Sodium-vapor lamp
A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.
Two varieties of such lamps exist: low pressure and high pressure. Low-pressure sodium lamps are highly efficient electrical light sources, but their yellow light restricts applications to outdoor lighting, such as street lamps, where they are widely used.[1] High-pressure sodium lamps emit a broader spectrum of light than the low-pressure lamps, but they still have poorer color rendering than other types of lamps.[2] Low-pressure sodium lamps only give monochromatic yellow light and so inhibit color vision at night.
Single ended self-starting lamps are insulated with a mica disc and contained in a borosilicate glass gas discharge tube (arc tube) and a metal cap.[3][4] They include the sodium-vapor lamp that is the gas-discharge lamp in street lighting.[5][6][3][4]
Development
The low-pressure sodium arc discharge lamp was first made practical around 1920 owing to the development of a type of glass that could resist the corrosive effects of sodium vapor. These operated at pressures of less than 1 Pa and produced a near monochromatic light spectrum around the sodium emission lines at 589.0 and 589.56 nanometres wavelength. The yellow light produced by these limited the range of applications to those where color vision was not required.[7]
First LPS commercial lamps were marketed since 1932, conceived respectively both in
Research into high-pressure sodium lamps occurred in both the United Kingdom and the United States. Increasing the pressure of the sodium vapor broadened the sodium emission spectrum so that the light produced had more energy emitted at wavelengths above and below the 589 nm region. The quartz material used in mercury discharge lamps was corroded by high pressure sodium vapor. A laboratory demonstration of a high pressure lamp was carried out in 1959. The development by General Electric of a sintered aluminum oxide material (with magnesium oxide added to improve light transmission) was an important step in construction of a commercial lamp. The material was available in the form of tubing by 1962, but additional techniques were required to seal the tubes and add the necessary electrodes—the material could not be fused like quartz. The end caps of the arc tube would get as hot as 800 degrees C in operation, then cool to room temperature when the lamp was turned off, so the electrode terminations and arc tube seal had to tolerate repeated temperature cycles. This problem was solved by Michael Arendash[8] at the GE Nela Park plant. The first commercial high-pressure sodium lamps were available in 1965 from companies in the United States, the United Kingdom, and the Netherlands; at introduction a 400 watt lamp would produce around 100 lumens per watt.[7][9]
Single-crystal artificial sapphire tubes were also manufactured and used for HPS lamps in the early 1970s, with a slight improvement in efficacy, but production costs were higher than for polycrystalline alumina tubes.[7]
Low-pressure sodium
Low-pressure sodium (LPS) lamps have a
LPS lamps have an outer glass vacuum envelope around the inner discharge tube for thermal insulation, which improves their efficiency. Earlier LPS lamps had a detachable dewar jacket (SO lamps).[11] Lamps with a permanent vacuum envelope (SOI lamps) were developed to improve thermal insulation.[12] Further improvement was attained by coating the glass envelope with an infrared reflecting layer of indium tin oxide, resulting in SOX lamps.[13]
LPS lamps are among the most
LPS lamps are similar to fluorescent lamps in that they are a low-intensity light source with a linear lamp shape. They do not exhibit a bright arc as do
Modern LPS lamps have a service life of about 18,000 hours and do not decline in lumen output with age, though they do increase in energy consumption by about 10% towards end of life. This property contrasts with mercury vapor HID lamps, which become dimmer towards the end of life to the point of being ineffective, while consuming undiminished electrical power.
In 2017 Philips Lighting, the last manufacturer of LPS lamps, announced they were discontinuing production of the lamps due to falling demand.[15] Initially, production was due to be phased out in the course of 2020, but this date was brought forward and the last lamps were produced at the Hamilton factory on December 31, 2019.[16]
Light pollution considerations
For locations where
Film special effects
Sodium vapor process (occasionally referred to as yellowscreen) is a film technique that relies on narrowband characteristics of LPS lamp. Color negative film is typically not sensitive to the yellow light from an LPS lamp, but special black-and-white film is able to record it. Using a special camera, scenes are recorded on two spools simultaneously, one with actors (or other foreground objects) and another that becomes a mask for later combination with different background. This technique originally yielded results superior to blue-screen technology, and was used in years 1956 to 1990, mostly by Disney Studios. Notable examples of films using this technique include Alfred Hitchcock's The Birds and the Disney films Mary Poppins and Bedknobs and Broomsticks. Later advancements in blue- and green-screen techniques and computer imagery closed that gap, leaving SVP economically impractical.[22]
High-pressure sodium
High-pressure sodium (HPS) lamps have been widely used in industrial lighting, especially in large manufacturing facilities, and are commonly used as
High-pressure sodium lamps are quite efficient—about 100 lumens per watt, when measured for photopic lighting conditions. Some higher-power lamps (e.g. 600 watt) have efficacies of about 150 lumens per watt.
