Lighting energy-saving design for architectural projects

1 Introduction
The energy issue has become a global hot issue. Today, with the increasing energy shortage, building energy conservation has received more and more attention from the society. With the sustained and steady development of China's national economy and the continuous improvement of people's living standards, the demand for lighting power is also constantly improving. How to maximize energy conservation on the basis of meeting high demand is particularly important. Doing a good job in lighting energy conservation during the electrical design phase will have a multiplier effect. In order to overcome the blindness in lighting design, correct the mistakes of many designers to use the power density value to reverse the number of lamps for lighting design, and to save energy. Some problems in lighting design are discussed below.

2 steps in lighting design
2.1 Reasonable determination of illuminance and power density values ​​Before lighting design, you should first understand the project overview, and determine the standard illuminance value and power density value (LPD) of the main room and location according to the nature, function, environment and scale of the project. Whether the design meets the required standard basis. The “Development Engineering Design Document Depth Regulations” (2008 Edition) has been approved and promulgated, effective as of January 1, 2009, of which 3.6.5, the new paragraph 6 is added to the calculation book – illuminance value and power density value. Calculations show that lighting energy-saving design is getting more and more attention [1]. Architectural lighting design standard GB50034-2004, 5.1~5.4 respectively stipulates the lighting standard values ​​of residential buildings, various public buildings, industrial buildings and other public places; Sections 6.1.2 to 6.1.7 respectively specify 108 items of commonly used 7 types of buildings. The LPD value of the lighting power density of a commonly used room or place, issued as a mandatory provision (except for residential buildings), must be strictly enforced [2].

2.2 Correct selection of lamps, light sources and ancillary devices Under the conditions of illumination, color rendering, start-up time, etc., according to the comprehensive evaluation and analysis of the efficiency, life and price of the light source, lamps and their attachments, select and select. In order to avoid the high-efficiency energy-saving lamps replaced by ordinary lamps when the construction tenders are purchased, the designed illumination can not reach the standard illumination value, which affects the use effect. It is recommended that the designer specify the model of the selected lamps in the design specification and the main equipment material table. The specifications, the luminous efficiency of the light source and the luminous flux ensure that the selected lamps and light sources can meet various technical requirements.

1) The choice of light source should strictly limit the application of low-efficiency ordinary incandescent lamps. When used in special cases, the rated power should not exceed 100 W; in industrial plants and road lighting, fluorescent high-pressure mercury lamps should not be used. In particular, self-ballasted fluorescent high-pressure mercury lamps should not be used. Metal halide lamps or high-pressure sodium lamps should be used; thin-tube straight-tube fluorescent lamps should be used in lower height places; metal halide lamps or high-pressure sodium lamps should be used in higher places, or large Power thin tube diameter fluorescent lamp. High-pressure sodium lamps are used for indoor places and road lighting where the color rendering requirements are not high; fluorescent lamps should use thin-tube lamps and three primary color lamps, which have significant energy-saving and environmental protection effects.

2) The principle of lamp selection is to use safety, limit glare, improve energy efficiency, and reasonably consider functionality. Regarding the efficiency of the luminaire, the building lighting design standard GB 50034-2004 is clearly defined in 3.3.2: the open fluorescent lamp should not be lower than 75%, the grille fluorescent lamp should not be lower than 60%, and the protective cover fluorescent lamp should not be low. At 60%, the open high-intensity gas discharge lamp should not be lower than 75%, and the grille or translucent cover high-intensity gas discharge lamp should not be lower than 60% [3].

3) Reasonably choose the ballast. Straight tube fluorescent lamps should be equipped with electronic ballasts (EB) or energy-saving magnetic ballasts (SLB); high-pressure sodium lamps and metal halide lamps should be equipped with energy-saving magnetic ballasts. Constant power ballasts, those with lower power can be equipped with electronic ballasts. The energy efficiency of the T8 fluorescent lamp ballast is compared below: 36 W fluorescent ballasts use about 14% more energy than low-loss electronic ballasts, while 18 W lamps consume 26.3 more. %. Harmonic and Power Factor Comparison of Straight Tube Fluorescent Electronic Ballast EB and Energy-Efficient Inductive Ballast SLB: Lamps above 25 W with EB harmonics are relatively large, but acceptable. For 25 W and below, the 3rd harmonic limit is as high as 86%, and the 3rd harmonic is superimposed on the neutral line by 3 times, which should be paid special attention. Therefore, a large number of lamps of 25 W and below (including T5-14 W and T8-18 W with EB) should not be used in a building. When using SLB, the harmonics are relatively low, but the power factor is also low, requiring reactive compensation. It can be seen that fluorescent lamps of 25 W and below should be used with caution. If selected, the power consumed by the ballast should be added (for example, when using 18 W ordinary magnetic ballast, it should be calculated according to 28 W).

2.3 Calculate the illuminance and verify its power density value The most common use in general office and commercial space is the calculation of the average illuminance, usually using the utilization coefficient method. The coefficient method is applicable to indoor general illumination with high uniform arrangement of lamps, high reflection coefficient of walls and ceilings, and no large equipment in space. It is also suitable for outdoor lighting with uniform arrangement of lamps. The calculation method is more accurate [3].

