specific applications, such as rendering artwork, or narrow spectral distribution, such Cool Beam as amber LED (i.e., LED lights without the blue component) for lighting beach boardwalks near turtle hatching areas Because the LED does not emit infrared light as does an where young turtles are at risk because they are attracted to incandescent lamp, the beam of light is cool. This makes it blue light similar to the ocean effervescence (Longcore and ideal for reducing heat on retail products and art work and Rich, 2005).

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SSL APPLICATIONS 77 Long Life When SSL is properly operated within its temperature and operating current ranges, it has a relatively long life, which reduces maintenance and improves reliability. Because SSL may not burn out but only decrease in light output, there is a potential liability issue if light output drops below design levels. Proactive maintenance strategies can be developed to alert users through intelligent controls when SSL drops below 70 percent of initial light output. SSL drivers can be made to adjust operating current so that when lamps are new, the operating current is lower. As lamps age, the operating current increases to maintain consistent light output. Near the end of usable life, indicators may be used to signal low light output. FIGURE 5.2  Example of multi-panel OLED (Canvis™ Twist by Acuity Brands). SOURCE: See http://www.acuitybrandsoled.com/ Luminaires with Entirely New Form Factors creations/canvis-twist/. Luminaires of entirely new form factors may be devel- oped to take advantage of the unique attributes of LEDs and OLEDs. For instance, neither replacement lamps nor retrofit consists of multiple, movable OLED panels (Figure 5.2). It luminaires capitalize on the very small size of individual is possible that future lighting will make luminaires invisible, LEDs. This characteristic alone, if fully exploited, has the as is done by some LED products that are small and thin and potential to completely change where and how electric intended to be installed in small ­ revices and recesses in the c lighting is used. The controllability of LEDs is also only built environment.4 At this stage, it is impossible to predict beginning to be explored. Common lighting controls now are all of the forms that future SSL luminaires will assume. limited to dimming, occupancy/motion sensing, and daylight sensing. The next generation of SSL luminaires will be able FINDING: Were OLEDs to become commercially to do those things and perhaps much more: change color, viable, they would provide an opportunity to change the change color rendering properties, and so forth. Because the form factors of how luminaires are designed with smaller ability to control different light properties is determined by sizes, less material, and fewer physical constraints and offer the components in the product, controls will most likely be an ability to change from traditional-looking luminaires to considered integral parts of the luminaires. OLED’s unique internally lighting surfaces and materials. properties naturally lend themselves to out-of-the-box think- ing, and truly novel luminaire designs may emerge with new OLED products. Other applications may include lighted SSL APPLICATION CHALLENGES surfaces such as walls, ceilings, and furniture systems. As with any new technology, the early adopters have Adoption of these new and novel types of luminaires highlighted areas in which further improvements are needed would require the most risk and investment by consumers. to make SSLs fully equivalent across the whole spectrum of If a consumer were to become dissatisfied with a very inno- lighting applications. Whenever a new technology is intro- vative SSL luminaire, reverting to other lighting technolo- duced, dissimilarities are noticed. For example, when the gies would be difficult and expensive. Installation of highly CFL was introduced to replace the incandescent lamp, users innovative luminaires in existing buildings may necessitate were unhappy with the flickering, slow start-up, color, light major retrofit work. Thus it is likely that early adoption of intensity, noise, radio static, and lack of dimming. It will be such luminaires will be in new construction projects that important not to make the same mistakes with SSL introduc- pay attention to lighting design from the early stages of tion (see the Chapter 2 section, “Compact Fluorescent Lamp architectural planning. Case Study”). A small sampling of these types of forward-looking lumi- At this point, the major challenges to full acceptance of naires has been developed. One interesting example is a closet SSL are cost, system and control compatibility, and heat rod embedded with LEDs, which becomes luminous when management. These issues are not well understood by most the closet door is opened (Reo, 2011). This custom-made end users, so it falls to the lighting industry to improve product illustrates a clever use of controls and great atten- tion to putting light where it is actually needed in a closet. Future lighting may emphasize flexibility and multi-function, as illustrated by a multi-functional OLED luminaire, which 4 See, for example, http://www.youtube.com/watch?v=_8e4iYlNyZI> and www.edgelighting.com.

