Lighting Research Center Lighting Research Center
    Volume 12 Issue 1
October 2013    
application - The use to which a lighting system will be put; for example, a lamp may be intended for indoor residential applications. ballast - A device required by electric-discharge light sources such as fluorescent or HID lamps to regulate voltage and current supplied to the lamp during start and throughout operation. lumen depreciation - The decrease in lumen output that occurs as a lamp is operated, until failure. Also referred to as lamp lumen depreciation (LLD). color rendering index (CRI) - A rating index commonly used to represent how well a light source renders the colors of objects that it illuminates. For a CRI value of 100, the maximum value, the colors of objects can be expected to be seen as they would appear under an incandescent or daylight spectrum of the same correlated color temperature (CCT). Sources with CRI values less than 50 are generally regarded as rendering colors poorly, that is, colors may appear unnatural. color shift - The change in a lampís correlated color temperature (CCT) at 40% of the lampís rated life, in kelvin (K). ultraviolet - Any radiant energy within the wavelength range 100 to 400 nanometers is considered ultraviolet radiation (1 nanometer = 1 billionth of a meter, or 1 X 10-9 m). wavelength - The distance between two corresponding points of a given wave. Wavelengths of light are measured in nanometers (1 nanometer = 1 billionth of a meter, or 1 X 10-9 m) arc tube - An envelope, usually quartz or ceramic that contains the arc of a discharge light source. electrodes - The structure that serves as the electric terminals at each end of electric discharge lamps. high-intensity discharge (HID) - An electric lamp that produces light directly from an arc discharge under high pressure. Metal halide, high-pressure sodium, and mercury vapor are types of HID lamps. power quality - The degree to which current and voltage wave forms conform to a sinusoidal shape and are in synchronous phase with each other. Poor power quality results when the wave forms are distorted and/or out of phase and can interfere with data communications, cause inefficient operation or failure of other electrical equipment on the same supply line, and result in excessive current in electrical distribution lines. grid - The combination of electric power plants and transmission lines operated by an electric utility. restrike time - The time required for a lamp to restrike, or start, and to return to 90% of its stabilized light output after the lamp is extinguished. Normally, HID lamps need to cool before they can be restarted. shielding - Blocking an electric or magnetic field with a metallic substance. The incident field induces currents in the metallic substance, and these currents induce a field that opposes the incident field. Shielding reduces radiated electromagnetic waves. Electronic components, wires, lamps, and devices can all be shielded. visual performance - The quantitative assessment of the performance of a visual task, taking into consideration speed and accuracy. warm-up time - The time it takes for a lamp to produce 90% of its stabilized light output when it is started, unless otherwise indicated. high-pressure sodium (HPS) - A high-intensity discharge lamp type that uses sodium under high pressure as the primary light-producing element. HPS lamps produce light with a correlated color temperature (CCT) of approximately 2000 kelvins, although CCTs for lamps having higher CRI values range from 2200 to 2700 kelvins. Standard lamps have a CRI value of 22; others have CRI values from 60 to 80. HPS lamps are among the most efficacious light sources, with efficacies as high as 150 lumens per watt, although those with higher CRI values have efficacies as low as 25 lumens per watt. initial light output - A lamp's light output, in lumens, after 100 hours of seasoning. lamp - A radiant light source. luminaire - A complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply. (Also referred to as fixture.) frequency - The number of cycles completed by a periodic wave in a given unit of time. Frequency is commonly reported in cycles per second, or hertz (Hz). correlated color temperature (CCT) - A specification for white light sources used to describe the dominant color tone along the dimension from warm (yellows and reds) to cool (blue). Lamps with a CCT rating below 3200 K are usually considered warm sources, whereas those with a CCT above 4000 K usually considered cool in appearance. Temperatures in between are considered neutral in appearance. Technically, CCT extends