LED Lighting - Phase 2, Irvine Parking Lot

Transcription

1 Design & Engineering Services LED Lighting - Phase 2, Irvine Parking Lot ET Final Report Prepared by: Design & Engineering Services Customer Service Business Unit Southern California Edison June 30, 2009

2 Acknowledgements Southern California Edison s Design & Engineering Services (D&ES) group is responsible for this project. It was developed as part of Southern California Edison s Emerging Technology program under internal project number ET D&ES project manager Jack Melnyk conducted this technology evaluation with overall guidance and management from Henry Lau. ADM Associates, Inc prepared this report for Southern California Edison. For more information on this project, contact jack.melnyk@sce.com. Disclaimer This report was developed by SCE and funded by California utility customers under the auspices of the California Public Utilities Commission. Reproduction or distribution of the whole or any part of the contents of this document without the express written permission of SCE is prohibited. This work was performed with reasonable care and in accordance with professional standards. However, neither SCE nor any entity performing the work pursuant to SCE s authority make any warranty or representation, expressed or implied, with regard to this report, the merchantability or fitness for a particular purpose of the results of the work, or any analyses, or conclusions contained in this report. The results reflected in the work are generally representative of operating conditions; however, the results in any other situation may vary depending upon particular operating conditions. Southern California Edison

3 ABBREVIATIONS AND ACRONYMS ADM CRI CTAC ev fc HPS IESNA ILC kw kwh LED LDD LLD LLF lm LPW N/A NIST nm RMS SCE SCLTC W ADM Associates, Inc. Color Rendering Index Customer Technology Application Center Electron Volt Footcandle High Pressure Sodium Illuminating Engineering Society of North America Integrated Lighting Concepts, Inc. Kilowatt Kilowatt-hour Light Emitting Diodes Lamp Dirt Depreciation Lamp Lumen Depreciation Light Loss Factor Lumen Lumens per Watt Not Available National Institute of Standards and Technology nanometer Root Mean Square Southern California Edison Company Southern California Lighting Technology Center Watt Southern California Edison Page i

4 FIGURES Figure 1. A Portion of the City Hall Parking Lot Showing Two Parking Lot Lights Spaced Approximately 100 Feet Apart. 5 Figure 2. An Aerial Photo of the Test Site, courtesy of the US Geological Survey...6 Figure 3. Lumen maintenance curves for HPS and LED lamps over a period of 50,000 hours. The HPS lights are relamped at 17,000 and 34,000 hours. No cleaning occurs for either fixture....9 Figure 4. Lumen maintenance curves for HPS and LED lamps over a period of 50,000 hours. The HPS fixtures are relamped and cleaned at 17,000 and 34,000 hours....9 Figure 5. A shoebox type fixture housing a 400W HPS lamp with ballast and reflective optics Figure 6. A multicolor sample illuminated by 75 CRI LED lights (left), 23 CRI HPS lights (center), and 100 CRI daylight (right) Figure 7. A multicolor sample illuminated by 75 CRI LED lights (left), 23 CRI HPS lights (center), and 100 CRI daylight (right) Figure 8. Beta 12-bar LED fixture Figure 9. Integrating sphere used for light output measurements at SCLTC Figure 10. Measured daily hours of operation for the area lights. The sinusoidal nature is due to the seasonal change in day length Figure 11. Iso-footcandle plot of the measured lighting distribution provided by the HPS area lights Figure 12. Iso-footcandle plot of the simulated lighting distribution provided by the HPS area lights Figure 13. Iso-footcandle plot of measured lighting distribution provided by LED area lights Figure 14. Iso-footcandle plot of simulated lighting distribution provided by LED area lights Figure 15. Parking lot as lighted by the HPS fixtures (top) and LED fixtures (bottom) Figure 16. (Left) Radiant flux vs wavelength for ten scans ranging from 1-25 minutes of run-time for the Beta LED fixture. (Right) A closeup of the 450 nm peak shows that the radiant flux decreases from 610 mw/nm to 560 mw/nm during 25 minutes of operation Southern California Edison Page ii

5 TABLES Table 1. Field Measured Power and lighting properties of HPS and LED area lights...2 Table 2. IESNA Recommended Parking Lot Illuminance...6 Table 3. Manufacturers specifications for the HPS and LED area lights Table 4. Power and power factors measured at the SCLTC Table 5. Rated and measured light output and CRI for HPS and LED lights Table 6. Rated Connected Watts and Field measured Watts and power factors for the HPS and LED lights Table 7. Measured (in field) power, annual hours of operation, and annual energy usage per fixture Table 8. Measured (at SCLTC) power, annual hours of operation, and annual energy usage per fixture Table 9. Measured and Simulated Light outputs and Uniformities Table 10. Life Cycle Cost Table for LED and HPS fixtures. This Scenario Assumes 2% above inflation discount rate for all labor and material costs and a 0% discount rate for energy costs Table 11. Total lifecycle costs at various fixture price points for the LED and HPS fixtures Table 12. Break-even price points for LED fixtures for four energy cost scenarios Southern California Edison Page iii

6 CONTENTS EXECUTIVE SUMMARY 1 INTRODUCTION 4 Background...4 Parking Lot Area Lighting...4 Project Goals and Objectives...5 Test Site...5 Lighting Recommendations...6 Achieving the Lighting Recommendations...7 Baseline Technology LED Area Lights TECHNICAL APPROACH 14 Lab Tests at the SCLTC Field Measurements Power Measurements Light Level Measurements Light Level Simulations Hours of Operation RESULTS 17 Results from Lab Tests Power Measurements Photometric Measurements Results from Field Power Measurements Power Measurements Hours of Operation Annual Power Usage Results from Field Light Level Measurements Light Levels and Quality Uniformity Ratio Simulated vs Measured Light Levels DISCUSSION 26 Comparison of LED and HPS Fixtures Rated vs Measured Lumen Outputs Ballast Factor (for HID) Fixture Efficiency Southern California Edison Page iv

7 Light Loss Factors Junction Temperature for LEDs Environmental Considerations Economics CONCLUSION 33 APPENDIX A 34 Light Emitting Diodes Semiconductors Light Emitting Diodes LED Performance APPENDIX B 36 REFERENCES 38 Southern California Edison Page v

