Author: Li Xinglin
As we all know, the “Water Cube†is a building with the theme of “waterâ€. The four façades and the top surface are composed of two layers of air pillows with a shape simulating the structure of water molecules. The middle of the two layers of air pillows is based on the “foam theoryâ€. The steel structure formed.
1.1 Research on lighting methods
The inner and outer air pillows of the four façades are composed of three layers of ETFE membranes, and the inner and outer air pillows of the top surface are composed of 4-5 layers of ETFE membranes. The ETFE film has a high transmittance for light of various wavelengths, as shown in Figure 1.
Figure 1 ETFE film optical characteristics
If the "external projection lighting method" is adopted, since there is no good reflecting surface, most of the light will be projected into the interior of the building through the air pillow to form interference light, and the surface brightness of the air pillow will not be high, and the expected effect will not be achieved. Especially for the top surface, it is impossible to achieve external projection illumination. Moreover, if external projection lighting is used, it is necessary to set up a bracket around the building, which will have an adverse effect on the environment.
If the "general internal light transmission method" is adopted, since the light needs to pass through the 6-8 film to be cast on the outer ETFE film of the outer air pillow, the loss of light is large, and the brightness of the outer surface of the air pillow is not high. It also failed to achieve the desired results.
Because the outer surface of the "water cube" is curved but smooth and flat, the frame size of the air pillow is small, it is not suitable for wiring and lighting, and if the "cage lighting method" is used, the facade effect of the building will be destroyed. It is also not advisable to use "contour lighting".
Through various arguments and field experiments, it was determined that the “light-transmitting illumination method in the cavity†was adopted, that is, the illumination method was installed on the inner side of the steel structure of the fixed outer air pillow, so that the light only passed through a single gas. Pillow, the loss of light is only half of the way of light transmission in the cavity, which can achieve better illumination effect. The adoption of this kind of lighting method has added a new way for building landscape lighting, creating a precedent for building landscape lighting, and is of great significance for building landscape lighting of membrane building and glass curtain wall building.
1.2 Research on light source selection
Due to the relatively small size between the two air pillows, the heat dissipation conditions are poor, and it is not suitable to install a light source with a large size and a large heat dissipation. Under such conditions, the more suitable light source is only two kinds of light sources: fluorescent light and LED light. Therefore, we have focused on the technical and economic comparison of these two light sources. LEDs have a long life span of 50,000 hours, 2.5 times that of T5 tubes. LEDs are the best value for money throughout their life cycle. LEDs are mercury-free, low-radiation, and waste-recyclable, which is good for the environment. The light distribution is easy to control, and the optical lens is used to project light to a desired location through primary and secondary optical design. Easy to integrate, integrates computer, network communication, image processing and other technologies into one, online programming, timely innovation. Fast response in nanoseconds, instantaneous scene change. More important is the rich color, using the three primary color principle, the illumination can form 256X256X256 colors; on the dot matrix screen can form 8192X8192X8192 colors. The size of the lamp body is small and it is easy to match the side length of the air pillow.
If fluorescent lamps are used, it is not conducive to environmental protection due to the presence of mercury. Due to the large size of the lamp body, it is impossible to use the lens to illuminate with the reflector, and the light distribution curve is difficult. Larger fluorescent lamps should not be matched with the side length of the air pillow. The fluorescent lamp is a gas discharge lamp, and the response speed is slow, and the scene cannot be quickly changed, which is not conducive to scene design. Moreover, the mixing of fluorescent lights RGB three colors will also be a problem, and new lamps need to be developed. Fluorescent dimming ballasts need to be stable at a certain current. If a fluorescent lamp is used, not only the required power but also the power consumed is significantly larger than that of the LED.
Through multiple demonstrations of many parties, the LED light source was finally determined.
1.3 Research on the way of lighting
"Water Cube" requires LED lamps not to affect the appearance of the building during the day, LED lighting at night does not affect the indoor lighting, so that you can see the light. Due to the large brightness of the surface of the LED light source, such as the projection direction and angle are not suitable, the spot will be seen at a certain position, affecting the lighting effect. After a large number of field tests, it was determined that the luminaires were mounted on the lower steel frame of the air pillow and projected upwards so that no spots were observed. We call this type of lighting a "one-way projection along the side of the cloth." This kind of lighting method will be the main lighting mode of "transparent lighting method in the cavity", and solves the big problem of the lighting mode when the "lighting illumination method in the cavity" is adopted for other buildings in the future.
1.4 Research on color composition
The "Water Cube" is a building with blue as the basic color. Whether the light still needs red light has also become a topic of discussion. Blue symbolizes "water", red symbolizes "fire", "water" and "fire" are contradictory unity, and red will increase the beauty of water. Especially during the Olympics or during the major festivals after the game, there must be red in order to coordinate with the festive atmosphere. Using RGB three primary colors, the lamps can be mixed with 256X256X256 colors, and the dot matrix screen can mix 8192X8192X8192 colors. The rich colors provide a wide space and stage for the scene design.
1.5 Study of scene composition
Although the above lighting scheme can meet the requirements of illumination uniformity and color to a certain extent, it cannot form an animation, and the composition is relatively simple, and can not meet the needs of the Olympic Games and post-game operations. After several field tests, it was determined that a 2000m2 dot matrix screen was installed on the south façade, which together with the four façades and the top surface lights formed a magnificent scene. Through system integration technology, it can also be linked with moat lighting, ambient lighting, and outdoor audio. Light color and sound together form a more grand scene. Poetry and painting will make people feel intoxicated.
