It is probably true to say that the lighting industry as we know it began around 1879. In the UK we know it was Joseph Swan who was the founder of electric lighting, though Americans seem to think it was Thomas Edison. The reality is that they both invented a light bulb at the same time, completely independently of each other, on opposite sides of the Atlantic. The result, after a bit of bickering, was the Edison and Swan United Electric Light Co.
The invention that both of these lighting pioneers came up with was the carbon filament lamp. Swan's first lamp used a carbon filament made from vegetable fibre sealed in a glass envelope with platinum wire leads. Edison's first successful lamp used carbonised cotton thread, though he soon found that a cardboard filament was better.
In 1909 the practical problems of drawing tungsten into a fine wire were solved, paving the way for William D Coolidge to develop the first tungsten filament lamp in 1911. In 1913 it was discovered that filling the evacuated bulb with an inert gas such as nitrogen retarded tungsten evaporation and increased the useful life of the lamp.
Later developments, the exact dates of which vary from one historical source to another, included the idea of coiling the filament, solving the problem of heat being conducted away from the filament by the gas that now filled the bulb. Further improvements were achieved by coiling the coiled filament around itself and by replacing the nitrogen in the bulb with argon, which has lower heat conductivity.
The fact that tungsten filament lamps could be made much smaller than carbon filament lamps was also a great help in spreading the use of these light sources. With the introduction of tungsten halogen lamps (or quartz iodine as they were originally called) powerful light sources became even smaller, with the opportunity for improved optical control.
Energy efficiency
The low output per watt of the early lamps meant that energy efficiency has been an issue virtually since the invention of electric lighting. This, combined with the need for higher light outputs, spawned a host of light source types over the years.
Discharge lamps have also been around for a long time. The first practical version was a mercury vapour lamp, developed by Peter Cooper Hewitt in 1901. This was a tubular source about 4 feet long producing a bluish green light. High pressures weren't introduced until 1934, giving higher light output and better colour appearance and colour rendering.
Low pressure sodium lamps had been researched as early as the 1920s but it was not until 1932 that these were used commercially, in a road lighting installation between Beek and Geleen in the Netherlands. Later the same year, the Purley Way just south of London was lit using low pressure sodium.
An illuminating experience
The fluorescent lamp was a major factor in transforming the way that light is used in buildings, raising the levels of illumination in many a workplace and home and getting people used to the idea that there were alternatives to the GLS lamp they were used to.
The French physicist A E Becquerel constructed a fluorescent lamp in 1867 and described the preparation of fluorescent tubes basically similar to those made today. Considerable progress in developing fluorescent lighting was made in several European countries, and during the 1920s high-voltage fluorescent tubes were used in advertising signs.
The first practical hot cathode, low voltage fluorescent lamp was shown to the public at the World Fair in New York in 1937 and these became commercially available in around 1938. In 1973 the discovery of narrow band phosphors paved the way for much higher light outputs per watt, combined with greatly improved colour characteristics. This came at an ideal time, with energy becoming a major factor in the UK economy as OPEC restricted distribution of oil.
A few years later (1978) there was a major change in linear fluorescent lighting, with the introduction of the T8 (26mm) lamp as a replacement for the T12 (38mm). It was also in 1978 that high frequency ballasts came onto the market.
A major advantage of the development of more advanced phosphors was their superior behaviour under high radiant loads, which allowed fluorescent lamps to be miniaturised. This enabled the development of the first compact fluorescent lamps in 1980.
A step in the right direction
Around 1940 someone, possibly one Daniel K Wright, had the bright idea of sealing a reflector and lens in with the filament, giving rise to the parabolic aluminised reflector (PAR) lamp.
In 1955 the dichroic reflector emerged, allowing some of the infra-red energy to dissipate out through the reflector to provide a cooler beam.
During this time, HID lamps had found a wide range of uses but were limited by the efficiency and the colour rendering. Attempts to improve these characteristics in mercury lamps included the addition of metal halides to the arc tubes, leading to the metal halide lamp. Similar attempts to improve on the colour rendering of low pressure sodium led, as you might expect, to the high pressure sodium lamp in 1966. In 1986 the white SON lamp took these improvements even further.
LEDing the revolution
The evolution of electric lighting has also seen a number of niche market products but the new(ish) light source that offers the greatest potential is the light emitting diode (LED).
For the electrical contractor, the LED could bring some interesting times indeed. As each 'light source' will actually be made up of a number of tiny individual LEDs, we can expect to see a much wider range of shapes and sizes of light fitting.
There is even talk of building them into the structure of the wall or ceiling – so we just have to hope that someone thinks about the wiring before that happens.
Some animals were used as lamps as an alternative to oil lamps and candles. Oily birds and fish needed only to be threaded with a wick to produce a working lamp. At least 500 species of fish have specialised organs for emitting electric discharges. Electric eels stun their prey with almost 600V, while catfish create an electric detection field around themselves to help them find their way in murky waters.
Source
Electrical and Mechanical Contractor