analysis on light environment and efficient creation in college student dormitory of chongqing
TRANSCRIPT
Analysis on Light Environment and Efficient Creation in College Student
Dormitory of Chongqing
Meng Liu1,2,a *, Ziqiao Li1,2,b, Liyang Ruan1,2, Runmu Yang1,2 , Junya Wu1,2 1 Key Laboratory of the Three Gorges Reservoir Region's Eco-environment (Chongqing University),
Ministry of Education, ChongQing, China 400045
2 Faculty of Urban Construction and Environmental Engineering, Chongqing University, ChongQing,
China 400045
Keywords: buildings lighting, college dormitory, photoconductive lighting, Scenario Analysis, energy efficiency and low-carbon, promoting
Abstract. This paper aims to probe into the feasibility and applying strategy of the energy-efficiency
optimization of college dormitory lighting system in Chongqing. It takes a college dormitory located
in chongqing as an instance, through questionnaire and field investigation, the conclusion indicated
that the indoor illumination during the daytime cannot meet the relevant national standards. And over
80 percent of the students are unsatisfied with the indoor lighting. The research on the optimization
program of Photoconductive lighting system and energy efficiency lamp system demonstrate these
two programs can save 5.7 tons of standard coal per year and 1.67 respectively. Then model the
photoconductive lighting system. Finally it takes the Photoconductive lighting system and energy
efficiency lighting systems promoted and compared in college dormitory of Chongqing to draw a
conclusion that the annual savings of the system are approximately 21.8-22.4 million kwh electricity
which equals to 8.72-8.94 one thousand tons of standard coal. This quantity is equivalent to a half of
the electricity consumption of Chongqing Dadukou 2012 January-April.
Introduction
The large quantity of existing housing construction in china results into a large proportion in total
energy consumption which takes up 20.9% [1]. So far China's 42 billion m2 urban and rural existing
buildings (urban buildings 14 billion m2), only 320 million m2 urban buildings are capable of energy
efficiency buildings, the remaining are all constructions of high energy consumption [2]. By the office
for national statics, the total energy consumption of china in 2010 is 3.25 billion tones of standard coal,
5.9% more than 2009. Notice of the State Council on issuing “”affirmative disclosure that realize the
purpose of saving 6.7 tons of standard coal during the 12th national five-year plan [3].
In construction energy consumption, lighting electricity consumption accounts for 15% of the total
generating capacity which approaches to 328.05 billion kwh. On the basis of experts’ survey, the
daytime lighting shares a half proportion of the total electricity used by lighting [4]. Thus reducing the
daytime lighting energy consumption will make a great contribution to construction energy efficiency.
As an important part of large public buildings, university buildings have increasingly drawn attention
in energy efficiency. In 2005, the energy consumption of universities and colleges is approximately
17.9 million tons of standard coal which make up 8.4% of the total energy consumption, and the
number presents ascendant trend all through [5]. At present, the number of colleges and universities in
China has exceeded 2160, and the current school students have reached 25 million, about 2% of the
total population. The implementation of energy-saving emission reduction program in Colleges and
Universities will be of tremendous assistance to social energy efficiency benefits.
Applied Mechanics and Materials Vols. 587-589 (2014) pp 276-282Online available since 2014/Jul/04 at www.scientific.net© (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.587-589.276
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Method and Progress of Investigation
This investigation analyzed the light environment of the student dormitory of a college in Chongqing,
from April 2013 to May 2013, which was adopted the method of questionnaires and field
measurements.
Questionnaires:(1) In order to investigate the using time of lighting equipments, totally 150
questionnaires were sent out, and 137 valid ones were recollected, and the effective rate was 92%; (2)
In order to investigate the subjective light environment in daylight and the operating of the lamps,
totally 200 questionnaires were sent out, and all were collected back, and the effective rate was 95%,
which including 91 females, 109 males, 39 top layer students, 119 middle layer students and 32 lower
layer students.
Field measurements: One of the college dormitories in Chongqing was selected as the research
subject, which was picked up 6 different orientations room from lower layer, middle layer and top
layer. Each room was selected 5 measurement points (including 3 points indoor, 1 point outdoor and 1
point for bathroom), while the daylight illumination was measured from 8 AM to 5:30 PM every half
hour under 3 different weathers (sunny, cloudy, overcast).
