Title: Reading Assignment – Lighting Technologies
Course: WGF 107 DEVELOPMENT > Section: Content

Title | Reading Assignment – Lighting Technologies
Image | New efficient lighting fixtures being implemented by Wal-Mart for exterior applications such as parking lots, loading dock areas, etc.

Sub-Title | Lamps – Incandescent, Halogen, Fluorescent, HID, Metal Halide, Induction, LED/SSL
Content
Commonly called 'light bulbs', lamps are the removable and replaceable part of a light fixture, which converts electrical energy into electromagnetic radiation. While lamps have traditionally been rated and marketed primarily in terms of their power consumption, expressed in watts, proliferation of lighting technology beyond the incandescent light bulb has eliminated the correspondence of wattage to the amount of light produced. For example, a 60 W incandescent light bulb produces about the same amount of light as a 13 W compact fluorescent lamp. Each of these technologies has a different efficacy in converting electrical energy to visible light. Visible light output is typically measured in lumens. This unit only quantifies the visible radiation, and excludes invisible infrared and ultraviolet light. A wax candle produces on the close order of 13 lumens, a 60 watt incandescent lamp makes around 700 lumens, and a 15-watt compact fluorescent lamp produces about 800 lumens, but actual output varies by specific design.^[10] Rating and marketing emphasis is shifting away from wattage and towards lumen output, to give the purchaser a directly applicable basis upon which to select a lamp.

Lamp types include:

- Ballast: A ballast is an auxiliary piece of equipment designed to start and properly control the flow of power to discharge light sources such as fluorescent and high intensity discharge (HID) lamps. Some lamps require the ballast to have thermal protection.
- fluorescent light: A tube coated with phosphor containing low pressure mercury vapor that produces white light.
- Halogen: Incandescent lamps containing halogen gases such as iodine or bromine, increasing the efficacy of the lamp versus a plain incandescent lamp.
- Neon: A low pressure gas contained within a glass tube; the color emitted depends on the gas.
- Light emitting diodes: Light emitting diodes (LED) are solid state devices that emit light by dint of the movement of electrons in a semiconductor material.^[11]
- Compact fluorescent lamps: CFLs are designed to replace incandescent lamps in existing and new installations.^[12]^[13]

Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total power (electric power, chemical energy, or others) consumed by the source.^[1]^[2]^[3] Which sense of the term is intended must usually be inferred from the context, and is sometimes unclear. The former sense is sometimes called luminous efficacy of radiation, and the latter luminous efficacy of a source.

The luminous efficacy of a source is a measure of the efficiency with which the source provides visible light from electricity.^[4] The luminous efficacy of radiation describes how well a given quantity of electromagnetic radiation from a source produces visible light: the ratio of luminous flux to radiant flux.^[5] Not all wavelengths of light are equally visible, or equally effective at stimulating human vision, due to the spectral sensitivity of the human eye; radiation in the infrared and ultraviolet parts of the spectrum is useless for illumination. The overall luminous efficacy of a source is the product of how well it converts energy to electromagnetic radiation, and how well the emitted radiation is detected by the human eye.

Efficacy and efficiency[edit]

In some systems of units, luminous flux has the same units as radiant flux. The luminous efficacy of radiation is then dimensionless. In this case, it is often instead called the luminous efficiency, and may be expressed as a percentage. A common choice is to choose units such that the maximum possible efficacy, 683 lm/W, corresponds to an efficiency of 100%. The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.

The luminous coefficient is luminous efficiency expressed as a value between zero and one, with one corresponding to an efficacy of 683 lm/W.
Links/Uploads
Wikipedia

Lighting                                               http://en.wikipedia.org/wiki/Lighting

Luminous Efficacy http://en.wikipedia.org/wiki/Luminous_efficacy

See also[edit]

- Photometry
- Light pollution
- Wall-plug efficiency – a related principle, but slightly different
- Coefficient of utilization

Energy Efficient Lighting – EERE   http://energy.gov/public-services/homes/saving-electricity/lighting
Attributions | Image courtesy of Energy Efficiency & Renewable Energy – U.S. Department of Energy Content courtesy of Wikipedia – The Free Internet Encyclopedia