lighting types
High-intensity discharge
(HID, including primarily metal halide, high-pressure sodium, and low-pressure sodium)
Solid-state lighting
(SSL, also referred to as LED lighting) efficiency, controllability,durability.
Light-emitting diode(LED)
Induction lighting
High-efficiency, long-duration
Incandescent
Compact fluorescent
Linear fluorescent
Halogen
Mercury vapor
Metal halide
High-pressure sodium
Low-pressure sodium
Induction
Solid-state lighting
Lighting power density(LPD)
Is defined as the electric power consumed by lighting divided by the net floor area of a space in a building, in units of watts per square foot. For example, a 100 square foot office with two 4-lamp fluorescent fixtures, at 170 watts per fixture, has an LPD of 2*170/100=3.4 watts per square foot(W/SF).
Lighting power allowance(LPA)
A maximum allowable LPD is called a lighting power allowance. IEEC(international energy conservation code) 2015 set an LPA of 1.11W/SF for enclosed offices.
Illuminance
Illuminance (sometimes called illumination) is a measurement of light reaching a surface.
International system of measurement (SI) unites: lux
English units:foot-candles(FC)
1 lux=10.8 foot-candles
Illuminance is measured with a light meter. Required Illuminance depends on the use of a space. A space used for activities requires higher illuminance than spaces like corridors or stairwells. Illuminance measurements are used for energy work to access if existing light levels are too high, and so provide an indication of portential for energy conservation, as a check on LPD measurements.
Illuminance is the quantity of light or luminous flux falling an a unit area of a surface the unit of illuminance
Unit: Lumen/㎡ or Lux
Luminance of a light-emitting object or surface is the luminous intensity emitted per unit of (apparent) area of that surface in a specific direction
Unit: candela /㎡
Luminous efficacy
Luminous efficacy is a measure of the energy-efficiency of a particular light source, in laments per watt(Lu/W). Luminous efficacy is useful for comparing types of lighting. For example, a standard 60-watt incandescent screw-in lamp with a rated luminous flux of 840 laments, having a luminous efficacy of 840/60=14lm/W.
Color-rendering index(CRI)
Color-rendering index(CRI) is a measure of a light source’s ability to show colours realistically. Over 80 is regarded as good, 100 is regarded as ideal.
Correlated color temperature(CCT)
It is a property of lamps that is related to their colour appearance.
Unit: degrees kelvin(K)
CCTs below 3200K are regarded as warm light, and above 4000 are considered cool light.
Codes and standards
Codes and standards address lighting in two ways: minimum illuminance and minimum energy efficiency.
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“Field Guide.” Energy Audits and Improvements for Commercial Buildings. Hoboken, NJ, USA: John Wiley & Sons, Inc, 2016. 17–26. Web.