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Lighting makes up 17% of electrical loads and the largest energy end use in commercial buildings. Linear fixtures are among the largest opportunities for energy efficiency improvement, given their long operating hours. With continued, rapid light-emitting diode (LED) development and more LED replacement products on the market, lighting replacement decisions become more complex and warrant re-examination. With a goal to inform building managers and other decision-makers with practical guidance on lighting replacement, this study is a life cycle cost (LCC) analysis that compares the cost–benefit of six replacement options (one fluorescent and five LED) for a 0.61 m by 1.22 m (2 ft by 4 ft) T8 recessed troffer based on data for 168 lighting products from an online vendor. Results show that direct wire (i.e. unballasted) LED retrofits are the least-cost option to replacing fluorescent lamps in terms of normalized LCC. Plug-and-play lamps suffer from a lock-in with ballasts, but their ease of installation can help spur LED adoption. In cases where an existing ballast is still usable, hybrid LED retrofits provide the least upfront cost option by deferring the cost of rewiring. LED luminaires can offer improved aesthetics and reliability; however, they have high upfront cost. Among them, luminaires with replaceable lamps offer lower cost than those without. [ABSTRACT FROM AUTHOR]

A hybrid concentrator photovoltaics (CPV) module that combines the production of electricity and transports sunlight is proposed as a means to reduce the energy needs of buildings by two complementary solar energy approaches. Both concepts share the need for a solar tracker and an infrastructure to concentrate the sunlight which allows a reduction in costs of the proposed system. The CPV part is a well-known technology to produce electricity that serves as a host for the light subpart that transports sunlight through optical fibres. Measurements of a proof-of-concept show that in nominal conditions the lighting subpart is more efficient in the task of transporting sunlight than converting sunlight to electricity and then to light again. The efficiency threshold is a direct function of the fibre material and distance transported and the generated light is very similar to the solar light in terms of spectral content. Based on PMMA optical fibres and conventional CPV technology, the hybrid module converts 28.7% of the sunlight into electricity. Regarding the light transported by the optical fibres they slightly shift sunlight to bluish white but the quality of light is still comparable to a typical fluorescent lamp used in offices. [ABSTRACT FROM AUTHOR]

With the great efforts made by their scientists and researchers, various Chinese lighting technologies, such as the silicon-based yellow LED, mini/micro-LED, OLED and laser diode, have also reached the frontier. The lighting industry in China can be traced back to the 1920s. In 1921, Xiyuan Hu made the first incandescent lamp in China and in 1923, the Shanghai Yaming Bulb Factory started to manufacture incandescent lamps. [Extracted from the article]

This paper describes two experiments that were designed to investigate the museum lighting environment in terms of correlated colour temperature and illuminance. The results are reported as visual perceptions and perception zone maps. Experiment 1 was conducted to investigate the impact of the illumination conditions on visual perceptions in a light cabinet. Experiment 2 was the same as Experiment 1, except that it was performed in a museum. The rating scores were combined to establish the perception zone maps on a correlated colour temperature–illuminance plane. Furthermore, two emotional response models, named the visibility model and the warmth model, suitable for museum indoor lighting in small- and large-scale spaces were established. The analytical results indicated that the pleasant zone found in this study partially agrees with Kruithof's rule. [ABSTRACT FROM AUTHOR]

The CIE General Colour Rendering Index is currently the criterion used to describe and measure the colour-rendering properties of light sources. But over the past years, there has been increasing evidence of its limitations particularly its ability to predict the perceived colour quality of light sources and especially some LEDs. In this paper, several aspects of perceived colour quality are investigated using a side-by-side paired comparison method, and the following criteria: naturalness of fruits and vegetables, colourfulness of the Macbeth Color Checker chart, visual appreciation (attractiveness/ preference) and colour difference estimations for both visual scenes. Forty-five observers with normal colour vision evaluated nine light sources at 3000 K, and 36 observers evaluated eight light sources at 4000 K. Our results indicate that perceived colour differences are better dealt by the CIECAM02 Uniform Colour Space. Naturalness is better described by fidelity indices even if they did not give perfect predictions for all differences between LED light sources. Colourfulness is well described by gamut-based indices and attractiveness was found to correlate best with gamut-based indices but also with a preference index or a memory index calculated without blue and purple hues. A very low correlation was found between appreciation and naturalness indicating that colour quality needs more than one metric to describe subjective aspects. [ABSTRACT FROM AUTHOR]