8 EXECUTIVE SUMMARY Southern California Edison s (SCE) Emerging Technology Program assesses products that have the potential to reduce electric energy use. Area lights that use light emitting diodes (LEDs) are a new application of evolving LED technology where potential energy savings has not been quantified to date. This project evaluates the amount of illumination delivered and the potential energy savings attributable to LED area lighting fixtures. SCE has documented the improved uniformity and color rendering performance of LED lights in comparison with high pressure sodium (HPS) lights in Phase I of this project. By the end of Phase I, LED bare chip luminous efficacy had improved so much (from 67 lumens per Watt to 87) that a Phase II study was clearly prudent. In Phase II, when compared to the current standard HPS area lights, the LED lights provide: A vastly superior color rendering index (CRI) of 75/100 LED vs. 23/100 HPS) Much better uniformity with a maximum intensity(i)/minimum I of 7/1 LED vs. 23/1 HPS), and A 29.5% energy savings Additionally, LED lights are expected to exhibit longer lifetimes and require less maintenance than HPS lights. The current Phase II study findings demonstrate that the LED fixtures show improved CRI and uniformity. At the same time, the LED fixtures used 29.5% less energy in comparison with HPS fixtures in this City of Irvine Parking Lot test site application. This project has the following objectives: Determine the baseline electric demand of the existing HPS area lights, Determine the post-retrofit electric demand of the new LED area lights, Determine the light level outputs of the HPS and LED area lights. In February of 2008, power and photometric measurements were performed on a sample of six new LED fixtures, and six existing freshly re-lamped and cleaned HPS fixtures installed at the Irvine City Hall parking lot. Monitoring of the on-off cycles for both the LED and HPS fixtures determined that the lights operate 4,430 hours per year. Photometric (footcandle) measurements were taken at approximately 15 intervals in a grid on a 200 x 130 parking lot section that was lit, at different times, by six HPS or six LED area lights. Photometric, spectral and power measurements were taken at the Southern California Lighting Technology Center (SCLTC). These measurements determined an average efficacy of 60.0 lumens per watt (LPW) for the LED fixtures and 58.6 LPW for the HPS fixtures. The power usage of the HPS and LED fixtures was also measured in the field. On average, the field power measurements were 282 watts (W) for the LED fixtures and 400 W for the HPS fixtures -- a difference of 29.5 %. The lighting levels achieved by the area lights were compared to the Illuminating Engineering Society of North America s (IESNA) recommendations for area lighting 1. IESNA recommended practice states that the lighting must maintain a minimum level of 0.2 footcandles (fc) over the targeted section of the parking lot. To compensate for the overall Southern California Edison Page 1

9 lumen depreciation over the fixture service life, caused by dirt and light-source depreciation, the minimum light levels achieved by the fixtures must initially exceed the 0.2 fc light level by margins determined by their expected overall lumen depreciations. The LED fixture must provide 0.54 initial fc, while the HPS must provide 0.41 initial fc. Additionally, the uniformity ratio (the ratio between the maximum and minimum light levels) must be under 20:1. Table 1 summarizes the power and lighting performance for the LED and HPS area lights. The LED fixtures achieved the Illuminating Engineering Society of North America (IESNA) recommended lighting level and uniformity. The initial light levels achieved by the LED surpass the IESNA recommended levels by such margins that the LED would exceed the requirements even if it exhibited lumen depreciation rates greater than those considered in this report. The HPS fixtures achieved the recommended minimum lighting level, but have a uniformity that is slightly worse than the IESNA recommended 20:1. This was probably due to non-uniformity in light output among the fixtures. TABLE 1. FIELD MEASURED POWER AND LIGHTING PROPERTIES OF HPS AND LED AREA LIGHTS Lamp Type Power (W per Fixture) Minimum Initial Light Level (fc) Average Initial Light Level (fc) Uniformity Ratio (max/min) HPS to 1 1,772 LED to 1 1,249 Difference 138 (0.86) 0.66 N/A 523 Estimated Annual Energy Usage per Fixture (kwh) Table 2 summarizes a 20-year lifecycle cost economic analysis, with energy costs escalating at 2% above inflation, indicates: TABLE 2. LIFECYCLE COST COMPARISON BETWEEN HPS AND LED AT VARIOUS LED FIXTURE PRICE POINTS HPS Fixture Price HPS Lifecycle Cost LED Fixture Price LED Lifecycle Cost * HPS Fixture Price HPS Lifecycle Cost $ $5, $1, $4, $ $5, $ $5, $1, $5, $ $5, $ $5, $2, $5, $ $5, $ $5, $2, $6, $ $5, * The breakeven LED fixture price is $ , manufacturer prices for fixture quantities of <250 and >250 are $2, and $ , respectively. Two important inputs to this report come from sources which SCE considers to be credible, though SCE has not verified these inputs through testing. The lamp dirt depreciation (LDD) for LED fixtures estimated by Integrated Lighting Concepts, Inc (ILC) has not been verified through testing. ILC is considered to be an expert in this field with significant experience in the area of lighting fixtures. The lumen depreciation over time for LED lamps is based upon the manufacturer's claim and has not been verified through independent testing. The 90,000 operating hours to 30% lumen depreciation are lower than the manufacturer s claimed 150,000 hours, but still represent over ten years of continuous operation. Due to this large time scale, it is not yet possible to validate or refute the manufacturer s claim, which is an extrapolation based on lab data with older LED chips. The manufacturer is an established supplier of LED lamps to Southern California Edison Page 2

10 the lighting industry. The information supplied by the same manufacturer for lumens per watt and CRI were in agreement with the values SCE measured at the SCLTC. Southern California Edison Page 3

11 INTRODUCTION The purpose of this study is to characterize the lighting performance of LED area lighting fixtures and to quantify the energy savings potential when compared to conventional highpressure sodium (HPS) area fixtures. BACKGROUND PARKING LOT AREA LIGHTING The primary purpose of fixed lighting of parking areas is to help create a safe and secure visual environment in which people can identify cars, persons, and potential obstacles along the paths to their cars. There are other important design considerations: Minimizing maintenance costs by reducing the frequency of lamp replacement and by increasing the ease of accessing the fixture, Improving energy efficiency. Secondary design considerations include glare, aesthetics, light trespass, light pollution, and fixture life. In the search for more energy-efficient area lighting, a number of options were considered and used: 1. Low-pressure sodium (LPS) lights have high luminous efficacies but are monochromatic and thus ill suited for applications, such as the one described in this report, that require good color rendering. 2. High-pressure sodium (HPS) lights have long lifetimes and high luminous efficacies. These lights are well suited for lighting parking lots and roadways, but sometimes cause negative public reactions because of (a) the amber color of the light, poor color rendering, and (b) their on/off cycling (sometimes lasting many months) at end of lamp life. 3. Pulse start metal halide (PSMH) lamps provide high luminous efficacies and white light with fair color rendering. They do not cycle at the end of lamp life, but their lifetimes can be equal to or considerably shorter than those of HPS lights. 4. Light emitting diodes (LED) have recently entered the area lighting market. These lights are rapidly improving and show great promise. LEDs have long lifetimes (50,000+ hours), high bare-chip luminous efficacies (85 to 115 LPW), and good color rendering (70 to 80+ CRI). Appendix A to this report provides a short technical introduction to LEDs. Southern California Edison Page 4

