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Use of natural light in underground space
2020-08-03 15:02:07

Abstract: With the growth of the world's population, the per capita living space is getting smaller and smaller. To this end, the construction of underground space has become the only choice to solve the traffic pressure of the future population. However, due to the closed structure and the dark features of the underground building, its function and use are greatly limited. Although the current lighting can solve the basic light demand, it cannot be avoided that the 24-hour uninterrupted power consumption and the resulting Unnatural light sensation, how to effectively use natural light to illuminate underground space, reasonable light utilization and distribution, making people feel relaxed and relaxed in underground buildings is an inevitable problem of current underground structures. This article will discuss the dilemma and new machine of current underground space lighting.

 

introduction

      With the acceleration of the pace of urbanization in modernization, people have gradually formed the concept that urban underground space is a valuable resource for human beings, and began to work on the development of urban underground space. Compared with above-ground space, underground space has the characteristics of constant temperature and humidity, heat insulation, shading, airtightness and concealment. People also gradually realize the huge development and utilization value of underground space, whether it is used for storage and transportation of goods or human. Activities and living are all major directions for future social development. However, after years of practice, the inadequacies of underground buildings are: underground space is a relatively closed space, it is difficult to use sunlight and natural ventilation conditions; dark and humid, air turbid, easy to make people boring and airtight Feeling; no external landscape and natural scenery; isolated from the external environment, easy to make people feel lonely, depressed and insecure. These unfavorable factors limit the pace at which humans use underground space as an environment for permanent or long-term living.

The design of the underground space of modern cities requires humanized design, that is, people-oriented, designing from the specific needs of people and the characteristics of psychological behavior [5], summed up is to meet the physiological needs, psychological needs, spiritual needs of people.

(1) Physiological needs. Through the necessary technical means to meet people's most fundamental needs, such as lighting, ventilation, dehumidification, can be achieved through the design of the Ministry of Population and appropriate mechanical means.

(2) Psychological needs. Through the harmonious proportion and scale, the processing of color, the easy identification of space, etc., it can meet the psychological requirements of both people's understanding and human experience.

(3) Spiritual needs. Through the ecological (mainly greening), the creation of natural space, and the inheritance and embodiment of urban context and regional characteristics, we can meet the requirements of people's spiritual pleasure.

In short, no matter what the needs, once the problem of daylighting can be solved, the light of the underground space is designed to be the effect of the ground building. It can greatly enhance the feelings and experiences of people in the underground environment and promote people to live and live in underground structures. In order to solve this difficult problem, experts in various industries have been making unremitting efforts to explore the lighting of underground projects, and have tried and applied them in some practical underground buildings, and achieved gratifying results.


1. Limitations of traditional underground building lighting

      Illumination can artificially create good lighting conditions, so that the human eye can identify the observed objects comfortably and efficiently without any difficulty and damage, engage in corresponding activities, ensure physical and mental health, improve labor productivity, improve product quality, and reduce each Kind of accident. Using different forms and sizes of luminaires, the directionality and gradation of the light can also be used to render the function of the building and to set off the atmosphere of the environment. For example, in the process of taking the subway, the feeling of setting billboards on both sides of the tunnel to the passengers is very different. Passengers with billboards in the subway section feel much easier than those without billboards. So the demand for light in underground space is very significant.

Compared with ground buildings, the biggest feature of underground buildings is that there is no natural daylighting, mainly relying on artificial lighting measures. Therefore, underground buildings have long lighting usage, high illumination and reliability requirements, and humidity has a large impact on lamps and lines. For a long time, the lighting design of underground buildings has followed the design standards of ground buildings, and the lighting efficiency has not been well utilized. So far, the research on the lighting efficiency of underground buildings is almost blank. The lack of scientific and reasonable illumination standards and the people-oriented environment model, coupled with the level of designers and experience, make the realization of lighting performance not guaranteed, even Light pollution, such as glare, stroboscopic, and color distortion, can occur due to improper design and application, resulting in some unwanted heat, infrared, and ultraviolet light [3].

