Solid state lighting : energy efficiency and lighting quality

Pao Yue-kong Library Electronic Theses Database

Solid state lighting : energy efficiency and lighting quality


Author: Cho, Ka-ming
Title: Solid state lighting : energy efficiency and lighting quality
Degree: M.Eng.
Year: 2011
Subject: Light emitting diodes -- Evaluation.
Light emitting diodes -- Energy consumption.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: xii, 108 leaves : ill. (chiefly col.) ; 30 cm.
Language: English
Abstract: Solid state lighting (SSL), which is referred as Light-emitting-diodes (LEDs), is a new and rapidly changing lighting technology and has been become an attractive choice to provide general illumination. Despite a considerable amount of research for the development of white LEDs for general illumination, the comprehensive investigations for commercial LED products are insufficient to compare practical performance with traditional light sources. This dissertation aims to compare the energy usage, the lumen maintenance and lighting quality between LED and traditional light sources in order to investigate the practical performance of LEDs for spotlight. This dissertation contains three main experiments in order to investigate following aspects: energy efficiency, thermal effect and color quality. Tungsten halogen lamps and compact fluorescent lamps (CFLs) regarded as the traditional light sources were examined to provide the comparisons with LEDs. The lumen maintenance test was used to analyze the performance of LEDs over time in following aspects: lumen maintenance, luminous efficacy and financial benefit. For thermal effect, LEDs were examined inside a temperature controlled chamber so as to study the relationship between an ambient temperature and total luminous flux. To investigate the visual performance for LED, a lighting preference survey for display inside cabinet illuminated by different light sources was conducted. In the lumen maintenance test, the result indicates that the total luminous flux and luminous efficacy of LEDs maintained a steady and high value over 4000 hours. Furthermore, the lumen maintenance of CFLs declined significantly below an acceptable state, and halogen lamps achieved its expected lifetime with the lowest efficacy and stable total light output about 80%~90% of initial state. With the result of thermal effect test, the higher ambient temperate could significantly decrease the total luminous flux and efficiency of LEDs. According to the color preference survey, LEDs could achieve 40% higher rating than CFLs and slight higher rating compared to halogen lamp which was regard as the baseline of visual performance for spotlight. Based on the results of this dissertation, the LED technology for spotlight is able to directly replace the tradition light sources in order to achieve better energy usage and color performance. Additionally, the proper installation can ensure that LEDs could perform at the optimal level. LED can enhance the flexibility of spotlight since it can provide a wide range of correlated color temperature.

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