12 PROJECT GOALS AND OBJECTIVES These are the main objectives of the project: Determine the baseline electric energy usage of the existing HPS area lights, Determine the post-retrofit electric energy usage of the new LED area lights, Determine the light level outputs of the High Pressure Sodium (HPS) and LED area lights. The following sections describe the tests and analyses used to achieve these main project objectives. TEST SITE The test site for this study is the Irvine City Hall parking lot. The portion of the parking lot that is illuminated by the tested area lights is approximately 130 feet wide and 300 feet long, and is lighted by six parking lot lights, 31 feet above grade, spaced approximately 100 feet apart along the long edges of the parking lot. The test area, over which illumination measurements were made, is approximately 130 feet wide and 200 feet long. Figure 1 shows a portion of the test site including two of the six light fixtures. These area lights are controlled by an astronomical time clock that turns the lights on and off at set times virtually identical to the local sunset and sunrise. Figure 2 shows an aerial view of the parking lot. FIGURE 1. A PORTION OF THE CITY HALL PARKING LOT SHOWING TWO PARKING LOT LIGHTS SPACED APPROXIMATELY 100 FEET APART. Southern California Edison Page 5

13 FIGURE 2. AN AERIAL PHOTO OF THE TEST SITE, COURTESY OF THE US GEOLOGICAL SURVEY. LIGHTING RECOMMENDATIONS Integrated Lighting Concepts (ILC), an independent contractor for SCE, examined the site and developed lighting criteria based on the IESNA Recommended Practice for area lighting. 1 Under typical conditions, the recommended average horizontal illuminance level maintained at pavement level is 1.0 fc. Note that maintained illuminance is the ratio of the illuminance at the end of a lamp s lifetime to a lamp s initial illuminance. This is recommended only as a starting point for design purposes. The official IESNA recommendations address the minimum maintained horizontal and vertical illuminances, which should be at least 0.2 fc and 0.1 fc, respectively. The uniformity ratio, which is the ratio of the maximum over minimum illuminance, should be less than 20:1. If enhanced security is desired, then the recommended light levels are to be increased by a factor of 2.5, and the uniformity ratio should be lower than 15:1. Table 2 summarizes the IESNA lighting criteria. TABLE 2. IESNA RECOMMENDED PARKING LOT ILLUMINANCE Basic Average Horizontal Illuminance (fc)* Minimum Horizontal Illuminance (fc) Minimum Vertical Illuminance (fc) Uniformity Ratio, Maximum-to-Minimum 20:1 15:1 Enhanced *The average horizontal illuminance levels are not explicitly IESNA recommendations. The last three rows of the Basic column are the criteria which the tested fixtures must satisfy. Southern California Edison Page 6

14 ACHIEVING THE LIGHTING RECOMMENDATIONS In lighting design it is customary to specify an initial illuminance that exceeds the design illumination goal in order to compensate for lumen depreciation that occurs over time. Typically, the minimum in-service illumination is estimated, and the initial lumens are specified such that the minimum in-service illumination meets or exceeds the design illumination goal. To achieve a minimum maintained illuminance of 0.2 fc, the HPS and LED lights must achieve an initial minimum illuminance above 0.41 fc. However, if the LED lights are expected to operate for 90,000 hours instead of 50,000 hours, then the LED lights initial minimum illuminance must be above 0.54 fc. The above estimates for initial illuminance levels are based on the light loss factors (LLF) for the LED and HPS lights, which are derived for the lights based on typical IESNA practice. The overall system depreciation LLF is 0.49 for the HPS light and for the LED at 50,000 hours, and for the LED at 90,000 hours. The LLF is a product of two separate factors. The first factor is the lamp lumen depreciation (LLD), which is the ratio of a lamp s illuminance at re-lamping time to a lamp s initial illuminance. The HPS lights are expected to be re-lamped after approximately 17,000 hours of operation, at which point the lumen output has typically dropped by 20%. The LED fixtures are expected to operate for 100,000 hours albeit with reduced light output. The operating hours are derived from a white paper by Phillips 2, which lists a single LED failure rate of 0.05% after 50,000 hours of operation. The effects of driver current and junction temperature on lifetime and lumen maintenance are also discussed in this white paper. 3 The LLD depreciation curve for LEDs is exponential. The manufacturer of the fixture claims that the average light level over 50,000 hours is 70% of the initial light level. This translates to an exponential decay curve that results in approximately 53% of initial light output after 90,000 hours(20 years of operation). This does seem rather optimistic compared to some of the older references from DOE. 3 A quick internet search, however, shows that many manufacturers are now claiming better lumen maintenance than 70% at 50,000 hours. This work honors the manufacturer s claim because (1) it is in agreement with ILC estimates of lumen depreciation, and (2) the manufacturers claims regarding power, luminous efficacy, and CRI all passed scrutiny at the SCLTC (admittedly, however, lumen depreciation is harder to measure than instantaneous observables such as light output/quality and power consumption). This report is written, therefore, with the assumption that the LED lights will be operational for 20 years. As such, the appropriate LLD for the LED lights is taken to be The second factor is luminaire dirt depreciation (LDD), which is the gradual decrease in fixture light output that is caused by dirt accumulation. LDD is the ratio of a lamp fixture s illuminance at replacement or cleaning time to initial illuminance, assuming that lamps of equal illuminance are in place at both times. The IESNA recommendations for LDD are 0.8 for moderate atmospheric conditions and 0.6 for dirty conditions, over a period of 8 years. ILC determined, based on data from IESNA 1, that the appropriate LDD to be 0.7 for both the HPS and LED fixtures. The IESNA table shows that the dirt depreciation curves are exponential in nature and the 0.8 factor for moderate conditions and 0.6 factors for dirty conditions occur over a period of eight years. The equal LDD rating for both fixtures is, in effect, a conservative LDD rating for the LEDs. The LED fixtures are expected to fare better with respect to dirt depreciation because the actual LEDs are housed in vacuum-sealed, weather-resistant packages. Southern California Edison Page 7