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78 ASSESSMENT OF ADVANCED SOLID-STATE LIGHTING components and to other professionals to establish standards operational characteristics. If a driver is not compatible, and recommendations that will ease the introduction of SSL. luminaires can flicker, have shorter lives, or not operate at all. Most quality manufacturers now supply the drivers with their luminaires, which avoids confusion. Cost Drivers must also be compatible with new and existing The cost for SSL luminaires needs to be reduced for them control systems. Currently, some integrated drivers have to be readily accepted. As noted in Chapter 2, it took a combi- power quality problems such as high THD of the line current nation of technical advances to improve quality and incentive and low PF. A designer must obtain the list of compatible programs to overcome the initial reluctance to adopt CFLs, drivers from the control manufacturer—a method of selec- and their initial cost is still an inhibiting factor. tion that is awkward, adds design time, and adds difficulty Both initial and replacement costs are major consider- when SSL equipment is substituted for standard fixtures. A ations, particularly for SSL luminaires. Many SSL compo- NEMA standard for controls, drivers, and SSL compatibility nents are integral with the luminaire, making component could streamline this process. replacement difficult if not impossible. Instead of replacing a lamp, the entire luminaire would need to be replaced Heat Management should one of these integral components fail. Progressive manufacturers now construct luminaires for easy component Heat management is a huge challenge with SSL appli- replacement, including such features as removable optical cations (see Chapter 4). Luminaires must dissipate heat cartridges and quick connects to drivers. Also, driver lives adequately to maintain life and light output expectations. are dependent on operating temperature but, none­heless, t For SSLs, mounting details can add heat management are increasing to match the life of the SSL luminaire complexity. For instance, operating temperatures can rise if (Figure 5.3). SSL luminaires are mounted in a confined space, adjacent While cost is still a significant barrier to more rapid intro- to insulation, in high temperature environments, or where duction of SSLs, the expectation is that with the current rate the heat otherwise cannot be dissipated. An example would of progress, they will become a cost-effective option in the be a recessed downlight adjacent to insulation in a non-­ near future (Bland, 2011). conditioned area. Another example would be one in which MR16 lamps are installed in open air luminaires where the only heat sink is the socket connection. As operating System and Controls Compatibility temperatures increase, life and light output decrease. Non- Lighting controls can include dimming, occupancy con- LED luminaires have an easier chance of dissipating heat trols, and color control. Current SSLs do not always grace- compared to LED lamps, where the heat sink is limited to fully mesh with existing installations. One great challenge the socket size and cooling fins around the lamp. OLED for designers is selecting compatible drivers for the SSL luminaires do not have as significant heat management issues luminaires. This is also related to dimming compatibility as LED (refer to Chapter 3) at room temperatures and below, issues. Different drivers have unique operating currents and which facilitates installations in more varied environments. FIGURE 5.3  LED driver life of Philips “Xitanium” driver versus case temperature. SOURCE: Philips Lighting North America (2012). 5.3.eps bitmap

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SSL APPLICATIONS 79 FINDING: Replacing existing incandescent lamps with specified equivalent wattage. The quantity of light (i.e., LED lamps in existing luminaires may under certain condi- the luminous flux measured in lumens) is the easiest metric tions cause the LED to overheat. Examples include down- to use, because it is easily predicted and measured. SSL has lights adjacent to insulation or in enclosed luminaires. This is been successful in producing a quantity of light similar to true also of the use of SSL in industrial applications having standard luminaires in the lower lighting level environments. higher ambient temperatures. LED lamp heat management High lighting