the practice of using temperature, in kelvins (K), for specifying the spectrum of light sources other than blackbody radiators. Incandescent lamps and daylight closely approximate the spectra of black body radiators at different temperatures and can be designated by the corresponding temperature of a blackbody radiator. The spectra of fluorescent and LED sources, however, differ substantially from black body radiators yet they can have a color appearance similar to a blackbody radiator of a particular temperature as given by CCT. efficacy - The ratio of the light output of a lamp (lumens) to its active power (watts), expressed as lumens per watt. electromagnetic interference (EMI) - The interference of unwanted electromagnetic signals with desirable signals. Electromagnetic interference may be transmitted in two ways: radiated through space or conducted by wiring. The Federal Communications Commission (FCC) sets electromagnetic interference limits on radio frequency (RF) lighting devices in FCC Part 18. horizontal illuminance - The average density of luminous flux incident on a horizontal surface, measured in footcandles (fc) or lux (lx). One fc equals 10.76 lx. mercury vapor (MV) lamp - A high-intensity discharge lamp type that uses mercury as the primary light-producing element. Mercury vapor lamps produce light with a CCT from 3000 to 7000 K. Mercury vapor lamps with clear outer bulbs have CRI values from 15 to 25, whereas phosphor-coated lamps have CRI values from 40 to 55. Mercury vapor lamps are less efficacious than other HID lamp types, typically producing only 30 to 65 LPW, but they have longer lamp lives and lower initial costs than other HID lamp types. metal halide (MH) lamp - A high-intensity discharge lamp type that uses mercury and several halide additives as light-producing elements. Metal halide lamps have better color properties than other HID lamp types because the different additives produce more visible wavelengths, resulting in a more complete spectrum. Metal halide lamps are available with CCTs from 2300 to 5400 K and with CRI values from 60 to 93. Efficacies of metal halide lamps typically range from 75 to 125 LPW. operating position - The manufacturer-recommended operating position for a lamp. power - The power used by a device to produce useful work (also called input power or active power). In lighting, it is the system input power for a lamp and ballast or driver combination. Power is typically reported in the SI units of watts. power line carrier (PLC) - A system that transmits high-frequency (50 to 500 kHz) analog or digital signals via the power lines of a building. These signals control devices such as luminaires or contain voice transmissions such as intercom messages. Some commercial and residential energy management systems also use power line carrier systems. glare - The sensation produced by luminances within the visual field that are sufficiently greater than the luminance to which the eyes are adapted, which causes annoyance, discomfort, or loss in visual performance and visibility. color rendering - A general expression for the effect of a light source on the color appearance of objects in conscious or subconscious comparison with their color appearance under a reference light source. sky glow - Brightening of the sky caused by outdoor lighting and natural atmospheric and celestial factors. ambient temperature - The temperature of the surrounding air that comes into contact with the lamp and ballast. Ambient temperature affects the light output and active power of fluorescent lamp/ballast systems. Each fluorescent lamp-ballast system has an optimum ambient temperature at which it produces maximum light output. Higher or lower temperatures reduce light output. For purposes of lamp/ballast tests, ambient temperature is measured at a point no more than 1 meter (3.3 feet) from the lamp and at the same height as the lamp. system efficacy - Also referred to as relative system efficacy, system efficacy is a measurement of a system'ís ability to convert electricity into light. Measured in lumens per watt (LPW), system efficacy is the ratio of the light output (in lumens) to the active power (in watts). rated lumen - Also referred to as rated light output from lamp in lumens. Lumen refers to a unit measurement of the rate at which a lamp produces light. A lampís light output rating expresses the total amount of light emitted in all directions per unit time. Manufacturers rate their lampsí initial light output after 100 hours of operation. lumen maintenance - The ability of a lamp to retain its light output over time. Greater lumen