15 The HPS fixtures, however, can accumulate dirt on four surfaces: The outer surface of the lens. The inner surface of the lens. The fixture is not sealed, and dirt and even insects can enter inside. This is significant because dirt that accumulates on the outside can be washed off, or may be removed by the elements and gravity, but dirt on the inside of the fixture is likely to remain there. The HPS luminaire itself. Again, exposure is limited as it is inside the fixture, but the dirt that does accumulate will not easily wash off. The reflective optics housed within the fixture. To compensate for light loss, the luminaires must achieve an initial illumination that is greater than the recommended minimum by a factor that is equal to the inverse of the LLF. Thus, the fixtures must achieve initial illumination levels that are 2.04 times higher than those listed in Table 2. Note that the LDD can be fully or partially recovered by washing/cleaning the fixtures. The overall light losses are plotted versus time for two hypothetical scenarios below. Both scenarios apply exponential lumen and dirt depreciation factors to the minimum initial light levels achieved by each fixture. The light level measurements are described in the section titled Field Measurements. Figure 3 shows the minimum initial light levels scaled by the LLF (combined LLD LDD) curves for LED and HPS lights for a scenario that assumes the fixtures are not cleaned for 50,000 hours. Figure 4 provides an alternate scenario in which the HPS fixtures are cleaned with each re-lamping. The LED fixtures are not assumed to undergo any such maintenance in either scenario, but compare favorably with HPS nonetheless. Both fixtures are able to meet the 0.2 fc minimum horizontal illumination levels in both scenarios. Over the 50,000 hour period shown in Figures 3 and 4, the LED also meets the enhanced security criterion of 0.5 minimum fc. It should be noted that both the HPS and LED lighting designs surpass the basic IESNA illuminance levels by substantial margins (see Figure 4). The LED fixtures were chosen to exceed the minimum in-service illuminances of the HPS lights. Southern California Edison Page 8

16 FIGURE 3. LUMEN MAINTENANCE CURVES FOR HPS AND LED LAMPS OVER A PERIOD OF 50,000 HOURS. THE HPS LIGHTS ARE RELAMPED AT 17,000 AND 34,000 HOURS. NO CLEANING OCCURS FOR EITHER FIXTURE. FIGURE 4. LUMEN MAINTENANCE CURVES FOR HPS AND LED LAMPS OVER A PERIOD OF 50,000 HOURS. THE HPS FIXTURES ARE RELAMPED AND CLEANED AT 17,000 AND 34,000 HOURS. Southern California Edison Page 9

17 BASELINE TECHNOLOGY The light poles at the test site originally had 400 W HPS shoebox type luminaires, as shown in Figure 5. Prior to monitoring and photometric measurements, the original light fixtures were cleaned and re-lamped with new 400 W HPS lamps, and then burned-in for 100 hours. This freshened HPS system defines the baseline for this report. Various manufacturers of 400 W HPS lamps rate their initial lumen output between 45,000 and 50,000 lm. Sylvania, for example, offers three standard 400W HPS lamps with lumen ratings ranging from 46,000 to 50, The rated wattage for such lamps (with ballast) is approximately 460 W. 5 The typical area light fixture has an efficiency of 50% to 75%, meaning that 50% to 75% of the light generated by the lamp exits the fixture. The remaining light is presumably lost to internal reflection. For example, this IES file provided by American Electric Lighting for simulations in AIG or VISUAL software, claims 62.7% total fixture efficiency. 6 The efficiencies may seem low, but the fixture directs a significant portion of its output toward the parking lot surface designated for illumination. A bare lamp would cast much less than 50% of its light toward the area designated for illumination. FIGURE 5. A SHOEBOX TYPE FIXTURE HOUSING A 400W HPS LAMP WITH BALLAST AND REFLECTIVE OPTICS. The baseline HPS fixture has the following ratings: A total initial light output of 50,000 lm A rated bare lamp initial luminous efficacy of LPW (50,000 lm/460w) with approximately 60% of the light exiting the fixture (58.6 LPW was measured exiting the fixture in lab tests described later in this report, which is approximately 54% of the rated bare-lamp efficacy). Southern California Edison Page 10

18 An EPA lighting sourcebook defines color rendering index (CRI) as ranging from 0 to 100 and as characterized by the ability of a light source to render the colors of an object lighted by the source. 7 The benchmark is blackbody radiation. Incandescent lights have a CRI near 100, as they are blackbody radiators to a good approximation. Fluorescent lamps typically have CRIs in the range. CRIs above 75 are considered excellent. As mentioned, HPS lamps typically render colors poorly. The color rendering index (CRI) for HPS lamps was measured to be only 22.5, compared to a maximum CRI of 100. To illustrate the poor color rendering of the HPS lamps with their low CRI, Figure 6 and Figure 7 show multicolored samples illuminated on the left by LED lights (CRI 75), in the middle by HPS lights (CRI 23), and on the right by daylight (CRI 100). A detailed discussion of the testing at SCLTC is included below in the section titled Lab Tests at the SCLTC. FIGURE 6. A MULTICOLOR SAMPLE ILLUMINATED BY 75 CRI LED LIGHTS (LEFT), 23 CRI HPS LIGHTS (CENTER), AND 100 CRI DAYLIGHT (RIGHT). FIGURE 7. A MULTICOLOR SAMPLE ILLUMINATED BY 75 CRI LED LIGHTS (LEFT), 23 CRI HPS LIGHTS (CENTER), AND 100 CRI DAYLIGHT (RIGHT). Southern California Edison Page 11