levels are currently harder to achieve because needs to be addressed for all such applications. of the amount of heat management required with the addi- tional wattage. As SSL modules become more efficacious, higher lighting levels will be achievable that do not encounter Power Quality these problems in operation. SSL products, similar to fluorescents and HID, contain electronic components and without appropriate design can Lighting Ambiance produce poor power quality and exhibit, for example, high THD and low PFs. This is a similar set of issues encountered Whether a scene is pleasant, spacious, intimate, or dra- by early deployments of electronic and hybrid ballasts for matic depends on the luminance balance within the scene compact fluorescents and linear fluorescents lamps. High (IES, 2011, p. 4.26) and how light is layered. For instance, THD can cause flickering and excess current on shared neu- spaciousness is implied when walls and ceilings are evenly tral conductors. Low PF results in line currents higher than lighted. Pleasant scenes may have non-uniform lighting with necessary to supply the required power. stronger accent lighting and peripheral wall emphasis (Flynn SSL drivers, similar to fluorescent electronic ballasts, can and Spencer, 1977; IES, 2011). SSLs based on LEDs per- cause radio interference, which can be annoying, especially form well for surface grazing for walls and ceiling coves and to residential users. SSL drivers are required by the Federal for accent lighting. Applications of SSLs based on OLEDs Communications Commission to adhere to similar protocols include lighted surfaces in addition to luminaires. as electronic ballasts in order to avoid these problems.5 This Examples of installations having lighting layers include includes the integral drivers in SSL lamps. uniform ceiling brightness balanced with select wall wash- Related to power quality, issues such as dimmer range ing and occasional accent lighting; personal work areas may and reliability, maximum/minimum units required on a con- have under-shelf lighting with adjustable task lighting. All of trol, repetitive peak voltage, and in-rush current can cause these layers should be separately controlled to provide the significant problems if not properly addressed (see “Electric desired luminance balance. The light output of SSL products Power Quality” in Chapter 4). can be very directionally controlled and, thus, has unique advantages in providing layers of light, especially for surface ambient, accent, and task lighting. Failure Process As an SSL product ages, its output gradually declines. It Brightness and Glare does not simply go dark, but its lumen output declines over time. This could be a liability issue in some applications Because SSL lighting is uni-directional, it has the pos- where a specific level of illumination is required. One prom- sibility of high brightness, giving luminaires the potential of ising option to address this is incorporating a driver that will producing glare if not controlled properly. Luminaires can increase the operating current as the LEDs age to keep the limit brightness through optical systems either at the module luminaire at its specified output. level or within the reflector and lens design. Methods include the use of remote phosphor modules or diffusing lenses or by indirectly lighting via reflectors or surfaces so the individual Lighting Quality Issues LEDs are not visible. If SSL is to compete successfully, then its lighting quality should be equal to or better than non-SSL luminaires (IES, Color Rendering, Appearance, and Consistency 2011, p. 7.64; IALD, 2006). Lighting quality issues include quantity of light, lighting ambiance, glare reduction, and To see colors as intended, the lighting system must pro- color rendering and consistency (ALA, IES, IALD, 2010). duce a desired spectral distribution. Lower color tempera- tures are associated with “warmer” looking light, appropriate in residential, hospitality, and retail applications. Higher Light Quantity color temperature represents “cooler” looking light, which When a user installs SSL, they expect that the light will is appropriate in commercial and industrial applications. be equivalent to (seem the same as) an incandescent of the Exterior applications show a preference for lower color t ­emperatures (Clanton and Associates and VTTI, 2009, 5 See discussion in Chapter 4, “Electric Power Quality.” 2010).

