 Electric Lighting -- Past, Present, and Future
|
 Podcast
|
 Intro
|
History
|
In most of the world, people take electrical lighting for granted. Really only the case for the last 100 years or so.
|
Carbon arc lamp -- first electric light
|
Works by connecting two carbon rods to a source of electricity (originally: just battery).
|
Invented by Humphrey Davy of England in early 1800's (various sources quote various dates between 1801 & 1810).
|
Davy went on to demonstrate an arc lamp to the Royal Society.
|
Later in the 19th century, electric generators were invented -- much longer-lasting way to feed arc lamps. Went on to provide light in applications where lots of illumination was required.
|
Incandescent light (incl. halogen)
|
When a solid or gas is heated, it gives off light of a color characteristic of the material and its temperature.
|
Heat thin strip of material with electric current -- due to resistance in filament, it heats to a high temperature & glows.
|
Humphrey Davy demonstrated incandescent light in 1801 (again, this date seems to vary by the source) by passing current through a thin strip of platinum in open air (high melting point).
|
Mid 19th century (beginning about 1840), number of incandescent lamps were invented. None commercially successful for a variety of reasons.
|
Swan
|
English physicist and chemist Joseph Wilson Swan, wanted to create a practical (long-lasting) electric light.
|
1860 -- carbon paper filament worked well -- but very dim, and burned up quickly
|
Swan put his bulb on the shelf until 1875, switched filament to compressed and carbonized fibrous cotton thread
|
1878 -- demonstrated new lamps in Newcastle, England
|
Edison
|
Often credited with inventing the light bulb, but didn't really -- invented research institute (but that's the topic for a later episode).
|
Two Canadian inventors had patented an incandescent lightbulb in 1875 -- Henry Woodward and Matthew Evans of Canada. Had the patent, but could not raise the financing to commercialize their invention.
|
Thomas Edison, who had been working on the same idea, bought the rights to their patent. Edison was flush with cash, since had developed a number of previous inventions, and had backing of a number of industrial companies. Used lower current, small carbonized filament, improved vacuum inside the globe -- successfully demonstrated his new bulb in 1879.
|
Oddly enough, Edison independently selected cotton for his filament (same as Swan's bulb from one year previously), after he and his assistants had tested 6000 alternative plant fibers from across the globe.
|
Swan's lamp ran for 13-1/2 hours, while Edison's lasted for a little under 15.
|
Again, Edison put his money to work and bought Swan's patent from the company that then owned it, and worked to improve on it. By 1880, was using bamboo fiber filament, bulb lasted 1200 - 1500 hours.
|
GE
|
Early 1900's -- invented tungsten-based filament, dramatically extended lifespan of incandescent bulbs.
|
Halogen lamps
|
Essentially an improved incandescent lamp, invented by GE in 1957. Probably have them in your car's headlights. Instead of having vacuum in the bulb, have high-pressure halogen gas.
|
Generally much smaller than standard incandescents -- very hot surface, over 200 deg. C. To handle this, filament is in a fused-quartz capsule, in an enclosed fixture for safety.
|
Compared to typical incandescent bulb
|
Vapor lamps (incl. fluorescent)
|
Unlike incandescent lamps, vapor lamps don't generate light via heat -- generate light from electrical excitation of various gasses in a glass tube. The internal discharge in mercury vapor generates UV light, which is converted into visible light by a luminescent material coating the inside of the glass tube.
|
History of these lamps is pretty messy -- lots of people contributed, and so various sources will point to various individuals as the creator of the "first" fluorescent light.
|
In 1856, a German glassblower named Heinrich Geissler created a mercury vacuum pump that could evacuate a glass tube to a near vacuum.
|
The French physicist Alexandre Becquerel then experimented with coating Geissler tubes with luminescent materials.
|
Edison also tinkered with fluorescent lamps in the late 19th century, but his tubes also had short lives.
|
An American named Peter Cooper Hewitt began experimenting with similar tubes in the late 1890, and found that they gave off an ugly bluish-green light. Since nobody wanted this kind of light in their homes, these lamps were just developed for industrial uses. Patented the first mercury vapor lamp in 1901, and it was produced commercially on a small scale.