maintenance means a lamp will remain brighter longer. The opposite of lumen maintenance is lumen depreciation, which represents the reduction of lumen output over time. Lamp lumen depreciation factor (LLD) is commonly used as a multiplier to the initial lumen rating in illuminance calculations to compensate for the lumen depreciation. The LLD factor is a dimensionless value between 0 and 1. uniformity - The degree of variation of illuminance over a given plane. Greater uniformity means less variation of illuminance. The uniformity ratio of illuminance is a measure of that variation expressed as either the ratio of the minimum to the maximum illuminance or the ratio of the minimum to the average illuminance. footcandle (fc) - A measure of illuminance in lumens per square foot. One footcandle equals 10.76 lux, although for convenience 10 lux commonly is used as the equivalent. nadir - In the lighting discipline, nadir is the angle pointing directly downward from the luminaire, or 0į. Nadir is opposite the zenith. rated lamp life - The number of hours at which half of a group of product samples fail. The rated life is a median value of life expectancy; any lamp or group of lamps may vary from the published rated life. Rated life is based on standard test conditions. driver - For light emitting diodes, a device that regulates the voltage and current powering the source. heat sinking - Adding a material, usually metal, adjacent to an object in order to cool it through conduction. spectral power distribution (SPD) - A representation of the radiant power emitted by a light source as a function of wavelength. rated light output - The sum of the initial rated lamp lumens of the lamp(s) that were supplied with the luminaire. chromaticity - The dominant or complementary wavelength and purity aspects of the color taken together, or of the aspects specified by the chromaticity coordinates of the color taken together. It describes the properties of light related to hue and saturation, but not luminance (brightness). gamut area - A measure of color rendering based upon volume in color space. It is the range of colors achievable on a given color reproduction medium (or present in an image on that medium) under a given set of viewing conditions. photopic - Vision mediated essentially or exclusively by the cones. It is generally associated with adaptation to a luminance of at least 3.4 cd/m2. CIE - Abbreviated as CIE from its French title Commission Internationale de l'Eclairage, the International Commission on Illumination is a technical, scientific, and cultural organization devoted to international cooperation and exchange of information among its member countries on matters relating to the science and art of lighting. standard deviation - A measure of the average distance of a set of data points from their mean. A set of data points that are all close to their mean will have a smaller standard deviation than a set of points that are further from their mean. MacAdam ellipse - Researcher David L. MacAdam showed that a just noticeable difference (JND) in the colors of two lights placed side-by-side was about three times the standard deviation associated with making color matches between a reference light and a test light (MacAdam 1942, Wyszecki and Stiles 1982). These JNDs form an elliptical pattern of "constant discriminability" in a chromaticity space, centered on the chromaticity of a reference light, known as MacAdam ellipse. fluorescent lamp - A low-pressure mercury electric-discharge lamp in which a phosphor coating on the inside of the glass tubing transforms most of the ultraviolet energy created inside the lamp into visible light. light-emitting diode (LED) - A solid-state electronic device formed by a junction of P- and N-type semiconductor material that emits light when electric current passes through it. LED commonly refers to either the semiconductor by itself, i.e. the chip, or the entire lamp package including the chip, electrical leads, optics and encasement. illuminance - The density of luminous flux incident upon a surface. Illuminance is measured in footcandles (lumens/square foot) or lux (lumens/square meter). One footcandle equals 10.76 lux. lamp life - The number of hours at which half of a large group of lamps have failed when operated under standard testing conditions. lumen (lm) - A unit measurement of the rate at which a lamp produces light. A lamp's lumen output rating expresses the total amount of light the lamp emits in all directions per unit time. This estimate of expanded uncertainty uses a coverage factor of k = 2, covering two standard deviations.