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80 ASSESSMENT OF ADVANCED SOLID-STATE LIGHTING An LED produces light in a narrow spectrum. In order to FINDING: Many LED lamps currently available do not produce white light from a single LED module, the module have the same light output and color rendering properties as is phosphor-coated. Another method of producing white light incandescent lamps. SSL products with improved light out- is combining several different color LEDs. Color rendering, put that are color consistent from product to product will be and color rendering indexes, are harder to apply to LED needed for the public to readily accept these as replacements luminaires than standard luminaires (see Chapter 1). Not for incumbent lighting technologies. all LED lamps available in the current market have good color rendering properties. Higher color temperature LED EVALUATING SSL LIGHTING APPLICATIONS modules are more efficacious, encouraging their application. But the cooler color (bluish tint) associated with them may SSL lighting applications are currently intended to dupli- not be as readily acceptable to users (Clanton and Associ- cate or be similar to incandescent and fluorescent lighting. SSL ates and VTTI, 2009; Clanton and Associates, VTTI, ETA, has many unique qualities that have not been present before in 2010). SSL luminaires need to increase the efficacy for lamp technology, and these may result in new applications in color temperatures below 3,800 K in order to satisfy user the future. The attributes of SSL make possible new ways of preference for the lower correlated color temperature (CCT) lighting such as uniform surface washing and grazing, close- (Figure 5.4). to-task effectiveness, and surface integrated light. Tunable One significant issue is the consistency of SSL luminaires’ spectral distribution adds flexibility for color adjustments. color appearance. If LEDs from different bins are used in the The current status of SSL applications is summarized same luminaire or in similar luminaires side by side, the light below. This is, of course, a snapshot of a moving target, as outputs will not match in color appearance (i.e., the CCT). the field is changing rapidly. This is an issue not only during initial installation, but also in deployment because of aging and replacement of lumi- Best. Because the current LED products have relatively naires. SSLs need to be consistent between products and low lumen output, the best current applications for SSL are guaranteed to provide color-consistent replacement modules those in which the light source is close to the task and the in the future. required lighting levels are low. Examples of these are task 250 200 Efficacy (lm/W) 150 Color-Mixed Cool 100 pc-LED Cool Color-Mixed Warm pc-LED Warm 50 Qual Data Warm Qual Data Cool 0 2005 2010 2015 2020 2025 FIGURE 5.4  Current and projected efficacies. NOTE: pc-LED = phosphor-converted LED; lm = lumen; W = watt; Qual = qualified data point having satisfied the criteria for cool white (color rendering index (CRI) of 70-80, correlated color temperature (CCT) of 4,746-7,040 K) or warm white (CRI of 80-90, CCT of 2,580-3,710 K). Results are 5.4.epsfor 25°C package temperature and are normalized to current densities of 35 A/cm2. SOURCE: DOE (2012b).

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SSL APPLICATIONS 81 (Figure 5.5), under-cabinet or under-shelf, step lighting, and wall washing (Figure 5.6) and cove grazing. Emerging. Emerging SSL applications include higher out- put directional lighting. Because heat management may be an issue with higher output lumen packages, higher-efficacy lamps will help with these applications. Examples are accent lighting, downlighting (Figure 5.7), large area grazing, and street (Figure 5.8) and area lighting. Difficult. Difficult SSL applications include omni-­ directional lighting. Because LED modules are uni-­ directional, it is difficult to fabricate luminaires that render them omni-directional. For fluorescent replacements, LEDs offer little advantage if any, and at higher initial cost. Replacements for high wattage A-lamps (i.e., 100 W and higher) are not yet available. Unique. When commercially available, OLEDs will facil- itate applications with new form factors, which is enabled by the manner in which the OLED is essentially the luminaire FIGURE 5.7  Example of downlighting. Sea Gull Lighting/Juice- Works. SOURCE: Next Generation Luminaires, PNNL. FIGURE 5.5  Example of task lighting. “Equo LED Desk Lamp” by Koncept Technologies, Inc. SOURCE: Next Generation Luminaires, ­ PNNL. FIGURE 5.8  Example of street lighting (“RoadStar” by Philips Roadway Lighting). SOURCE: Next Generation Luminaires, PNNL. FIGURE 5.6  Example of wall washing. “Stile Styk” by STILE, a brand of SPILIGHTING, Inc. SOURCE: Next Generation ­Luminaires, PNNL.

