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词条 Luminous efficacy
释义

  1. Luminous efficacy of radiation

     Explanation  Mathematical definition  Examples  Photopic vision  Scotopic vision  Examples 

  2. SI photometry units

  3. See also

  4. Notes

  5. References

  6. External links

{{short description|Measure of how well a light source produces visible light}}Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt in the International System of Units (SI). Depending on context, the power can be either the radiant flux of the source's output, or it can be the total power (electric power, chemical energy, or others) consumed by the source.[1][2][3]

Which sense of the term is intended must usually be inferred from the context, and is sometimes unclear. The former sense is sometimes called luminous efficacy of radiation, and the latter luminous efficacy of a source or overall luminous efficacy.[4][5]

Not all wavelengths of light are equally visible, or equally effective at stimulating human vision, due to the spectral sensitivity of the human eye; radiation in the infrared and ultraviolet parts of the spectrum is useless for illumination. The luminous efficacy of a source is the product of how well it converts energy to electromagnetic radiation, and how well the emitted radiation is detected by the human eye.

==Efficacy and efficiency==

Luminous efficacy can be normalized by the maximum possible luminous efficacy to a dimensionless quantity called luminous efficiency. The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.

Luminous efficacy of radiation

Explanation

Wavelengths of light outside of the visible spectrum are not useful for illumination because they cannot be seen by the human eye. Furthermore, the eye responds more to some wavelengths of light than others, even within the visible spectrum. This response of the eye is represented by the luminosity function. This is a standardized function which represents the response of a "typical" eye under bright conditions (photopic vision). One can also define a similar curve for dim conditions (scotopic vision). When neither is specified, photopic conditions are generally assumed.

Luminous efficacy of radiation measures the fraction of electromagnetic power which is useful for lighting. It is obtained by dividing the luminous flux by the radiant flux. Light with wavelengths outside the visible spectrum reduces luminous efficacy, because it contributes to the radiant flux while the luminous flux of such light is zero. Wavelengths near the peak of the eye's response contribute more strongly than those near the edges.

Photopic luminous efficacy of radiation has a maximum possible value of {{nowrap|683 lm/W}}, for the case of monochromatic light at a wavelength of {{nowrap|555 nm}} (green). Scotopic luminous efficacy of radiation reaches a maximum of {{nowrap|1700 lm/W}} for monochromatic light at a wavelength of {{nowrap|507 nm}}.

Mathematical definition

Luminous efficacy, denoted K, is defined as[6]

where

  • Φv is the luminous flux;
  • Φe is the radiant flux;
  • Φe,λ is the spectral radiant flux;
  • {{nowrap|1=K(λ) = KmV(λ)}} is the spectral luminous efficacy.

Examples

Photopic vision

Type Luminous efficacy
of radiation (lm/W)		efficiency{{efn>group=note|name=max|Defined such that the maximum possible luminous efficacy corresponds to a luminous efficiency of 100%.
Tungsten light bulb, typical, 2800 K 15[7] 2%
Class M star (Antares, Betelgeuse), 3000{{nbsp}}K 30 4%
Black-body, 4000 K, ideal 54.7[8] 8%
Class G star (Sun, Capella), 5800{{nbsp}}K 93[7] 13.6%
Black-body, 7000 K, ideal 95[8] 14%
group=note|Most efficient source that mimics the solar spectrum within range of human visual sensitivity.}}[7]{{efn>group=note|name=ideal_white|Integral of truncated Planck function times photopic luminosity function times 683 W/sr, according to the definition of the candela.}}[12] 37%
group=note|name=max-eff-truncated|Omits the part of the spectrum where the eye's sensitivity is very poor.}} 292[9] 43%
group=note|name=max-eff-truncated}} 299[9] 44%
group=note|name=max-eff-truncated-1|Omits the part of the spectrum where the eye's sensitivity is low (≤ 5% of the peak).}} 343[9] 50%
group=note|name=max-eff-truncated-1}} 348[9] 51%
Ideal monochromatic 555 nm source 683[10] 100%

Scotopic vision

Type Luminous efficacy
of radiation (lm/W)		efficiency{{efn>group=note|name=max
Ideal monochromatic 507 nm source 1699[11] or 1700[12] 100%

==Lighting efficiency==

{{main|Wall-plug efficiency}}

Artificial light sources are usually evaluated in terms of luminous efficacy of the source, also sometimes called wall-plug efficacy. This is the ratio between the total luminous flux emitted by a device and the total amount of input power (electrical, etc.) it consumes. The luminous efficacy of the source is a measure of the efficiency of the device with the output adjusted to account for the spectral response curve (the luminosity function). When expressed in dimensionless form (for example, as a fraction of the maximum possible luminous efficacy), this value may be called luminous efficiency of a source, overall luminous efficiency or lighting efficiency.

