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Solar LED road light flux and photosynthetic efficiency
1, the initial luminous flux ( Initial luminous flux） Per unit time, left, or the number of light through the surface unit: lumen ( lm） 。 Luminous flux Φ usually said.
2, the actual flux ( 实际的光通量) Refers to the open lighting equipment, light energy from the light source, through the lighting equipment ( Such as lens or chimney, etc. ) Need it, until it reaches the working plane so far the number of light energy. We arrived at work said flat luminous flux to the actual flux.
through the above two points, can know that the actual flux values less than the initial luminous flux. See below.
by the definition of luminous flux, we then leads to another important concept: photosynthetic efficiency.
photosynthetic efficiency, Efficacy） Is the total luminous flux of light sources and the ratio of the light source of electrical power consumption, unit: lumens per watt ( lm / w) 。
with initial luminous flux and the actual flux of two kinds of data, so the light efficiency also have initial photosynthetic efficiency and actual photosynthetic efficiency of two different data.
we know that the 'ten city wan light engineering' is promoting led street light, is the need of energy conservation and carbon reduction. Chip initial luminous flux through the lens of chimney, reached the road for traffic lighting effect, also is the actual flux. What we need is the actual flux of high photosynthetic efficiency, does not need the initial luminous flux of high photosynthetic efficiency.
now LED street lamp industry, the expansion of the blind initial luminous flux of high photosynthetic efficiency, many manufacturers also played their part in it. Some businessmen played 120 lm/w high photosynthetic efficiency of LED street light, LED street lamp lighting one of the largest in the world, such as propaganda. The cause of this to happen, it is because of the unity of the national or industrial standards formulated, the relevant testing standards implementation. In addition, although some local introduced local standards, such as guangdong province DB44 standard, shenzhen LED specification, etc. , but the standard is not unified. Take DB44, rules for LED street lamp used in high-speed highway, under the precondition of 4000 k to 6500 k color temperature, class I standard is not less than 78 lm/w, Shenzhen specification defines initial photosynthetic efficiency highest shall not be less than 60 lm/w, but shenzhen specification mentioned additional energy efficiency level evaluation standard is: I level minimum of energy efficiency is not less than 80 lm/w. DB44 specification and shenzhen have released according to the local actual situation, it can be seen that all the differences of the spring. Therefore, countries should formulate a unified industry standard as soon as possible, unified standards, so that there will be ways from region to region.
although domestic for the unification of the standard is still under discussion, but foreign on December 3, 2009, after three times in the draft released, the U. S. department of energy (DOE) DOE for the energy star standard final version of the LED lamps and lanterns, request to take effect on August 31, 2010.
to this end, we study through a large amount of data. DOE for the department of energy (DOE) released on July 1, 2009 on three kinds of lamps and lanterns of SSL performance standard draft second draft, and points out that other indicators can not be fully measure the energy efficiency of lamps and lanterns. Therefore this paper proposes a new draft metrics - - - - Specific performance targets, FTE 拟合目标功效) 。 And ask the outdoor road lighting lamps and lanterns is the lowest light output will reach 1000 lm, The initial luminous flux) 。
FTE will light 'target area' as the research object. FTE is, therefore, the two key assumptions:
1, the rectangular distribution can cover the largest area, more efficient than circular distribution. See below.
2, white circle is light, the green part is the target area illuminated by the effective lighting area, the red part is the goal not area illuminated by the effective lighting area, outside the black areas in targeted lit area, fell on the black area flux should be abandoned. See below.
FTE computation formula is as follows:
FTE = ( Green area flux * green area percentage of the total area of green and red) / lamps and lanterns of the input power,
from that, the U. S. department of energy (doe) released on FTE as LED energy efficiency in the future, it is very reasonable.
we are very much against blind extension initial luminous flux of high photosynthetic efficiency. In road lighting, need only a reasonable illumination, the so-called 'the brighter the better, the higher light efficiency is better', already is not suitable for the need of energy conservation and carbon reduction form now, at the same time also does not conform to the real pursuit of human visual health. We should be rational to treat the prospect of LED lights, do not blindly follow. Only have the correct and objective, mature attitude, with the analysis of the rational, solid, has a base, steadfast, to make the LED industry rapid and healthy development.