Light Environment Analysis
Dormitory Description. Dormitory gets daylight from unclosed balcony with 6 m2 transparent
area. The balcony’s depth is 2 meters, connected with the indoor room by the plate glass door. The
installed lighting equipments in the room are two T8 fluorescent lamps (40W) for interior and one
compact fluorescent lamp (8W) for bathroom. According to the statistical analysis, there are 244 T8
fluorescent lamps in indoor areas, 122 compact fluorescent lamps in bathrooms and 76 compact
fluorescent lamps in aisles.
Indoor Light Environment Analysis. The poor light environment of dormitories would not only
increase the lighting energy consumption, but cause bad influence on students’ physical and mental
health, which would cause emotional disorders so that impact the study and living[6]. According to
STANDARD FOR LIGHTING DESIGN OF BUILDINGS (GB50034-2004), the minimum
illumination standard is required: 100lx for interior, 100lx for bathroom and 50lx for aisle. The
factors affected the indoor light environment of dormitories were layers, orientations, weathers and
gender differences through the analyses on original data. The conclusions are as follows:
(1) Fig. 1 shows that indoor illumination of dormitories increased along with the layers in the same
prerequisite. And under the same condition, the higher the outdoor illumination was, the higher the
indoor illumination was [7]. At noon of sunny days, the illumination of the top layer room reached
250lx, while the lower layer was just under 100lx. At the same weather condition, the time that indoor
illuminations could not reach the standard (under 100lx) rose dramatically from the top layer to the
lower layer;
Fig. 1 Relations between floor and dormitory illumination
(2) 97% lower layer students prefer bright dormitories, while 85% for top layer ones. And students
who lived in the higher layer were more used to using fluorescent lamps. Therefore, when outdoor
light illumination was insufficient, students would increase the lighting demands automatically,
which would increase the lighting energy consumption;
Applied Mechanics and Materials Vols. 587-589 277
(3) The indoor illumination of southern room was notablely higher than the room faced to north. As
there is the least direct sunlight but the most diffused light in Chongqing [8], even if in the optimum,
there was still 4 hours which do not reach the standard. Meanwhile, south-facing rooms’ students
preferred the brighter dormitories and aisles than north-facing rooms’ students by 3% and 14%
respectively. Unlike 53% for students living in the south-facing rooms, 60% students living in the
north-facing rooms got up before 10 AM. Thus, the results shows that sleep time would be extended
by the poor quality of the light environment, which could cause bad influence on students’ study and
health;
(4) The results indicate that 81% students felt unsatisfied with the fluorescent lamps closed in
overcast days. However, Chongqing, belonging to the unavailable region of solar recourses, locates in
the No. IV region of solar irradiance of China [9]. Overcast days accounts for the majority during a
year when excepted holidays. Therefore, students thought daylight was not satisfied in most of the
time and regulated the light environment by operating lighting equipments;
(5) Female students had more dependence on high quality light environment than male students.
Female students preferred opening the lamps than male students by 14%, while the number of female
students got up after 10 AM was less than male students by 20%.
Outdoor Light Environment Analysis.
Table 1 Time of outdoor illumination below 2000lx (h)
South-Facing
Sunny
South-Facing
Cloudy
South-Facing
Overcast
North-Facing
Sunny
North-Facing
Cloudy
North-Facing
Overcast
Top layer 0 0 0 0 0 0.5h
Middle
layer 0 0 1h 0 0 1h
Lower
layer 0 0 1.5h 0 0 1.5h
Due to all kinds of reasons, the results indicate that outdoor illumination could not reach 2000lx
only in the minority time of an overcast day, shown as Table 1, while the lowest outdoor illumination
was 1480lx. Although indoor environment with the relatively poor lighting quality could not reach the
standard, there was still superb lighting condition outside.
Energy Saving Scheme of Lighting
Reference Scheme. In order to compare the difference of light environment and energy
consumption of the dormitory pre and post energy creation, the present lighting design of one of the
student dormitory of a college in Chongqing is used as reference scheme. Calculate the using time of
lighting equipments in cloudy daytime basis for questionnaire. According to 1KW·h consuming
0.4KGce (1tce=1t standard coal), producing 1KG CO2 and 0.03KG SO2 [10], calculate the energy
consumption of this dormitory in a year in the cloudy daytime is about 5.86tce.
Energy Creation Scheme
Efficient lighting Equipment and System Control Scheme. The extension of using efficient and
energy saving electrical lighting is a important way to implement “green lighting” [11]. On the
premise of meeting the requirement of indoor illumination of dormitories, using efficient electrical
light source, lighting equipment and control equipment is beneficial to implement “green lighting
project”, and the cost of lighting exchanging is low with good feasibility.
