Indoor lighting is facing a massive retrofit to LED lighting. Research is needed to assess whether LED-based lighting can promote energy efficiency, boost visual comfort and support biological functions. This field study considered the lighting of four identical classrooms in an upper secondary school in Helsingborg, Sweden. Two classrooms were fitted with state-of-the-art ceiling pendants containing T5 fluorescent tubes and that had a direct/indirect light distribution (the control rooms). The other two classrooms were fitted with an experimental LED indirect lighting system (the experimental rooms). In the classrooms, 72 students aged 17–18 years performed their usual educational activities over a whole academic year. The light environment, electricity consumption, and students’ mood, light perception and saliva cortisol concentration were monitored. The two lighting systems produced only marginal differences. Overall, the experimental rooms were slightly preferred but achieved only small energy savings due to high parasitic losses.
The use of light emitting diodes (LEDs) in outdoor lighting has energy-saving potential, but users' responses to this light source are largely unknown. An intervention study in two residential areas compared conventional lighting installations (high pressure sodium in Area 1 and high pressure mercury in Area 2) to a retrofitted LED-alternative regarding residents' perceptions of quality of light, visual accessibility and danger. Moreover, energy use was calculated. Residents' (N ¼ 60) visual accessibility improved and perceived danger remained low in both areas after retrofitting. In Area 2 the perceived quality of light increased, whereas in Area 1 the results were mixed. The retrofitted application reduced energy use by 41-76% and might be a feasible alternative to conventional outdoor lighting in relatively safe areas.
Ambient light is taken more into account in today's lighting design as it has a major impact on human well-being as well as reduction of glare. LED lighting provides new opportunities to design more efficient lighting systems in terms of improved color rendering and possibilities to vary the color temperature in order to mimic daylight.Today there is a trend to use dynamic lighting in working environments to set the circadian rhythm by varying the CCT over the day by using higher colour temperatures and illuminance levels in the morning and lowering the values in the afternoon toward nigh t. This study investigated preferred color temperatures within an ordinary workplace area using various light levels and different ratios between task area and the ambient light in a laboratory environment. Furthermore we also compared different age group s and gender in order to examine if there were any such differences in preferences.
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