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82 ASSESSMENT OF ADVANCED SOLID-STATE LIGHTING (with the addition of a driver). Examples of new form factors for SSL focus on different stages of the integration of com- include lighted surfaces and objects, which eliminates tradi­ plete lighting products, including LED packages, LED arrays tional luminaire aesthetics. Some new forms include foils and modules, LED light engines, and integrated LED lamps and moldable and conformable materials. Both OLEDs and and luminaires. Additional standards focus on terminology. LEDs could be used, for example, in a recessed cavity or in Within documentary standards, test and measurement places where, for reasons of repair and maintenance, it would standards simply detail how a device or product is to be otherwise be awkward to install a luminaire. measured but do not indicate the desirable results of those Both LED and OLED applications may use dynamic con- measurements. A lighting product does not adhere to a mea- trols with spectral distribution tuning, allowing, for example, surement standard; the manner in which its characteristics cooler color temperature appearance during the day and are measured does. Performance standards, on the other warmer color temperature appearance in the evening. In areas hand, set rules and/or give permissible ranges of measure- where spectral distribution restrictions are required, such as in ment outcomes. A lighting product would be said to adhere environmentally sensitive areas or in areas where melatonin to a certain performance standard if it met the latter’s suppression is avoided (i.e., places of sleep for residential requirements. Safety standards, including electrical safety and healthcare properties), dynamic tuning could provide and photobiology (the effects of light on organisms, often solutions. concerned with the potential for light sources to damage the human eye), are one type of performance standard. A number of standards development organizations are Post-Occupancy Assessment involved in recommending test procedures for the measure- Post-occupancy assessment (POA) is a valuable tool, ment of LEDs, OLEDs, and SSL products. The Illuminating especially when deploying a new or emerging technology. Engineering Society of North America (IES), a professional POAs can provide valuable positive and negative feedback organization dedicated to advancing the art, science, and from users to manufacturers, lighting designers, utilities for practice of lighting, has been one of the leaders in the devel- rebate programs, and to the Department of Energy’s (DOE’s) opment of standards specifically for SSL and is accredited SSL programs. Organized POAs may discover an issue by the American National Standards Institute (ANSI). ANSI that requires mediation before it becomes an established establishes the consensus procedures that are the basis for association with SSL, such as dimmer compatibility. Assess- the development of American National Standards7 and is ments can gather opinions on lighting quality, performance, the U.S. representative to the International ­ lectrotechnical E l ­ongevity, economic value, and general expectations. Spe- Commission (IEC) and International Organization for Stan- cific issues may include glare, color, dimming, and flicker. dardization (ISO). The IEC is an international consensus POAs should be performed in both the commercial and standards organization for electrotechnology. The Interna- residential applications with subjective evaluations given to tional Commission on Illumination (CIE) is recognized by the end users. Additionally, issues such as energy use, power ISO and the IEC as an international standards body. Its activi- quality, longevity, and maintenance could be gathered from ties include the development of standards and procedures building managers and utility groups. for the measurement of light and publication of standards There are several existing POA formats such as Berkeley’s and technical reports related to light and lighting. NEMA is Center for the Built Environment “Occupant Indoor Environ- primarily a trade association for the electrical manufacturing mental Quality (IEQ) Survey,”6 but none of them delves into industry but is also an ANSI-accredited standards develop- specific SSL issues. ment organization. The Underwriters Laboratory is ANSI- accredited and sets safety standards for lighting products. Test and measurement standards for SSL are rapidly being TESTING AND MEASUREMENT STANDARDS developed, both within the United States and internationally. Because of the different spectral, electrical, and thermal Because of the volume of standards produced and frequent characteristics of LEDs, OLEDs, and SSL products, existing new publications, an exhaustive discussion of standards will standards to measure the photometric properties (i.e., mea- not be included here. Instead, a few important areas of testing sures of perceived light intensity) and colorimetric properties and measurement of SSL are highlighted. (i.e., measures of perceived color characteristics) of other The United States has taken early leadership on several lighting technologies frequently cannot effectively be used influential standards, such as IES LM-79-08 “Electrical for SSL. For instance, the temperature of an LED package and Photometric Measurements of Solid-State Lighting will affect measurements of light output, lifetime, and color. Products,” which specifies the procedures for measuring In such cases, the applicability of a measurement will depend total luminous flux, electrical power, luminous efficacy, and on the effectiveness of the thermal management of that LED chromaticity of SSL integral lamps and luminaires (IES, package in its ultimate application. Because of this, standards 7 Furtherinformation is available at http://web.ansi.org/about_ansi/faqs/ 6 See http://www.cbe.berkeley.edu/research/survey.htm. faqs.aspx?menuid=1.