1.6 Research on RGB power ratio of LED lamps
In the case of normal white balance, the luminance ratio (light flux) of RGB is 3:6:1. Since the ETFE film is light blue, after the light passes through the multilayer ETFE film, color shift occurs, and the X and Y values ​​of the color coordinates change. In addition, the luminous flux of the blue LED is lower than that of the red or green LED. How to configure RGB power to provide a good hardware platform for future scene design is a very critical issue. The power ratio was determined to be RGBB through several field tests.
1.7 Research on main parameters selection of LED chip and light source
The semiconductor lighting industry is a high-tech industry and a sunrise industry. It is gradually moving toward large-scale applications, and its application range is gradually expanding. Due to environmental protection and energy conservation, governments in developed countries have formulated their own development plans. China's semiconductor lighting industry has experienced rapid development in recent years, but there is still a big gap compared with developed countries. Some important patents are in the hands of foreign companies. On the basis of in-depth investigation of related products at home and abroad, it is finally determined to adopt chips of international famous brands, and the facade lighting LEDs are packaged in foreign countries. The top lighting LED can be used in domestic packaging, and the dot matrix display LED can be used in domestic chips and packages.
The top lighting of the tender results has also become a foreign package. Because LEDs have some parameters that distinguish them from traditional light sources and luminaires. How to select and determine these parameters has also become a research topic.
(1) Selection of single high power LED power and rated operating current
According to the power classification of LEDs, LEDs of 0.5W and above are generally referred to as high-power LEDs. The internationally renowned brands lumilaids, Creen, Osram's product line, rated working current is 350, 500, 700, 1000, 1500mA and other grades. Under the same technology, the larger the power of a single LED, the lower the light efficiency, but the number of lamps can be reduced, which is conducive to saving investment; the smaller the single power, the greater the light efficiency, but the LED needs in each lamp. As the number of particles increases, the size of the lamp body increases, which increases the technical difficulty of the optical lens and adversely affects the light distribution curve. On the basis of comprehensive consideration of factors such as technology, economy, product maturity and actual use experience, it is determined that the rated operating current of a single LED is 350 mA, that is, the power is 1 W.
(2) Peak current selection
According to the products of several famous international brands, the peak current of 350mA LED has two series of 500mA and 700mA. Products with a peak current of 700mA are newer and more expensive. Finalize the peak current selection for the 500mA series.
(3) Selection of single LED luminous flux
The products of international famous brands have different luminous fluxes of different LED series products. Taking into account the price and maturity of the product, it was finally determined that the luminous flux of the RGB LEDs was 35, 60, and 15 Lm at the rated operating current.
(4) Selection of LED main wavelength
The dominant wavelength is the main parameter that determines the color of the LED. Choosing the correct or not will affect the scene effect. We choose the main wavelength of LED: R: 622-629nm, G: 520-525nm, B: 465-470nm.
(5) LED half-wavelength width and color purity selection
These two parameters actually represent the same optical performance of the LED. LED half-wavelength width selection: R: 20-25nm, G: 35-40nm, B: 25-30nm; LED color purity selection: R: ≥ 97%, G: ≥ 75%, B: ≥ 95%.
(6) LED chip allows the choice of working junction temperature
The higher the working junction temperature is allowed, the better the product performance and the more expensive the price. Taking into account product maturity and price factors, LED chips allow working junction temperatures greater than 125 °C.
(7) Choice of maximum working shell temperature
This is a parameter for the packaging technology requirements. The lower the maximum working case temperature, the higher the heat dissipation requirement for the package. Indicates the better the package cooling technology . The maximum working case temperature is 110 °C.
(8) Selection of thermal resistance of LED light source
The thermal resistance parameter directly reflects the level of packaging technology. The better the heat dissipation technology, the lower the thermal resistance, the smaller the light decay, and the longer the lamp life. We choose the thermal resistance of the PN junction to the package base: R: ≤ 12 ° C / W, G, B: ≤ 10 ° C / W.
(9) LED life and choice of light decay
The theoretical life of LED is 100,000 hours, but now the actual international can reach 50,000 hours, that is, after 50,000 hours, the light decay does not exceed 30%, and the luminous flux can still maintain 70% of the initial value.
1.8 requirements for luminaire efficiency
Based on the examination of the efficiency of international famous brand lamps, we put forward the requirements for the efficiency of LED lamps. The output luminous flux of the luminaire is not less than 80% of the luminous flux after chip packaging.
1.9 requirements for drive power efficiency
Water Cube LED building landscape lighting can be driven by several power sources. In order to reduce the power consumption of the system and save energy, on the basis of examining the parameters of international famous brand products, we put forward the requirements for the overall efficiency of the driving Power Supply, and the efficiency from the AC power supply to the chip is more than 75%.
1.10 Requirements for the communication protocol of the lighting network control system
The popular communication protocol for international lighting network control systems is DMX512, ARTnet in Europe, and CAN in the United States. According to China's experimental application of IPv6, there is already some experience. The entire Olympic Park lighting network control system adopts the IPv6 protocol. The upper layer of the water cube lighting network control system adopts the IPv6 protocol and is compatible with the DMX512 protocol. (small soup)
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