Artificial Lighting Types and Design

In the previous topic, Electrical Load Classification and Types – Part Four , I indicated that the main sources of light will be the daylight and Artificial light sources and I explained the daylight source and its effects on electrical lighting design.

And today, I will explain the second source of light; Artificial light and show its types and design requirements.

You can review the following previous topics for more information and good following.

Artificial lighting 

Artificial light sources are other sources of light which developed to compensate for or assist the natural light. It will have different frequencies and wavelengths that determine the light color.

First :Artificial light sources 

Artificial light sources are categorized by the technology used to produce the light. There's dozens of sources, with a few common in household applications and others more suitable for industrial uses. The five most common light sources are as follows:

  1. Incandescent lamp. 
  2. Compact fluorescent lamp. 
  3. Fluorescent tube. 
  4. Discharge lamps. 
  5. Light Emitting Diode (LED). 

1- Incandescent lamp:

Incandescent lamp

Until recently the most common electric light source was the incandescent lamp. This is still widely used, although its relatively low energy efficiency is leading to its replacement by other more efficient lamps such as the CFL.

The connection to a light fitting is either by screw thread or bayonet.

A large variety of shapes, sizes and power is available, as well as different colour ranges. Typical lamps for household use range from about 40 to 100 W, giving a light output of 420 to 1360lm at the typical lamp efficiency of about 12%.

2- Compact fluorescent lamp:

Compact fluorescent lamp

The compact fluorescent lamp (CFL) was designed as a more efficient replacement for incandescent lamp. It is supplied with the same fixing system (screw or bayonet), and can be used in many light fittings designed for incandescent lamps.

Power ratings of CFLs that can provide approximately the equivalent light output to incandescent lamps are shown in the table below, together with their efficacy ratings.

3- Fluorescent tube:

Fluorescent tube

Fluorescent tubes are the main form of lighting for offices and commercial buildings.

They are a form of gas discharge lamp, and are formed in a long thin glass cylinder with contacts at either end that secure them to the fitting (or luminaire) and provide the electrical connection.

The tube contains mercury vapour at low pressure, and the inner wall of the glass is coated with a phosphor that reacts to ultra-violet radiation. When electricity is passed through the vapour it emits UV radiation that is converted by the phosphor to visible light.

The most efficient fluorescent tubes are the T5. With a smaller diameter (16mm) than earlier tubes, these can achieve a luminous efficacy of up to 104lm/W

4- Discharge lamps:

Discharge lamps

Discharge lamps work by striking an electrical arc between two electrodes, causing a filler gas to give off light.

Different metals and filler gasses can be used to provide a range of colour and brightness.

Discharge lamps provide high luminous efficacy combined with long life, resulting in the most economical light source available

Types of gas-discharge lamps:
The gas discharge lamps have three types as follows:

A- Low pressure discharge lamps:

Low-pressure lamps have working pressure much less than atmospheric pressure. For example common fluorescent lamps operate at a pressure of about 0.3% of atmospheric pressure.

- Compact fluorescent lamp,

- Fluorescent lamps,

- Low pressure sodium lamps: the most efficient gas-discharge lamp type, producing up to 200 lumens per watt, but at the expense of very poor color rendering. The almost monochromatic yellow light is only acceptable for street lighting and similar applications.

B- High pressure discharge lamps:

High-pressure lamps have a discharge that takes place in gas under slightly less to greater than atmospheric pressure. For example, a high pressure sodium lamp has an arc tube under 100 to 200 torr pressure, about 14% to 28% of atmospheric pressure; some automotive HID headlamps have up to 50 bar or fifty times atmospheric pressure.

- Metal halide lamps: These lamps produce almost white light, and attain 100 lumen per watt light output. Applications include indoor lighting of high buildings, parking lots, shops, sport terrains.

- High pressure sodium lamps: producing up to 150 lumens per watt. These lamps produce a broader light spectrum than the low pressure sodium lamps. Also used for street lighting, and for artificial photoassimilation for growing plants

- High pressure mercury-vapor lamps: This lamp type is the oldest high pressure lamp type, being replaced in most applications by the metal halide lamp and the high pressure sodium lamp.