Since the high-pressure sodium arc is extremely chemically reactive, the
"White" high pressure sodium lamp
A variation of the high-pressure sodium introduced in 1986, the White HPS has a higher pressure than the typical HPS lamp, producing a color temperature of around 2700 kelvins with a color rendering index (CRI) of about 85, greatly resembling the color of an incandescent light.[25] These lamps are often used indoors in cafes and restaurants for aesthetic effect. However, white HPS lamps have higher cost, shorter service lives, and lower light efficiency, and so they cannot compete with HPS at this time.
Theory of operation
An amalgam of metallic sodium and mercury lies at the coolest part of the lamp and provides the sodium and mercury vapor that is needed to draw an arc. The temperature of the amalgam is determined to a great extent by lamp power. The higher the lamp power, the higher will be the amalgam temperature. The higher the temperature of the amalgam, the higher will be the mercury and sodium vapor pressures in the lamp and the higher will be the terminal voltage. As the temperature rises, the constant current and increasing voltage consumes increasing energy until the operating level of power is reached. For a given voltage, there are generally three modes of operation:
- The lamp is extinguished and no current flows.
- The lamp is operating with liquid amalgam in the tube.
- The lamp is operating with all amalgam evaporated.
The first and last states are stable, because the lamp resistance is weakly related to the voltage, but the second state is unstable. Any anomalous increase in current will cause an increase in power, causing an increase in amalgam temperature, which will cause a decrease in resistance, which will cause a further increase in current. This will create a runaway effect, and the lamp will jump to the high-current state (#3). Because actual lamps are not designed to handle this much power, this would result in catastrophic failure. Similarly, an anomalous drop in current will drive the lamp to extinction. It is the second state that is the desired operating state of the lamp, because a slow loss of the amalgam over time from a reservoir will have less effect on the characteristics of the lamp than a fully evaporated amalgam. The result is an average lamp life in excess of 20,000 hours.
In practical use, the lamp is powered by an AC voltage source in series with an inductive "
The light from the lamp consists of
End of life
At end of life, high-pressure sodium (HPS) lamps exhibit a phenomenon known as cycling, caused by a loss of sodium in the arc. Sodium is a highly reactive element and is lost in a reaction with the aluminum oxide of the arc tube. The
- 6 Na + Al2O3 → 3 Na2O + 2 Al
As a result, these lamps can be started at a relatively low voltage, but, as they heat up during operation, the internal gas pressure within the arc tube rises, and more and more voltage is required to maintain the arc discharge. As a lamp gets older, the maintaining voltage for the arc eventually rises to exceed the maximum voltage output by the electrical ballast. As the lamp heats to this point, the arc fails, and the lamp goes out. Eventually, with the arc extinguished, the lamp cools down again, the gas pressure in the arc tube is reduced, and the ballast can once again cause the arc to strike. The effect of this is that the lamp glows for a while and then goes out, typically starting at a pure or bluish white then moving to a red-orange before going out.
More sophisticated ignitor designs detect cycling and give up attempting to start the lamp after a few cycles, as the repeated high-voltage ignitions needed to restart the arc reduce the lifetime of the ballast or the ignitor, depending on the ignitor configuration. If power is removed and reapplied, the ballast will make a new series of startup attempts.
LPS lamp failure does not result in cycling; rather, the lamp will simply not strike or will maintain the dull red glow of the start-up phase. In another failure mode, a tiny puncture of the arc tube leaks some of the sodium vapor into the outer vacuum bulb. The sodium condenses and creates a mirror on the outer glass, partially obscuring the arc tube. The lamp often continues operating normally, but much of the light generated is obscured by the sodium coating, providing no illumination.
See also
- Arc lamp – Lamp that produces light by an electric arc
- High-intensity discharge lamp – Type of electric lamp/bulb (HID)
- History of street lighting in the United States – History of street lights
- Light pollution – Excess artificial light in an environment
- List of light sources – Devices and processes that produce light
- Mercury-vapor lamp – Light source using an electric arc through mercury vapor
- Metal-halide lamp – Type of lamp
- Neon lamp – Light source based on gas discharge
- Street light – Raised source of light beside a road or path
- Sulfur lamp – Lighting system
References
- ^ Department of Public Works (1980). San Jose: Study and report on low-pressure sodium lighting. San Jose: City of San Jose. p. 8. Archived from the original on 2016-03-04. Retrieved 2013-12-06.
