A Study on Energy Saving and Light Pollution of LED Advertising Signs

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1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland A Study on Energy Saving and Light Pollution of Advertising Signs Chen-Ying Ho 1,a, Hsien-Te Lin 1,b, Kuang-Yu Huang 1,c 1 Department of Architecture, National Cheng Kung University, Tainan City, Taiwan a gazehochen@gmail.com, b linsiraya@yahoo.com.tw, c h193850@gmail.com Keywords:, energy saving, luminance limit, light trespass, advertising sign, vertical illuminance Abstract. Lighting advertising signs not only play an important role in outdoor lighting environment in Taiwan, but also become the main factor of energy consumption in urban areas at night. Light-emitting diode () has been gradually used in advertising signs due to its advantages. However, in order to be conspicuous and legible in the daytime, signs that are excessively bright may result in considerable light pollution and energy waste at nighttime. Therefore, this research aims to measure the luminance of signs and traditional internally lighted signs, and analyze the light trespass from each signage. Based on the research results, the energy consumption from a full color screen is 12 times more than a traditional internally lighted sign per day. Statistically, all kinds of signs are much higher than traditional internally lighted signs in the percentage of excessive brightness and average luminance value. As for the light trespass, since the vertical illuminance on facade facing the signs increases with the increase of the sign area or the decrease of the distance between the sign and the facade, the vertical illuminance on facade facing the signs would exceed the limit of CIE even if the luminance of the signs achieves the standard of CIE in terms of the general conditions in Taiwan. This happens to full color screens in particular and thus results in considerable obtrusive light. To sum up, in order to reduce unnecessary energy consumption and improve the nighttime lighting quality for outdoor environment, this research recommends the luminance limitation for light dimming of advertising signs should refer to the zoning, time period, and sign area. Introduction Because of the prosperous commercial activities in Taiwan at night, lighting advertising signs not only plays an important role in outdoor lighting environment, but also become the main factor of energy consumption in the urban area. Light-emitting diode () has been gradually used in advertising signs due to its advantages, such as high luminous efficiency, energy saving, and dynamic performance. However, in order to be conspicuous and legible in the daytime, signs that are excessively bright may result in considerable light pollution and energy waste at night. Consequently, the energy-saving ability of advertising signs should be further reviewed and discussed. Issues about light pollution can be traced back to 1970s. Nowadays many countries have been paying more and more attention on these issues. Light pollution, also known as obtrusive light and stray light, is a broadly-employed term to describe light that is either too bright for its intended purposes or light that shines where it is not needed or wanted [1]. According to statistics, outdoor lighting beyond the planned area costs over a milliard per year in USA, which is an outrageous amount. Furthermore, according to the study by Ding-chin Chou [2], within 1200 questionnaires, 29 percent of the residents feel affected by light pollution and 73 percent of those interviewed believe that the light pollution mainly comes from advertising signs, which result in serious light trespass. In addition, signs that are excessively bright represent energy waste. In order to control and save energy, energy consumption of advertising signs would be reviewed in this study. And according to the results of luminance measurement and light trespass level analysis of signs and traditional internally lighted signs, luminance recommendation of advertising signs would be suggested. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-13/09/16,08:27:07)

2980 Frontiers of Manufacturing and Design Science II Light Control Ordinances for Signage As light pollution has gradually been taken more seriously, many countries begin to study relative issues

Instead, appropriate zoning system should be adopted. The zoning system defined by International Commission on Illumination (CIE) is in widespread use.

