Browsing by Subject "Street lighting"

Now showing 1 - 3 of 3

Open Access
Energy-saving quality road lighting with colloidal quantum dot nanophosphors
(Walter de Gruyter GmbH, 2014) Erdem, T.; Kelestemur, Y.; Soran-Erdem, Z.; Ji, Y.; Demir, Hilmi Volkan
Here the first photometric study of road-lighting white light-emitting diodes (WLEDs) integrated with semiconductor colloidal quantum dots (QDs) is reported enabling higher luminance than conventional light sources, specifically in mesopic vision regimes essential to street lighting. Investigating over 100 million designs uncovers that quality road-lighting QD-WLEDs, with a color quality scale and color rendering index ≥85, enables 13-35% higher mesopic luminance than the sources commonly used in street lighting. Furthermore, these QD-WLEDs were shown to be electrically more efficient than conventional sources with power conversion efficiencies ≥16-29%. Considering this fact, an experimental proof-of-concept QD-WLED was demonstrated, which is the first account of QD based color conversion custom designed for street lighting applications. The obtained white LED achieved the targeted mesopic luminance levels in accordance with the road lighting standards of the USA and the UK. These results indicate that road-lighting QD-WLEDs are strongly promising for energy-saving quality road lighting. © 2014 Science Wise Publishing & De Gruyter 2014.
Open Access
Lighting monuments: reflections on outdoor lighting and environmental appraisal
(Elsevier, 2006-06) Tural, M.; Yener, C.
For more than 10 years, highlighting urban pattern, revealing the artifacts in our surroundings, and providing relationships among the elements of cities, outdoor lighting practice gained more significance. The following study aims at suggesting the needs for monument lighting, taking it as an essential architectural and outdoor lighting issue, and focuses on aspects to be considered both in the approach and application phases by discussing some examples from Ankara, the capital of Turkey. In order to determine approaches in attaining an effective lighting scheme, a case study was conducted. The participants were shown a series of photographs of the Bilkent University Atatürk Monument and its model taken under daylight and artificial lighting conditions, and the differences and tendencies in their perceptional preferences were examined. The results implied that lighting the monument with down-lighting technique is more preferable compared to up-lighting. The findings also suggested that there is no significant perceptional difference on the figure when daylight condition (direction) is imitated using artificial lighting sources. In the analyses, it was also observed that the difference in the incident angle (45° and 60°) of light did not considerably change the perception of participants. © 2005 Elsevier Ltd. All rights reserved.
Open Access
Wavelength dependent color conversion of CdSe/ZnS core/shell nanocrystals for white LEDs
(IEEE, 2009) Nizamoğlu, Sedat; Demir, Hilmi Volkan
Nanocrystals (NCs) provide narrow emission spectrum that can be conveniently tuned using quantum size effect. This ability to adjust and control emission spectrum of NCs makes them strong candidates for use in white color conversion light emitting diodes. For example, they are possibly be used for solid state lighting applications including indoor lighting, architectural lighting and scotopic street lighting, where spectrally tuned color conversion is necessary. In device research CdSe/ZnS core/shell nanocrystals are the most commonly used ones because of their good electronic isolation coming from ZnS shells and the resulting high quantum efficiency (QE) (i.e., >50% in solution) [1]. However, when these nanocrystals are integrated into the solid film, e.g., for white light generation, their in-film QE undesirably drops (despite their high QE in solution). Hence, this adversely affects the overall efficiency of the integrating devices that incorporate these NCs [2]. There have been various studies to understand the in-film optical properties of CdSe/ZnS core/shell NCs [3-5]. However, their spectrally resolved in-film quantum efficiency (i.e., the ratio of the number of photons emitted by the nanocrystal film to the number of photons absorbed in the nanocrystal film) and their photon conversion efficiency (i.e., the ratio of the number of photons emitted by the nanocrystal film to the number of photons incident to the nanocrystal film) have not been investigated in these previous studies. © 2009 IEEE.