 

2, the new underground building lighting concept

      Natural light is indispensable to human beings, just like air and water. This is especially important in a closed underground space environment. Natural light in the underground space has many effects on improving the underground building environment, which can satisfy people's feelings of sunlight and perception. The psychological needs of natural information such as day and night, alternating shades, and seasonal changes. At the same time, the introduction of natural lighting can also increase the openness of the underground building space, improve the ventilation effect, and greatly alleviate the negative impact of the underground space due to the closed monotonous direction and the isolation from the external environment.

Introducing natural light sources into underground building space has always been a hot issue in recent years, but due to the different functional requirements, it is necessary to further demonstrate whether the natural lighting technology of underground buildings is reasonable. Based on the theoretical level of Maslow's demand, the paper analyzes the requirements of economy, practicability, comfort and energy conservation to demonstrate the rationality of using natural lighting technology for underground buildings based on functional requirements [11].

2.1 Economics - reducing business costs   

      As we all know, large underground buildings have high requirements for lighting design. The light environment of most commercial display spaces is basically built by artificial lighting design, and does not use natural light sources. The creation of high-quality commercial display space brings high lighting operating expenses. In contrast, the general retail space that is ubiquitous in underground commercial streets is different from the large commercial space. While meeting the basic lighting requirements, retail owners pay more attention to the impact of economic costs brought by lighting system operations. . On this basis, the rational use of natural lighting technology can greatly reduce the commercial operating costs of retailers in underground commercial streets, making underground commercial streets more attractive for investment.

2.2 Practicality - meeting basic needs   

      Since humans cannot control the changes of natural light sources, most of the existing natural daylighting is only used as an auxiliary method of artificial lighting, and it is impossible to achieve certain special lighting requirements through natural lighting. Because of the demand for people's activities in public space, the public space part of the unified lighting design requires relatively low lighting quality. Therefore, natural lighting is suitable for the needs of lighting in underground public spaces. The application of natural daylighting technology to underground buildings has great practical significance and development prospects.

2.3 Comfort - improve space quality   

      Research shows that among the factors affecting the underground space environment, the demand for natural light is listed as the main factor by respondents. It is generally believed that artificial light sources cannot replace natural light sources, and artificial light sources do not change much, making the space seem dull and boring. If the entire underground building does not have the introduction of natural light sources, the long-term staff will have an anxiety and anxiety, and will also cause people who enter the underground space to escape. Therefore, how to introduce natural light into the ground is the key to solving the harmonious relationship between good people and underground buildings.

2.4 Energy saving - creating energy saving space

      China's lighting power accounts for about 12% of the total electricity consumption in the country's electricity consumption. Therefore, saving electricity in buildings is of great importance. In underground buildings, lighting energy consumption is a major component of its total energy consumption. Natural light resources are inexhaustible, and the use of clean and environmentally friendly natural light is conducive to energy conservation and environmental protection. Therefore, in the situation of energy conservation and emission reduction, the lighting of underground space should make full use of and develop natural light to create a low-carbon energy-saving underground space light environment.

      In summary, the use of natural daylighting technology in underground space has several advantages. However, in practical projects, the application of natural lighting technology is often affected by many factors such as the shape, scale and cost of underground buildings. Therefore, the key to introducing natural light sources into underground space is to rationally use different natural lighting methods according to actual conditions.

 

3. New natural light lighting method

The common way of natural lighting in underground buildings is divided into two categories: direct lighting and indirect lighting.

3.1 direct lighting [12]

      Direct lighting is a design method that introduces natural light directly into the ground, and is mainly used in shallow underground buildings. Direct daylighting is usually at the ceiling of a building hall or atrium, with skylights that are directly connected to the ground. The space atmosphere created by direct lighting is also the closest to nature in underground buildings. For underground buildings with a small number of layers and a relatively large plane volume, an open space is needed to improve the sense of orientation of the underground buildings. The famous glass pyramid of the Louvre in France, designer Beyue Ming boldly conceived, using the ancient pyramid form, the transparent glass pyramid and the surrounding three small glass pyramids as the skylights of the underground buildings. Even if 15,000 visitors enter the natural lighting hall and cloister within 1 hour, you can still enjoy the fascinating art of the underground palace without any discomfort. The design uses natural light almost perfectly, creatively solving the natural lighting problems of underground buildings.  

