5B -i

APPENDIX 5B. MODIFIED SPECTRUM INCANDESCENT REFLECTOR LAMPS

T ABLE OF CONTENTS

5B.1 INTRODUCTION ......................................................................................................... 5B-1 5B .2 BACKGROUND ........................................................................................................... 5B-1 5B .2.1 Spectral Power Distribution and Commonly Used Color Properties........... 5B-1 5B .2.2 Methods of Modifying Spectral Power Distributions .................................. 5B-4 5B .3 APPLICATION OF “MODIFIED SPECTRUM” DEFINITION TO IRLS ................. 5B-4 5B .3.1 Color Requirements ..................................................................................... 5B-5 5B .3.2 Black-Body Locus Requirements ................................................................ 5B -5 5B.3.3 MacAdam-Step Requirements ..................................................................... 5B-6 5B .4 METHODOLOGY FOR STANDARD AND MODIFIED SPECTRUM

COMPARISON ....................................................................................................... 5B-7 5B .5 SELECTION OF SCALING FACTOR....................................................................... 5B-12 R EFERENCES ........................................................................................................................ 5B -13

LIST OF FIGURES

Figure 5B.2.1 Spectral Power Distribution of Two Tested IRLs ..............................................5B-2 F igure 5B.2.2 The C.I.E. 1931 Chromaticity Diagram ..............................................................5B-3 F igure 5B.3.1 Combined Black-Body Locus and Color Requirements of the “Modified

Spectrum” Definition ...................................................................................5B-6 F igure 5B.3.2 Example of IRLs That Meet the Definition of “Modified Spectrum;”

Modified Spectrum IRLs Color Points Lie to the Lower Left of the Red Circle ....................................................................................................5B-7 F igure 5B.4.1 Transmittance of a Specific Lamp Cover Glass Featuring Neodymium,

Relative to the Standard Spectrum Cover Glass Transmittance ..................5B-9 F igure 5B.4.2 Relationship Between Light Output Reduction and MacAdam-Step Shift

For Lamps Tested ......................................................................................5B-11

L IST OF TABLES

Table 5B.4.1 MacAdam-Step Shifts and Light Output Reductions for Lamps Tested ...........5B-105B -1

APPENDIX 5B. MODIFIED SPECTRUM INCANDESCENT REFLECTOR LAMPS

5 B.1 INTRODUCTION

A modified spectrum incandescent lamp is an incandescent lamp with special coatings or other features that modify the wavelengths of light that exit the lamp, changing the perceived color of the lamp’s light. These lamps are noticeably different in color than unmodified spectrum (or standard spectrum ) incandescent lamps. Some incandescent reflector lamps (IRLs) are sold with features that modify their spectra, and the U.S. Department of Energy ( DOE ) believes that such IRLs pr ovide a

unique utility to users. For example, a number of these lamps are marketed

a s being able to reproduce the spectrum of natural daylight. The features that modify the spectra of incandescent lamps usually reduce the efficacies of the lamps. Thus, DOE creat ed a modified spectrum IRL product class and established candidate standard levels (CSLs) for these lamps by

sc aling from CSLs established for the standard spectrum IRL product classes. The same

a pproach was taken in setting standards for modified spectrum IRLs in the first cycle of amendments to IRL standards published in a final rule in July 2009 (hereafter the “2009 Lamps Rule”). 74 FR 34080 (July 14, 2009).

In the 2009 Lamps Rule, DOE determined the scaling facto r that shoul d be applied to efficacy requirements for standard spectrum IRLs to establish efficacy requirements for modified
spec trum IRLs. Using the definition of “modified spectrum” specified in Code of Federal R egulations (CFR), 10 CFR 430.2, DOE determined what lamps would be included in the modified spectrum IRL product class. DOE concluded in that rulemaking that the definition of modi fied spectrum was created for general service incandescent lamps (GSILs) because it requires the testing of clear lamps as a reference for spectrum comparison, and IRLs are not clear lamps due to their reflective coating. Therefore, DOE ad a pted the definition of “modified spectrum ” for IRLs and developed the factor used to set the efficacy requirements for the modified spectrum IRL product class. In particular, DOE tested IRLs marketed as featuring
spe ctral modification (such as lamps marketed as “daylight” lamps) and used similar standard
spec trum IRLs as references for spectrum comparison. The following sections discuss the methodolog y used in the 2009 Lamps Rule to develop the scaling factor for the modified spectrum IRL product class.

