The Nighttime Blues
IES Portland Chapter
March 15, 2017
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Bruce Kinzey
Senior Research Engineer
Pacific Northwest National Laboratory
PNNL-SA-123348
What are the concerns about street lighting?
• Natural systems have
evolved under 24-hour
cycles of light and dark
• Most plants and animals
have receptors to detect
and align biological clocks
• “Blue light” readily
scatters in our
atmosphere, day or night
• Electric lighting can prompt
similar responses that may
be detrimental due to their
unnatural timing
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How did concerns reach the public consciousness?
• Widespread conversion
of HID sources to LED
attracted attention from
both the medical
community and dark
skies advocates.
• Ongoing discussion
contains many
misperceptions and
mischaracterizations of
the facts established to
date
• Our position has always
been to make accurate
information available to
enable educated
decisions
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https://www.ama-assn.org/ama-adopts-guidancereduce-harm-high-intensity-street-lights
What are we questioning about the guidance?
• Not the science behind it!
– Blue wavelengths do scatter
more readily
– Short wavelengths can trigger
the responses cited in a
laboratory setting
• But how do any associated
risks translate into the larger
context, and what should we
do about them…?
Photo Source: Hanifin, J.P. “Circadian, Neuroendocrine and
Neurobehavioral Effects of Polychromatic Light in Humans,”
Thomas Jefferson University, Department of Neurology Doctoral
Thesis, March 2015.
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Color 101: What is “blue light?”
• No universal definition
• Effects are caused by
wavelengths, not by
colors
• Different effects have
different action spectra
• “Short wavelengths” is a
more apt descriptor,
though not perfect
either
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Source: http://physics.info/color/
CCT is insufficient as both a measure and solution
• Color temperature
describes only the
appearance of a light
source…
• And is only a rough gauge
of its spectral content or
associated influences
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6500 K
4000 K
Photo: Sacramento Municipal Utility District
2700 K
Melanopic content is driven by more than “blue”
• Melanopic content – an
indicator of the ability of a
light source to stimulate the
intrinsically photosensitive
retinal ganglion cells (ipRGCs)
• ipRGCs play a key role in
setting the 24-hour biological
clock in mammals
• Contributing wavelengths
extend well beyond “blue”
on either side
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The Melanopic Action Spectrum
Typical Characteristics of Various Light Sources
2700 K
4000 K
†
2836 K
Source: MSSLC Light Post (http://energy.gov/eere/ssl/downloads/light-post-july-2016)
†
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Moonlight CCT measured and provided by Telelumen, LLC.
1.90 – 2.68
2.35 – 3.40
2.73
The LED “blue spike?”
• Two LEDs, one incandescent all at nominal 2800 K
Melanopic action spectrum peak
Relative format (in %)
Absolute format (in W)
• Each chart shows the same three products, normalized for light output
Illustrates why incandescent in the table had a higher melanopic
content than LED at the same or even sometimes higher CCTs.
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Why not just eliminate short wavelengths?
E.g., to address glare or circadian system stimulation potential.
• Short wavelengths contribute to color rendering and help improve color
contrast
• IES TM-12 “Spectral Effects of Lighting on Visual Performance at Mesopic
Lighting Levels” acknowledges some enhanced peripheral vision benefit.
• Does the increased risk of, e.g., cancer in the population outweigh an
increased risk in, e.g., pedestrian collisions?
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What has been the public reaction to LED street lighting?
• Opinion pieces and media reports
often focus on negative reviews,
but the bulk of public feedback
has been overwhelmingly
positive, as reported by LA,
Seattle, Boston, etc., and yes, NYC
• All street lighting installations
have some number of legitimate
complaints – business as usual
Source: New York Times, October 17, 2015
How do these appear
with HID lights?
Source: BBC News, March 13, 2017
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How do exterior lighting sources compare with interior?
Readings taken
parallel to eye
at typical
viewing position
Exterior
illuminance at
window had:
• max of 4.9
• median 0.1
• min of 0.0
(LUX)
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Incorrect Assumptions Overstate the Effects
“Star Light
Index”
(modeled)
Location:
Chicago
CCT: 2700 K
From: “World
Atlas of Artificial
Night Sky
Brightness,”
Fabio Falchi et al,
Sci Adv 2016;
2:e1600377
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Incorrect Assumptions Overstate the Effects
“Star Light
Index”
(modeled)
Location:
Chicago
CCT: 3000 K
From: “World
Atlas of Artificial
Night Sky
Brightness,”
Fabio Falchi et al,
Sci Adv 2016;
2:e1600377
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Incorrect Assumptions Overstate the Effects
“Star Light
Index”
(modeled)
Location:
Chicago
CCT: 4000 K
From: “World
Atlas of Artificial
Night Sky
Brightness,”
Fabio Falchi et al,
Sci Adv 2016;
2:e1600377
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In this simulation,
lumen output and
distribution have
been held
constant, varying
only spectral
content.
Actual Installation of 4000 K Street Lights
• Photo taken above Portland,
OR January, 2017
• Darkened areas in
foreground are residential
that have been converted to
LED
• Compare these areas to
others with previous
incumbent products
•
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How much more attention do
these areas require?
Arterials
DOE Sky Glow Investigation Results - Obs1
• Variables modeled
with realistic
characteristics
• Baseline is HPS with
2% uplight; LEDs have
0% uplight and half
the light output of
the HPS
• All unweighted
results show reduced
sky glow for all CCTs
• Scotopic weighting
yields equivalent
results around 4000 K
• Dimming further
reduces impacts in a
linear fashion
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Observer’s position at the edge of the
city (but still within)
DOE Sky Glow Investigation Results – Obs2
• Eliminating 2%
uplight almost
eliminates street
lighting
contributions to sky
glow for all LED
CCTs
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Observer’s position 40 km (25 mi)
outside the city
The many benefits of dimming
• Melanopic content / sky glow scale linearly with output, so dimming by
50% yields equivalent reductions.
• Dimming offers additional benefits too:
–
–
–
–
–
Reductions are independent of SPD
Reductions are possible incrementally all the way to 100%, when acceptable
Reductions are accompanied by energy, emissions and cost savings
May lead to extended life of luminaires and offer other maintenance value as well
Dimming can be used to help address glare and brightness complaints on a light by
light basis
– Dimming capability may coincide with other adaptive lighting and smart city
benefits
• All street lighting systems will eventually be dimmable
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How common is dimming today?
• Not many systems employed to date, but expected to be a major
component of “smart city” infrastructure in the future
• Systems installed to date are demonstrating the advantages, e.g.,
Cambridge, MA
• Between midnight
and morning the
4000 K LED system
is dimmed by 50%
and produces less
melanopic content
than the HPS
system it replaced
Initial illuminance
Photos: WSP | Parsons Brinckerhoff
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50% dimmed
Thank you
Bruce Kinzey
Pacific Northwest National Laboratory
Bruce dot Kinzey at pnnl dot gov
Related resources: https://energy.gov/eere/ssl/street-lighting-and-blue-light
Includes, among others:
• Frequently Asked Questions: Street Lighting and Blue Light
• Webinar: Get the Facts on LED Street Lighting
• SSL Posting: Getting the Facts Straight About LED Street Lighting
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