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8/8/2019 Lighting L&L Sept2010_final
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Interior Electric Lighting
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lumen
candela
was
Mini-Glossary
lux or
footcandle
luminance
(luminous ux, a
rang of a lamp)
(luminousintensity)
(perceived bright-
ness of a surface)
(luminous
ux incident
on a surface;
the factor of
concern for
visual tasks)
(electricity input
to the lamp)
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Luminous Efficacy (Lumens per Watt)
lumen: luminous fux (can-
dela * steradian), photomet-
ric power radiated into a unit
solid angle (steradian) from
a point source having a lumi-
nous intensity of one candela
candela: luminous intensity
(lumens/steradian); a candle
emits about 1 candela
steradian: solid angle with
area equal to the radius
squared
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Performance Ranges
http://newbuildings.org/advanced-lighting-guidelines
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Light Color Temperature
Design: warm light for relaxaon,cool light for concentraon
The absolute temperature (K) at which
an ideal blackbody would radiate light
at a parcular color
Chromacity diagram describes eye
cone percepon (x,y) of wavelengths
Blackbody curve traces photon wave-
lengths released by perfect radiator as
its temperature increases correlated
color temperature (CCT)
Red is a warm color, low temperature Blue is a cool color, high temperature
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Color Rendering
CRI describes comparison of 8 test colorsbetween a reference (sunlight if >5000K;
blackbody if
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Illumination Shape Light Distribuon Curve
Luminous Intensity Distribuon Curve
Photometric Curve
Polar plots show candelas at each angle
Series of plots show symmetry around
vercal axis
http://www.nyserda.org/sclp2/tech-nicalguide/design/curve.asp
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How Atoms Emit Light
Energy can be kinec (from collisions)
or electromagnec (from heat or photons)
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Incandescent Lamps:Light from Heat
hp://www.treehugger.com/les/2006/10/gluh_lampe_
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Mechanism of light producon = heat
Tungsten wire resists electricity ow and
gets hot
Metal atom electrons absorb heat and
move to higher energy levels High-energy electrons are unstable, so re-
turn to ground state by giving o energy
as light
Photons color corresponds to the energy
given o
Red hot is about 1750K
White hot is about 4500K
Result: only ~10% of the input electricity
is recovered as light
5-15 lumens/wa
Whats so bad about
ordinary lamps?
http://www.explainthatstu.com/energysav-ingfuorescentlamp.html
Incandescence is the emission o light (visible electromagnetic
radiation) rom a hot body due to its temperature.
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tungsten-halogenlamps
tungsten (W) lament
inert (noble) gas (Ne, Ar, Xe)
small amt of halogen gas (Br2, I
2)
halogen gas reacts with vapor-
ized tungsten to keep it from de-posing on inside of bulb
result: lile loss of light output
over lamp life
can operate at higher tempera-
ture 10-30 lumens / wa
requires high-melng-point glass
Is High-Performance Incandescence an Oxymoron?
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Fluorescent Lamps:Light from Collisions
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Fluorescence is the emission o light by a substance that hasabsorbed light or other electromagnetic radiation o a difer-
ent wavelength.
1. Base that plugs into socket2. Circuit with transformer to boost voltage + ballast to
regulate current
3. Electrodes (tungsten), that release electrons as elec-
tricity ows in, eventually to be captured at other end
4. Mercury atoms collide with electrons
5. Excited mercury electrons jump to higher energy lev-els, then fall back, releasing ultraviolet photons
6. UV photons strike phosphors (CaSiO4, ZnSiO
4, CaWO
4)
