Bulb Technologies

Light bulbs are made using a range of technologies. The 4 main ones are:-

1. Incandescent Light Bulbs

Traditionally the majority of light bulbs were Incandescent Light Bulbs. The term incandescent refers to the general term for light emissions driven by heat which includes the simple case of black body radiation. These bulbs have a thin wire filament through which current passes and causes the filament to heat up and very quickly radiate light. The filament is encased in a glass container which has no oxygen and as a result prevents the wire from oxidising and being destroyed. This type of bulb produces light but also produces a high proportion of heat which makes incandescent bulbs inefficient from an energy efficiency perspective. Conversely where heat and light is necessary, for example in incubation units for poultry or reptile boxes, this light bulb technology is a good solution. Incandescent light bulbs are cheap to manufacture and do not need any external electrical control equipment which has contributed to their widespread adoption.
Incandescent lamps are usually manufactured to have a lifespan of around 750 hours or 1,000 hours

Compact Fluorescent Lights (CFL) Light Bulbs

In simple terms the CFL is a compact version of the traditional strip lights which are commonly used in commercial premises, garages and in domestic environments where light efficiency is more significant than the aesthetic appearance. There are two main parts in CFL energy saving light bulbs : the gas-filled tube (also called bulb or burner) and the magnetic or electronic ballast. An electrical current from the ballast runs through the gas which is ordinarily mercury vapour, which causes it to emit ultraviolet light. The ultraviolet light activates a phosphor coating on the inside of the tube which radiates visible light. Electronic ballasts have a miniature circuit board containing rectifiers with a capacitor and usually two transistors for switching connected to form a high frequency direct to alternating current inverter. The resulting high frequency, usually 40 plus kHz, is connected to the lamp tube. Because the resonant converter stabilises the lamp current and corresponding light output across the range of input voltages, normal CFLs do not work well in dimming applications and specialist technology is needed for lamps used in diming applications. Old technology CFLs flicker on start up due to their primitive magnetic ballasts but CFLs with new electronic ballast technology rectify this problem. Fluorescent lights are available in two types, the integrated or non-integrated type. The non integrated type has a separate electronic ballast, called a starter, and in the integrated version the ballast and tube are a single combined unit which that is attached by either an Edison screw or bayonet fitting to form the bulb. By designing the CFL in this manner it can be used as a direct replacement for the traditional incandescent light bulb. The first generation compact fluorescent bulbs flickered when they were turned on because it took several seconds for the ballast to produce sufficient electricity to excite the gas within the bulb. With more modern technology compact fluorescent bulbs, this process is accelerated and accordingly there is typically less than 1 second of flicker. However, one disadvantage is that these bulbs require a short warm-up time until full brightness is reached, so accordingly they can appear dim when initially turned on. For this reason it is often best to use compact fluorescent bulbs in fixtures that are left on for prolonged periods of time, as opposed to fixtures that will turned on and off regularly.
The average rated life of a CFL is between 8 and 15 times that of incandescents giving them a lifespan around 6000-15000 hours.

Halogen Light Bulbs

Halogen bulbs have similarities to an incandescent lamp in that a tungsten filament is sealed within a compact transparent container which is filled with an inert gas together with a small quantity of a halogen chemical element for instance iodine or bromine. The tungsten filament within the halogen gas combines together producing a chemical reaction known as the halogen cycle which increases the lifetime of the bulb and in addition prevents its darkening by repositioning tungsten from the inside of the bulb back onto the filament.
One key factor in the quality of the bulb is the fill gas additive used which can be argon, krypton or xenon. The best technology is xenon as this gives a fast start up reaching 80% of brightness in a few seconds, a longer life and a good warm white light colour. The halogen light bulb operates at a higher temperature than a conventional incandescent bulb giving it a higher efficiency and typically realising a 30% reduction in energy operating costs. In a similar manner to standard incandescent technology light bulbs, a halogen lamp produces a continuous spectrum of light through the range from close to ultraviolet right through the infrared spectrum. One effect of the lamp filament operating at a higher temperature than a traditional incandescent lamp, is that the spectrum is shifted toward blue, which means that the resultant light has a higher colour temperature. The halogen lights higher colour temperature gives a blue light colour which is characteristic of the halogen lamp as opposed to a traditional incandescent bulbs which produces light with a characteristic yellow colour containing shades of red and white. Another manufacturing feature of the halogen bulb technology is the ability to produce a bulb of small dimensions which means the bulbs are particularly suited for precision applications and universally adopted for car headlights. Another spin off benefit of halogen bulb technology is that they operate well with dimmer switches to reduce light levels and energy consumption. Typical life-spans for halogen bulbs would be around 2000 hours for a 28 Watt bulb but a reduced figure of 1000 hours for a 18 Watt bulb.

Light Emitting Diode (LED) Light Bulbs

LED bulbs use a semiconductor technology and were originally just used for indicator lamps emitting a low intensity red light. Technology advancement now mean that LED's can be made which emit light with high brightness across the visible, ultraviolet and infrared spectrums. To switch an LED on the diode is forward biased which means that electrons are forced to recombine with holes within the device having the effect of releasing energy in the form of photons. This phenomena is known as electroluminescence and the colour of the light emitted which corresponds to the energy of the photon is determined by the energy gap of the semiconductor. A LED usually has a small area, typically less than 1 mm2, and the LED contains integrated optical lenses which are used are used to shape the radiation pattern and aid with reflection to produce an effective light beam. There are many advantages of LEDs over incandescent light sources including lower energy consumption, longer lifetime and improved robustness. However, the initial cost of these bulbs traditioanlly was considerably higher than incandescent bulbs but has now reduced with the advancement in technology and production methods. Although the initial cost outlay is still higher the full lifetime savings are considerable.
The typical lifespan of a LED bulb would be around 50,000 hours about 50 times the lifespan of a traditional incandescent bulb. This not only makes the use of LED's cost effective but also has environmental benefits by reducing landfill and because LED's do not contain any hazardous waste.