Study On Classroom Healthy Lighting During Daytime In Chongqing District

According to the students’ health report by ministry of education in 2011,the myopia rate of university student is extremely high,up to 84.72%.the database,derived from the national survey of adolescent health,conducted every five years,shows that the myopia rates have steadily climbed in recent decades.Relative research shows that there is a strong relationship between visual health and lighting quality.The foundation of intrinsic photosensitive retinal ganglion cell(ipRGC)means light affects not only human’s visual performance but also psychological and physiological effects.This dissertation relies on National Natural Science Foundation “Research on Photobiological Security of Classroom lighting”(Grant No 51178483).This study focuses on the relationship between lighting environmental factors and students’ visual performance,psysiology and phychology during daytime.This research is divided into 3 parts:the first part is analysis on the indoor daylight quality in Chongqing area.The second part is learning students preference of lighting intensity and CCT during daytime through dimming adjustment.The third part is a series of experimental test on subjective evaluation,work performance and physiological rhythm.At last,the best illuminance in different times of a day and in different regions of the classroom space will be deprived through qualitative and quantitative analysis.Dynamic lighting scheme during daytime will also be designed integrating the experimental results and the daylight standards.This research uses white LED as objective due to its wide application prospects.Daylight quality is the basis of indoor lighting environment during daytime.Only fully learn the daylight characteristics,can make reasonable artificial supplemental scheme.In the first research part of daylight performance,climate features of Chongqing and annual variation of typical south and north facing classrooms were analyzed by computer simulations and field measurements.The results showed that the ratio of overcast sky in Chongqing is extremely high,especially in winter.Considering the academic calendar in China,indoor lighting analysis divided the year into 72 typical time periods.Average daylight illuminance and the spatial ratio that fulfills standard threshold were calculated using ASRC-CIE sky model and Hourly Typical Meteorological Year(TMY2)data.It turns out that the annual daylight performance of south-facing classroom is much better than north-facing.There needs artificial lighting in the region far from window in nearly all 72 time periods for north-facing classroom while it needs supplemental lighting in all day of winter and before 9:00,after 16:00 in other seasons for south-facing classroom.The experimental results in the second part indicated that human’s preference of lighting intensity and CCT are quite various in different times of a day and in different regions of the classroom space.Therefore,the principle of time slicing and space partitioning is proposed in the lighting design during daytime.The preference in the region near window is higher in morning and dust while lower in noon that is adverse to the changing pattern of daylight.The preference in the region far away from window presents downward trend from morning to dust.The dimming range in region near and far away from window is almost within 200-400 lx.The average value of preference CCT is as the same of daylight all day long,about 5000 K.In addition,there are always some people chose not to add artificial light in the near-window space.The higher the levels of daylight illumination are,the higher ratio of choosing not to turn on the artificial light.This means quite large potential of energy saving in the near-window space.The third part tested a series of subjective and objective response to different levels of lighting intensity in the regions near and far away from window.The testing content includes subjective questionnaires,work performance and physiological rhythm.The subjective questionnaires comprise the Positive and Negative Affect Scales(PANAS),Physical and Visual Discomfort Scale,Lighting Quality Survey and Satisfaction Questionnaires.Test of work performance includes Alphanumeric verification Task(AVT),Short-term memory of number and words,and numerical calculation.These tests respectively correspond to the ability of perception,memory and thinking.Records of physiological rhythm contain subjective alertness,core temperature,heart rate and blood pressure.At last,the best illuminance in different times of a day and in different regions of the classroom space has been drawn by comprehensive analysis of the three parts test.It can provide Theoretical reference to the classroom lighting design during daytime.Considering the climate feature of Chongqing,this dissertation focused on the mainreasonable artificial lighting supplement to solve the issue of inadequate daylightinglevle under overcast sky.The unstable experimental conditions caused by time andspatial variation of daylight were overcame through the manner of time-slice andspace-partition.We also deepened the application of research results.Considering thegap between the best theoretical levels and the recommended value by daylightstandards,energy saving scheme was proposed beside the theoretical best scheme.Italso pointed out that only integrating the students’ subjective and objective response,the characteristics of study contents,energy saving demands,the refine andhumanizing lighting environment can be achieved.The innovations of this dissertation are as follow:(1)Combining the daylight temporal metric and Chinese academic calendar,this paper divided the year into 72 typical periods.It calculated the indoor average illuminance of 72 typical periods by ASRC-CIE sky model and Hourly Typical Meteorological Year(TMY2)data.Through goal-orientated manner,the spatial ratio fulfilled the standard threshold also deprived for the 72 typical periods(2)The principle of time-slice and space-partition was proposed to solve the unstable experimental conditions caused by daylight time and spatial variation.This principle can ensure the rationality and reliability of research during daytime.(3)The mathematical model comprised by comprehensive index and average standards has been built to unified diverse order of magnitude within different tests.