19 LED AREA LIGHTS The six baseline HPS parking lot lights at the Irvine City Hall parking lot test site were replaced one-for-one in February 2008 with fixtures equipped with a 12 bar LED lamp configuration, manufactured by Beta, a subsidiary of Ruud Lighting, based in Racine, Wisconsin. Figure 8 shows an LED area light installed at the test site. These LED area lights are rated at: 306 W connected including the driver (ballast losses) (and measured at 304 W in the SCLTC laboratory) The 12 bar LED fixture has a rated total light output of 20,400 lm The LED chips, manufactured by CREE, deliver 100 lm at 1.15 W, resulting in a luminous efficacy of 87 LPW 8 with 60 LPW measured (exiting the fixture) LEDs tend to have significantly longer rated lifetimes than the 24,000 hour rated life of the HPS. The LED fixture manufacturer claims that at 50,000 hours the system will have depreciated just 10% in light output. This report uses the more conservative estimate of 30% depreciation over 50,000 hours. Individual LED burn-out is so rare that the accepted lifetime definition is solely based on lumen depreciation, provided that the LED drivers (akin to the ballast for HID lights) are replaced at 50,000 hours. The CRI of these LEDs is rated at 75 (SCLTC lab results showed 76.2), which is significantly higher than that of the HPS at 23, as shown above in Figure 6 and 7. FIGURE 8. BETA 12-BAR LED FIXTURE. The LED fixtures are considerably more costly than the standard HPS fixtures. However, the economic analysis presented in this report indicates that the 20-year energy cost for an HPS fixture (assuming a 2% above-inflation discount rate, but also a 2% above-inflation rate of increase in energy costs) is $5,316.00, while the present value of all maintenance expenditures (assuming a 2% above-inflation Southern California Edison Page 12

20 discount rate) is $ An HPS fixture can be purchased at $275, bringing the 20-year lifecycle cost to $5, The LED fixture s 20-year energy cost is $3,747.78, with a maintenance cost of $ At price points below $ , the 20-year cost of the LED fixture is lower than that of the HPS fixture. Southern California Edison Page 13

21 TECHNICAL APPROACH Comparative measurements were made of the two types of lighting fixtures the HPS and the LED. The measurements included: Light output levels, Light quality, Lighting levels at the pavement surface, Power usages, Power factors, and Hours of operation. This section describes these measurements. LAB TESTS AT THE SCLTC The total light outputs, spectral compositions, and power were measured at SCLTC for the HPS fixtures and LED light fixtures. All three tests used a Labsphere SLMS LED integrating sphere, shown in Figure 9. The integrating sphere is equipped with a 2048 pixel charge coupled device (CCD) spectrometer with a calibrated spectral range sensitivity of 350 nm- 850 nm and a photometric range of 0.08 to 100,000 lm. Each light fixture was placed in the integrating sphere, one at a time, and left on for at least 25 minutes. At 10 times after the start of each test, at 0.5,1, 1.5, 2, 2.5, 5, 10, and 15, 20, and 25 minutes, two measurements were taken: The total light output was measured in lumens, and The spectral composition was measured in mw/nm for the range 350 nm < λ < 850 nm, where λ is the wavelength of the light. This range spans the visible spectrum (400 nm < λ < 700 nm). In addition to the photometric measurements, the power usage and power factors were measured at 1-second intervals throughout the test. Power measurements were taken with a PQL120 power meter that, for the wattages of interest, is accurate to 3% 10. It should be noted that, at the SCLTC, the fixtures were tested at a line voltage of 120 V, as opposed to the 277 V of the parking lot line. Both fixtures are able to operate with a range of voltages that includes 120 V. The 120 V taps for the ballasts internal transformers were used for the SCLTC measurements. Southern California Edison Page 14

22 FIGURE 9. INTEGRATING SPHERE USED FOR LIGHT OUTPUT MEASUREMENTS AT SCLTC FIELD MEASUREMENTS In addition to the laboratory tests conducted at the SCLTC, two types of field measurements were taken: (1) one-time power measurements were made at the base of each pole, and (2) light level measurements were made over a uniform horizontal and vertical grid at the site. POWER MEASUREMENTS One-time power measurements were made at the base of each pole using a true RMS hand-held power meter that has a rated accuracy of ±5.3% for AC power measurements involving currents under 25 amps. To make the power measurements during the day, arrangements were made with the City of Irvine to turn the lights on for the test periods. The supply voltages and currents, along with power and power factor were recorded for the six HPS and for six LED luminaires. To obtain accurate power measurements, the lights were left on for at least 15 minutes prior to the power measurements. LIGHT LEVEL MEASUREMENTS Lighting measurements were made at the site in January and February for the HPS and LED lights to characterize their photometric distributions. The measurements for both HPS and LED lights were taken in full darkness, between 90 minutes and 150 minutes after sunset. Southern California Edison Page 15

23 Horizontal light-level measurements were taken at the pavement level on a 15-foot by 15-foot grid. The grid measured approximately 200-feet long and 130-feet wide. Measurements were made for 126 points in the grid. The measurement values and corresponding grid locations enabled the construction of iso-footcandle diagrams that appear later in this report. Vertical light level measurements were also made on site. The vertical light levels achieved at the site by both the HPS and LED area lights exceeded the IESNA recommendations by such large margins that a random sampling of eight random vertical light level measurements at the site sufficed to establish compliance with IESNA recommendations. LIGHT LEVEL SIMULATIONS The HPS and LED lighting levels at pavement level were also simulated using AGI lighting analysis software 11. Comparison of the simulation results to actual photometric measurements can help to identify malfunctioning fixtures in the case that there is general agreement, but localized disagreement between the simulated and measured results. Such comparisons can also serve to gauge the accuracy of the manufacturers.ies files that are used to describe the product. Note that an argument can be made that the.ies file describing the product is in fact another component of the product itself, akin to an application manual. Comparison of simulation outputs that result from the ies files with field measurements is in its own right a relevant part of this technology assessment. The simulation output included light levels at the pavement level in 15-foot by 15- foot intervals on a 200-foot by 130-foot grid similar to that used during the actual light level measurements, enabling direct comparison between simulated and measured data. The simulations use data from.ies files, provided by the manufacturers, that describe the light outputs of the fixtures. Iso-footcandle diagrams were constructed from the simulated data. The measured and simulated iso-footcandle diagrams are provided below in the section titled Results from Field Light Level Measurements. HOURS OF OPERATION All area lights in the test site are controlled by an astronomical time clock. As the on-off state changes are related to sunset and sunrise, the seasonal behavior of the astronomical time clock is similar to that of photocells. The hours of operation for the area lights were recorded daily between January 25 th and March 3 rd. To obtain the annual hours of operation, the data were compared to the sunrise and sunset times in Irvine, CA obtained from a solar calculator 12. The hours of operation for the monitored period were eight minutes longer per day than the sunset-tosunrise times reported by the calculator. The annual hours of operation, then, are the sum of the sunset-to-sunrise times plus eight minutes per day. A day year is used to account for leap years. Southern California Edison Page 16