In order to determine user acceptance for light-emitting diode (LED) office lighting, a full-scale experiment was conducted in two mock-up office rooms with different light spectra at two different illuminances. Six LED spectra and two fluorescent lamp spectra were used for the study. There were four spectra (three LED spectra and one fluorescent lamp spectrum) at a correlated colour temperature (CCT) of 4000 K and four spectra (three LED spectra and one fluorescent lamp spectrum) at a CCT of 6500 K. Forty observers evaluated the lighting environments under different spectra and rated the lighting environments sitting at a working desk and at a meeting table. The observers preferred the task illuminance of 500 lux to 300 lux and the CCT of 4000 K to 6500 K. The observers preferred the spectral power distributions (SPDs) under which they found the lighting environment to look brighter and more spacious. The observers’ preferences showed that spatial brightness was affected by illuminances and SPDs. The lighting with a SPD having higher values of a reference-based metric (CQS Colour Preference Scale) and an area-based metric (CQS Gamut Area Scale or Gamut Area Index) was preferred most at a CCT of 4000 K. It was also found that the lighting with the fluorescent lamp was least preferred among the other SPDs at the CCT of 4000 K. The observers preferred both the simple and complex SPDs over fluorescent lamps at 4000 K in the office environment. It would be a good option to develop simple LED SPDs while maintaining the criteria of good lighting for an office environment. [ABSTRACT FROM AUTHOR]

Two mock-up office rooms, one with a spectrally tuneable LED lighting system and the other with a fluorescent lamp (FL) lighting system were built for user acceptance studies for office lighting. One room was illuminated with six LED luminaires and the other with six FL luminaires. Each LED luminaire has 480 LEDs (20 different LED types and 24 of each type). Each FL luminaire has eight fluorescent lamps, four with a correlated colour temperature of 4000 K and four of 6500 K. User acceptance studies in the office environments were conducted with 40 observers, each observer having 16 sessions (six LED spectral power distributions (SPDs) + two FL SPDs and two illuminances (500 lux and 300 lux)). The observers performed office-related tasks while being totally immersed in one of these lighting conditions. The objective of this study was to verify previous results obtained in small-scale booth experiments and to further study peoples’ preferences for LED office lighting. The small-scale experiments showed that LEDs with a higher value of reference-based colour metrics (such as colour quality scale (CQS) colour preference scale) and with a higher value of area-based or volume-based metrics (such as CQS gamut area scale or gamut area index) were preferred by the observers. The office room study of the present work validated the findings of the earlier experiments but now in an office lighting environment. Furthermore, the observers preferred 4000 K to 6500 K at a light level of 500 lux and the light level of 500 lux over 300 lux. It was also found that the simplest LED SPD with three peaks has similar colour quality characteristics to complex LED SPDs with several peaks. [ABSTRACT FROM AUTHOR]

Environmental impacts of light sources and control gears have been analysed in several life cycle assessments (LCAs). In contrast, this paper analyses the environmental impacts of an entire fluorescent lamp/luminaire combination. The environmental impacts of a fluorescent lamp luminaire with two T5 lamps and an electronic ballast are analysed in a variety of potential environmental impacts. The results show that the energy consumption during use dominates the total environmental impacts by 93% on the average, while manufacturing accounts for 7% and end-of-life less than 1%. The importance of energy consumption is dependent of the used energy source. Compared to a previous LCA of fluorescent lamp luminaire, the division of the results into life cycle stages is similar but there are differences in the numerical results. [ABSTRACT FROM PUBLISHER]

In order to extend the length of the coaxial cable connection between an electrodeless fluorescent lamp and the associated electronic ballast, a new structure for electrodeless lamp systems is proposed in this paper. Impedance matching networks in the structure are analyzed and designed based on the transmission characteristics of coaxial cable. Efficient topologies and formulae for the matching networks are put forward. Experimental results for a 2.65 MHz electrodeless lamp system with up to 25 m of coaxial cable which validate the structure are presented. [ABSTRACT FROM PUBLISHER]

Limited natural energy resources compel humankind to search for efficient utilization of energy, and thus increasing number of fluorescent lamps are adopted for lighting systems. However, previous study showed that there exists a tradeoff between energy saving and lifespan for fluorescent lamps. Consequently, it becomes an important topic on how to design an efficient and effective automatic control algorithm in illuminating engineering. This problem has been traditionally studied by conducting surveys and experiments, which are unavoidably costly and rather time-consuming. This paper presents a novel application of teletraffic engineering modelling techniques in studying automatic lighting control systems. A queuing model is proposed to study typical lighting systems and a simple closed-loop algorithm is illustrated to effectively adapt the system control parameters. Through computer simulation, it is shown that the proposed method provides an alternative way of studying lighting systems in a cost-effective manner, while providing adequate accuracy. [ABSTRACT FROM PUBLISHER]