What has been the experience of those who have installed HID plasma luminaires?

NLPIP interviewed an individual associated with each of four plasma lighting demonstrations and pilot studies, detailed below. These applications were either mentioned in the popular press, were funded by governmental or private agencies, or were brought to NLPIP's attention from specifiers who participated in the 2012 survey (as discussed in the section "What are the claimed and perceived advantages of plasma lighting systems?").

Scottsburg Municipal Electric Utility, Scottsburg, Indiana (2009 - 2011)

Interview summary

  • Scottsburg Municipal Electric Utility partnered with Stray Light Optical Technologies to replace 56 existing 400 W HPS streetlights with 40 streetlights containing plasma lighting systems, in a pilot project funded by the American Public Power Association (APPA) Demonstration of Energy and Efficiency (DEED) program (Rea 2011). A 51% reduction in total lighting power was accompanied by a 68% decrease in average illuminance.
  • During the pilot project, many of the 40 installed plasma streetlights failed and were repeatedly replaced over the 20-month observation period (Rea 2011). One-third of the plasma streetlights did not start when the ambient temperature was less than approximately 15įF. Most of the 40 plasma streetlights failed due to a faulty component in the power supply. In addition, most of the 40 plasma streetlights had incompatible gaskets that caused significant off-gassing. The off-gassing created an opaque film on the plasma arc tube, which led to increased lumen depreciation, discoloration of the arc tube, and failure. All three quality issues were addressed by the luminaire manufacturer under warranty.
  • Despite these issues, Scottsburg Municipal Electric Utility has since continued to replace more than 300 HPS streetlights with plasma streetlights. There have been no failures in these replacements due to cold weather (ambient temperature less than approximately 15įF) (Jim Binkley, Scottsburg Municipal Electric Utility, personal communication, 2013).
  • Scottsburg Municipal Electric Utility plans to replace up to 527 HPS streetlights with plasma streetlights in total. They are satisfied with the way the manufacturer has replaced the products as needed (Jim Binkley, Scottsburg Municipal Electric Utility, personal communication, 2013).
Sacramento Municipal Utility District, Sacramento, California (2011)

Interview summary

  • Sacramento Municipal Utility District (SMUD) published a technology brief on light-emitting plasma in December 2011 (SMUD 2011). One demonstration project that received a Customer Advanced Technologies program research grant is mentioned in this report. At this site, LUXIM wall-mounted luminaires replaced existing MH floodlights. SMUD also provided NLPIP with information about two other demonstration sites that received Customer Advanced Technologies program research grants. In one of the demonstration sites, LUXIM wall-mounted luminaires replaced existing MH floodlights. At the other demonstration site, LUXIM area lighting luminaires replaced existing HPS area lighting luminaires. In all three demonstration sites, uniformity ratios improved under the plasma luminaires.
  • At one of the wall-mounted lighting demonstration sites, average light levels decreased by approximately 30% while total lighting power decreased by approximately 50%. Although there were multiple failures at this location with earlier generations of the plasma luminaires, there have been no failures at this location since November 2012. At the other wall-mounted lighting demonstration site, light levels increased even though total lighting power decreased. Although there were failures at this site, this customer plans to install more plasma luminaires and a wireless control system by December 2013 (Dave Bisbee, SMUD, personal communication, 2013).
  • In the area lighting demonstration site, the decrease in total lighting power was accompanied by an even larger decrease in light level. At this site, there were multiple failures and this customer has replaced the plasma area lights with LED luminaires (Dave Bisbee, SMUD, personal communication, 2013).
  • SMUD indicated that there was an average failure rate of 25% across the three sites with multiple generations of luminaires and noted that the manufacturer had been replacing luminaires as needed. In some cases, the luminaire replacement was not due to outright failure but due to a green color shift after 8000 h of use (Dave Bisbee, SMUD, personal communication, 2013).
Ports America, Oakland, California and Newark, New Jersey (2010 - 2012)

