The different lamp technologies

Artificial luminous radiation can be produced from electrical energy according to two principles: incandescence and luminescence.

Incandescence is the production of light via temperature elevation. The most common example is a filament heated to white state by the circulation of an electrical current. The energy supplied is transformed into heat by the Joule effect and into luminous flux.

Luminescence is the phenomenon of emission by a material of visible or almost visible luminous radiation. A gas (or vapors) subjected to an electrical discharge emits luminous radiation (Electroluminescence of gases). The material can be a gas or a solid.

• Electroluminescence of gases : a gas (or vapours) subjected to an electrical discharge emits luminous radiation
• Electroluminescence in solid : electronic semi-conductor component having the ability to emit visible radiation when traversed by an electrical current.

About electroluminescence of gases since this gas does not conduct at normal temperature and pressure, the discharge is produced by generating charged particles which permit ionization of the gas. The nature, pressure and temperature of the gas determine the light spectrum.

Photoluminescence is the luminescence of a material exposed to visible or almost visible radiation (ultraviolet, infrared).

When the substance absorbs ultraviolet radiation and emits visible radiation which stops a short time after energization, this is fluorescence.

Fig. N34 – Lighting technologies

Incandescent lamps

Incandescent lamps are historically the oldest and the most often found in common use.

They are based on the principle of a filament rendered incandescent in a vacuum or neutral atmosphere which prevents combustion.

A distinction is made between:

Standard bulbs

These contain a tungsten filament and are filled with an inert gas (nitrogen and argon or krypton).

Halogen bulbs

These also contain a tungsten filament, but are filled with a halogen compound and an inert gas (krypton or xenon). This halogen compound is responsible for the phenomenon of filament regeneration, which increases the service life of the lamps and avoids them blackening. It also enables a higher filament temperature and therefore greater luminosity in smaller-size bulbs.

The main disadvantage of incandescent lamps is their significant heat dissipation, resulting in poor luminous efficiency.

Fluorescent lamps

This family covers fluorescent tubes and compact fluorescent lamps.

In fluorescent tubes, an electrical discharge causes electrons to collide with ions of mercury vapor, resulting in ultraviolet radiation due to energization of the mercury atoms. The fluorescent material, which covers the inside of the tubes, then transforms this radiation into visible light.

Fluorescent tubes dissipate less heat and have a longer service life than incandescent lamps, but they do need an ignition device called a “starter” and a device to limit the current in the arc after ignition. This device called “ballast” is usually a choke placed in series with the arc.

Compact fluorescent lamps are based on the same principle as a fluorescent tube. The starter and ballast functions are provided by an electronic circuit (integrated in the lamp) which enables the use of smaller tubes folded back on themselves.

Compact fluorescent lamps (see Fig. N35) were developed to replace incandescent lamps: They offer significant energy savings (15 W against 75 W for the same level of brightness) and an increased service life.

Lamps known as “induction” type or “without electrodes” operate on the principle of ionization of the gas present in the tube by a very high frequency electromagnetic field (up to 1 GHz). Their service life can be as long as 100,000 hrs.

Fig. N35 – Compact fluorescent lamps

• 

  [a] standard

• 

  [b] induction

Discharge lamps

(see Fig. N35b)

Fig. N35b – Discharge lamps

The light is produced by an electrical discharge created between two electrodes within a gas in a quartz bulb. All these lamps therefore require a ballast to limit the current in the arc. A number of technologies have been developed for different applications.

Low-pressure sodium vapor lamps have the best light output, however the color rendering is very poor since they only have a monochromatic orange radiation.

High-pressure sodium vapor lamps produce a white light with an orange tinge.

In high-pressure mercury vapor lamps, the discharge is produced in a quartz or ceramic bulb at high pressure. These lamps are called “fluorescent mercury discharge lamps”. They produce a characteristically bluish white light.

Metal halide lamps are the latest technology. They produce a color with a broad color spectrum. The use of a ceramic tube offers better luminous efficiency and better color stability.

Light Emitting Diodes (LED) (see Fig. N36)

Fig. N36 – led lamps

The principle of light emitting diodes is the emission of light by a semi-conductor as an electrical current passes through it.