2 2980 Frontiers of Manufacturing and Design Science II Light Control Ordinances for Signage As light pollution has gradually been taken more seriously, many countries begin to study relative issues and regulate against it. Since different activities take place in different areas around the world, the light trespass restriction measures do not have to be equally stringent. Instead, appropriate zoning system should be adopted. The zoning system defined by International Commission on Illumination (CIE) is in widespread use. Shown in Table 1, this system divides the environment into four main zones, from E1 to E4. The CIE zoning system for general purposes is closely related to the system of urban zoning in use in many countries. The limits of sign luminance and vertical illuminance on facade facing the signs were referred in the No.150 technical report of CIE in 2003 [3] and extracted in Table 1 as a criterion for judging if the sign luminance and the light traspass level are appropriate and acceptable. Table 1 Sign Luminance and Obtrusive Light Limitation for outdoor Lighting Installations Limit project Time Zone E1 E2 E3 E4 Vertical Illuminance on facade before curfew(07:00-23:00) facing the signs (Ev)[lux] after curfew(23:00~07:00) Sign luminance(l)[cd/m 2 ] Environmental Zones: E1 - Areas with intrinsically dark landscapes: National Parks, Areas of outstanding natural beauty E2 - Areas of low district brightness: outer urban and rural residential areas E3 - Areas of medium district brightness: generally urban residential areas E4 - Areas of high district brightness: generally urban areas havingmixed residential and commercial land use with high night-time activity. Method The main subjects discussed in this study are the energy consumption and the obtrusive light from advertising signs to the ambient environment. Since the advertising signs exist mostly in cities, the sampling scope is delimited in E3 and E4 zone by the CIE zoning system, defined as residential and commercial districts by the urban planning in Taiwan. Samples are located in the three main metropolis of Taiwan, that is, Taipei, Taichung, and Kaohsiung city. Further, they are installed parallel to facade. The most popular signs in Taiwan are selected to be the target samples, and traditional internally lighted signs are used to be a comparison group. In addition, advertising signs are divided into three types by display characteristics in Table 2 to more accurately analyze the luminance and energy consumption from each of them. Table 2 Advertising Sign Categories Type Signs texts/patterns text display panels full color screens texts/patterns composed of chips Explanation panels composed of mono-color or two-color chips, with dynamic text messages and dark background screens composed of RGB color model to present full-color dynamic messages and patterns Illustration Measurement of Signs. The Luminance meter LS-100 of Konica Minolta is adopted. Observers stood in front of the sign across the road, and measured its luminance in a different order, which was chosen according to the length-to-width proportion and dimension in Fig. 1. Reading scope must not be overlapped. Moreover, the length and width of the sign was measured to evaluate the sign area; the road width in front of the sign was consulted from urban planning.

3 Applied Mechanics and Materials Vols Calculation of Vertical Illuminance. Vertical illuminance on facade facing the signs (E v ) is adopted to estimate the level at which the sign light invades the interior environment right across the road. According to Inverse Square Law, E v could be obtained from Eq. 1. In addition, the sign area, including the dark background, is the product of the length and width of the message display area. In Taiwan, since buildings are generally built right beside the road, the road width could be regarded as equal to the distance between the sign and the facade across the road. LAvg. A Ev = [lux]... (1) 2 D Notes: L Avg. : average luminance [cd/m 2 ] A: sign area [m 2 ] D: distence between the sign and the facade facing the sign or the width of the road in front of the sign [m] Result Ninety nine advertising signs have been surveyed, including 33 internally lighted signs, 26 texts/patterns, 22 text display panels, and 18 full color screens. The results and analysis of the field research are as follows: Fig. 1 The distribution of measuring points by the length-to-width proportion and dimension of signs Energy Consumption of advertising signs. signs are getting more and more popular in recent years while the internally lighted signs are still the most traditionally used sign type in Taiwan. Table 3 shows the energy consumption of advertising signs. The luminous efficiency of light source is higher than that of fluorescent light, however, advertising signs relied on dense dot matrix to transmit message, the power consumption per square meter for text display panels and full color screens are 200 and 350[W/m 2 ], much higher than 150[W/m 2 ] of traditional internally lighted signs. On the other hand, to maintain its display function during the daytime, signs would have to keep themselves operated, with the required operation time 2.5 times more than the internally lighted signs. The energy consumption per day from a sign in average size would be gained if power consumption per square meter multiples by operating time per day and the average sign area. Therefore, when it comes to energy consumption per day from a sign in average size, text display panels, due to its small average sign area, is slightly lower than traditional internally lighted signs. As for full color screens, since the covered area and the average power consumption per square meter are huge, and since they lack dimmer to reduce the brightness at night, their energy consumption is 12 times than traditional internally lighted signs. That reveals that full color screens result in not only light pollution but serious energy waste. Table 3 Energy Consumption of Advertising Signs Comparison Internally Lighted Signs Text Display Panels Full Color Screens Popular Source of Light fluorescent light Power Consumption Max. 400 Max. 900 per square Meter [W/m ] Avg. 200 Avg. 350 Operating Time per Day [hr] 18:00-24:00 9:00-24:00 9:00-24:00 6 hr 15 hr 15 hr Average Sign Area [m 2 ] Energy Consumption per Day from a Sign in Average Size [Wh/day]

