5C-i APPENDIX 5C. MODIFIED-SPECTRUM INCANDESCENT REFLECTOR LAMPS

TABLE OF CONTENTS

5C.1 INTRODUCTION .........................................................................................................5C-1 5C.2 BACKGROUND ...........................................................................................................5C-1 5C.2.1 Spectral Power Distribution and Co mmonly-Used Color Properties ..........5C-1 5C.2.2 Methods of Modifying Spectral Power Distributions..................................5C-4 5C.3 APPLICATION OF “MODIFIED SPEC TRUM” DEFINITION TO IRL....................5C-4 5C.3.1 Color Requirements .....................................................................................5C-5 5C.3.2 Black-Body Locus Requirements ................................................................5C-5 5C.3.3 MacAdam-Step Requirements.....................................................................5C-6 5C.4 METHODOLOGY ........................................................................................................5C-7 5C.5 ANALYTICAL RESULTS .........................................................................................5C-10 5C.6 SELECTION OF FINAL SCALING FACTOR..........................................................5C-13 REFERENCES ........................................................................................................................5C-14

LIST OF FIGURES

Figure 5C.1: Spectral Power Distri bution of Two IRL Tested By DOE ...................................5C-2 Figure 5C.2: The CIE 1931 Chromaticity Diagram ...................................................................5C-3 Figure 5C.3: Combined Black-Body Locus a nd Color Requirements of the “ModifiedSpectrum” Definition ...................................................................................5C-6 Figure 5C.4: Example of IRL That Meet the Definition of "Modified Spectrum;” Modified-Spectrum IRL Color Points Lie to the Lower Left of the Red Circle ............................................................................................................5C-7 Figure 5C.5: Transmittance of a Specific Lamp Cover Glass Featuring Neodymium, Relative to the Standard-Spectrum Cover Glass Transmittance ................5C-10 Figure 5C.6 Relationship Between Light Out put Reduction and MacAdam-Step Shift For Lamps Tested by DOE ...............................................................................5C-12 Figure 5C.7: Comparison of Standard-Spect rum and Modified-Spectrum IRL Efficacy Requirements .............................................................................................5C-13

LIST OF TABLES

Table 5C.5.1: MacAdam-Step Shifts and Light Output Reductions for Lamps Test ed by DOE ...........................................................................................................5C-115C-1 APPENDIX 5C. MODIFIED-SPECTRUM INCANDESCENT REFLECTOR LAMPS

5C.1 INTRODUCTION

A modified-spectrum in candescent 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. The definition of “modified-spectrum” in the Energy Policy and Conservation Act (EPCA) as amended by the Energy Independence and Security Act of 2007 (EISA 2007) applies to general se rvice incandescent lamps (GSIL) that are noticeably different in color than unmodified-spectrum (or standard-spectrum ) GSIL, with specific additional color requirements described in this appendix. Some in candescent reflector lamps (IRL) are also sold with features that modify their spectra, and DOE believes that such IRL provide a unique utility to users. For example, a number of these lamp s are advertised as 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 is creating a m odified-spectrum IRL product class and setting standards for these lamps by scaling efficacy re quirements from the standard-spectrum IRL product classes. As discussed in chapter 3, Market and Technology Asse ssment, DOE used the EPCA definition of “modified sp ectrum” to determine what lamps would be included in this product class. DOE believes that the definition of “modified spectrum” was created for GSIL, as the EPCA definition requires the testing of cl ear lamps as a reference for spectrum comparison, but IRL are not clear lamps due to their reflec tive coating. This appendix describes how DOE adopted the EPCA definition of “modified spectrum” for IRL and developed the factor used to set the efficacy requirements for the modified-sp ectrum IRL product class. In particular, DOE tested IRL advertised as featur ing spectral modification (such as lamps advertised as “daylight” lamps) by using similar standard-spectrum IRL as references for spectrum comparison.

5C.2 BACKGROUND
Objects absorb, reflect, and ra diate a for m of energy known as electromagnetic radiation
, which can be visualized as waves of energy that travel through ope n 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 wavelength s roughly between 380 and 750 nanometers (nm). Various wavelengths of visible light are perc eived as various colors by humans.