Interview summary

  • Ports America is the largest terminal operator in the U.S., operating in more than 42 ports and 80 locations nationwide. Most terminal lighting is provided by 1000 W HPS high-mast luminaires (1280 W input power per luminaire) using poles that are 80 to 150 ft (24 to 46 m) in height, spaced 250 to 400 ft (76 to 120 m) apart with 8 to 12 luminaires on each pole. Some of the marine terminals are at the end of the utility grid distribution lines and power supply fluctuations are an ongoing issue.
  • Ports America is evaluating lighting upgrades in order to reduce sky glow; meet OSHA standards of 5 footcandles (54 lux) average in work areas; reduce its energy use; use existing poles; augment safety and reduce maintenance costs. The HPS lamps and ballasts need to be replaced annually because of power quality issues. The HPS luminaires also have a high energy cost of $818 per luminaire per year.
  • Ports America, along with the Pacific Gas and Electric Company (PG&E), evaluated successive generations of plasma luminaires for the past two years (Ward 2012, 2013 and personal communication, 2013; Douglass et al. 2013).
  • In this demonstration, 12 new 1000 W HPS luminaires were replaced with twelve, ten, or eight 560 W high mast plasma luminaires from Bright Light Systems. The plasma luminaires required less power but also had lower average horizontal illuminance by approximately the same ratio (Douglass et al. 2013; Ward 2013). The measured uniformity was better under the plasma luminaires (Douglass et al. 2013; Ward 2013), and the plasma luminaires produced higher light levels at some key locations, such as the wharf "bull rail" (Thomas Ward, personal communication, 2013).
  • The plasma luminaires were able to be individually dimmed and switched in groups, although the 50% dimming setpoint produced approximately 35% of the full light output and used approximately 60% of the full power demand (Douglass et al. 2013).
  • Ports America investigated the potential visual benefits of white light (Ward 2012; Douglass et al. 2013). However, light levels at these sites were high enough that there would be very little, if any, improvement in peripheral visual performance due to spectral effects (ASSIST 2009; Douglass et al. 2013). The improved color rendering capabilities of the plasma luminaires make it easier for workers to see ground striping, to differentiate container edges, and to read container markings, and the workers prefer the "whiter" light source (Thomas Ward, personal communication, 2013). In some situations, there was a direct view of the plasma luminaires and glare was an issue. Ports America is considering adjusting the task locations to overcome this problem (Thomas Ward, personal communication, 2013).
  • Over the course of the evaluation, Ports America found that the plasma luminaires were also sensitive to power supply fluctuations and the luminaires were replaced under warranty. Recent generations of the luminaire include updated electronics that have stabilized the luminaire's output (Thomas Ward, personal communication, 2013). Ports America believes that the Bright Light Systems luminaires produce less sky glow, compared to the base case, likely due to luminaire shielding and lower light levels.
  • Ports America has determined that the plasma luminaires meet the OSHA illumination criteria (Thomas Ward, personal communication, 2013). Ports America has determined that the plasma luminaires are suitable for the Outer Harbor installation, and is working with the manufacturer to use the plasma luminaires in other port installations. Ports America is also evaluating LED systems for this application, but has found the proposed luminaires to be too heavy to be suitable (Thomas Ward, personal communication, 2013).
Hydro One, Leamington, Ontario, Canada (2010)

Interview summary (David Forgione, Hydro One, personal communication, 2013)

  • Hydro One, a utility in Ontario Canada, incentivized the replacement of 370 existing 1000 W HPS luminaires with 295 W Plasmalyte plasma luminaires on a one-for-one basis for a greenhouse application. The luminaires were incentivized under the Ontario Power Authority saveONenergy RETROFIT program administered by Hydro One's conservation demand management department.
  • Hydro One was interested in the energy and demand savings provided by the retrofit, whereas the client is interested in produce growth, particularly that of green peppers.
  • The client has indicated that there are no major differences in the growth rate of the green peppers under the HPS or the plasma luminaires.
  • When the plasma luminaires were cycled on and off, there were problems with the electronic drivers due to voltage fluctuations. The drivers were replaced and there have been no further problems with the plasma luminaires.

 

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