Lighting L&L Sept2010_final

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

Documents

Lighting L&L Sept2010_final