5C.2.1 Spectral Power Distribution and Commonly-Used Color Properties

Som e portion of the electroma gnetic radiation emitted by lamps exists in the spectrum of visible light. Most lamps emit multiple wavele ngths of light simultaneously, and the radiant power (energy radiated per unit time) of each wa velength can be plotted as a spectral powerdistribution (SPD). 1 Example SPDs are shown in Figure 5C.1 for a specific standard-spectrum IRL and a specific modified-spectrum IR L tested by DOE for this rulemaking.

350 400 450 500 550 600 650 700 750 800 0 0.002 0.004 0.006 0.008

0.01 0.012 0.014 0.016 0.018

Wavelength (nm)Spectral Power (W/nm) Modified spectrum Standard spectrum

Figure 5C.1: Spectral Power Distribution of Two IRL Tested By DOE

The measurement of a lamp’s SPD allows th e characterization of the lamp’s perceived light color. Three color propert ies in particular are commonly computed for lamps based on the SPD. One is the chromaticity , which refers to the color of th e lamp’s light as indicated by a mapping onto a chromaticity diagram such as the CIE 1931 chromaticity diagram a shown in Figure 5C.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 regi on 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 reference color point are generally perceived by most humans as being differe nt in color than the reference point.

5C-2 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 I llumination, 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 th e space are composed of a distribution of wavelengths of various powers.Figure 5C.2: The CIE 1931 Chromaticity Diagram

The curved line in the center of Figure 5C.2 is known as the bl ack-body locus and represents the perceived light color emitted by a black body heated to the indicated temperature (in Kelvin). In the field of phys ics, a black body is a theoretical obj ect that is considered to be the simplest emitter of electromagnetic radiation. It absorbs all electro magnetic radiation falling onto it (and thus reflects no radiation), and wa velengths of the radiation emitted by the body are related only to its temperature. Black bodies are so named beca use at room temperature they would emit mostly infrared radiation, which ha s 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 black body increases, its emitted radiation increases in frequency while

5C-35C-4 shortening in wavelength and begins to be perceived as visible light. Any object hot enough to emit visible light is said to incandesce, and the phenomenon of visible-light emission due to high temperature is known as incandescence

. A lamp’s correlated color temperature (CCT) is another commonl y-computed color property and is based on the behavi or of black bodies. The CCT of a lamp is the temperature of a black body that produces roughly the same spect ral power distribution 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 is similar to the SPD generated by a black body; thus, the temperature of the heated filament is near th e CCT of the lamp. Many IRL 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 illumina ted 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 with high CRIs illuminate objects such that humans perceive colors similar to what they would perceive if those objects were illuminated by daylight, or by a black body radiator. Most incandescent lamps without modified spectrums have a CRI near 100.

5C.2.2 Methods of Modifying Spectral Power Distributions
The spectral power distributi ons that can be generated by in candescence are such that incandescing objects can only produce a narrow subset of all of the colors that the human eye can perceive. To produce colors that are dist ant 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 incandescent reflector lamps. Some methods utilize spec ific chemicals, such as neodymium, that are introduced into the cove r glass of the lamp. Other methods rely on layers of material that are sandw iched into the cover glass or coatings that are applied to the outside or inside faces of the glass. The compoun ds, layers, or coatings used to modify the SPD operate by reducing the power of sp ecific wavelengths of light; thus, they act as selective filters. Because the total light output of the IRL is reduc ed when selective filteri ng is applied, IRL with modified spectrums are less efficacious than sta ndard-spectrum IRL of the same filament type, bulb shape, rated voltage, and rated wattage.

5C.3 APPLICATION OF “MODIFIED SPECTRUM” DEFINITION TO IRL

The Energy Policy and Conservation Act (EPCA), as am ended by the Energy Independence and Security Act of 2007 (EISA 2007) , defines “modified spectrum” as follows (42 U.S.C. 6291(30)(W)):

“The term ‘modified spectrum’ means, with re spect to an incandescent lamp, an incandescent lamp that— (i) is not a colored incandescent lamp; and (ii) when operated at the rated voltage and wattage of the incandescent lamp—5C-5 (I) has a color point with (x,y) chromaticity coordinates on the Commission Internationale de l’Eclairage (C.I.E.) 1931 chromaticity diagram that lies below the black-body locus; and (II) has a color point with (x,y) chromaticity coordinates on the C.I.E. 1931 chromaticity diagram that lies at least 4 MacAdam steps (as referenced in IESNA LM16) distant from the color point of a clear lamp with the same filament and bulb shape, operated at the same rated voltage and wattage.”