24 RESULTS This section presents and discusses the data collected from the lab tests, the field measurements and the AGI simulations. First, a summary of the manufacturer s specifications for the HPS and LED lights is presented in Table 3Error! Reference source not found.. TABLE 3. MANUFACTURERS SPECIFICATIONS FOR THE HPS AND LED AREA LIGHTS. Luminaire Light Output (lumens)* CRI Lifetime (hours) HPS 30, , Rated Watts (including ballast) LED 20, , *The 30,000 lumens are the product of 50,000 lm HPS light source and typical 60% fixture efficiency. The LED 20,400 lumens are the product of 24,000 bare-chip lumens (240 LED s 100 lm/chip) and 85% fixture efficiency. Actual fixture efficiencies are difficult to measure, as only the light that is generated by the combination of the fixture, driver/ballast, and source are measured at the SCLTC. RESULTS FROM LAB TESTS The results from the SCLTC measurements on two LED fixtures and six HPS fixtures are summarized below. The HPS measurements occurred after a 100-hour burn-in period. POWER MEASUREMENTS SCLTC measured the power usage and power factors for the LED and HPS lights. Results from six HPS measurements and two LED measurements are listed in Table 4. For unknown reasons, one of the HPS fixtures was measured at an aberrant 371 W. This measurement is regarded as suspect and removed from consideration. Nevertheless, the HPS fixtures performed adequately in field light-level and uniformity tests despite this uncharacteristic variance in fixture connected load. The average power for the remaining five HPS fixtures was 442 W, while the two LEDs measured averaged 304 W. PHOTOMETRIC MEASUREMENTS SCLTC measured the total luminous flux, radiant spectrum, and CRI were measured for HPS and LED fixtures. Results from six HPS measurements and two LED measurements are listed in Table 5. Specific photometric data regarding the specific HPS fixture s make/model is not available at the time of this writing. The CRI ratings are in good agreement with measured data for both the HPS and LED fixtures. Southern California Edison Page 17

25 TABLE 4. POWER AND POWER FACTORS MEASURED AT THE SCLTC. Luminaire Rated Watts Measured Watts Measured Power (including ballast) (including ballast) Factor HPS # HPS # HPS # HPS # HPS # HPS # HPS Average * 0.97 LED # LED # LED Average * This average excludes the outlying 371 W measurement for HPS #6 TABLE 5. RATED AND MEASURED LIGHT OUTPUT AND CRI FOR HPS AND LED LIGHTS. Rated Lumens Luminaire estimated fixture Measured Lumens Rated CRI Measured CRI efficiency* HPS #1 30,000 24, HPS #2 30,000 27, HPS #3 30,000 25, HPS #4 30,000 26, HPS #5 30,000 25, HPS #6 30,000 22, HPS Average 30,000 25, LED #1 20,400 18, LED #2 20,400 18, LED Average 20,400 18, *The HPS 30,000 lumens are the product of 50,000 lm light source and 60% typical fixture efficiency. The LED 20,400 lumens are the product of 24,000 lm bare-chip (240 LED s X 100 lm/chip) and 85% rated fixture efficiency. Actual fixture efficiencies are difficult to measure, as only the light that is generated by the combination of the fixture, driver/ballast, and source are measured at the SCLTC Southern California Edison Page 18

26 RESULTS FROM FIELD POWER MEASUREMENTS POWER MEASUREMENTS The power usage and power factors for the LED and HPS lights were measured at the Irvine City Hall parking lot test site using a calibrated true RMS power meter. The rated and measured results for the lights are listed in Table 6. The measured Watt values and power factors shown are averages for the area lights. The field power measurements are approximately 7% lower than the power measurements taken in the lab at SCLTC. One reason may be that the line voltage measured in the field was below 277 V. The power factors measured in the field were, on average, 1% lower than those measured at the SCLTC (compare Table 6 with Table 4). The relative energy savings of the LED (approximately 30%) from the HPS, however, are consistent between the field and lab energy measurements. TABLE 6. RATED CONNECTED WATTS AND FIELD MEASURED WATTS AND POWER FACTORS FOR THE HPS AND LED LIGHTS. Luminaire Rated Watts Measured Watts Measured Power Factor (with ballast) (with ballast) HPS LED HOURS OF OPERATION The observed and estimated daily hours of operation for the area lights are shown in Figure 10. On average, the lights are on for hours per day, or 4,430 hours annually. Southern California Edison Page 19

27 FIGURE 10. MEASURED DAILY HOURS OF OPERATION FOR THE AREA LIGHTS. THE SINUSOIDAL NATURE IS DUE TO THE SEASONAL CHANGE IN DAY LENGTH. ANNUAL POWER USAGE The annual power usage per fixture, expressed in kwh, is the product of the fixture s measured power and the monitored annual hours of operation. Table 7 lists the measured power, annual hours of operation, and annual energy usage per fixture. The annual estimated energy savings based on field kw measurements per LED fixture over HPS is 523 kwh. This is a savings of 29.5% relative to the HPS fixtures. The power measurements in the lab at the SCLTC, listed in Table 8, were slightly higher than those in the field. However, the relative savings, as calculated by the SCLTC power measurements, are 31.2 %. Thus, the relative savings from the laboratory measurements are consistent with the relative savings derived from the field measurements. TABLE 7. MEASURED (IN FIELD) POWER, ANNUAL HOURS OF OPERATION, AND ANNUAL ENERGY USAGE PER FIXTURE. Luminaire Measured Watts (with ballast) Annual Hours of Operation Annual Energy Usage (kwh) HPS 400 4,430 1,772 LED 282 4,430 1,249 Difference 118 N/A 523 Southern California Edison Page 20