The main difference between the luminous efficacy of radiation and the luminous efficacy of a source is that the latter accounts for input energy that is lost as heat or otherwise exits the source as something other than electromagnetic radiation. Luminous efficacy of radiation is a property of the radiation emitted by a source. Luminous efficacy of a source is a property of the source as a whole.

Examples

The following table lists luminous efficacy of a source and efficiency for various light sources. Note that all lamps requiring electrical/electronic ballast are unless noted (see also voltage) listed without losses for that, reducing total efficiency.

Category TypeOverall luminous
efficacy (lm/W)		Overall luminous
efficiency{{efn|group=note|name=max
Combustion Candlegroup=note|1{{nbsp}}candela × 4π{{nbsp}}steradians/40{{nbsp}}W}} 0.04%
Gas mantle 1–2[13] 0.15–0.3%
Incandescent 15, 40, 100{{nbsp}}W tungsten incandescent (230 V) 8.0, 10.4, 13.8[14][15][16][17] 1.2, 1.5, 2.0%
5, 40, 100{{nbsp}}W tungsten incandescent (120 V) 5, 12.6, 17.5[18] 0.7, 1.8, 2.6%
Halogen incandescent 100, 200, 500{{nbsp}}W tungsten halogen (230 V) 16.7, 17.6, 19.8[19][17] 2.4, 2.6, 2.9%
2.6{{nbsp}}W tungsten halogen (5.2 V) 19.2[20] 2.8%
Halogen-IR (120 V) 17.7–24.5[21] 2.6–3.5%
Tungsten quartz halogen (12–24 V) 24 3.5%
Photographic and projection lamps 35[22] 5.1%
Light-emitting diode LED screw base lamp (120 V){{#expr:550/5.4}}|0}}[23][24][25]{{#expr:550/5.4/6.83002}}|1}}%
11{{nbsp}}W LED screw base lamp (230{{nbsp}}V) 138[26] 20.3%
21.5{{nbsp}}W LED retrofit for T8 fluorescent tube (230{{nbsp}}V) 172[27] 25%
Theoretical limit for a white LED with phosphorescence color mixing{{#expr:260}}|0}}–{{Rnd|{{#expr:300}}|0}}[28]{{#expr:260/6.83002}}|1}}–{{Rnd|{{#expr:300/6.83002}}|1}}%
Arc lampCarbon arc lamp 2–7[29] 0.29–1.0%
Xenon arc lamp 30–50[30][31] 4.4–7.3%
Mercury-xenon arc lamp 50–55[30] 7.3–8%
Ultra-high-pressure (UHP) mercury-vapor arc lamp, free mounted 58–78[32] 8.5–11.4%
Ultra-high-pressure (UHP) mercury-vapor arc lamp, with reflector for projectors 30–50[33] 4.4–7.3%
Fluorescent 32{{nbsp}}W T12 tube with magnetic ballast 60[34] 9%
9–32{{nbsp}}W compact fluorescent (with ballast) 46–75[17][35][36] 8–11.45%[37]
T8 tube with electronic ballast 80–100[34] 12–15%
PL-S 11{{nbsp}}W U-tube, excluding ballast loss 82[38] 12%
T5 tube 70–104.2[39][40] 10–15.63%
70–150{{nbsp}}W inductively-coupled electrodeless lighting system 71–84[41] 10–12%
Gas discharge 1400{{nbsp}}W sulfur lamp 100[42] 15%
Metal halide lamp 65–115[43] 9.5–17%
High-pressure sodium lamp 85–150[17] 12–22%
Low-pressure sodium lamp 100–200[17][44][45] 15–29%
Plasma display panel 2–10[46] 0.3–1.5%
Cathodoluminescence Electron stimulated luminescencedate=December 2012}} 5%
Ideal sourcesgroup=note|name=ideal_white}} 251[7] 37%
Green light at 555 nm (maximum possible luminous efficacy) 683.002[10] 100%