Some years ago, LED technology was reserved for applications requiring small power light such as signalling, traffic lights, exit signs or emergency lighting.

Now thanks to the development and availability of power LED (several watts per component) lighting manufacturers offer comprehensive solutions having capability to retrofit every applications in any domains (residential, commercial and industrial buildings, infrastructures).

In fact, LED is the first technology for lighting having the capacity to be implemented in any applications with the right level of efficiency and opening the use of control functions not accessible for other technologies.

LEDs are low-voltage and low-current devices, thus suitable for battery-supply.

A converter is required for a line power supply, called driver.

The main advantages of LEDs are their low energy consumption, robustness, long life, and capacity to be control without limits. (dimming, switching, very low voltage, no delay time for full lighting flux)

In addition, LED is easier to recycle than the fluocompact technology.

Technology	Application	Advantages	Disadvantages
Standard incandescent	Domestic use Localized decorative lighting	Direct connection without intermediate switchgear Reasonable purchase price Compact size Instantaneous lighting Good color rendering	Low luminous efficiency and high electricity consumption Significant heat dissipation Short service life
Halogen incandescent	Spot lighting Intense lighting	Direct connection Instantaneous efficiency Excellent color rendering	Average luminous efficiency
Fluorescent tube	Shops, offices, workshops Outdoors	High luminous efficiency Average color rendering	Low light intensity of single unit Sensitive to extreme temperatures
Compact fluorescent lamp	Domestic use Offices Replacement of incandescent lamps	Good luminous efficiency Good color rendering	High initial investment compared to incandescent lamps
HP mercury vapor	Workshops, halls, hangars- Factory floors	Good luminous efficiency Acceptable color rendering Compact size Long service life	Lighting and relighting time of a few minutes
High-pressure sodium	Outdoors Large halls	Very good luminous efficiency	Lighting and relighting time of a few minutes
Low-pressure sodium	Outdoors Emergency lighting	Good visibility in foggy weather Economical to use	Long lighting time (5 min.) Mediocre color rendering
Metal halide	Large areas Halls with high ceilings	Good luminous efficiency Good color rendering Long service life	Lighting and relighting time of a few minutes
LED	any lighting application in residential, commercial or industrial building, and infrastructures	Low energy consumption, Low temperature in front face, No emission in the ultraviolet and few infrared, Robustness against vibrations, Life time, Insensitive to the number of switching operations immediate relighting	Cost (steadily declining), Blue spectrum for white LED, Management of temperature

Technology	Power (watt)	Efficiency (lumen/watt)	Service life (hours)
Standard incandescent	3 – 1,000	10 – 15	1,000 – 2,000
Halogen incandescent	5 – 500	15 – 25	2,000 – 4,000
Fluorescent tube	4 – 56	50 – 100	7,500 – 24,000
Compact fluorescent lamp	5 – 40	50 – 80	10,000 – 20,000
HP mercury vapor	40 – 1,000	25 – 55	16,000 – 24,000
High-pressure sodium	35 – 1,000	40 – 140	16,000 – 24,000
Low-pressure sodium	35 – 180	100 – 185	14,000 – 18,000
Metal halide	30 – 2,000	50 – 115	6,000 – 20,000
LED	1 – 400	>100 (continuous increase)	20,000 – 50,000

Fig. N37 – Usage and technical characteristics of lighting devices

The different power supply modes

(see Fig. N37b)

Technology	Power supply mode	Other device
Standard incandescent	Direct power supply	Dimmer switch
Halogen incandescent
ELV halogen incandescent	Transformer	Electronic converter
Fluorescent tube	Magnetic ballast and starter	Electronic ballast  Electronic dimmer + ballast
Compact fluorescent lamp	Built-in electronic ballast
Mercury vapor	Magnetic ballast	Electronic ballast
High-pressure sodium
Low-pressure sodium
Metal halide
LED lamps & fixtures	Driver	Driver with dimming control (1-10V or DALI mainly)

Fig. N37b – Different power supply modes