3.1.1 Skylight natural lighting system

      Skylights are suitable for underground spaces where the depth is shallow and the ground is square or green. Natural light is introduced into the underground space by setting a skylight in the ceiling. This method has high lighting efficiency and flexible use, and various types of skylights can be selected according to the requirements of internal functions, such as rectangular sunroofs and zigzag sunroofs. In order to break the boring and boring linear commercial space, most underground buildings are treated by setting atrium nodes. The glass ceiling is used to attract natural light in the atrium, which is also a variant of the skylight natural lighting system. However, this method has a great influence on the thermal environment of the underground space, and it is easy to cause thermal uncomfort in the internal space.

3.1.2 sinking square type natural lighting system

      The sunken plaza type often exists in the large underground commercial street in the central area of the city, so that a part of the ground sinks to a certain height, which causes the square to have a spatial shape change, and combines the underground commercial street to form a multi-level composite space. The façade side windows of the sinking section provide a large amount of natural light to the underground space around the square. This method is limited by the height of some underground commercial streets, and its attractive natural light has a limited range. Some underground commercial streets have transformed this way to form an atrium-style underground commercial street.

3.2 Indirect lighting

      Indirect lighting uses a number of ancillary equipment to transport natural light into underground buildings, often in deep underground buildings. Common methods include specular reflection and optical fiber.

3.2.1 Specular reflection lighting

      Specular reflection is the use of plane mirrors, curved mirrors and lenses to reflect natural light through one or more times into underground buildings, thus solving the problem of underground building lighting. For example, in the civil engineering construction building of the University of Minnesota, 95% of the building is below the ground. In order to attract sunlight, the designer uses the principle of periscope to transmit natural light to the underground 33.5 m.

3.2.2 Optical fiber lighting

      Optical fiber lighting is a lighting method that uses optical fibers to pass through underground buildings (Figure 3.1). It takes full advantage of the principle of total reflection of light, and almost all of the light travels through the core, with virtually no loss. Tsinghua University's ultra-low-cost building uses a kind of optical fiber lighting technology called "sunflower", which has achieved good results when lighting the basement. Although the optical fiber has a high price, it has a high light-collecting efficiency, a small footprint, and can be flexibly bent. Therefore, in some underground environments, the optical fiber light guiding system is schematic.

      It is widely used in buildings. In combination with the transmission components of the optical fiber, two different lighting systems are combined, namely an active light pipe system and a passive light pipe system.

      Light pipe technology is a new and effective lighting technology that utilizes natural daylighting. The main feature of the light pipe technology is that it has less limitations in the use of underground space, and can effectively redistribute natural light, which not only achieves the effect of energy saving and environmental protection, but also avoids direct introduction of natural light. Dizziness and heat uncomfortable issues. For underground underground space, the light pipe technology can also distribute natural light into each functional space according to the lighting requirements of different use spaces. The light pipe system is mainly composed of a light collector, a light guide tube and a diffuser. The outdoor natural light is redistributed through the light collector guiding system, and then transmitted to the diffusing device at the bottom of the system through a specially made light guiding tube, and the natural light is uniformly and efficiently irradiated into the room. According to different lighting methods, the existing light pipe technology is mainly divided into active and passive.