According to the calculation formula Eav=N×Φ×U×K/A by the coefficient method, the calculation formula of the number of available light sources is: N= Eav×A/(Φ×U×K). Where: N is the number of light sources; Eav is the average illuminance on the working surface, lx; A is the working surface area, m2; Φ is the luminous flux of the source, lm; U is the utilization factor; K is the maintenance factor of the luminaire. Eav, Φ, A are known numbers or can be queried; the maintenance factor K can be selected according to the environmental pollution characteristics and the number of annual lamp wipes from Table 4.1.6 of the architectural lighting design standard GB50034-2004, generally taking 0.7 to 0.8; U is utilized The coefficient and the determination of the utilization factor are cumbersome. It is necessary to find the light distribution curve of the lamp and understand the reflection coefficient of the wall, the ground and the ceiling of the room or place. In the second edition of the Lighting Design Handbook, Table 5-1 lists the utilization factors for each case. However, it is still quite cumbersome to understand the various reflection coefficients in detail and determine the chamber shape index. Here, after analysis and verification of many different engineering examples, the calculation is simplified as follows, taking the product of the maintenance coefficient and the utilization coefficient. ×U, generally 0.4 to 0.5 is appropriate, verified, the simplified calculation results and the actual situation is not much deviation, basically can meet the requirements.

When calculating the illumination, the number of light sources should be calculated according to the illumination requirement, then rounded up, and then the lamps should be arranged according to the room size. After determining the number of light sources, check whether the illumination requirements are met, and calculate the power density value to see if the specifications are exceeded. Power density refers to the lighting installation power per unit area. The installed power should include the power of the light source and the ballast. "Architectural Lighting Design Standards" GB 50034-2004 Article 4.1.7 stipulates that, under normal circumstances, the design illuminance may have a deviation of -10% to +10% compared with the standard value of illuminance. However, the power density value cannot be exceeded, and this article needs to be strictly enforced. In the actual design work, it is necessary to resolutely eliminate the calculation of the illuminance, and simply calculate how many luminaires are needed to calculate the power density value. For most indoor spaces, although the mandatory standard power density value does not exceed the standard, the actual illuminance value often exceeds the specified illuminance by more than 10%, resulting in waste of energy, contrary to the principle of designing energy conservation. In places with 2 renovations, the designer should determine the illuminance and power density standards in the design documents. This is the design basis for the 2 renovations. In addition, the building lighting design standard GB 50034-2004 6.1.8, 6.1.9 also stipulates that there is a place with decorative lighting, which can calculate 50% of the total power of the decorative lighting used in the calculation of the lighting power density value. . Stores and business halls with accent lighting, with a power density value of 5 W per square meter.

For example: an ordinary office with a length of 9 m and a width of 7.2 m requires an illumination of 300 lx. The design uses embedded grid fluorescent lamps, the lamp efficiency is 60%, and the light source uses high-efficiency trichromatic fluorescent lamps. The output is 3 350 under standard voltage. Lm, each light source installation power 36 + 4 = 40 W. Use the formula for simplified calculations and select 12 sources. The calculated illuminance value Eav=310 lx, exceeding the specified illuminance value of 3.4%, meeting the specification requirements. The power density value is calculated again, LPD = 7.4 W/m2, <11 W/m2, which also satisfies the requirements. If the power density value is calculated as: LPD = 11 W/m2, a total of 18 light sources are required. The illuminance requirement is Eav=465.28 lx, which exceeds the standard illuminance value of 55.09%. Although it meets the requirements of power density value, it does not meet the energy-saving design principle and greatly exceeds the requirement of 4% deviation of 4.1.7 illuminance value in GB50034-2004. . This office lighting consumes 240 W of electricity, 8 hours per day, and consumes 1.92 kW·h of electricity per day. There are many offices in the whole building. It can be imagined that more energy is consumed.

It can be seen that it is very important to calculate the illumination and power density values ​​of a representative room during design. Simply determining the number of lamps according to the power density value will cause a great waste of energy.

2.4 Rationality of lighting control measures Architectural lighting design standard GB 50034-2004 lists many lighting control measures. Among them, 7.4.5 points out that the number of light sources controlled by each lighting switch should not be too much. This means that the lighting design should consider turning on the lights as needed when only a few people work, without having to illuminate more light sources to avoid waste. 7.4.6 states that when two or more columns of lamps are installed in a room or place, they should be grouped and controlled as follows: 1) the columns of controlled lamps are parallel to the side windows; 2) the production sites are grouped by workshop, section or process; 3) Electrified classrooms, conference halls, multi-purpose halls, lecture halls, etc., grouped close to or away from the podium. The implementation of the above three measures has played a very important role in lighting energy conservation. Most office and commercial room lighting loads are energy-consuming loads that are used in large quantities and in a long period of time. They make full use of sunlight to reduce power consumption, and the accumulation of energy is not too small.

3 Conclusion
Through the above analysis and calculation, the requirements and basic practices of lighting design are clarified, and the importance of building energy saving in lighting design is fully recognized. Although the lighting design with reverse push method is simple, it does not meet the energy saving requirements and should be avoided. Conduct lighting design.

[1] Ministry of Housing and Urban-Rural Development of the People's Republic of China. Depth of Construction Engineering Design Document [M]. Beijing: China Planning Press, 2009.
[2] Ministry of Construction of the People's Republic of China. Architectural Lighting Design Standard GB 50034-2004 [S]. Beijing: China Building Industry Press, 2004.
[3] Beijing Lighting Society Lighting Design Committee. Lighting Design Manual [M].2 Edition. Beijing: China Electric Power Press, 2006.

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