- U.S. Naval Observatory. Archived from the originalon 2015-09-10. Retrieved 2013-12-05.
- ^ a b "The Low Pressure Sodium Lamp".
- ^ a b "The Low Pressure Sodium Lamp".
- ^ "Lighting Comparison: LED vs High Pressure Sodium/Low Pressure Sodium". StouchLighting.com.
- ^ "The Sodium Lamp - How It Works and History". EdisonTechCenter.org.
- ^ a b c Raymond Kane, Heinz Sell, Revolution in Lamps: A Chronicle of 50 Years of Progress, Second Edition, Fairmont Press, 2001. pp. 238–241.
- ^ USA patent US3737717A, Arendash, Michael, "High intensity lamp containing thermal shorting fuse", published 1972-03-13, issued 1973-06-05, assigned to General Electric Co.
- ISBN 1349091960. pp. 13-17.
- ^ "SLI/H Sodium". LampTech.co.uk. Jun 11, 2018. Retrieved 2012-03-03.
- ^ "SO/H Sodium". LampTech.co.uk. Jun 4, 2015. Retrieved 2012-03-03.
- ^ "SOI/H Sodium". LampTech.co.uk. Jun 16, 2015. Retrieved 2012-03-03.
- ^ "SOX Sodium". LampTech.co.uk. Nov 2, 2015. Retrieved 2012-03-03.
- ^ "MASTER SOX-E 131W BY22d 1SL/6". Philips lighting. September 19, 2023. Archived from the original on 24 Jan 2024.
- ^ Root, Doug (28 September 2017). "Heads Up! Philips Low Pressure Sodium SOX Bulbs Are Going the Way of the Dodo". AtlantaLightBulbs.com. Archived from the original on May 23, 2022.
- ^ "End of an era as remaining 70 jobs at former Philips factory are to be axed". Daily Record. 11 July 2019. Archived from the original on Nov 22, 2021.
- ^ "Council policy - outdoor lighting on private developments" (PDF). City of San José, California. June 20, 2000 [March 1, 1983]. Archived from the original (PDF) on 2012-05-15. Retrieved 2012-10-14.
- ^ "Flagstaff Zoning Code" (PDF). Archived from the original (PDF) on 13 September 2014. Retrieved 14 April 2014.
- ^
Luginbuhl, C. B. (12–16 July 1999), "Why Astronomy Needs Low-Pressure Sodium Lighting", in R. J. Cohen; W. T. Sullivan (eds.), Why Astronomy Needs Low-Pressure Sodium Lighting, Preserving the Astronomical Sky, Proceedings of IAU Symposium 196, vol. 196, Vienna, Austria: International Astronomical Union (published 2001), p. 81, Bibcode:2001IAUS..196...81L, archivedfrom the original on Jan 24, 2024
- ^ Luginbuhl, C. B.; Boley, P. A.; Daviws, D. R. (May 2014). "The impact of light source spectral power distribution on sky glow". Journal of Quantitative Spectroscopy and Radiative Transfer. 139: 21–26. .
- ^
Aubé, M.; Roby, J.; Kocifaj, M. (5 July 2013). "Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility". PLOS ONE. 8 (7): e67798. PMID 23861808.
- ^ Hess, John P. (January 6, 2017). "Yellow Screen and the Revenge of the Blue Screen". Filmmaker IQ. Archived from the original on 2018-11-28. Retrieved 2019-09-08.
- ^ http://www.lightingassociates.org/i/u/2127806/f/tech_sheets/high_pressure_sodium_lamps.pdf[bare URL PDF]
- ^ "Mesoptic Street Lighting Demonstration and Evaluation Final Report" (PDF). Lighting Research Center, Rensselaer Polytechnic Institute. January 31, 2008. Retrieved 2011-08-29. (Comparison is with HPS and MH lamps)
- ^ "Philips SDW-T High Pressure Sodium White SON". LampTech.co.uk. Retrieved 2007-09-24.
Sources
- de Groot, J J; van Vliet; J A J M (1986). The High-Pressure Sodium Lamp. OCLC 16637733.
- Waymouth, John F (1971). Electric Discharge Lamps. OCLC 214331.
- USA patent US3737717A, Arendash, Michael, "High intensity lamp containing thermal shorting fuse", published 1972-03-13, issued 1973-06-05, assigned to General Electric Co