Coefficient of utilization
Encyclopedia
A coefficient of utilization (CU) is a measure of the efficiency of a luminaire in transferring luminous energy
to the working plane in a particular area. The CU is the ratio of luminous flux
from a luminaire incident upon a work plane to that emitted by the lamps within the luminaire. Luminous flux is usually measured in lumen
s.
For example, some of the light emitted by a luminaire may exit away from the desired plane and is therefore wasted. A CU measures the light actually reaching the desired plane as a percentage of the total light produced by the fixture.
Luminous energy
In photometry, luminous energy is the perceived energy of light. This is sometimes also called the quantity of light.Luminous energy is not the same as the radiant energy, the corresponding objective physical quantity. This is because the human eye can only see light in the visible spectrum and has...
to the working plane in a particular area. The CU is the ratio of luminous flux
Luminous flux
In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of...
from a luminaire incident upon a work plane to that emitted by the lamps within the luminaire. Luminous flux is usually measured in lumen
Lumen (unit)
The lumen is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux...
s.
For example, some of the light emitted by a luminaire may exit away from the desired plane and is therefore wasted. A CU measures the light actually reaching the desired plane as a percentage of the total light produced by the fixture.
See also
- Luminous efficacyLuminous efficacyLuminous 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 electric power consumed by the source.Which sense of the term is...
- Luminous efficiency
- Wall-plug efficiencyWall-plug efficiencyIn optics, wall-plug efficiency or radiant efficiency is the energy conversion efficiency with which the system converts electrical power into optical power...