luminous efficacy


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Luminous efficacy

There are three ways this term can be used: (1) The luminous efficacy of a source of light is the quotient of the total luminous flux emitted divided by the total lamp power input. Light is visually evaluated radiant energy. Luminous flux is the time rate of flow of light. Luminous efficacy is expressed in lumens per watt. (2) The luminous efficacy of radiant power is the quotient of the total luminous flux emitted divided by the total radiant power emitted. This is always somewhat larger for a particular lamp than the previous measure, since not all the input power is transformed into radiant power. (3) The spectral luminous efficacy of radiant power is the quotient of the luminous flux at a given wavelength of light divided by the radiant power at that wavelength. A plot of this quotient versus wavelength displays the spectral response of the human visual system. It is, of course, zero for all wavelengths outside the range from 380 to 760 nanometers. It rises to a maximum near the center of this range. Both the value and the wavelength of this maximum depend on the degree of dark adaptation present. However, an accepted value of 683 lumens per watt maximum at 555 nanometers represents a standard observer in a light-adapted condition. See Luminous efficiency, Luminous flux, Photometry

luminous efficacy

[′lü·mə·nəs ‚ef·ə·kə·sē]
(optics)
The ratio of the total luminous flux in lumens emitted by a light source over all wavelengths to the total radiant flux in watts. Formerly known as luminous efficiency.
The ratio of the total luminous flux emitted by a light source to the power input of the source; expressed in lumens per watt.

luminous efficacy

The ratio of the total emitted luminous flux, in lumens, to the total electric power consumption in watts.
References in periodicals archive ?
Littlefair [6] suggested an all-sky luminous efficacy model using measured sky diffuse and ground-reflected diffuse with cloud cover in the UK.
According to luminaire measurements described in 3.1, the luminous efficacy of all the three measured luminaire types reduced when the luminaires were dimmed.
The candela, symbol cd, is the unit of luminous intensity in a given direction; its magnitude is set by fixing the numerical value of the luminous efficacy of monochromatic radiation of frequency 540 x [10.sup.12] Hz to be equal to exactly 683 when it is expressed in the SI unit[s.sup.3] [m.sup.-2] [kg.sup.-1] cd sr, or cd sr [W.sup.-1], which is equal to lm [W.sup.-1].
This AC input flood light series is also more economically friendly, consuming less power while providing more light than traditional lighting products.Specifications Type GL-FL30S-WW GL-FL30S-CW Energy Used 28W Rated Life 30,000 Hours Input Voltage 100-240V AC CCT (color) 3000K 6000K Luminous Flux (lm) 1570lm 1900lm Luminous Efficacy 56.1lm/W 67.9lm/W CRI 80 70 Dimension 225x208x120 Beam Angle 30D / 60D Net Weight 2.1Kg Package/ Weight 4Box/Carton
They provide a high 2370-lm luminous flux and the industry's highest luminous efficacy of 91 lm/W.
It is not sufficient to compare light sources based on the luminous efficacy of the bulb alone because the overall light delivery efficiency also depends on the efficiency of the light fixture, or luminaire.
In addition to opportunities for higher luminous efficacy, LED retrofit options for TFL luminaires also present opportunities for increased energy savings and peak demand reduction through occupancy/vacancy, daylighting and demand response controls.
w-WLEDs constantly require adequate red light; therefore, recycling as much red light as possible before it is absorbed is essential to improving the luminous efficacy.
On average, outdoor luminaires had higher luminous efficacy than indoor luminaires, with averages of 54.1 vs.
More energy efficient than traditional light sources, the MR1605AC typically offers a luminous efficacy of up to 70, even as it cuts energy usage.
Visible LEDs have a high luminous efficacy as compared to incandescent and fluorescent bulbs - and while incandescent and fluorescent bulbs have already reached near-maximum luminous efficacy - the efficacy of visible LEDs is forecasted to increase in the future.
However, Epistar's HV chip, producing 100 lumen per watt, reportedly tops competing products from other suppliers in terms of luminous efficacy. Chou said his company has applied for many patents to ensure that the chips can reach every market.