Sources that depend on thermal emission from a solid filament, such as incandescent light bulbs, tend to have low overall efficacy because, as explained by Donald L. Klipstein, "An ideal thermal radiator produces visible light most efficiently at temperatures around 6300 °C (6600 K or 11,500 °F). Even at this high temperature, a lot of the radiation is either infrared or ultraviolet, and the theoretical luminous [efficacy] is 95 lumens per watt. No substance is solid and usable as a light bulb filament at temperatures anywhere close to this. The surface of the sun is not quite that hot."[22] At temperatures where the tungsten filament of an ordinary light bulb remains solid (below 3683 kelvin), most of its emission is in the infrared.[22]

SI photometry units

{{SI light units}}

See also

  • Photometry
  • Light pollution
  • Wall-plug efficiency
  • Coefficient of utilization
  • List of light sources

Notes

{{noteslist|group=note}}

References

1. ^{{cite book |author=Allen Stimson |title=Photometry and Radiometry for Engineers |publisher=Wiley and Son |location=New York |year=1974}}
2. ^{{cite book |title=Optical Radiation Measurements, Vol 1 |publisher=Academic Press |location=New York |author1=Franc Grum |author2=Richard Becherer |year=1979}}
3. ^{{cite book |title=Radiometry and the Detection of Optical Radiation |publisher=Wiley and Son |location=New York |author=Robert Boyd |year=1983}}
4. ^{{cite book |title=Photovoltaic systems engineering |edition=2 |author1=Roger A. Messenger |author2=Jerry Ventre |publisher=CRC Press |year=2004 |isbn=978-0-8493-1793-4 |page=123}}
5. ^{{cite book |title=Color imaging: fundamentals and applications |author1=Erik Reinhard |author2=Erum Arif Khan |author3=Ahmet Oğuz Akyüz |author4=Garrett Johnson |publisher=A K Peters, Ltd |year=2008 |isbn=978-1-56881-344-8 |page=338}}
6. ^{{cite web|url=http://eilv.cie.co.at/term/730|title=Luminous efficacy (of radiation)|publisher=CIE|accessdate=2016-06-07}}
7. ^1 2 3 {{cite web |title=Maximum Efficiency of White Light |url=http://physics.ucsd.edu/~tmurphy/papers/lumens-per-watt.pdf |accessdate=2011-07-31}}
8. ^1 Black body visible spectrum
9. ^1 2 3 4  {{cite journal|doi=10.1063/1.4721897 | title=Maximum spectral luminous efficacy of white light|journal=Journal of Applied Physics | volume=111 | issue=10 | page=104909 | year=2012 | last1=Murphy | first1=Thomas W. | arxiv = 1309.7039 | bibcode = 2012JAP...111j4909M }}
10. ^1  {{cite book | author1=Wyszecki, Günter | author2=Stiles, W.S. | lastauthoramp=yes | title=Color Science – Concepts and Methods, Quantitative Data and Formulae | edition=2nd | publisher=Wiley-Interscience | year=2000 | isbn =0-471-39918-3 }}
11. ^ {{cite book | title = Light Pollution Handbook | author1 = Kohei Narisada | author2 = Duco Schreuder | publisher = Springer | year = 2004 | isbn = 1-4020-2665-X }}
12. ^ {{cite book | title = Handbook of Applied Photometry | author = Casimer DeCusatis | publisher = Springer | year = 1998 | isbn = 1-56396-416-3 }}
13. ^{{cite journal | title=Recent Developments in Gas Street Lighting | journal=The American City |volume=22 |issue=5 |publisher=Civic Press |location=New York | page=490 | first=F. V. |last=Westermaier | year=1920 | url=https://books.google.com/books?id=rWxLAAAAMAAJ&dq=mantle%20lamp&pg=PA490#v=onepage&q=mantle%20lamp}}
14. ^{{cite web |url=http://www.lighting.philips.com/main/prof/lamps/incandescent-lamps/standard-t-a-e-shape/classictone-standard/920119143329_EU/product |title=Philips Classictone Standard 15 W clear}}
15. ^{{cite web |url=http://www.lighting.philips.com/main/prof/lamps/incandescent-lamps/standard-t-a-e-shape/classictone-standard/920053843329_EU/product |title=Philips Classictone Standard 40 W clear}}