This scheme aims to reduce energy consumption by exchanging present lighting equipment and
lighting control system. The main way as follows,
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(1) The exchanging of indoor fluorescent lamp. Using T-5 type fluorescent lamp of which rated
power is 29W instead of T-8 type fluorescent lamp of which rated power is 40W.
(2) The exchanging of toilet lighting equipment and control mode. Using LED infrared induction
lamp of which rated power is 7W instead of energy saving lamp of which rated power is 40W.
(3) The exchanging of the control mode of corridor lamp.Using sound control switch instead of
common switch, after which, the using time of corridor lamp will reducing about 60%.
Compared with reference scheme, under the same condition of habit and weather, the energy
consumption of energy creation scheme in the daytime in a year is 4.19tce, which is less than
reference scheme by 1.67tce.
Natural lighting scheme. Photoconductive make people work in the sunshine with healthy and
pleasure mood, which greatly improve the working efficiency. According to the statistics of expert,
electric consumption on lighting in the daytime account for more than 50% on total, and this is major
in industry and commerce. Popularization of using optical lighting system can reduce electric
consumption on lighting more than 50% [12]. Applying natural lighting in the dormitory by optical
lighting system can improve the study efficiency and meet the energy saving requirement.
This scheme use optical lighting system instead of the lighting system of the reference scheme. On
the aspect of ray transmission, the transmission distance of small aperture optical lighting system
achieves about 10m, and big aperture can achieve above 20m. When the outdoor illumination is above
2000lx, the indoor illumination can reach national standard, and it has good effect in winter [13].
According to the analyzing of outdoor light environment in front matter, there is little time when the
outdoor illumination lower than 2000lx, therefore, installing optical lighting system in the corridors,
rooms and toilets. It shows Table 2 respectively. Table 2 Photoconductive Type of Each Functional Area
Installing areas rooms toilets corridors
Light pipe type 530 250 530
In view of above analyzing, simulated arrange the light pipe in these area by Google Sketchup.
The model diagrams are shown as Fig.2
Fig.2 Installation model in dormitory
After the application of optical lighting system, the energy consumption in the daytime in a year is
0.16tce, which is less than reference scheme by 5.7tce.
Compared in the potential of energy saving and emission reduction and capital.
(1) Compared in the potential of energy saving and emission reduction
The comparing of the predict energy consumption and emission reduction of energy creation
scheme with reference scheme, shown as Tab.3. Tab.3 Energy saving potential (a year)
Scheme Energy
consumption/tce
Energy
saving/tce SO2 emission reduction /kg
Reference 5864 0 0
Energy saving
lamp 4194 1670 125.3
Natural
lighting 165 5699 427.4
Applied Mechanics and Materials Vols. 587-589 279
(2) Compared in capital
Compare the capital of each scheme when apply them, shown as Tab.4.
(3) Comparative analysis
The potential of energy saving and emission reduction of natural lighting scheme is about 3.5 times
than energy saving lamps scheme, however, the capital is about 41 times. Consequently, based on
short-term, energy saving lamp scheme has high performance and feasibility.
Tab.4 Comparison of the each energy efficiency project investment
Schemes Capital/
￥10 thousand
Reference 0
Energy saving lamps 4.82
Natural lighting 199.4
From long term point, natural lighting scheme are better: (1) Its manufacturing cost will decreased
greatly, with the improvement of natural lighting technique; (2) The renewal period of light pipes is
much longer; (3) The emission reduction is better obviously, and has huge environmental benefit.
Discussion of lighting energy saving scheme
Assumptions. The total number of university students in Chongqing area is around 660 thousand.
Assuming each dormitory with four individual and there are some 165 thousand dormitories in the
city. If two rooms are designed with one lamp installed between, then there will be some 82500
corridor lamps. And assuming: (1) Every year consists of 40 week, 280 days; (2) Dormitory buildings
have the major building axis pointing east/west; (3) All lighting installation work 9.5 hours in daytime.