5B.2 BACKGROUND Objects absorb, reflect, and radiate a form of energy known as e lectromagnetic radiation

, which can be visualized as waves of energy that travel through open space. Different wavelengths of electromagnetic radiation have different common names; for example, radio waves have wavelengths ranging from millimeters to hundreds of thousands of kilometers, and visible light has wavelengths roughly between 380 and 750 nanometers (nm). Various

wa velengths of visible light are perceived as various colors by humans.

5B.2.1 Spectral Power Distribution and Commonly Used Color Properties Some portion of the electromagnetic radiation emitted by lamps exists in the spectrum of visible light. Most lamps emit multiple wavelengths of light simultaneously, and the radiant5B -2

power (energy radiated per unit time) of each wavelength can be plotted as a spectral power distribution (SPD). 1 Example SPD s are shown in Figure 5B.2. 1 for a specific standard spectrum I RL and a specific modified spectrum IRL tested for the 2009 Lamps Rule.

Figure 5B.2.1 Spectral Power Distribution of Two Tested IRLs

The measurement of a lamp’s SPD allows the characterization of the lamp’s perceived light color. Three color properties in particular are commonly computed for lamps based on the SPD . One is the chromaticity , which refers to the color of the lamp’s light a s indicated by a mapping onto a chromaticity diagram such as the Commission Internationale de l’Eclairage (C.I.E.) 1931 chromaticity diagram a shown in Figure 5B.2. 2

. 2 Subtle differences in color can be quantified using MacAdam steps, named after David MacAdam, who studied color perception in the 1940s. 3 A 3 -step MacAdam ellipse is an ellipse that encircles a region of points on the chromaticity diagram that appear to be indistinguishable to most humans (in other words, they appear to be the same color). Points further than a distance of three MacAdam steps from any

re ference color point are generally perceived by most humans as being different in color than the reference point.

a This particular figure is the chromaticity diagram for the CIE 1931 color space, created by the Commission Internationale de l’Eclairage (International Commission on Illumination, or CIE) in 1931. The colors on the outer curved boundary are composed of single wavelengths of electromagnetic radiation, with wavelengths indicated by the numbers. All colors inside the space are composed of a distribution of wavelengths of various powers.5B -3

Figure 5B.2.2 The C .I.E. 1931 Chromaticity Diagram

The curved line in the center of Figure 5B.2.2 is known as the black-body locus and represents the perceived light color emitted by a black body heated to the indicated temperature (i n k elvin). In the field of physics, a black body is a theoretical object that is considered to be an ideal emitter of electromagnetic radiation. It absorbs all electromagnetic radiation falling onto it (and thus reflects no radiation), and wavelengths of the radiation emitted by the body are related only to its temperature. Black bodies are so named because at room temperature they would emit
most ly infrared radiation, which has a lower frequency and longer wavelength than visible light. Because they would also reflect no radiation, they would appear black. As the temperature of a blac k body increases, its emitted radiation increases in frequency while shortening in wavelength and begins to be perceived as visible light. Any object hot enough to emit visible light is said to5B -4

incandesce, an d the phenomenon of visible-light emission due to high temperature is known as incandescence

. A lamp’s correlated color temperature ( CCT) is another commonly computed color property and is based on the behavior of black bodies. The CCT of a lamp is the temperature of a blac k body that produces roughly the same SPD of light (and thus roughly the same perceived color). Incandescent lamps produce light when electric current is sent through the filament inside the lamp, causing the filament to heat up and incandesce. The SPD generated by incandescent lamps i s similar to the SPD generated by a black body; thus, the temperature of the heated filament is near the CCT of the lamp. Many IRLs have a CCT between 2,700 K and 3,000 K.

The color rendering index (CRI) of a lamp is also commonly computed and refers to how closely the perceived color of an object illuminated by that lamp matches the perceived color of the same object illuminated by daylight or black-body radiation. The CRI ranges from 0 to 100; lamps wit h high CRIs illuminate objects such that humans perceive colors similar to what they would pe rceive if those objects were illuminated by daylight, or by a black body radiator. Most incandescent lamps without modified spectrums have a CRI near 100.

5B.2.2 Methods of Modifying Spectral Power Distributions

The SPDs that can be generated by incandescence are such that incandescing objects can only produce a narrow subset of all of the colors that the human eye can perceive. To produce

c olors that are distant from the black-body locus, the SPD of an incandescent object’s radiation must be modified in some way. Various methods are used to modify the SPD of IRLs. Some methods utilize specific chemicals, such as neodymium, that are introduced into the cover glass of the lamp. Other methods rely on layers of material that are sandwiched into the cover glass or

c oatings that are applied to the outside or inside faces of the glass. The compounds, layers, or

c oatings used to modify the SPD operate by reducing the power of specific wavelengths of light; thus, they act as selective filters. Because the total light output of the IRL is reduced when

se lective filtering is applied, IRLs with modified spectrums are less efficacious than standard spectrum IRLs of the same filament type, bulb shape, rated voltage, and rated wattage.