The following sections will address each componen t of the definition in turn as it relates to modified-spectrum IRL.

5C.3.1 Color Requirements

The “m odified spectrum” definition require s that the modified-spectrum lamp meet specific color requirements; namely, that it not be a “colored incandescent lamp.” (42 U.S.C. 6291(30)(W)(i)) The amended EPCA defines “co lored incandescent lamp” as follows (42 U.S.C. 6291(30)(EE)):

“The term ‘colored incandescent lamp’ means an incandescent lamp designated and marketed as a colored lamp that has— (i) a color rendering index of less than 50, as determined according to the test method given in C.I.E. publication 13.3–1995; or (ii) a correlated colo r temperature of less than 2,500K , or greater than 4,600K, where correlated temperature is computed accordi ng to the Journal of Optical Society of America, Vol. 58, pages 1528–1595 (1986).” b

Most IRL with unmodified spectrums have a CRI near 100 and a CCT between 2700 K and 3,000 K. Colored incandescent lamps are lamps that have been modified, using coatings or other methods, so that they produ ce light that is percei ved as blue, red, green, or other colors. These lamps are used for aesthetic or artistic e ffects and thus are not meant to reproduce object colors accurately.

5C.3.2 Black-Body Locus Requirements

The “m odified spectrum” definition also requ ires that a modified-spectrum incandescent lamp produce a perceived color wi th a “color point . . . that li es below the black-body locus” on the CIE 1931 chromaticity diagram when the lamp is operated at its rated voltage and wattage. (42 U.S.C. 6291(30)(W)(ii)(I)) The chromaticity diagram and black-body locus are shown in Figure 5C.3 along with red straight line s indicating color requireme nts. The combined color and black-body locus requirements of the “modified spectrum” definition exclude all lamps with color points outside of the da rk grey area in the figure.

b Note that EISA 2007 included “1986” as the year of publication of the ar ticle. However, 1986 is the incorrect year for the Journal of Optical Society of Amer ica reference; the co rrect year is 1968.1931 CIE Chromaticity Diagram

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

xy

Figure 5C.3: Combined Black-Body Locus and Color Requirements of the “ModifiedSpectrum” Definition

5C.3.3 MacAdam-Step Requirements
Finally, the “modified-spectrum ” definiti on 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 fila ment and bulb shape, operated at the same rated voltage and wattage.” (42 U.S.C. 6291(30)(W)(ii)(II)) Re quiring 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 noticeably different in colo r than similar clear lamps. Figure 5C.4 Error! Reference source not found. shows a magnification of the CIE 1931 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 m odified-spectrum IRL samples in this pair are shown as blue dots in the figure. The modifi ed-spectrum IRL have color points located below the black-body locus, shown in black. In a ddition, they meet the color requirements bounded by the red straight line at th e right (the left bound is located outside of the area shown by the figure). Finally, their color points meet the MacAda m step requirement established by the three corresponding standard-spectrum la mps located in the center of the red ellipse; the red ellipse represents a distance of four MacAdam steps from the average color point of the standardspectrum IRL.

5C-6Figure 5C.4: Example of IRL That Meet the Definition of "Modified Spectrum;” Modified-Spectrum IRL Color Points Li e to the Lower Left of the Red Circle

Applying the definition of “m odified spectrum” requires comp aring the color point of the IRL in question to the color point of a clear la mp. IRL, however, are not clear lamps because they have reflectors; IRL also commonly have fros ted or textured faces. In order to apply the definition of “modified spectrum,” DOE developed a normalization method to model a clear lamp. This method is discussed in the section below.

5C.4 METHODOLOGY
In order to explore the efficacy differen ces between standard-spectrumand modifiedspectrum IRL, DOE paired commercially availabl e standard-spectrum IRL with available IRL in the same product line that were advertised as f eaturing spectral modificat ion (for example, IRL advertised as “daylight” or “full-spectrum” la mps). First, DOE surveyed the market of commercially-available IRL. DOE then selected lamp models that could be identified as featuring spectral modification based on the manuf acturers’ catalogs or marketing literature. Standard-spectrum lamp models were paired with the lamps featuring spectral modification such that the lamps in each pair had the same bulb shap e, the same rated life, the same rated voltage and wattage, and the same class of filament shap e. All lamps had a rate d voltage of 120V.

