0 Preface
According to statistics, in 2012, the national automobile sales volume was 19,360,400, and it is predicted that the national automobile sales volume will reach 30 million in 2015. With the increasing popularity of automobiles and the increasing demand for housing, the underground garage has become a must for urban housing. Indispensable facilities. Compared to outdoor garages, the most important feature of underground garages is that they do not have natural daylight and require 24 hours of all-day artificial lighting. For buildings, lighting energy consumption accounts for about 10% to 12% of electricity consumption, while underground building lighting consumes a higher proportion, accounting for about 35% [1]. With the gradual exhaustion of traditional energy sources, research and application of new energy sources have become the focus of technology and industrial development [2], energy conservation, environmental protection, and the economy have gradually gained popularity, which puts higher demands on underground garage lighting.
The LED light source theoretically has the potential advantages of high luminous efficiency, long life, small volume, fast response, shock and impact resistance, environmental protection, safe use, etc. [3], which is an emerging solid-state light source after incandescent lamps and gas discharge lamps. At present, with the rapid development of LED lighting technology and the continuous improvement of functions, LED light sources have been used more and more in lighting engineering, especially in recent years, outdoor night landscape lighting has played an irreplaceable role in other light sources, due to LED light source has the advantages of strong controllability, energy saving and environmental protection. The application prospect of LED light source in underground garage lighting is very extensive.
1 LED lighting in the underground garage
1.1 Energy saving and cost analysis of LED light source
The theoretical white light effect of LED white light can reach above 350lm/W, the theoretical life can reach more than 100,000 hours, the experimental light efficiency has reached 208lm/W, and the whole lamp efficiency has exceeded 100lm/W [4]. We assume that the garage is powered for 20 hours a day, 0.7 yuan per kilowatt hour:
Table 1 Comparison of lamp life and cost
Table 2 Analysis of energy efficiency
Table 3 Comparison of comprehensive benefits
Through analysis and comparison, it can be seen that the cost of using LED luminaires is almost half of that of ordinary luminaires. In the cost of parking lots, lighting costs account for 30-35% of the total cost of parking operations, which highlights the LED luminaires in underground garages. The advantage in the application.
1.2 LED light source without radiation, easy to control
The LED light source is a "clean" light source that is purely luminescent and contains no ultraviolet or infrared radiation. The fluorescent lamps, mercury lamps and other light sources that we use now contain mercury that is harmful to human health. Their production process and discarded lamps can pollute the environment. In addition, the use of LED luminaires with fast response and easy control can combine LED lighting with smart sensors to further effectively realize energy saving in underground garages. When someone has a car moving around the lamp, the LED light is running at full power to meet the lighting needs. When no one is without the car, the lamp is in a dormant state, maintaining a low-power illumination of about 3W, maintaining the minimum required for safe lighting. Illumination, energy saving, and its power saving rate can reach more than 80% [5].
2 Computing environment modeling
2.1 Features of DIALUX software and standards for underground garages
DIALux is a lighting design software for all luminaire manufacturers. It is also the most effective lighting calculation software, which can meet all current lighting design and calculation requirements. DIALux not only imports scenes from the outside but also comes with powerful modeling capabilities. DIALux increases the complexity of room modeling for software in indoor lighting calculations. Through the modeling elements in RoomElement, you can create sloping roofs, roofs with height differences, columns, interior steps and slopes. In terms of furniture models, DIALux has many furniture to choose from. And provide some basic shapes for the specific styles that the user needs. In addition, DIALux can attach materials to walls, floors, ceilings, furniture, etc. In addition to the default materials and colors, the external image can be imported as a material [6].
2.1 3D Modeling in DIALUX
This paper adopts a comprehensive optimal column network, namely 8.1m×8.1m, and the actual size is 57×33.3m2 medium-sized underground garage, as shown in Figure 1. The driveway is 5.6m and 7.1m, the parking space is 2.4×5.7m2 standard parking space, the garage floor height is 3.4m, the net height is 2.2m, and the column with 0.6×0.6m2 section is adopted.
Figure 1 Plan of a 57×33.3m2 medium-sized underground garage
Then model a medium-sized underground garage of the same size in the DIALux optical software and set the material and reflection coefficient of the underground garage floor and the internal structure of the garage, as the lighting level in the garage is measured by the floor brightness. Correctly setting the reflection coefficient of the ground and garage internal structure is important for the accuracy of lighting calculation. Generally, the reflection coefficient of cement floor and wall surface is 27%, as shown in Figure 2.
Figure 2 3D modeling diagram of the underground garage in DIALux
2.2 Selection and arrangement of lamps
The lamp selects the 15W LED fluorescent lamp of NVC's SSLS series. According to the "GB50034-2004 Architectural Lighting Design Standard", the long axis direction of the channel lighting in the underground parking lot should be consistent with the direction of the vehicle entering and exiting, because the underground garage has a lower floor height. The light source of the luminaire should not be too large, and the light distribution angle should not be too small. Try to improve the uniformity of the illumination. As shown in Figure 3, the illuminance standard value of the underground parking lot lighting should meet the requirements of Table 4 [7].
Figure 3 Garage lighting layout in DIALux
Table 4 Illumination standard values ​​for underground parking lot lighting
3 Calculation results
The result of the calculation is to calculate whether the illumination of the ground in the garage has reached the requirements of Table 4. DIALux optical software can automatically calculate the average brightness of the ground and other related data, the calculation results are obtained according to the following formula:
Where Uo is the total brightness uniformity, Lmin is the minimum floor brightness (cd/m2) in the calculation area, and Lav is the ground average brightness (cd/m2) in the calculation area.
After DIALux modeling and calculation, the calculation results are compared with the specified values ​​of the specification. By adjusting the arrangement spacing and arrangement of the lamps, the calculation results are consistent with the specification values. Because DIALux is adopted, the calculation process is greatly simplified, and various luminaire layouts can be compared in a short time to find the optimal solution. In addition, it should be noted that the garage lighting design should reduce the garage as much as possible while meeting the specification brightness requirements. Lighting power density to reduce power loss and improve the economic indicators of garage lighting. Adjusted to the final DIALux software actual calculation results shown in Figure 4.
Figure 4 Point illumination value of the ground