C- High-intensity discharge lamps:

A high-intensity discharge (HID) lamp is a type of electrical lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. Compared to other lamp types, relatively high arc power exists for the arc length. Examples of HID lamps include:

  • Mercury-vapor lamps.
  • Metal halide lamps.
  • Ceramic discharge metal halide lamps.
  • Sodium vapor lamps.
  • Xenon arc lamps.
  • Ultra-High Performance (UHP).

HID lamps are typically used when high levels of light and energy efficiency are desired.

5- Light Emitting Diode (LED):

Light Emitting Diode (LED)

LEDs use semi-conductors to convert electrical energy directly into light. They are only recently becoming available as a light source for lighting purposes, and are highly efficient and long lasting.

LED torches are becoming very popular, as they provide a far longer battery life than other types of light source.

Second: Forms of Artificial lighting:

There are two forms for Artificial lighting as follows:

  1. Indoor lighting 
  2. Outdoor lighting 

1- Indoor lighting:

Indoor lighting is usually accomplished using light fixtures, and is a key part of interior design, these light fixtures or light luminaires can be defined as follows:

Luminaire is a device that distributes filters or transforms the light emitted from one or more lamps. The luminaire includes all the parts necessary for fixing and protecting the lamps, except the lamps themselves. In some cases, luminaires also include the necessary circuit auxiliaries, together with the means for connecting them to the electric supply. The basic physical principles used in optical luminaire are reflection, absorption, transmission and refraction.

Types of Indoor Light fixtures/luminaires:

Light fixtures/luminaires are classified according to the following:

  1. The light function. 
  2. Lamp type. 
  3. Installation method. 
  4. The percentage of light output above and below the horizontal. 

1- Types of Light fixtures according to light function:
There are five basic types of light fixtures according to the function or aim of using it as follows:

  • Ambient (general lighting).
  • Task.
  • Accent.
  • Informational lighting/Guidance Lighting.
  • Decorative lighting.

A- Ambient lighting 

Ambient lighting provides an area with overall illumination. Also known as general lighting, it radiates a comfortable level of brightness without glare and allows you to see and walk about safely. Ambient lighting is often provided by traditional pendant type fixtures, down lights, chandeliers, or ceiling mounted fixtures etc. The general decor and aspect of the room will affect the amount of general lighting required. Having a central source of ambient light in all rooms is fundamental to a good lighting plan

B- Task lighting 

Task lighting, or directional lighting, is aimed at a specific task; It is a way to provide more light on a specific area to perform a task that requires more light than the ambient fixtures can give. It can be provided by recessed and track lighting, pendant lighting and undercabinet lighting, as well as by portable floor and desk lamps.

Task lighting should be free of distracting glare and shadows and should be bright enough to prevent eye strain.

C- Accent lighting 

Accent lighting is also a sort of a directional lighting that adds drama to a place by creating visual interest. As part of an interior design scheme, it is used to draw the eye to houseplants, paintings, sculptures and other prized possessions. It can also be used to highlight the texture of a brick or stone wall, window treatments or outdoor landscaping.

To be effective, accent lighting requires as least three times as much light on the focal point as the general lighting surrounding it.

Accent lighting is usually provided by recessed and track lighting or wall-mounted picture lights

D- Informational lighting (Guidance Lighting) 

It is designed to help us see our way safely. The light in your closet, the light by your doorbell, and night lights, as well as path lighting and motion lights, are all good examples of informational lighting. The photo to the right is a typical night light with a photosensor. Informational lighting can be beautiful as well as functional, and can create dramatic statements. Lights inset on stairs can create pathways that enhance architecture, while outdoor informational lighting can create

E- Decorative lighting 

Light strips, pendants, chandeliers, and sconces are all examples of light fixtures that draw attention to themselves and add character to the place being lighted. Many are also used for general lighting.

In the next Topic, I will explain other type of light fixtures according to Lamp type , Method of installation and The percentage of light output above and below the horizontal. so, please keep following.