5 B.3 APPLICATION OF “MODIFIED SPECTRUM” DEFINITION TO IRLS

The definition of “modified spectrum” as specified in the CFR is as follows:

“ Modified spectrum means, with respect to an incandescent lamp, an incandescent lamp that— (1 ) I s not a colored incandescent lamp; and (2 ) W hen operated at the rated voltage and wattage of the incandescent lamp—

( A ) Has a color point with (x,y) chromaticity coordinates on the C.I.E. 1931 chromaticity diagram, figure 2, page 3 of IESNA LM-16 (incorporated by

re ference; see § 430 .3) that lies below the black-body locus; and (B ) Has a color point with (x,y) chromaticity coordinates on the C.I.E. 1931 chromaticity diagram, figure 2, page 3 of IESNA LM-16 (incorporated by reference; see § 430.3) that lies at least 4 MacAdam steps, as referenced in IESNA LM-16, distant from the color point of a clear lamp with the same filament and bulb shape, operated at the same rated voltage and wattage.”5B -5

10 CFR 430.2

The following sections will address each component of th is definition in turn as it relates
to modified spectrum IRLs.

5B.3. 1 Color Requirements As noted in the definition of “modified spectrum” a modified spectrum lamp cannot b e a “colored incandescent lamp.” The statutory definition of “colored incandescent lamp” is as follows:

“ Colored incandescent lamp means an incandescent lamp designated and marketed as a colored lamp that has— ( 1 ) A color rendering index of less than 50, as determined according to the test method given in C.I.E. 13.3 (incorporated by reference; see § 430.3); or (ii) A correlated color temperature of less than 2,500K, or greater than 4,600K, where correlated temperature is computed according to the “Computation of Correlated Color Temperature and Distribution Temperature,” Journal of the Optical Society of America, (inc orporated by reference; see § 430.3) .”

10 CFR 430.2

Most IRLs with unmodified spectrums have a CRI near 100 and a CCT between 2,700 K

a nd 3,000 K, and therefore would not be considered colored incandescent lamps. Colored incandescent lamps are lamps that have been modified, using coatings or other methods, so that the y produce light that is perceived as blue, red, green, or other colors. These lamps are used for

a esthetic or artistic effects and thus are not meant to reproduce object colors accurately. Although colored incandescent lamps are modified, they are excluded from the definition of modi fied spectrum.

5B.3.2 Black-Body Locus Requirements The “modified spectrum” definition also requires that a modified spectrum incandescent lamp pr oduce a perceived color with a “color point ... that lies below the black-body locus” on the C .I.E. 1931 chromaticity diagram when the lamp is operated at its rated voltage and wattage. 10 CFR 430.2 The chromaticity diagram and black-body locus are shown in F igure 5B.3.1

, along with red straight lines indicating color requirements. The combined color and black-body locus requirements of the “modified spectrum” definition exclude all lamps with color points outside of the dark grey area in the figure.5B -6

Figure 5B.3.1 Combined Black-Body Locus and Color Requirements of the “Modified Spectrum” Definition

5B.3.3 MacAdam-Step Requirements Finally, the “modified spectrum” definition requires that a modified spectrum incandescent lamp have a color point that “lies at least 4 MacAdam steps ... distant from the color point of a clear lamp with the same filament and bulb shape, operated at the same rated voltage and wattage.” 10 CFR 430.2 Requiring the color point to be “at least 4 MacAdam steps

... distant from the color point of a clear lamp” ensures that modified spectrum lamps will be noti ceably different in color than similar clear lamps.

Figure 5B.3. 2 shows a magnification of the C.I.E. 193 1 chromaticity diagram with an example of three IRL samples that meet the definition of “modified spectrum.” The color points of the three standard spectrum and three modified spectrum IRL samples in this pair are shown as blue dots in the figure. The modified spectrum IRLs have color points located below the blac k -body locus, shown by the black line. In addition, they meet the color requirements bounded by the red straight line at the right (the left bound is located outside of the area shown by the figure ). Finally, their color points meet the MacAdam-step requirement established by the three corresponding standard spectrum lamps located in the center of the red ellipse; the red

e llipse represents a distance of four MacAdam steps from the average color point of the standard spectrum IRLs.5B -7

Figure 5B.3.2 Example of IRLs That Meet the Definition of “Modified Spectrum;” M odified Spectrum IRLs Color Points Lie to the Lower Left of the Red Circle

Applying the definition of “modified spectrum” requires comparing the color point of the I RL in question to the color point of a clear lamp. IRLs, however, are not clear lamps because they have reflectors; IRLs also commonly have frosted or textured faces. In order to apply the de finition of “modified spectrum,” DOE developed a normalization method to model a clear lamp in the 2009 Lamps Rule. This method is discussed as part of section 5B.4

.