28 TABLE 8. MEASURED (AT SCLTC) POWER, ANNUAL HOURS OF OPERATION, AND ANNUAL ENERGY USAGE PER FIXTURE Luminaire Measured Watts Annual Hours of (with ballast) Operation Annual Energy Usage (kwh) HPS 442 4,430 1,958 LED 304 4,430 1,347 Difference 138 N/A 611 RESULTS FROM FIELD LIGHT LEVEL MEASUREMENTS Table 9 shows for the HPS and LED lights the measured and simulated maximum, average, and minimum light levels over the 200-foot by 130-foot measurement area, as well as the uniformity ratios. Figure 11 and Figure 12 show the iso-footcandle plots of the HPS lights for the measured and simulated horizontal lighting distributions respectively. Figure 13 and Figure 14 show the iso-footcandle plots of the LED lights for the measured and simulated horizontal lighting distributions respectively. Comparison of Figure 11 and Figure 13 reveals that the LEDs achieve dramatically superior uniformity of light cast upon the parking lot. Figure 11 features a band of darkness along the center of the parking lot, parallel to the rows of light poles. This band, highlighted in red in Figure 11, corresponds to light level measurements of below 1.0 fc. Figure 11 also reveals intense bright spots underneath the HPS fixtures, where the light levels are above 12 fc. Note that, just 15 feet away from the brightest spots, the light levels are at 3-4 fc. Figure 13, on the other hand, lacks any points below 1 fc (no red spots in the graph), and also lacks points above 10 fc. The gradients surrounding the fixtures are much more gradual than those associated with the HPS fixtures. The uniformity of light cast from the LED fixtures helps them achieve minimum light levels on pavement that are much higher than those of the HPS fixtures. TABLE 9. MEASURED AND SIMULATED LIGHT OUTPUTS AND UNIFORMITIES Luminaire HPS (Horizontal Measured) HPS (Horizontal Simulation) HPS (Vertical Measured) LED (Horizontal Measured) LED (Horizontal Simulation) LED (Vertical Measured) Uniformity Average Light Maximum Light Minimum Light Ratio Level (fc) Level (fc) Level (fc) (Max/Min) to to N/A to to N/A Southern California Edison Page 21

29 FIGURE 11. LIGHTS. ISO-FOOTCANDLE PLOT OF THE MEASURED LIGHTING DISTRIBUTION PROVIDED BY THE HPS AREA FIGURE 12. LIGHTS. ISO-FOOTCANDLE PLOT OF THE SIMULATED LIGHTING DISTRIBUTION PROVIDED BY THE HPS AREA Southern California Edison Page 22

30 FIGURE 13. ISO-FOOTCANDLE PLOT OF MEASURED LIGHTING DISTRIBUTION PROVIDED BY LED AREA LIGHTS FIGURE 14. ISO-FOOTCANDLE PLOT OF SIMULATED LIGHTING DISTRIBUTION PROVIDED BY LED AREA LIGHTS Southern California Edison Page 23

31 LIGHT LEVELS AND QUALITY Both the HPS and LED lights meet the IESNA recommended minimum lighting level of 0.2 fc over the entire measurement area. The LED lights achieve at least 1.30 fc over the entire measurement area. The HPS lights achieve at least 0.56 fc over the entire measurement area. Both the HPS and LED lights also meet the recommended IESNA lowest in-service 1 illumination values of 0.2 fc or greater. The lowest in-service light levels are the products of the initial light levels and the previously discussed LLFs. For the LEDs, the lowest in-service light levels are 1.30 fc 0.49 LLF = 0.64 fc. For the HPS, the lowest in-service levels are 0.56 fc 0.49 LLF = 0.27 fc. Both the HPS and LED area lights achieve the recommended light levels. The LEDs surpass the recommended light levels by a factor of three. The LED lights, due to their higher CRI, achieve superior color rendering, as demonstrated by the test site pictures in Figure 15. FIGURE 15. PARKING LOT AS LIGHTED BY THE HPS FIXTURES (TOP) AND LED FIXTURES (BOTTOM). Southern California Edison Page 24

32 UNIFORMITY RATIO The HPS lights have a uniformity ratio of 23.0 to 1 from the field measurements. This does not quite meet the IESNA recommended maximum uniformity ratio of 20 to 1. It should be noted that the AGI computer simulation predicted a 15:1 uniformity ratio. The non-uniformity in the field measurements may be due to several factors, including non-uniformity between the light outputs of the six HPS fixtures, light spillage from nearby light sources into the measurement area, improperly aligned fixtures (both vertically and horizontally these could be transient effects caused by the wind), and obstruction from nearby vegetation. In particular, some of the light poles were not perfectly aligned across the parking lot due to physical restrictions (this is apparent in both the HPS (Figure 11) and LED (Figure 13) measurements. Additionally, one of the six HPS fixtures had a light output that was approximately 10% lower than average. These factors may have degraded the uniformity for the HPS lights to the measured 23 to 1 value. The LED lights have a uniformity ratio of is 7 to1, which easily surpasses the IESNA recommended maximum uniformity ratio of 20 to 1. The importance of this achievement should not be under-stressed. The LEDs provide much higher minimum light levels that HPS (1.30 fc vs fc), despite having overall light outputs and power requirements approximately 30% below those of HPS. This is made possible primarily by the exceptional uniformity of the light cast by the LED fixtures. SIMULATED VS MEASURED LIGHT LEVELS For the HPS lights, the simulated lighting levels are within 30% of the measured values for all measurements except for the minimum lighting level. The relatively large discrepancy between simulation and survey data for the minimum light level may be due to specific irregularities in the field including a single underperforming light fixture, as discussed above. Another potential reason for the discrepancy may be that the.ies input file for the exact make/model of the HPS fixture was not available at the time of simulation, so the fixture was approximated by a comparable make/model. Comparison of Figure 11 and Figure 12 reveals that the simulation predicts a somewhat more uniform illumination pattern than was measured in the field. For the LED lights, the simulated and measured lighting levels are generally in good agreement. A comparison of Figure 13 and Figure 14 show that the simulation predicts a somewhat more uniform illumination pattern than that measured in the field in this case, as well, although the light level distribution is generally consistent with measured data. Southern California Edison Page 25

