Semiconductor light-emitting diode LEDs have a history of more than 40 years and have received more attention in recent years. In particular, the advent of white LEDs and their rapid development have been highly valued by lighting companies all over the world. Ren Yuanhui, a researcher at China Aviation Industry Planning and Design Institute and honorary director of the Indoor Lighting Professional Committee of China Lighting Association, said that white LED has many advantages: rapid improvement of light efficiency; good starting performance, fast and reliable; convenient dimming and strong controllability; Good resistance to vibration, weather resistance, long life; no mercury, good environmental performance; directional radiation within a certain beam angle, used for spotlights, downlights, etc., is conducive to improve the downlight ratio... These advantages, the industry recognizes that LED has a fairly broad application space in indoor lighting.
Follow the principle of appropriateness and energy saving
Indoor lighting is different from night lighting and emphasizes the function of lighting. Compared to road lighting, indoor lighting is a much broader space. Different use places, different functions, different decorative requirements, determine a wide variety of indoor lighting fixtures, different types of light distribution.
Ren Yuanhui believes that the application of LED in indoor lighting should follow several principles: First, it should meet the requirements of Architectural Lighting Design Standards, including illumination, uniformity, glare, color rendering index and appropriate color temperature. Achieve good visual conditions and LPD limits. Secondly, in the application, we should pay attention to the choice of places, and gradually advance through pilot application and gradual expansion. Finally, we must highlight the concept of energy conservation. The current primary goal is to replace inefficient incandescent lamps, and instead to replace halogen lamps, and ultimately strive to gradually replace compact fluorescent lamps.
In addition, it is necessary to give full play to the characteristics of LEDs, such as the advantages of LED color light to meet higher decorative requirements; to take advantage of LED quick start, convenient dimming, priority in the requirements of sound, light control and needs Dimming or frequent switching lights, etc.; using LED directional lighting features, applied to areas that require directional lighting, such as spotlights, downlights, etc. The use of space in indoor lighting follows these principles extensively, and LEDs have a very wide space for use in indoor lighting. Ren Yuanhui cited one by one: the lighting of the self-extinguishing switch installed in the stairwell of a residential or similar place is now almost always using incandescent lamps. In fact, it is very suitable to replace with LEDs, and the energy saving effect is considerable; evacuation lights, evacuation signs and Other sign lights, partial lights, maintenance lights with safety extra low voltage, and some spare lights. When HID lamps are used for normal lighting, LEDs can be used; LEDs can be used instead of PAR38 reflective incandescent lamps. Research to replace MR16, MR25 halogen lamps, but it should be noted that these requirements LED has a higher color rendering index, color temperature is less than 3300K; shopping malls for spotlights, spotlights for museums, exhibition halls, public buildings LEDs, spotlights, etc. can use LEDs; hotels use more incandescent lamps and halogen lamps, which is a suitable place for the application of LED lights; in addition, the auxiliary facilities of general buildings, such as corridors and toilets, which do not require high visual conditions. LEDs can be applied to general-purpose warehouses, fans, and pump houses, and the technology is relatively mature.
In addition, crystal glass chandeliers such as hotels with high decoration requirements, dimming halls, multi-purpose halls and other similar places are now basically used with incandescent lamps, and it is also possible to study the use of LED lamps that can achieve similar effects.
In the general lighting of offices, classrooms, shopping malls, control rooms, and various industrial sites, there are currently no conditions for applying LEDs. The lighting of such places is mainly functional lighting, which requires high color rendering, suitable color temperature, good glare control and good uniformity to ensure a good visual environment, and also requires high lighting efficiency. The three-color straight tube fluorescent lamp used now has high light efficiency and good visual effect. It is difficult to achieve such a standard at present, so it is not suitable for use.
The problem still needs to be solved
Despite the continuous improvement of white LED technology in applications, as a functional lighting, it has not reached a mature stage in terms of product or technology. Ren Yuanhui believes that, first of all, LED chips mainly rely on imports, and there are few domestically produced chips. The chips lack their own technology and intellectual property rights. At present, China has a large-scale LED packaging industry with better equipment, but there are still some gaps in packaging technology, materials and processes. Second, the industry lacks uniform standards, including LED lighting systems, drive circuits and other standards. Some enterprises have developed their own products by taking advantage of their own advantages. Some enterprises have borrowed or copied them. Each product has different scales, poor interchangeability and difficult maintenance. In addition, the test methods of LED lighting are still not unified, and some parameters are still to be tested.
From a technical point of view, LED lighting products are still in the initial stage, and there are still many problems. For example, the heat problem that is generally concerned in the industry, how to effectively reduce the junction temperature to the allowable level, is still being explored and practiced. In addition, the color temperature of most LEDs is currently high. In indoor places, too much blue spectrum makes people's visual discomfort, produces a sense of excitement, is incompatible with the environment, and is not conducive to protecting the eyes. Furthermore, when LEDs are used for indoor functional lighting, how to design a light distribution and light control system for lamps is also a new topic. The driver circuit for LED lighting also needs further optimization and standardization.
In addition, LED price is too high, it is another obstacle to promote the application. Ren Yuanhui believes that government subsidies alone are not a good development strategy. Because LEDs are used to replace inefficient light sources such as incandescent lamps, they have significant energy-saving effects and can be subsidized. Compared with the more efficient light sources such as tri-color straight-tube fluorescent lamps, LEDs have no significant energy-saving effect, and excessive initial construction costs. It is not economically justified.
Another problem in the development of LED lighting is the lack of a smooth and orderly development. In just a few years, thousands of companies have squeezed into LED lighting, and low-level repeat construction is serious. Therefore, it is necessary to establish a complete set of technical standards and objective evaluation mechanisms to guide their healthy development.
Of course, LED is still in constant development. Ren Yuanhui believes that in the future, efforts should be made to further improve its light efficiency and color rendering, and to study a variety of color temperatures suitable for indoor lighting. At the same time, the semiconductor discipline and the lighting discipline are organically combined to deeply study the lamp form and the light distribution system suitable for LED characteristics, and further reduce the cost. It is believed that LEDs will be widely promoted and applied in the field of indoor functional lighting through 5 to 10 years.
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