5C-7In total, DOE tested seven pairs of pa rabolic a luminized reflector (PAR) lamps c from two major manufacturers. Six pairs consisted of ha logen lamps, and one pair consisted of halogen infrared (HIR) lamps. Each pair contained three samples of an IRL model advertised as featuring spectral modification al ong with three samples of a corresponding standard-spectrum IRL model in the same product line. Halogen and HIR lamps were selected because the IRL design options that meet the proposed IRL standa rds in this rulemaking consist of both halogen and HIR technologies. Non-haloge n incandescent lamps were not selected, as th ese non-halogen IRL have significantly different radiation sp ectra over wavelengths contributing to the calculation of lumens (in general their light outputs ar e shifted toward longer wavelengths) than HIR and halogen sources. Therefor e, it is likely that the resulti ng scaling factor based on these lamps would be significantly different than for halogen sources. Because non-halogen IRL (representing the IRL lamp types exempted from standards) ar e not regulated in this rulemaking, DOE believes that it would be inappropriate to include non-halogen lamps in its scaling factor analysis. Therefore, DOE considered only ha logen and HIR IRL for the computation of the modified-spectrum IRL scaling factor. DOE did, how ever, test one lamp pair featuring a smaller diameter (PAR16) than IRL covered by this rule making, in order to supplement its analysis of larger-diameter lamps.

DOE measured and recorded the SPDs of the standard-spectrum IRL samples in each pair, in accordance with the guidelines in 10 CFR Appendix R to Subpart B of Part 430 for incandescent lamps. Using the same guidelines, DOE also measured and recorded the SPDs of the samples of lamps advertised as featuring sp ectral modification IRL. DOE then utilized the SPDs to compute 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.

In order to do this, DOE first had to account for the fact that st andard-spectrum IRL are not clear lamps due to the impact of their cover glass and their reflectors. DOE thus developed a methodology to isolate the effects of spectrum modification in order to determine the relative reduction in lumen output and the relative change in color that would be obs erved if a spectrallymodified IRL were compared to a clear la mp. The method also assumes that spectrum modification is achieved through the usage of neodymium in th e cover glass of a modifiedspectrum lamp. The heart of the method is a mode l that simulates the spectral power distribution of a halogen capsule without any cover glass, termed H SPD in the equation below. This spectral power distribution is then used to simulate a clear lamp. The methodology utilizes the equation shown below in Eq. 5C.1 :

SPD CGNW 780

380 T c 5 9

1 SPD CGN SPD M***

1e 10*c *SA* M**H

2       

 

     

 

     

 

    

 

          

    Eq. 5C.1

5C-8 c Other IRL bulb shapes, such as BR and R shapes, are not covered by the standards proposed in this rulemaking.W h ere:

W

 m 2 2 1 hc2c 

k hc c 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 distri bution 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) 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, whic h models a tungsten filament

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

τ CG : transmittance of a clear cover glass β : combined effect of neodymium concentr ation and thickness of neodymium in a spectrally-modified cover glass

Transmittance is the fraction of light (at a specifi c wavelength) hitti ng an object that travels through the object and can be measur ed on the other side. To determine the transmittance, DOE measured the transmittance of a standard-spectrum cover glass, τ CG , between the 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 Figure 5C.5 . Sharp dips in the plot clearly indicate which light wavelengths are absorbed by the com b ination of neodymium and cover glass.

5C-90.0 0.2 0.4 0.6 0.8 1.0 1.2

380 430 480 530 580 630 680Spectral Transmittance

Wavelength (nm)

Figure 5C.5: Transmittance of a Specific Lamp Cover Glass Featuring Neodymium, Relative to the Standard-Spect rum Cover Glass Transmittance

DOE utilized an unconstrained nonlinear optimization program to compute α , β , and T and thus model the spectral power distribution of the capsule inside of a spectrally-modified lamp, H SPD . DOE then used H SPD and the transmittance of a c over glass without any spectrummodifying features in Eq. 5C.2 in order to obtain I SPD , the spectral power di stribution of a clear lamp:

SPD CG SPD I*H   Eq. 5C.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. Results are presented below.