5B.4 METHODOLOGY FOR STANDARD AND MODIFIED SPECTRUM

COMPARISON

To explore the efficacy differences between standard spectrum and modified spectrum I RLs, DOE paired commercially available standard spectrum IRLs with available IRLs in the

sa me product line that were marketed as featuring spectral modification (for example, IRLs marketed as “daylight” or “full-spectrum” lamps) in manufacturers’ catalogs or marketing li terature. Standard spectrum lamp models were paired with the lamps featuring spectral modification such that the lamps in each pair had the same bulb shape, the same rated life, the

sa me rated voltage and wattage, and the same class of filament shape. All lamps had a rated voltage of 120 volts.

In total, DOE tested seven pairs of parabolic aluminized reflector (PAR) lamps from two major manufacturers. Six pairs consisted of halogen lamps, and one pair consisted of halogen infr ared (HIR) lamps. Each pair contained three samples of an IRL model marketed as featuring5B -8

spectral modification along with three samples of a corresponding standard spectrum IRL model in the same product line. Halogen and HIR lamps were selected because the se design options are required to meet the standards adopted by the 2009 Lamps Rule. DOE also test ed one lamp pair featuring a smaller diameter (PAR16) than IRLs covered by this rulemaking, in order to suppl ement its analysis of larger-diameter lamps.

DOE measured and recorded the SPDs of the standard spectrum IRL samples in each pair, in accordance with DOE test procedures as specified in 10 CFR Appendix R to Subpart B of Part 430. Using the same guidelines, DOE also measured and recorded the SPDs of the

sa mples of lamps marketed as featuring spectral modification. DOE then utilized the SPDs to

c ompute the MacAdam-step shift and corresponding lumen output reductions between the standard spectrum and spectrally modified lamps across the lamp samples in every lamp pair.

Because the MacAdam-step shift specified in DOE’s definition of modified spectrum lamp is relative to a clear lamp, DOE had to account for the fact that standard spectrum IRLs are not cle ar lamps due to the impact of their cover glass and their reflectors. DOE thus developed a methodolog y to isolate the effects of spectrum modification in order to determine the relative

re duction in lumen output and the relative change in color that would be observed if a spectrally modified IRL were compared to a clear lamp. The method also assumes that spectrum modi fication is achieved through the usage of neodymium in the cover glass of a modified spectrum lamp. DOE used a model that simulates the SPD of a halogen capsule without any cover glass, termed H SPD in the equation below. This SPD is then used to simulate a clear lamp. The methodology utilizes the equation shown below in Eq. 5B. 1 :

Eq. 5B. 1

Where:

W

 m 2

m  K

c = 2.99792458 ×10 8 m/s (velocity of light) h = 6.626176 ×10 - 34 J

 s (Planck constant) k = 1.380662 ×10 - 23 J/K (Boltzmann constant)

and: H SPD : the simulated spectral power distribution of a halogen or HIR capsule M SPD : the measured spectral power distribution of a spectrally modified lamp  : wavelength of light emitted from the lamp filament (in meters) T: temperature of the filament (in kelvin)5B -9

SA: surface area of the filament (in square meters), determined by selecting a black-body radiator with the same radiant power as the measured standard spectrum IRL

α : correction term for the filament surface area

ε W : emissivity of tungsten, which models a tungsten filament

τ N : transmittance of neodymium in a spectrally modified cover glass

τ CG : t ransmittance of a clear cover glass β: combined effect of neodymium concentration and thickness of neodymium in a spectrally modified cover glass

Transmittance is the fraction of light (at a specific wavelength) hitting an object that travels through the object and can be measured on the other side. To determine the transmittance, DO E measured the transmittance of a stand ard spectrum cover glass, τ CG , between th e wavelengths of 380 nm and 780 nm. DOE also measured τ N using a spectrally modified lamp cover glass. The cover glass transmittance for a specific lamp featuring spectral modification tested by DOE is shown relative to the corresponding standard spectrum lamp transmittance in F igure 5B.4.1

. Sharp dips in the plot clearly indicate which light wavelengths are absorbed by the combination of neodymium and cover glass.