33 DISCUSSION COMPARISON OF LED AND HPS FIXTURES The LED fixtures tested in this study provided significant energy savings while maintaining adequate lighting levels. Although the HPS lamp has a very high nominal luminous efficacy (approximately 100 LPW), the fixture efficiency degrades this by over 40%. At the SCLTC, the LED Beta 12-bar fixtures achieved 60.0 LPW while the HPS achieved 58.6 LPW. In addition to providing adequate lighting at 30% energy savings, the LED fixtures provide longer lifetimes and much better color rendition. The significance of the improvement in color rendition is noteworthy. It has been shown that drivers peripheral vision and reaction times are better under metal halide lamps (white light, like LED) than under HPS lamps. The improvements have been attributed to the superior color rendition of metal halide lamps. 13 LED has about a 20% better color rendition than metal halide. HPS lights are the most commonly used light source for roadway and area lighting, mainly due to their long service lives and high luminous efficacies (LPW). Solid-state (here, LED) lighting is experiencing simultaneous improvements in lumens per Watt, and lumens per dollar. 14 Note that the price, based on manufacturers estimates for volume purchase, has decreased from $250/kilo-lumen in 2004 to $50/kilo-lumen in Optical performance is steadily improving. It is likely that, as costs decrease and efficacies increase, solid-state lighting will reduce the HPS (and Metal Halide) market share in area lighting because of reduced energy costs, longer life, reduced maintenance, improved uniformity, and improved color rendition. Although the LED luminaire is currently much more expensive than its HPS counterpart, the cost over life favors the LEDs when luminaire lifespan and energy cost savings are considered (see the economics subsection at the end of this section). It should also be noted that the price differential is expected to significantly decrease as larger volume jobs are negotiated with manufacturers. RATED VS MEASURED LUMEN OUTPUTS Efficacy comparisons of different lighting technologies are often based on the luminous efficacies of the light sources. For example: A 400W HPS light with an initial luminous output of 50,000 lm can be said to have a luminous efficacy of 125 LPW. Likewise, the LED light-sources manufactured by CREE and used in the Beta area light are rated at 87 LPW. However, several efficiency factors apply to each particular light source, and the efficacies as measured in the lab and in the field are significantly lower than those that solely pertain to the light-sources. The following salient factors account for that reduction: Southern California Edison Page 26

34 BALLAST FACTOR (FOR HID) The ballast typically increases the power usage by about 10%, thereby lowering the luminous efficacy by about 10%. The LEDs also have some relatively small losses due to their drivers, and, if applicable, losses due to active cooling mechanisms, such as microfans. The LED fixtures tested in this report employ passive cooling mechanisms, and have no microfans. FIXTURE EFFICIENCY Not all the light exits the fixture. Nearly all of the light that is coming directly from the light source will pass through the fixture lens. However, some of the light that is redirected downwards by the reflectors within the fixture may approach the lens at a glancing angle and experience internal reflection. For area lights, fixture-related losses are typically between 25% and 50%. Premium fixtures with superior optics and anti-reflective coatings on the inner surfaces of the lenses are available. According to the manufacturers, such fixtures can have efficiencies between 80% and 90%. The LED lights typically have sophisticated, computer-designed optics that encapsulate each diode. Beta claims that the optics has been independently verified to be 85% efficient (light exiting the luminaire). The measurements at SCLTC confirm that the LED fixtures are more efficient than the baseline HPS fixtures. The LED fixtures had an initial efficacy of about 65 LPW (after 15 minutes of operation, this was reduced to 60 LPW this phenomenon is discussed below), which is about 69% of the initial 87 LPW of the bare chips. The HPS fixtures, on the other hand, averaged 58.6 LPW, which is about 54% of the lm/w (assuming 50,000 initial rated lumens divided by 460 connected Watts with ballast). OPTICAL EFFICIENCY The light that exits the fixture is typically traveling downward, but it is not possible to cast 100% of the available light onto a given patch of ground nearby the fixture and to simultaneously provide sufficient uniformity of illumination. To approach full efficiency, the reflectors and lens would need to have customized geometry that accounts for the fixture height and the size/shape of the area intended for illumination. Most fixtures are optimized for a range of mounting heights and angles rather than for a specific application. In this report, ILC measured lumens on target by systematically recording light levels over the area targeted for illumination. If the proper.ies descriptor files are available for a fixture, simulation through AGI or visual software can yield reliable estimates. The LED fixtures seem to have superior optical efficiency. Although the LEDs were measured to be 71% as bright as the HPS in the integrating sphere (18,231 lm vs. 25,807 lm), they managed to achieve 78% of the 400W HPS average light levels on target (2.4 average footcandles vs fc for HPS). LIGHT LOSS FACTORS. As discussed, lumen depreciation and dirt depreciation can be substantial, and can vary dramatically among various light-sources. JUNCTION TEMPERATURE FOR LEDS The power and luminosity ratings for LEDs are taken from a short, 1 millisecond pulse at 25 C junction temperature. The luminous efficacy tends to drop as junction temperature rises. The manufacturers ratings tend to be somewhat higher than measurements at the SCLTC for this reason. Figure 16 demonstrates that the luminous output dropped by 8% during the 25 minute test. The power usage also dropped by 3% during Southern California Edison Page 27

35 the course of the test. The corresponding loss in luminous efficacy was approximately 5%. The power and light levels seem to stabilize after the first 20 minutes, perhaps suggesting that the fixture was approaching thermal equilibrium at the time. It should be noted that there is little airflow inside the integrating sphere. Airflow and low nighttime temperatures in the field would provide better cooling, and may mitigate this effect. FIGURE 16. (LEFT) RADIANT FLUX VS WAVELENGTH FOR TEN SCANS RANGING FROM 1-25 MINUTES OF RUN-TIME FOR THE BETA LED FIXTURE. (RIGHT) A CLOSEUP OF THE 450 NM PEAK SHOWS THAT THE RADIANT FLUX DECREASES FROM 610 MW/NM TO 560 MW/NM DURING 25 MINUTES OF OPERATION. LUMENS-ON-TARGET PER WATT Lumens-on-target per Watt is a useful metric for comparing the initial lighting efficacies of two fixtures. This quantity helps to define the electric demand associated with illuminating a given surface area (the target ) to a specified level. The lumens-on-target per Watt for the LED and HPS fixtures can be approximated from the data above. The spacing of fixtures (100 feet between fixtures by 130 feet across the parking lot) means that each fixture covers an area of 100 feet x 65 feet, or 6,500 square feet. Note that the fixtures are directional and cast light only in the forward direction see Figure 2. In addition, the test area only covered 26,000 ft 2 while the total area lighted by the area lights is 39,000 ft 2. Given average illumination levels of 3.06 and 2.40 fc for the HPS and LED fixtures respectively, the total lumens on target are 19,890 for the HPS and 15,600 for the LED. The results are derived by dividing by the wattage as measured in the field (400 for HPS, 282 for LED). The results are 49.7 lm-on-target/w for HPS and 55.3 lm-ontarget/w for LED. The maintained efficacy, taken to be the lowest lm-on-target/w expected while the fixtures are in service, results from multiplying the lm-on-target per watt values above by the appropriate combined LLD and LDD (0.49 for LEDs and HPS). For Southern California Edison Page 28