coang glass tubes
7. Phosphor electron excitaon / relaxaon releases vis-
ible photons
8. Result: 65-90 lumens / wa (4-6x more than incandes-cent lamps!)
How they Work
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ballasts = circuits that regulate current ow
necessary because ionized Hg has very low
resistance, and heat lowers resistance fur-
ther unchecked, explosion would occur
magnec:inductor (L1) establishes a mag-
nec eld when current travels around its
iron core and creates counter-EMF that op-
poses current change, protecng FL1
note posions of the FL1 electrodes
electronic: use analogous but more in-
volved circuits, in solid-state form; increase
AC frequency from 60Hz to ~20,000 Hz
eliminates flicker and increases lumens/
watt by keeping more Hg gas ionized instantstart: begins current without heat-
ing the electrodes by using high voltage;
most energy ecient but shortens lamp life
rapid start: applies voltage & heats elec-
trodes simultaneously; prolongs lamp life;
dimmable while maintaining heang
programmable start: heats electrodes
rst, then applies voltage; best for lamps
expecng frequent starts (e.g. on mo-
on detectors)
Ballast Issues
http://www.eleccircuit.com/40w-magnetic-ballast-with-elec-tronic-ignition/
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lamptypes: standard (20,000h)
premium (+4,000h)
low-Hg, premium low-Hg
color temperature
lampwaages:
standard: 32 W
low waage: 30, 28, 25 W
phosphoropons:
standard 75 CRI (2800 lumens)
new 78-82 CRI (2850 lumens)
standard 82-85 CRI (2950-3000 lm)
high-lumen 86 CRI (3100-3200 lm)
ballastopons: magnec or electronic
standard, ecient, or dimming
instant, rapid, or programmed start
normal, high, or low ballast factor
low-waage lamps only compable with
instant-start, non-dimming ballasts
A T8 is a System
Range of 2 lamp system
(non dimming)
Worst 3930 L 52w
Best 6986 L 72w
Less lamp power, same
maintained output
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0
20
40
60
80
100
120
Mean Lumens Per Watt
T-8 3100/EIS
T-8 3100/EPS
T-8 3000/SIS
T-8 3000/SPS
T-8 30w/EIST-8 30w/SIS
T-8 28w/EIS
T-8 28w/SIS
T-8 25w/EIS
T-8 25w/SIST-8 2800/SIS
T-8 2800/SPS
T-12 ES Mag
T-12 ES/ES Mag
32 30 28 25
Are Low-Wattage T8s Better?
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compactuorescentlamps(CFLs)
coolcathodeuorescentlamps(CCFLs)
electrodelesslamps
power is transferred by (electro)magnec elds
extended lamp life: electrodes usually limit life
can use high eciency light-generang substances
that would react with metal electrodes
plasmalampsuse radio waves to create a plasma
in a noble gas with metal halides, Na, Hg, or S
magnetcinductonlampsuse windings around a
magnec core to create current inside the bulb
For Further Investigation
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Metal Halide (MH) Lamps:Light from Plasma
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A high potenal dierence is placed across two electrodes
within a gas (Ar, Hg) seeded with metal salts (ScBr, NaI).
Gases lose electrons to the cathode, creang a plasma
(ionized, electrically conducve gas-phase substance).
Ongoing plasma discharge constutes an electrical arc.
Establishment of the arc is called striking.
Once the arc is established, increased current results in a
lower voltage between the arc terminals and resistance
drops.
Heat generated by the arc vaporizes the mercury and
metal halides, which produce light as the temperatureand pressure increases.
The mixture of halides determines the color and intensity
of light produced.
65-115 lumens / wa
How they Work
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Metal Halide Issues strikingthearc:
tradional standardprobestart: uses a third, start-
ing electrode to establish the arc pulsestart:an ignitor generates a high-voltage (1-
5kV) pulse to start the arc; no starng electrode
warmup:a cold metal halide lamps inner arc chamber
requires me to reach the operang-level temperature
(2000F) and pressure (70-90 psi)
few seconds to strike the arc up to 5 min to reach full operang condions
bluish color while warming up
restrike:if power is interrupted, the arc will exnguish,
and high pressure in the arc tube will prevent restriking
normal ignitor: a cool-down period of 510 min re-
quired before the lamp can be re-started, but with specialignitors:arc can be immediately re-established
in some pulse-start lamps with >30kV pulse
ballasts:required - why?
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VentureLighng
dimmingballasts
wireless: LeafNut
integral: eLamp with electronic ballast
EnergyMasterlamps(90-100lm/W)
tracklighngballasts
designercolors
For Further Investigation
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Solid-State Lamps (SSLs)light from electroluminescence
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How they Work
First a bit about semiconductors:
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LED Issues
eciencyis greater than incandescents;
comparable to uorescents
light is typically strongly colored at the
wavelength corresponding to the energy
band gap
whitelight created by mixing RGB LEDs
or passing blue LED light through a phos-
phor (the laer is more common, cheap-er, less ecacious)
smallsize; form characterisc groups for
high-lumen applicaons
instantstartup
on/o cycling: no shortening of lamp life
cool; verylileheatemission
lowfragility
easily dimmable
can be focused without a reector, by
shaping the solid-state poron
expensive
sensive to high temperatures
color rendering is beer than incandescents,
but not always great for reds
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For Further Investigation T8 replacements
linear oce lighng
square light bulbs
anything with dots!
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An Emerging Resource