Figure 5B.4.1 Transmittance of a Specific Lamp Cover Glass Featuring Neodymium, Relative to the Standard Spectrum Cover Glass Transmittance

DOE utilized an unconstrained nonlinear optimization program to compute α, β, and T and thus model the SPD of the capsule inside of a spectrally modified lamp, H SPD
. DOE then used H SPD and the transmittance of a cover glass without any spectrum-modifying features in Eq. 5B. 2 in order to obtain I SPD , the SPD of a clear lamp:5B

- 10 Eq. 5B. 2

The light output reduction is obtained by dividing M SPD by I SPD . In addition, both I SPD and M SPD were used to calculate color points. Then, the color separation from the I SPD color point to the M SPD color point was determined in terms of MacAdam steps.

DOE determined the relationship between MacAdam-step shift and light output

re duction, as shown in T able 5B.4. 1 and Figure 5B.4.2

, for every individual lamp combination tested (21 combinations of standard spectrum and spectrally modified lamps, derived from the

se ven lamp pairs that each contained three standard spectrum and three spectrally modified lamp

sa mples ).

Table 5B.4.1 MacAdam-Step Shifts and Light Output Reductions for Lamps Tested

Lamp ID alpha beta T MacAdam

Step Shift Light

Output Reduction Standard S pectrum Spectral ly

Modified 105352 105349 1.249 1.076 2

, 746.221 5.4 19.2% 105353 105350 1.239 1.146 2

, 746.022 5.7 20.1% 105354 105351 1.290 1.116 2

, 741.640 5.6 19.7% 105374 105371 1.323 1.086 2

, 715.983 5.5 19.3% 105375 105372 1.344 1.096 2

, 707.611 5.5 19.5% 105376 105373 1.273 1.029 2

, 726.019 5.2 18.6% 106705 106702 1.275 0.981 2

, 845.517 5.0 17.9% 106706 106703 1.296 1.066 2

, 838.923 5.4 19.0% 106707 106704 1.271 1.055 2

, 857.426 5.4 18.9% 106751 106748 1.498 0.473 2

, 699.566 2.4 10.0% 106752 106749 1.488 0.374 2

, 678.070 1.8 8.2% 106753 106750 1.803 0.395 2

, 653.760 1.9 8.6% 105355 105276 1.337 0.425 2

, 739.313 2.1 9.1% 105356 105277 1.411 0.500 2

, 750.256 2.5 10.5% 105357 105278 1.305 0.430 2

, 751.663 2.1 9.2% 105358 105269 1.315 0.456 2

, 818.707 2.3 9.7% 105359 105270 1.272 0.448 2

, 818.681 2.3 9.5% 105360 105271 1.256 0.473 2

, 821.212 2.4 10.0% 105363 105287 1.208 0.547 2

, 760.137 2.8 11.3% 105364 105288 1.337 0.541 2

, 784.910 2.7 11.2% 105377 105289 1.325 0.495 2

, 770.849 2.5 10.4%5B

- 11

Figure 5B.4.2 Relationship Between Light Output Reduction and MacAdam-Step Shift For L amps Tested5B

- 12

5B.5 SELECTION OF SCALING FACTOR

The results of DOE’s analysis of commercially available lamps for the 2009 Lamps Rule indicated that a 4-MacAdam-step shift between a standard spectrum IRL and a lamp featuring
spec tral modifications correspond ed with an approximate efficacy reduction of 15 percent, which was the scaling factor used in the 2009 Lamps Rule. For this rulemaking, DOE is maintaining 15
pe rcent as the efficacy reduction factor required of IRLs that meet the “modified spectrum” de finition. A comparison of the baseline and candidate standard level put forth in this rulemaking for standard spectrum and modified spectrum IRLs with this scaling factor applied is shown in F igure 5B.5.1

.

Figure 5B.5.1 Comparison of Standard Spectrum and Modified Spectrum for Candidate S tandard Level 15B

- 13 REFERENCES

1 Rea, Mark S., ed. The IESNA Lighting Handbook: Reference & Application, 9th Edition

. 2000. The Illuminating Engineering Society of America: New York, New York.

2 International Energy Agency. Light’s Labour’s Lost: Policies for Energy-efficient Lighting. OECD/ IEA, 2006.

3 D. L. MacAdam, "Visual Sensitivities to Color Differences in Daylight," J. Opt. Soc. Am. 32, 247 -273 (1942).