1 Introduction
Chongqing is one of the six old industrial bases in China, and is also the birthplace of modern industry in Southwest China and an important industrial city in China [1, 2]. During the 11th Five-Year Plan period, Chongqing has built 41 municipal-level industrial parks. From January to September 2011, these parks achieved a total industrial output value of 57.06 billion yuan, a year-on-year increase of 45.7%. In 2011, the planned fixed industrial investment was 150 billion yuan. In the first half of the year, industrial fixed investment was 75.57 billion yuan, of which the park completed infrastructure investment of 13.86 billion yuan. As of September, the city's industrial park has newly built 1,644,000 square meters of standard factory buildings (excluding the construction and rental of factory buildings), and has built a total of 838,900 square meters of standard factory buildings [3]. In the new round of the “Twelfth Five-Year Plan†of Chongqing, “the five major trillions of industrial sectors will be formed by 2020â€, and the corresponding industrial construction will receive more policy support and development space in the next few years. With the development of industrial parks, energy consumption has also increased: In 2009, the comprehensive energy consumption of industrial enterprises above designated size was 2767. 01 × 10 000 tons of standard coal, accounting for 43% of the total energy consumption of the city; The comprehensive energy consumption is 3207. 27 × 10 000 tons of standard coal, accounting for 45% of the total energy consumption of the city [4]. In the context of the ever-increasing energy crisis, how industrial plant design can reduce energy consumption while effectively improving the indoor physical environment is a problem worthy of further discussion.
Making full use of natural light can not only reduce lighting energy consumption, but also help users' physical and mental health and improve work and study efficiency. Due to the non-visual effect of the human eye, spectral differences can affect the circadian rhythm, body temperature, and alertness of the human body, which in turn affects work efficiency and human health [5]. Tom DeMarco et al. found that the office environment under natural lighting can significantly improve people's work efficiency and work ability [6]. A sample of 141 medical nurses conducted by MustafaKemal Alimoglu et al. found that at least 3 hours of daylight exposure per day helped reduce work stress and job satisfaction [7]. Therefore, how to introduce more high-quality and reasonable natural light on the premise of energy-saving and humanized design, while taking into account the light and thermal environment, is a key point in the design and transformation of modern factories.
The main sources of natural light in single-storey buildings are side lighting and top lighting. Due to the large span and depth of single-storey buildings, top lighting (sunlight lighting) can more effectively improve the utilization of natural light. There are three main types of common sunroof: rectangular sunroof, zigzag sunroof and flat skylight. Domestic scholars have conducted comparative studies on these three types of skylights, such as: Wang Gang and Shao Wei of Shandong Jianzhu University, etc. compared the parameters such as the ratio of window to window and the number of sunroofs and spacing to the lighting index, uniformity and light direction of the indoor stadium. The influence of sex, etc. [8]. Peng Peng and Zheng Jie of Chongqing University analyzed the changes of cooling, heating and lighting energy consumption of different skylight areas [9]; Yan Yonghong and Wang Ning further studied the best of the skylight through energy simulation software. Window range ratio and arrangement [10]; Peng Xiaoyun of East China Jiaotong University analyzed the relationship between sunroof type, dip angle, orientation and energy consumption [11]. Studies have shown that flat skylights have the highest light extraction efficiency, but glare and overheating problems are difficult to solve; rectangular skylights and zigzag skylights have slightly lower light extraction efficiency, but have obvious advantages in terms of uniformity of illumination, prevention of glare and control of heat intake. The author investigates the actual use of these kinds of skylights in single-storey buildings in Chongqing, and hopes to find out the types of skylights that are more suitable for the climate characteristics of Chongqing, and further optimize the design.
2 Investigation on the current situation of skylighting in single-storey factory buildings in Chongqing
The author selected some single-storey buildings in the Industrial Park of Chayuan New District of Chongqing for field investigation and related data collection and analysis.
The planned area of ​​Chongqing Chayuan Industrial Park is 120 square kilometers, mainly for mechanical equipment and electronic (IT) manufacturing (see Figure 1). The type of skylight in a single-storey factory building in the park is mostly flat skylights, with a small number of rectangular skylights and no zigzag skylights. Five typical single-storey workshops built after 2005 were selected to investigate the current status of natural daylighting.
