All lighting systems no matter how complex are made up of three basic components:
- Lamp: the source of the light, for example, the bulb.
- Luminaire: a light fitting that holds the lamp and includes the optics, drivers, heat sink and control gear.
- Controls: manual or automatic switching equipment, that operates the lighting system, including daylight sensoring, occupant sensing and zoning.
The light from each type of lamp can be defined in terms of:
Luminous Flux:
Total light produced by lighting source, measured in lumens or lumens/m2
Colour Rendering Index:
Accuracy with which a lighting source reveals colours, measured in an ascending scale from 1 to 100, with 100 being ‘ideal’.
Correlated Colour Temperature:
Colour of the light, ranging from warm to cool, measured in Kelvin. Candle light is 1,800K, incandescent lamps are 2,700K, office fluorescent light is between 3,000K and 5,000K and natural sunlight is 5,500K.
Lamps can also be compared by their efficiency (lumens/watt) and life.
There are three main categories of lamp which create light differently: filament lamps, discharge lamps and light emitting diodes (LEDs).
1. Filament lamps
Light is produced when the filament gets hot and so glows. This is the way all ‘traditional’ tungsten light bulbs work. Filament lamps include the incandescent light bulbs often seen in the home as well as halogen lamps and are very common. However, their poor efficiency means that they are increasingly being replaced with alternatives which use less energy. Many varieties of filament lamps are being phased out by EU Directive over the next 3 years, with frosted incandescent light bulbs of 100 watts or above already phased out as of September 2009.
2. Discharge lamps
Electricity creates a charge which, when applied to a gas filled lamp at the correct voltage, causes the gas to emit energy. Compared with incandescent lamps, gas-discharge lamps offer a higher luminous efficacy since a greater proportion of their radiation is in visible light as opposed to heat. However, they are more complicated to manufacture, and they require additional control gear, called a ballast, to obtain and maintain the correct voltage. This is how most non-tungsten lights work including fluorescent, high and low pressure sodium, metal halide and mercury.
3. Light emitting diodes (LEDs)
LEDs are solid-state devices (semi-conductors) which are small, solid, extremely energy-efficient and with no moving parts. They also offer the prospect of longer lifetimes when compared to all existing technologies.
LEDs emit light when a current passes through a die or substrate. The LED is usually small in area (less than 1 mm2). It requires other components within a luminaire to ensure proper performance:
- Optical components to shape the light radiation pattern and assist in reflection.
- Heat sink to draw heat away from the lamp
- Driver to ensure a constant electric current passes through the LED
- Control gear to manage the operation of the light and its intensity.
At the moment, common business applications of LEDs include illuminated signage, auto lighting, traffic lights, and emergency lighting. Recent advances in the technology have led to a new generation of LEDs which offer better colour properties than previous models. Manufacturers have expanded the application of LEDs by "clustering" the small bulbs. Today, LED bulbs can be manufactured in ways that allows either very focussed light or wider beam angles. This has led to new possible applications, such as downlighters, display lighting and floodlighting.
For further information, see the low carbon technology directory or view lighting energy saving advice.