16. ^{{cite web |url=http://www.bulbs.ch/index.php?cPath=49_41_55_61_94 |title=Bulbs: Gluehbirne.ch: Philips Standard Lamps (German) |publisher=Bulbs.ch |date= |accessdate=2013-05-17}}
17. ^1 2 3 4 Philips Product Catalog {{dead link|date=January 2018|bot=medic}}{{cbignore|bot=medic}} (German)
18. ^{{cite web |title=The Nature of Light |last=Keefe |first=T.J. |year=2007 |url=http://www.ccri.edu/physics/keefe/light.htm |accessdate=2016-04-15 |archiveurl=https://web.archive.org/web/20120118001547/http://www.ccri.edu/physics/keefe/light.htm |archivedate=2012-01-18}}
19. ^{{cite web |url=http://www.osram.de/_global/pdf/osram_de/tools_services/downloads/allgemeinbeleuchtung/halogenlampen/haloluxhalopar.pdf |title=Osram halogen |work=osram.de |language=German |accessdate=2008-01-28 |format=PDF |archiveurl=https://web.archive.org/web/20071107054500/http://www.osram.de/_global/pdf/osram_de/tools_services/downloads/allgemeinbeleuchtung/halogenlampen/haloluxhalopar.pdf |archivedate=November 7, 2007}}
20. ^{{cite web |url=http://www.bulbtronics.com/Search-The-Warehouse/ProductDetail.aspx?sid=0000747&pid=OS6406330&AspxAutoDetectCookieSupport=1 |archive-url=https://web.archive.org/web/20160213071457/http://www.bulbtronics.com/Search-The-Warehouse/ProductDetail.aspx?sid=0000747&pid=OS6406330&AspxAutoDetectCookieSupport=1 |dead-url=yes |archive-date=2016-02-13 |title=Osram 6406330 Miniwatt-Halogen 5.2V |publisher=bulbtronics.com |accessdate=2013-04-16 }}
21. ^{{cite web |url=http://www.gelighting.com/LightingWeb/na/images/71886_HIR_Plus_Halogen_PAR38_SellSheet_tcm201-20752.pdf |title=GE Lighting HIR Plus Halogen PAR38s |publisher=ge.com |accessdate=2017-11-01}}
22. ^1 2 {{cite web|author=Klipstein, Donald L. |year=1996 |title=The Great Internet Light Bulb Book, Part I |url=http://freespace.virgin.net/tom.baldwin/bulbguide.html |archive-url=https://web.archive.org/web/20010909055127/http://freespace.virgin.net/tom.baldwin/bulbguide.html |dead-url=yes |archive-date=2001-09-09 |accessdate=2006-04-16 |df= }}
23. ^{{cite web |url=http://en.item.rakuten.com/alllight/lelaw8l_toshiba/ |title=Toshiba E-CORE LED Lamp |publisher=item.rakuten.com |date= |accessdate=2013-05-17}}
24. ^{{cite web |title=Toshiba E-CORE LED Lamp LDA5N-E17 |url=http://www.tlt.co.jp/tlt/new/lamp/hp_led/minikry_lda5.htm |archiveurl=https://web.archive.org/web/20110719165551/http://www.tlt.co.jp/tlt/new/lamp/hp_led/minikry_lda5.htm |archivedate=2011-07-19}}
25. ^Toshiba to release 93 lm/W LED bulb Ledrevie
26. ^{{Cite web|url=http://www.p4c.philips.com/cgi-bin/cpindex.pl?ctn=8718696742396&hlt=Link_ProductInformation&mid=Link_ProductInformation&scy=FR&slg=AEN|title=8718696742396 Philips LED Bulb 8718696742396 11W (100W) E27 Warm white Non-dimmable - Philips Support|last=Care|first=Philips Consumer Electronics Global Consumer|website=www.p4c.philips.com|access-date=2017-09-07}}
27. ^{{Cite web|url=http://www.lighting.philips.com/main/prof/led-lamps-and-tubes/led-tubes/master-ledtube-em-mains-t8/929001377002_EU/product|title=MAS LEDtube 1500mm UE 21.5W 840 T8|access-date=2018-01-10}}
28. ^White LEDs with super-high luminous efficacy physorg.com
29. ^{{cite web | title=Arc Lamps | publisher=Edison Tech Center | url=http://www.edisontechcenter.org/ArcLamps.html|accessdate=2015-08-20}}
30. ^1 {{cite web | title=Technical Information on Lamps | work=Optical Building Blocks | url=http://www.pti-nj.com/products/High-Speed-Spectrofluorometer/TechNotes/TechnicalInformationLamps.pdf | format=PDF|accessdate=2010-05-01}} Note that the figure of 150 lm/W given for xenon lamps appears to be a typo. The page contains other useful information.
31. ^{{cite book|title=OSRAM Sylvania Lamp and Ballast Catalog|year=2007}}
32. ^REVIEW ARTICLE: UHP lamp systems for projection applications{{Dead link|date=November 2016 |bot=InternetArchiveBot |fix-attempted=yes }} Journal of Physics D: Applied Physics