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SSL APPLICATIONS 83 2008). Despite rapid progress, a number of important test ing products, some with very little experience in lighting, and measurement standards still need to be developed for and the metrics used to evaluate light sources need to give SSL to be successful. users accurate predictions of performance. Furthermore, the There is currently no way to measure or estimate the problems of the CRI are particularly pronounced for some lifetime of SSL luminaires. LEDs do not typically “burn SSL sources (CIE, 2007). For example, certain LED spectra out” or abruptly fail at end-of-life, like an incandescent can render the reflective samples of the CRI very well, but lamp. Instead, they get dimmer over time, the speed of which render other object colors poorly. depends on exposure to heat and other variables. Standards There is now widespread agreement that a new method have made progress on measuring and predicting lumen is needed to evaluate the color rendering quality of light maintenance (the relationship between temperature, operat- sources (CIE, 2007), and many different approaches and ing time, and light output) for individual LED packages, but methods have been proposed (reviewed in Davis and Ohno, the life of an integral lamp or luminaire is determined by 2009; Guo and Houser, 2004). DOE has publicly supported more than the LEDs. For example, the failure of an electrical one proposed metric (DOE, 2010), the Color Quality Scale component or darkening of an optical component may limit (CQS) (Davis and Ohno, 2010). Although it still uses the the lifetime of an SSL luminaire. Predicting and measur- CRI, it is the current standard. A technical committee in ing the lifetime of the integration of varying subcomponents the CIE was formed in 2006 to recommend a new procedure makes this topic very technically complicated. for evaluating the color rendering of light sources. Because the CIE committee consists of a diverse international group FINDING: There is no standardized method for measur- of stakeholders, consensus has not yet been achieved. This ing the lifetime of SSL products. is problematic for SSL manufacturers, particularly small companies incapable of performing detailed colorimetric The CRI is the internationally accepted metric for the simulations, as they optimize their products to the metric. evaluation of a light source’s color rendering abilities (CIE, 1995) and was developed in response to the advent of fluo- FINDING: The CRI does not always yield results that rescent lamps. Fluorescent lamps had spectral power dis- predict or evaluate performance well, so manufacturers can- tributions (SPDs) unlike anything the lighting industry had not rely on it to guide product development. used before, and the quality of color rendering from these light sources was highly variable. The calculation of the DOE has actively supported the consensus process for CRI requires only the spectral power distribution of the light the development of testing and measurement standards. source of interest and is basically a series of colorimetric DOE has provided experts and supported their work time simulations. In these simulations, the appearance of a pre- for numerous SSL standards committees. The agency also defined set of reflective samples (object colors) is compared organized and sponsored an SSL standards workshop, as when illuminated by the test source and when illuminated well as several related round-table meetings. Furthermore, by a reference illuminant (blackbody radiator or daylight DOE uses its demonstration projects to provide input on simulator). If the samples appear identical in both cases, the additional needed standards and provides financial support test lamp would receive a general CRI (Ra) of 100. Devia- to the U.S. national committee of the CIE. DOE also funds tions in the appearance of the test sample colors lower the measurement and standards research at the National Institute score. A number of flaws of the CRI have been recognized for of Standards and Technology. years, but the problems have not been considered important The Commercially Available Light-Emitting Diode enough to warrant change (CIE, 1999). The problems of the Product Evaluation Reporting (CALiPER) component of CRI include the use of outdated and obsolete colorimetry the DOE program includes verification testing that produces (the math used to calculate the appearance of the reflective extensive data on individual products. DOE funds indepen- samples), a set of reflective samples that do not detect certain dent laboratories to conduct the testing, each focused on one color rendering problems, and, according to some, an under- product type (e.g., high-bay luminaires; small replacement lying definition of color rendering that does not correspond lamps (MR16, PAR lamps, and so forth)). The testing follows to actual users judgments of color rendering quality (Davis the IESNA LM-79-08 method of electrical and photometric and Ohno, 2009). measurements to verify that lamps are performing according For much of the history of electric lighting, a small num- to specifications. ber of very large companies produced nearly all of the light sources sold in the world. Each of these companies had the REFERENCES resources and expertise to understand the limitations and flaws in their measurements and ensure that metrics did not ALA (American Lighting Association), IES (Illuminating Engineering Society), and IALD (International Association of Lighting Designers). lead them to inadvertently create poor products. However, the 2010. What’s Your Quality of Light? The Lighting Industry’s Call for lighting industry has changed considerably, largely because a Practical Lighting Energy Policy. Dallas, Chicago, and New York: of SSL. 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