4 2982 Frontiers of Manufacturing and Design Science II Luminance of Advertising Signs. The samples in this research are evenly collected from signs in residential and commercial districts. The average luminance by sign type is shown in Fig. 2. As the statistical result shows, there is no remarkable difference between samples from residential and commercial district. Several high-luminance signs are even located at low-density residential district, and seriously affect the living quality at night and endanger the health of the inhabitants. The average luminance of texts/patterns, text display panels, and full color screens is 720, 814, and 1085[cd/m 2 ], respectively. The last two exceeds the limit of 800[cd/m 2 ] regulated by CIE for residential district, and are approximately two to four times higher than traditional internally lighted signs. Moreover, there are respectively 19%, 32%, and 44% these three types of signs whose luminance exceed the limit of 1000[cd/m 2 ] by CIE for commercial district. These signs produce dramatically more light pollution than traditional internally lighted ones. Furthermore, there is even a full color screen whose luminance is as high as 4045[cd/m 2 ], four times higher than the limit of CIE for E4 zone. Light Trespass of Advertising Signs. Vertical illuminance is the standard used by CIE to estimate the level of light trespass. The standard helps Fig. 3 Vertical illuminance on facade facing the signs us to testify about the impact that advertising signs with different luminance, size, and road width have on actual conditions. Therefore, vertical illuminance on facade facing the signs is adopted to analyze whether the sign luminance is appropriate or not. The related statistical result is shown in Fig. 3. texts/patterns and text display panels produce less obtrusive light because the sign area is small. On the contrary, the average vertical illuminance of full color screens is 13.2[lux], which exceeds the limit of CIE for residential district before curfew by approximately 30%. However, because of its message display characteristics, most signs in Taiwan operate around the clock even after midnight. After curfew the average vertical illuminance of the research samples in residential and commercial district is 10.9 and 15.5[lux] respectively, 5.5 and 3 times higher than the after-curfew limit of CIE. Consequently, to improve the condition of light trespass, the luminance of full color screens should be massively reduced. Further, excessive brightness, an indicator of unnecessary energy consumption, should be under control as well. Energy Saving Strategies for Advertising Signs. Because the luminous efficiency of would increase while the current decreases [4], the excessive luminance of signs may be lowered down to the reasonable value by dimmer to save energy. Therefore, based on the afore-mentioned luminance [cd/m 2 ] Vertical Illuminance [lux] Internally Lighted Signs Fig. 2 Average Luminance by Sign Types 4.6 Internally Lighted Signs 720 Texts or Patterns 3.6 Texts or Patterns 814 Display Panels 1.3 Display Panels 1085 Full Color Screens Residential district Commercial district Total Percentage of Signs whose luminance exceed the limit of CIE for E3 Zone Percentage of Signs whose luminance exceed the limit of CIE for E4 Zone 6% 27% 41% 67% 6% 19% 32% 44% 13.2 Full Color Screens Residential district Commercial district Total

