LED indoor lighting can use traditional lighting calculation methods, but the utilization factor is different. Many readers have some incomprehensible and confused LED utilization factor greater than 1, and believe that it has broken through the law of conservation of energy.
The Architectural Lighting Terminology Standard JGJ/T119-2008 gives a definition of the utilization factor, ie the ratio of the luminous flux projected onto the reference plane to the luminous flux of the light source in the illumination device. Can be expressed by a formula:
U=φ1/φ2=(φ1d+φ1r)/φ2
In the formula,
Φ1——the luminous flux projected onto the reference plane, including the direct luminous flux φ1d and the reflected luminous flux φ1r;
Φ2 - the luminous flux of the light source.
The LED has better directionality, and its luminous flux projected onto the reference plane (generally the working surface) is relatively large, unlike the traditional light source and the luminaire, which loses so much during the light transmission process, and the LED lamp φ1d that satisfies certain conditions is close. Φ2, therefore, there is a case where U>1.
Figure 1 is a utilization factor table of a certain LED lamp of OSRAM. The table is from the experimental test, in which the utilization factor of the red line enclosing part is greater than or equal to 1. The RCR in the table is the room-to-space ratio, RCR=5h(a+b)/ab, where a and b are the length and width of the room, and h is the installation height of the luminaire.
Figure 1 Osram's utilization factor table for an LED luminaire
Similarly, Figure 2 is a utilization factor table for a certain LED lamp of Panasonic Lighting. The utilization factor of the red wire frame in the figure is also greater than or equal to 1. The table shape index RI is used in the table, and RI and RCR are reciprocal relations.
Figure 2 utilization factor table of a certain Panasonic LED lamp
It can be seen from Fig. 1 and Fig. 2 that the necessary conditions for utilizing the coefficient greater than or equal to 1 are as follows:
1) Direct type lamps, the light reaches 100%, and the lamps are efficient;
2) Narrow beam, wide beam is difficult to have a higher utilization coefficient value;
3) The ceiling, wall and ground have better reflection performance;
4) The room space ratio is small, or the chamber shape index is large, and the installation height of the lamp is not high.
Therefore, the utilization factor of the LED lamp is greater than one, which is why the LED lamp is more energy efficient than the conventional illumination source and illumination device.
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