The estimated dormitory lighting energy consumption in a year of a university in Chongqing is
showing as Table 5. Table 5 The Total Energy Consumption in A Year of A University in Chongqing
Total energy
consumption
(million kwh)
42.5
Standard coal
(thousand tons)
17
CO2 (thousand
tons)
42.7
SO2 (thousand
tons)
1.28
Promotional program of energy-saving lamp. By calculating the cost of energy-saving lamp
program, based on the assumption, the whole program would save 11.2 million kwh which is
equivalent to 4.48 thousand tons of standard coal. Moreover, carbon dioxide emission will be reduced
by 11.2 thousand ton while sulfur dioxide reduced 0.336 thousand ton.
Promotional program of photoconductive lighting system. According to the photoconductive
lighting system, we promote analysis through scenario analysis and assume three different scenarios.
Combined with statistical results in the questionnaire, distribute the students who have the same habit
of opening light. In the end, calculate the energy consumption by proportion.
(1) Scenario one: Taking the Chongqing college student's gender as a reference volume
On the basis of proportion of female and male students in a Chongqing college as well as the total
energy consumption, the male students’ maximum energy consumption is around 20.9 million kwh
while the females’ is 21.6 kwh. According to the survey, the rate of opening daylight lamp of male and
female are 45% and 59%, respectively, as shown below in Fig.3. Assuming the students who have the
same habit of opening light is distributed in the same room.
W=Q1●θ1+Q2●θ2 (1)
W—total energy consumption, million kwh；
Q1, Q2—the female and male students’ maximum energy consumption, million kwh；
θ1, θ2—the rate of opening daylight lamp of male and female, %
The energy-saving benefit of photoconductive lighting system replacing the daylight lamp is shown
in Fig.4.
280 Sustainable Cities Development and Environment Protection IV
Fig.3 Proportion of keeping the lamp on Fig.4 Photoconductive lighting energy efficiency in scenario 1
(different gender)
(2) Scenario two: Taking the Chongqing college students’ living floor as a reference volume
Setting the proportion of low, middle and high floor are 20%, 20% and 60% respectively, combined
with the total energy consumption, the energy consumption are 8.51 million kwh, 25.5million kwh
and 8.51 millon kwh, respectively. The rates of opening daylight lamp of different floor are shown
below in Fig.5. As well the energy-saving benefit of replacing the daylight lamp by photoconductive
lighting system is shown in Fig.6.
Fig.5 Proportion of keeping the lamp on Fig.6 Photoconductive lighting energy efficiency in scenario 2
(diffenrent floor)
(3) Scenario 3: Taking the Chongqing college dormitories’ window orientation as a reference
volume
Same as previous two scenarios, the energy consumption of windows which faces south is 21.25
million kwh. The rates of opening daylight lamp of different window orientations and Energy saving
emission reduction are shown in Fig.7.
Fig.7 Photoconductive lighting energy efficiency in scenario 3
(4)Comparative discussion
From the effect analysis of three scenarios, we may safely draw the conclusion that when the
conventional lighting are substituted by photoconductive lighting system, the amount of energy
efficiency and Pollutant emissions are very considerable in terms of university dormitories. If the
system are promoted across the country, the energy and environmental effects it brought are
tremendously respectable.
It takes the Photoconductive lighting system and energy efficiency lighting systems promoted and
compared in college dormitory of Chongqing to draw a conclusion that the annual savings of the
system are approximately 21.8-22.4 million kwh electricity which equals to 8.72-8.94 one thousand
tons of standard coal. This quantity is equivalent to a half of the electricity consumption of Chongqing
Dadukou 2012 January-April
Conclusions
(1) Most of the lighting measurements of the dormitory in the survey didn’t reach the standard. More
than 90% students are hopeful to having bright room and aisle available for living.
Applied Mechanics and Materials Vols. 587-589 281
(2) At present, high energy consumption lamps are extensive used in dormitory. If these lamps were
substituted by Photoconductive lighting system, the energy consumption would be reduced
significantly, while the degree of comfort would greatly enhance that divert a positive impact on the
mental and physical health of students.
(3) The energy-saving emission reduction potential of photoconductive lighting system is 3.5 times
energy saving lamp program, but the investment cost is 41 times as much as the latter. In the short
term, energy saving lamp program is cost-effective and feasible. In the long term, photoconductive
lighting system has advantages that: Manufacturing costs will be reduced dramatically with the
development of technology; the replacement cycle of photoconductive lighting system is much longer
than ordinary energy-saving lamps; Emission reduction potential is clearly better than ordinary
energy-saving lamps which will bring tremendous environmental benefits.
(4) If the photoconductive lighting system is promoted to the whole Chongqing area, the energy
efficiency benefit will be very considerable.
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