|
As a side note, the early 20th century also saw the development of neon lights -- essentially Geissler tubes filled with various inert gasses (neon for red, argon for blue, etc.). Never really used for lighting per se, but their development contributed some technologies to the development of fluorescent lighting.
|
By the end of the 1920's, all the technologies needed for fluorescent lighting were in place, and a rush to build a workable system ensued.
|
Edmund Germer, Friedrich Meyer and Hans Spanner filed for a patent on a "metal vapor lamp" as a source of UV light.
|
Meanwhile, General Electric had filed a number of patents on elements of fluorescent lighting, as had others.
|
Eventually GE bought the rights to Germer's patent for $180,000, and brought the first practical fluorescent lamp to market in 1938. By 1951, more light was produced in the US by fluorescents than by incandescents.
|
1974 -- GE invented the compact fluorescent bulb. Commercialized in the early 1980's -- the fluorescent tube is twisted around in a convoluted way to minimize its size.
|
The current (& potential future) state of affairs -- focusing on indoor use
|
Incandescent lights
|
Efficiency -- less than 3%, most of energy goes into heat (fine for cold climates, but doubly inefficient in warmer climatees, where AC has to be used to remove the waste heat.
|
Halogen
|
Can be up to twice as efficient, but in some cases only slightly more efficient than regular incandescent lights.
|
Dimmable with regular dimmer switches; now can even buy light bulbs (same base as regular incandescent) with a halogen element packaged inside.
|
Fluorescent, compact fluorescent
|
Far more efficient than incandescents -- 3x - 4x. Basically, generate less heat.
|
Typically fluorescent tubes last 10 to 20 times as long as an incandescent.
|
Cost more than incandescents up front because fluorescent bulbs need a ballast.
|
Mercury
|
Since fluorescent bulbs contain mercury, need to pay heed when its time to dispose of one.
|
Perspective: a modern CFL bulb contains a minor fraction of the amount of mercury that an old mercury thermometer used to contain.
|
Recycle if possible; otherwise, double-bag and toss in the trash.
|
Dimmer -- need special electronics to dim fluorescents (either regular or CFL)
|
Other promising (future?) technologies
|
LEDs
|
LEDs -- popular as indicator lights since the 1970's, can have extremely long life (up to 100,000 hours = 11.4 years)
|
Efficiency and output have risen to where LEDs are being used in niche lighting applications (but in this case are operated much less conservatively, and have much shorter lives.
|
Main problem with LEDs -- relatively high cost per watt. Currently most cost-effective in low power applications -- holiday lighting, accent lighting, flashlights.
|
Can have significantly higher efficiency than incandescents, if handled correctly.
|
Dimmable
|
Quantum dots, microcavity plasma panels
|
Very futuristic potential technology
|
Wrapup
|
In U.S. -- recently passed legislation mandates future lighting energy efficiency standards
|
Doesn't specifically outlaw incandescent lights, but sets efficiency standard high for all but a few bulb types (oven lights, chandelier bulbs, etc.).
|
Other countries (UK, Australia, France) have banned or are planning to ban incandescent lights outright
|
Best comparison of efficiency -- lumens per watt (light output per unit of power)
|
Incandescent: 10 - 17
|
Halogen: 12 - 22
|
White LED, mercury vapor: 20 - 60
|
Fluorescent: 30 - 110 (CFL: 40 - 70)
|
High-pressure sodium: 50 - 140
|
We'll just have to see what the future holds here -- GE says it can produce an incandescent light by 2010 that will be as efficient as a CFL. Meanwhile, LED & more exotic technologies are getting lots of emphasis.
|
Since the US (at least) expends about 20% of its energy on lighting, cutting this in half or better would be a big help -- economically, as well as ecologically
|
Sources and other links
|
General lighting
|
|
|
|
|
|
Arc lamps
|
|
Incandescent lamps
|
|
|
|
|
|
|
|
|
|
|
|
Halogen lamps
|
|
|
Fluorescent lamps
|
|
|
|
New(er) technologies
|
|
|
|
Efficiency
|
|
|
|
Regulations
|
|
|