LED Street Light Research Project

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Unlike many available lighting products, LEDs will not burn skin LED example assembly for thermal management 24 Pittsburgh LED Street Light Research Project September 2011 LEDs Heat sink
Efficiency (GIB Credit 13). This credit promotes the use of LED technology in traffic lights and street lights as a means for reducing overall energy use in a development. LED Street Lighting Concerns During the past decade, the cost, color performance, light output, efficacy, reliability, lifetime, and manufacturability of SSL technology has greatly improved. For example, the dollars per kilolumen cost of LED packages has declined at a rate of 25 percent per year since 2005. The DOE estimates that LED lighting packages will reach their maximum efficacy, defined as the desired illuminance level and lighting quality at the lowest practicable energy input, of around 250 lm/W by about 2020, up to 15 times that of incandescent lighting. In spite of these improvements, LED technology as applied to street lights has many of the problems experienced with traditional street lighting as well as some additional issues: › Comparatively high purchase cost The current purchase cost of LED lighting products is higher than standard options and varies widely, with good quality products at a cost premium. However, the DOE reports that the cost per lumen of LEDs falls by a factor of 10 every decade while the amount of light generated increases by a factor of 20. From 2009 to 2010, the prices for warm white LED packages declined by half, from approximately $36 to $18 per thousand lumens (kilolumens/ klm). Prices are expected to fall to $2/klm by 2015. When operational costs, such as electricity, maintenance, and lamp replacement, are considered, the overall value of LEDs rise. September 2011 › Early technology LEDs have been used in outdoor lighting applications for less than 10 years. As such, they have a short history over which to benchmark their performance. › Thermal management While LEDs will not burn skin like some lighting products, only 20 to 30 percent of the power created by white LEDs is actually converted into visible light (lumen/lm); the rest, 70 to 80 percent, is converted to heat. Excess heat affects both the short- and longterm performance of LEDs. Amber and red LEDs are the most sensitive colors while blue is the least. As a result, the short-term (but reversible) effects of overheating include color shifting in addition to reduced light output. The long-term effects are accelerated lumen depreciation and a shorter useful life. LED lights include heat sinks that are often integrated into the design of the fixture, for example converting the chassis into a heat diffusing element. Higher quality LED products will have a better heat diffusing component. Thermal management of highpower LEDs is a priority for solid-state lighting (SSL) research and development. › Inconsistent color The need for color consistency spans all illumination technologies. With LEDs specifically, color (including white) is produced by mixing red, green, and blue LEDs. The wavelength distribution of red, green and blue LEDs is narrow, which allows for a very pure, saturated color. However any shift in the dominant wavelength, particularly with green, will create color inconsistency. It is impossible for manufacturers to produce uniform color points in white LEDs. Manufacturers overcome this issue by sorting their LEDs into Pittsburgh LED Street Light Research Project 25
Page 1 and 2: LED Street Light Research Project R
Page 3 and 4: Acknowledgements City of Pittsburgh
Page 5 and 6: Contents Executive Summary Backgrou
Page 7 and 8: Executive Summary Background The Ci
Page 9 and 10: lighting of sidewalks or streets. L
Page 11 and 12: › LED luminaires should be guaran
Page 13 and 14: Background Overview The City of Pit
Page 15 and 16: Street Lights: A Brief History The
Page 17 and 18: Electric Street Lighting Technologi
Page 19 and 20: and development focus of the U.S. D
Page 21 and 22: Data Collection LED Street Lighting
Page 23: › Lower operating costs: energy e
Page 27 and 28: color bins based on identical or ve
Page 29 and 30: Lighting Standards in the U.S. In t
Page 31 and 32: Existing Infrastructure The City of
Page 33 and 34: Since 2008, the City’s Office for
Page 35 and 36: Business District Case Studies Thre
Page 37 and 38: September 2011 Central Business Dis
Page 39 and 40: September 2011 Mid-Sized Business D
Page 41 and 42: September 2011 Neighborhood Busines
Page 43 and 44: Research Modes of Human Vision Huma
Page 45 and 46: How Uniformity of Illuminance Affec
Page 47 and 48: Overview There is a wide range of i
Page 49 and 50: and landscape is highly contextual.
Page 51 and 52: uilding, pedestrians can see less t
Page 53 and 54: Another factor is the surrounding r
Page 55 and 56: This provides what many lighting pr
Page 57 and 58: will generate up to 130,000 lux. Of
Page 59 and 60: › Use shielded or cut-off luminai
Page 61 and 62: › LEDs are the most efficient, du
Page 63 and 64: The Plan recommends retrofitting st
Page 65 and 66: There is an established link betwee
Page 67 and 68: Biological/Public Health Considerat
Page 69 and 70: Lighting Plans: Comprehensive Plann
Page 71 and 72: › Helsinki, Finland: Master Light
Page 73 and 74: › Dial4Light: Licht per Anruf (Li
Page 75 and 76:
Overview Focus group sessions were
Page 77 and 78:
Tools for Measuring Street Lighting
Page 79 and 80:
During this measure, the luminance
Page 81 and 82:
Overview In February, 2001, Minneap
Page 83 and 84:
Recommendations Overview The City o
Page 85 and 86:
The revised approach became one of
Page 87 and 88:
luminaires. Manufacturers are respo
Page 89 and 90:
Base Criteria: Design › Contempor
Page 91 and 92:
Evaluation Procedure for Business D
Page 93 and 94:
Upgrade Option: Basic Controls In a
Page 95 and 96:
› The mounting system will be aff
Page 97 and 98:
Pittsburgh. The findings would be s
Page 99 and 100:
› Testing of the submitted lumina
Page 101 and 102:
References American Association of
Page 103 and 104:
Gehl, Jan, Lotte Johansen Kaefer an
Page 105 and 106:
U.S. Department of Energy. 2008. LE
Page 107 and 108:
Appendices BULB: The light source w
Page 109 and 110:
› LUCI (Lighting Urban Community
Page 111 and 112:
Sorento Streetlight, Cambridge, UK
Page 113:
› Principal Investigator Don Cart
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LED Street Light Research Project

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