5 Applied Mechanics and Materials Vols analysis, this research proposes some reasonable recommendations of luminance in Table 4 for dimming signs at night. As most of the mixed residential and commercial activities take place at road width of 20 meters in Taiwan, the value of luminance limit for the signs in different size could be calculated by Eq 1, which is based on the assumed value of illuminance value, defined by CIE for each district and time period, and road width of 20 meters. If the calculated value is smaller than the luminance limit of CIE, the calculated value would be adopted, whereas the limit of CIE would be adopted. However, if the calculated value is lower than 200[cd/m 2 ], it would be better to close or uninstall the sign since it is dimmer than the surrounding general signs, and thus lose its advertising effect. For example, the signs with the size of 8 sq. meters in residential district are recommended to be closed after curfew and those with size greater than 16 sq. meters should be not allowed in residential districts. Finally, advertising signs must install a dimmer to adjust the luminance of the sign to be lower than the recommendations mentioned above for saving energy and better nighttime environmental quality. Table 4 Luminance Recommendations for Advertising Signs Luminance Recommendations [cd/m 2 ] Note: E3a:Residential district after curfew (23:00-6:00) E4a:Commercial district after curfew (23:00-6:00) Sign Area [m 2 ] E3a must be closed not allowed to be installed E3b not allowed to be installed E4a must be closed E4b E3b: Residential district before curfew (18:00-23:00) E4b: Commercial district before curfew (18:00-23:00) Conclusions This research aims to improve the energy saving efficiency of advertising signs and avoid the light pollution by focusing on advertising signs at residential and commercial districts. The research results are listed below: 1. signs would lose the advertising function if being closed. To maintain its daytime legibility, advertising signs have to illuminate and thus result in dramatic increase of energy consumption. The energy consumption per day of a full color screen in average size is 12 times more than traditional internally lighted signs. 2. signs are much higher than traditional internally lighted signs in the percentage of excessive brightness and average luminance value. The average luminance of texts/patterns, text display panels, and full color screens is 720, 814, and 1085[cd/m 2 ] respectively. 3. texts/patterns and text display panels produce less obtrusive light because the area coverage is small. On the contrary, the average vertical illuminance of full color screens is 13.2[lux], which exceeds the limit of CIE for residential district by approximately 30%.The average vertical illuminance of the research samples in residential and commercial district is 10.9 and 15.5[lux] respectively, 5.5 and 3 times higher than the after-curfew limit of CIE. The fact shows that energy waste and light pollution of full color screens is a serious problem. 4. Based on the research result, some reasonable recommendations of luminance by district, time, and sign area are listed in Table 4 for dimming signs at nighttime. 5. advertising signs must install a dimmer to adjust the luminance of the sign and suit the recommendations of luminance mentioned above to maintain reasonable luminance at night and reduce unnecessary energy consumption.

6 2984 Frontiers of Manufacturing and Design Science II Acknowledgements The authors would like to thank the Bureau of Energy, Ministry of Economic Affairs of Taiwan, R.O.C. for the partial financial support under Contract No. 99-D and the Lighting Research Center, NCKU for the assistance of device characterization. References [1] Information on [2] Ding-Chin Chou, A Study on Light Pollution in Residential for Night Lighting in Taipei as Example, The Illuminating Engineering Society of Taiwan, Vol (2000), p [3] CIE, Guide on the Limitation of the Effects of Obtrusive Light from Outdoor Lighting Installations (CIE, Vienna, 2003), p. 11 [4] N. Narendran, Y. Gu, J. P. Freyssinier-Nova, and Y. Zhu, Extracting Phosphor-scattered Photons to Improve White Efficiency, Physica Status Solidi (a), Vol (2005), p. 60

Simulation and Analysis of Light Trespass of Advertising Signs on the Shophouse in Taiwan

Simulation and Analysis of Light Trespass of Advertising Signs on the Shophouse in Taiwan Chen-Ying Ho Department of Architecture, National Cheng Kung University, Tainan City, Taiwan gazehochen@gmail.com