3.2.2.1 Active light pipe system

      Such a light pipe system mainly relies on heliostats as the main daylighting device. Heliostat is a device that reflects and locates sunlight. By tracking the sun, it can accurately reflect sunlight to a fixed position. Due to this characteristic, it is very good in natural lighting in underground space. Applications. The use of parabolic mirrors and plane mirrors to design the sunlight collected by the heliostats through the light pipes to the interior of the light path design is more suitable for solving the problems of light-buried underground or windowless buildings. There is a mirror above the heliostat. The mirror sunflowers follow the sun, but they do not “face” the sun like sunflowers. Instead, they refract sunlight to the mirrors above the heliostats. The sunlight is collected, the mirrors are facing down, and the sunlight is “conveyed”. underground space.

The active light pipe system has high efficiency in natural light collection, and the lighting effect in the underground space is also better. However, the cost of the technology is relatively expensive, and the construction technology and the later maintenance and repair work are very complicated. If the quality of maintenance and maintenance in the later stage cannot be guaranteed, there are still major problems in the practice and promotion of such technologies.

3.2.2.2 Passive light pipe system

      Such a light pipe system is a commonly used light guide lighting system. The main working principle is similar to the active one. The difference is that the lighting device is a concentrating hood, and the concentrating hood and the light pipe are connected together and fixed. The concentrating cover is mostly made of PC or plexiglass, and the surface has triangular total reflection. Concentrated edge. Light pipes can be used to fully or partially utilize natural light during the day, which saves a lot of energy. Moreover, the construction requirements and technical difficulty are much lower than the active type, and the later maintenance is relatively easy, but the lighting efficiency is lower than the active one.

      The natural lighting of underground space realized by high-tech means is still in its infancy in China. Due to various reasons such as cost and construction technology, such technology can not be applied to practical projects in large quantities, but it has achieved better results in some pilot projects. Results. However, due to its flexible lighting method, it can be combined with different lighting, light guiding, diffusing and diffusing devices according to different lighting needs. With the maturity and improvement of such technologies, the introduction of natural light for underground buildings by means of high-tech means will become the main trend in the selection of natural lighting methods.

 


4, the application of direct lighting

Due to the maturity of direct lighting technology, its concept has been widely adopted in many underground buildings and is summarized as the end light guiding, central light guiding, and strip light guiding according to the position of the lighting opening in the underground space. the way. As shown in Figure 4.1:


4.1 end light guide

      The method of guiding the end light is mostly used in the underground building with linear layout. The underground space of this layout has a strong sense of direction, but due to the closed space and the lack of familiar ground reference objects, it is difficult for the user to determine the specific location. . The traditional design method is to enlarge the space on the axis of the flow sequence such as the entrance hall of the main entrance and exit, the intersection of the passage and the end of the road, and set the node space to organize some functions for people to collect and rest, so that the space is Organizations make changes to alleviate problems such as monotony caused by long passages. However, due to the lack of communication with outside information due to the lack of communication in the relatively closed interior space, users are mostly reluctant to stay too much. Therefore, the expected effect of setting the node space is not achieved. If the design is combined with the node space set up in the atrium of the atrium, the sunken plaza, etc., and the natural light is introduced in the upper or lateral direction, the spatial characteristics of the underground space can be completely changed, and the space characteristics can be effectively improved. The internal environment of the node space has achieved the purpose of communicating with the external urban environment. Especially in large-scale underground buildings, it is also possible to adopt a continuous setting of daylighting day to create a series of transitional spaces, and to enhance the sense of direction and spatial orientation of people in the underground streets through the transformation of light.

      Taking the Lianhua Road Underground Commercial Street in Zhuhai as an example, Zhuhai Lianhua Road Commercial Tourism Pedestrian Street is located in the south of Zhuhai City Center. It is the most urban atmosphere and urban characteristic of Zhuhai City. In the process of realizing the organic renewal of the old city, in order to maintain the Lotus Road The continuity of the historical place of the commercial block and the integrity of the urban space form, the construction of a 1000m long underground co

Related information

Suzhou sunaite Energy Saving Technology Co., Ltd. address: building A1, No. 192 Tinglan lane, Suzhou Industrial Park, Jiangsu Province, main products: light guide lighting system light guide lighting system light guide tube lighting system light guide tube light guide tube light guide tube