Simulation Study on Factors to be Considered for Each Type of Indoor Luminaires and Light Sources when Converting to LEDs

As high-efficiency lighting has become mainstream, conversion of lighting equipment is under way, starting with government agencies. Existing fluorescent luminaires are being converted with LED luminaires. The main method used for conversion is to remove the fluorescent lamp (case 1) and replace it to a tubular LED lamp, and convert the luminaire itself with a LED panel luminaire (case 2). However, focusing only on energy efficiency, the existing luminous environment are not considered, such as illuminance, illuminance uniformity, and UGR. Therefore, the optical characteristics were measured using the actual luminaire used in the conversion. Simulations were performed comparing the luminous environment and power consumption before/after conversion. Case 1 had advantages in power consumption and UGR over case 2, and the illuminance was slightly reduced, but it met the criteria. These results confirmed that the conversion of lighting devices at least ensured the existing luminous environment.

A case study of lighting retrofit to improve building energy efficiency and lighting quality by using luminaires with nano optical coating

Lighting retrofit is a common technique to reduce lighting energy use and to improve lighting quality. It is usually performed by replacing the lamps in the existing luminaires with more efficient lamps. Despite the high potential to enhance lighting performance by improving other parts of the luminaires such as reflectors, lighting retrofits usually keep their designs unchanged and focus on the change of the lamps. In this case study, an alternative lighting retrofit method - the replacement of reflectors using a nano optical coating - was tested in a typical office in Hong Kong. The case study used a luminaire with a highly reflective nano optical coating. The pre- and post-retrofit illuminance level, illuminance uniformity, glare and lighting energy use were measured. The results show that the use of the nano optical coating enables the reduction of light tubes in the office and thus the lighting energy consumption without lowering the lighting quality. The lighting retrofit enhances the illuminance uniformity in the office by 14.6% while keeping the illuminance level and discomfort glare within the satisfactory level. It also lowers the lighting energy use of the office by 37.5%.

The Importance of Light in Our Lives

The light that enters through our eyes is not only for vision. The human circadian system responds to light differently than the visual system. The timing of each biological function in mammals is directed by the main clock located in the Supraquiasmic Nucleus, which is regulated by light. However, until now, only the interaction of light with our visual system has been taken into account when choosing the parameters of indoor lighting sources, including those in the classroom. In the publications about school lighting, the first concern was the common parameters of indoor lighting such as horizontal workplane illuminance, illuminance uniformity, and avoiding reflections on different surfaces. In this chapter, the authors show publications about new findings on the effects of light on people, studies carried out in different countries aimed at improving classroom lighting, current regulations on lighting related to classroom lighting, and new parameters that are being considered, along with those already used for new and better lighting.

Optical design of LED high mast lamp based on TIR freeform lens for annular lighting

The traditional square spot of street lamp is not suitable for the lighting requirements of the annular road lighting. In this paper, a lens design method for producing annular spot of high mast lamp is proposed. The method mainly contains three optical surfaces, in which the inner surface collimates the energy of the centre part of the light source, the total internal reflection surface collimates the light with large angle and low energy and the outer surface refracts all the collimated light to realise the annular illumination distribution on the target surface. In this design, we can change the diameter of the lighting spot through the variation of the inclination angle of the outer surface from 14° to 19° and the diameter of the spot changes from 10.2 m to 12.3 m at the distance of 30 m. The lighting requirements of high mast lighting are realised based on the TIR lens array, in which the average illuminance is more than 20 lx, the illuminance uniformity is more than 0.7 and the light optical utilisation factor is more than 90%.