5C.5 ANALYTICAL RESULTS
Once DOE determined MacAdam-step variatio ns and light output reductions for every tested lamp pair. DOE then used a relationshi p between MacAdam-step shift and light output reduction for lamps featuring spectral modifi cation. This information is shown in Table 5C.5.1 and Figure 5C.6 for every individual lamp combination tested (21 combinations of standard5C-105C-11 spectrum and spectrally-modified lamps, derived fr om the 7 lamp pairs that each contained three standard-spectrum and three spectrally-modified lamp samples).

Table 5C.5.1: MacAdam-Step Shifts and Light Output Reductions for Lamps Tested by DOE Lamp IDStandardSpectrum SpectrallyModified alpha beta T MacAdamStep Shift Light Output Reduction 105352 105349 1.249 1.076 2746.221 5.4 19.2% 105353 105350 1.239 1.146 2746.022 5.7 20.1% 105354 105351 1.290 1.116 2741.640 5.6 19.7% 105374 105371 1.323 1.086 2715.983 5.5 19.3% 105375 105372 1.344 1.096 2707.611 5.5 19.5% 105376 105373 1.273 1.029 2726.019 5.2 18.6% 106705 106702 1.275 0.981 2845.517 5.0 17.9% 106706 106703 1.296 1.066 2838.923 5.4 19.0% 106707 106704 1.271 1.055 2857.426 5.4 18.9% 106751 106748 1.498 0.473 2699.566 2.4 10.0% 106752 106749 1.488 0.374 2678.070 1.8 8.2% 106753 106750 1.803 0.395 2653.760 1.9 8.6% 105355 105276 1.337 0.425 2739.313 2.1 9.1% 105356 105277 1.411 0.500 2750.256 2.5 10.5% 105357 105278 1.305 0.430 2751.663 2.1 9.2% 105358 105269 1.315 0.456 2818.707 2.3 9.7% 105359 105270 1.272 0.448 2818.681 2.3 9.5% 105360 105271 1.256 0.473 2821.212 2.4 10.0% 105363 105287 1.208 0.547 2760.137 2.8 11.3% 105364 105288 1.337 0.541 2784.910 2.7 11.2% 105377 105289 1.325 0.495 2770.849 2.5 10.4%

### y = 44.091x 1.2694 

### R2 = 0.9997

0 1 2 3 4 5 6 7

0% 5% 10% 15% 20%MacAdam Steps

Light Output Reduction Figure 5C.6 Relationship Between Light Ou tput Reduction and MacAdam-Step Shift For Lamps Tested by DOE

5C-125C.6 SELECTION OF FINAL SCALING FACTOR
The results of DOE’s analysis of commerc ially-available lamps indicated that a 4- MacAdam-step shift between a standard-spe ctrum IRL and a lamp featuring spectral modifications corresponds with an approximate efficacy reduction of 15 percent. DOE thus selected 15 percent as the efficacy reduction fact or required of IRL that meet the “modified spectrum” definition. A comparison of the e fficacy requirements for standard spectrum and modified-spectrum IRL is shown in Figure 5C.7 . The IRL standard that currently exists in EPCA is shown as the do tted s tair-step line labe led “Baseline EPCA.” Note that the smoothed lines for the modified spectrum efficiency levels ( ELs) 1 and 2 have been raised in some areas so that the EPCA standard is met. This is becau se DOE “may not prescribe any amended standard which increases the maximum allowable energy use . . . or decreases the minimum required energy efficiency, of a covered product.” (42 U.S.C. 6295(o)(1))

Baseline

EPCA EL 1 EL 2 EL4
EL 3 EL5

9.0 11.0 13.0 15.0 17.0 19.0 21.0 23.0

30 40 50 60 70 80 90 100 110Lamp Efficacy (lm/W)

Lamp Power (W) Mod EL1 Mod EL2 Mod EL3 Mod EL4 Mod EL5 Standard Spectrum

Modified Spectrum

Figure 5C.7: Comparison of Standard-Spect rum and Modified-Spectrum IRL Efficacy Requirements

5C-135C-14 REFERENCES

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

. 2000. The Illuminating Engineering Societ y 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).