33. ^OSRAM P-VIP PROJECTOR LAMPS Osram
34. ^1 {{cite journal|url=http://www1.eere.energy.gov/femp/procurement/eep_fluortube_lamp.html |archive-url=https://web.archive.org/web/20070702014038/http://www1.eere.energy.gov/femp/procurement/eep_fluortube_lamp.html |dead-url=yes |archive-date=2007-07-02 |title=How to buy an energy-efficient fluorescent tube lamp |author=Federal Energy Management Program |publisher=U.S. Department of Energy |date=December 2000 |df= }}
35. ^{{cite web|title=Low Mercury CFLs |url=http://www.energyfederation.org/consumer/default.php/cPath/25_44_3006 |publisher=Energy Federation Incorporated |accessdate=2008-12-23 |deadurl=yes |archiveurl=https://web.archive.org/web/20081013115302/http://www.energyfederation.org/consumer/default.php/cPath/25_44_3006 |archivedate=October 13, 2008 }}
36. ^{{cite web|title=Conventional CFLs |url=http://www.energyfederation.org/consumer/default.php/cPath/25_44_784 |publisher=Energy Federation Incorporated |accessdate=2008-12-23 |deadurl=yes |archiveurl=https://web.archive.org/web/20081014010312/http://www.energyfederation.org/consumer/default.php/cPath/25_44_784 |archivedate=October 14, 2008 }}
37. ^{{cite web | title=Global bulbs | url=http://www.1000bulbs.com/32-Watt-Compact-Fluorescents/37889/ | publisher= 1000Bulbs.com |accessdate=2010-02-20}}|
38. ^{{cite web | author=Phillips | title=Phillips Master | url=http://skinflint.co.uk/a416644.html| accessdate=2010-12-21}}
39. ^{{cite web|author=Department of the Environment, Water, Heritage and the Arts, Australia |title=Energy Labelling—Lamps |url=http://www.energyrating.gov.au/appsearch/download.asp |accessdate=2008-08-14 |deadurl=yes |archiveurl=https://web.archive.org/web/20080723003909/http://www.energyrating.gov.au//appsearch/download.asp |archivedate=July 23, 2008 }}
40. ^{{cite web|url=http://www.bulbamerica.com/osram-24w-t5-miniature-bi-pin-compact-fluorescent-light-bulb-1.html |publisher=Bulbamerica.com |accessdate=2010-02-20 |title=BulbAmerica.com |deadurl=yes |archiveurl=https://web.archive.org/web/20121201003233/http://www.bulbamerica.com/osram-24w-t5-miniature-bi-pin-compact-fluorescent-light-bulb-1.html |archivedate=December 1, 2012 }}
41. ^{{cite web | author=SYLVANIA | title=Sylvania Icetron Quicktronic Design Guide | url=http://www.acuitybrands.com/products/-/media/files/acuity/products/lighting/featured%20technology/induction/icetron.pdf | accessdate=2015-06-10}}
42. ^{{cite news |url=http://www.iaeel.org/IAEEL/iaeel/newsl/1996/ett1996/LiTech_b_1_96.html |title=1000-watt sulfur lamp now ready |work=IAEEL newsletter |year=1996 |issue=1 |publisher=IAEEL |archiveurl=https://web.archive.org/web/20030818061414/http://195.178.164.205/IAEEL/iaeel/newsl/1996/ett1996/LiTech_b_1_96.html |archivedate=2003-08-18}}
43. ^{{cite web |url=http://www.venturelighting.com/TechCenter/Metal-Halide-TechIntro.html |title=The Metal Halide Advantage |year=2007 |work=Venture Lighting |accessdate=2008-08-10}}
44. ^{{cite web |title=LED or Neon? A scientific comparison |url=http://www.signweb.com/content/led-or-neon?page=0%2C1}}
45. ^{{cite web |url=http://webexhibits.org/causesofcolor/4.html |title=Why is lightning coloured? (gas excitations) |publisher=webexhibits.org}}
46. ^{{cite web |url=ftp://ftp.panasonic.com/pub/Panasonic/consumer_electronics/whitepapers/Future_Looks_Bright_for_Plasma_TVs.pdf |title=Future Looks Bright for Plasma TVs |publisher=Panasonic |year=2007 |accessdate=2013-02-10}}

External links

  • Hyperphysics has these graphs of efficacy that do not quite comply with the standard definition
  • Energy Efficient Light Bulbs
  • Other Power
{{Artificial light sources}}

4 : Photometry|Physical quantities|Lighting|Energy economics
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