Ceiling and Wall Illumination, Utilance, and Power in Interior Lighting

The common use of electric lighting in interiors has led to the need to search for user- and environmentally-friendly solutions. In this research, the impact of the luminaires and room parameters on the selected parameters of general lighting in interiors was assessed. To achieve the objective of this work, a computer simulation and statistical analysis of results were conducted. The illuminance uniformity on work plane, ceiling and wall relative illuminances, utilance, and normalized power density of lighting installations for 432 situations were analyzed in detail. The scenarios were varied in terms of room size, reflectance, lighting class, luminaire downward luminous intensity distribution, and layout. The lighting class was a factor having the highest impact on ceiling and wall illumination, utilance, and power. It was also shown that the impact of lighting class on ceiling illumination, utilance and power, was different in interiors of various sizes. The impact of reflectances and luminaire layouts on the analyzed parameters was significantly lower. The results also demonstrated that the use of different lighting classes gave the possibility of reducing the power of general lighting in interiors at a level of 30% on average. Based on the results, a classification of energy efficiency in general lighting in interiors was also proposed. Understanding the correlations between the lighting system used and the effects achieved is helpful in obtaining comfortable and efficient lighting solutions in interiors.

Optical design of light guide prisms with surface roughness for automotive tail lights

This study presents the optical design of light guide prisms for automotive tail light applications to obtain the optimum luminous intensity and the illuminance uniformity. The design was achieved using optical design software, SPEOS. By considering the axial luminous intensity and legal requirements, the optimum prism angles of light guides were determined by simulations. After determining the prism angles, the effect of different surface roughness on the luminous intensity and the illuminance uniformity was investigated. The light guides designed by considering data from the simulation were manufactured as prototypes and their photometrical measurements were made. These measurements were compared to the simulation results. It was observed that simulation and prototype results are well in agreement with each other. Furthermore, it was found that as the surface roughness increases both the luminous intensity decreases and the illumination becomes more uniform.

A study of luminous environment with prism daylight redirecting fenestrations in classrooms

This study explored the classroom luminous environment with prism daylight redirecting fenestrations. The differences between the International Commission on Illumination standard sky and the Perez all-weather sky models were analysed. The study described the method of generating a valid bi-directional scattering distribution functions .xml data for the prism daylight redirecting fenestrations. A new evaluation metric, daylight evenness, was proposed to describe indoor illuminance dispersion. Radiance simulation results indicate that at various solar altitude angles, compared with conventional glazing, the micro-prism film and micro-prism with an added diffuse layer on clerestories can improve the space average illuminance levels 23.2% and 18.7% under the International Commission on Illumination sky, as well as 15.4% and 10.6% under the Perez sky, respectively. The analysis results indicate that prism daylight redirecting fenestrations clerestories can improve indoor illuminance uniformity and daylight evenness when the solar altitudes range from 23.8° to 75°. A method combined field questionnaire and high dynamic range image analysis were conducted for discomfort glare study. Adding a diffused layer to the prism film clerestory is expected to alleviate discomfort glare for east- and west-facing prism daylight redirecting fenestrations clerestory with the daylight glare probability reduction of 3.8% to 21.7% at various solar altitudes. The research results present promising advantages of applying prism daylight redirecting fenestrations at classroom clerestories to improve the daylight luminous environment.

Investigation of indoor environment comfort in large high-speed railway stations in Northern China

The indoor environment of high-speed railway stations is more complex than in traditional railway stations. This could lead to complex indoor environment problems. In this study, indoor environmental measurements and passenger satisfaction surveys were conducted in two high-speed railway stations in summer and winter, considering the indoor thermal, natural light, acoustic and air environment. The results indicate that the air temperatures in winter were far below comfort standards. The mean illuminance met the standard requirements in both stations. However, the illuminance uniformity was very low in the summer. The acoustic and air environments were satisfactory and have positive impacts on the overall environmental comfort of passengers. The evaluated acoustic environment indicated this has a worst effect on passengers’ comfort. The depth of the waiting halls affected the air environment. The subjective survey revealed the following: Females were more sensitive to the indoor environment than males in winter. Northerners were more satisfied with the environment than Southerners. Older passengers were slightly more tolerant to the environment. Passengers with a longer waiting time would have higher demands for a better indoor environment. Also, passengers were more tolerant in summer than in winter.