A study was carried out in light booths to investigate user preference for different light spectra. Twenty-one LED spectra and three fluorescent lamps, all at three different correlated colour temperatures were used for the study. Sixty observers evaluated the lit scenes under different spectra for naturalness of selected objects, colourfulness of a Macbeth Colour Checker Chart, and the visual conditions of the lighting booths. The observers preferred the spectral power distributions (SPD) under which the chroma and colourfulness values of the object colours were higher. The CIE Colour Rendering Index was not a good indicator of the observers’ preference for the LED SPDs. It seemed that light sources with a higher CQS Gamut Area Scale and CQS Colour Preference Scale values were preferred by the observers as far as LED spectra were concerned. However, the CQS Gamut Area Scale calculated with a new version of the software (version 9.2) and the Gamut Area Index were suitable as indicators of observers’ preference for both the LEDs and the fluorescent lamp spectra. Because chroma and colourfulness values of object colours influence the observers’ preference, they should be considered as important factors for the selection of a colour preference index for light sources. [ABSTRACT FROM PUBLISHER]

To understand people's judgement of the naturalness of object colours and preference for the lit environment, lighting booth experiments were conducted. Seven different LED spectral power distributions, all at correlated colour temperatures of 2700 K, 4000 K and 6500 K, were simulated for high CIE colour rendering index (Ra), high colour quality scale (CQS) colour preference scale (Qp) keeping Ra = 80, high feeling of contrast index (FCI) keeping Ra = 80, high CQS relative gamut area scale (Qg) keeping Ra = 80, low FCI keeping Ra = 80, low Qp keeping Ra = 80, and for a mimic of a fluorescent lamp (FL) in terms of the closest possible value of the Ra, FCI and Qp to the reference FL. Other metrics such as the gamut area index (GAI), memory CRI, and nCRI were also considered in the analysis. Sixty observers evaluated 24 lighting situations. This paper deals with a comparison evaluation, where LED lighting was compared to FL lighting. It was found that Ra does not explain the subjective naturalness of objects and the subjective preference of the lit environment for the different light sources. The results also indicate that people's judgement of naturalness and overall preference were explained better when a reference-based metric (such as Qp) and an area or volume-based metric (such as Qg or GAI) were both considered while maintaining the light source chromaticity difference (Duv) value within the limit ± 0.0054. [ABSTRACT FROM PUBLISHER]

Laboratory tests were carried out to investigate lighting for pedestrians at mesopic levels under lamps of different spectral power distribution. This paper reports an evaluation of lamp spectrum effects on visual acuity, using Landolt ring charts of high and low luminance contrast, and forced choice judgements of the preferred appearance of human hands, a colour array and an illuminated space. These were carried out alongside judgements of brightness reported in a previous paper. Five types of lamp were used, including standard high pressure sodium, two metal halide and a fluorescent lamp of broader spectral distribution and a two-colour solid state device (LED). It was found that lamp spectrum affected judgements of preferred appearance, with the high pressure sodium and LED lamps being considered poor compared with the two metal halide lamps; these results correlated better with the CIE General Colour Rendering Index than other metrics of lamp spectral characteristics. It was also found that acuity was affected by lamp spectral power distribution, with the high pressure sodium (HPS) lamp enabling more Landolt rings to be correctly read than lamps of higher S/P ratio. [ABSTRACT FROM AUTHOR]

This paper proposes a method for predicting fluorescent lamp lifetimes based on a minimum number of accelerated life tests. This prediction allows the life of the lamp in continuous operation to be estimated without having to know the nominal lifetime. This paper evaluates the possibility of making this prediction based on two accelerated tests, and finds that this is not generally to be recommended. It also evaluates the advisability of making the prediction based on three accelerated tests and fitting the results by a non-analytical iterative method. We conclude that under certain conditions, this method makes reasonable life predictions for fluorescent lamps associated with specific ballasts. [ABSTRACT FROM AUTHOR]

Based on experimental data published by others, this paper examines the veracity of an expression relating the lifetime of fluorescent lamps, with ballasts to factors that contribute to electrode degradation, using different on and off times in the durability tests. Further, the relationship between conventional and accelerated durability tests characterised by different fluorescent lamp continuous operation and off times are analysed, revealing that the accelerated tests are not always shorter. Finally, based on experimental measurements of the parameters that determine lamp lifetime, the effect of applying accelerated testing to a set of lamps that had previously been subjected to a conventional durability test is analysed. [ABSTRACT FROM AUTHOR]

This paper approaches lifetime prediction of fluorescent lamps in photovoltaic systems by means of an analytical model. This can assist in improving ballast design and extending the lifetime of fluorescent lamps. As a result of our work, the temporal integral of the glow current to starting and the lamp voltage during normal operation normalised to nominal voltage appear to be the two independent variables that describe the influence of startup and continuous operation on lamp lifetime with an acceptable degree of accuracy. The analytical expression found explains 92.4% of the variability in lifetime. Model agreement with original data and its range of application and limitations are also analysed. [ABSTRACT FROM AUTHOR]

Data on the exposure of the human eye to light are essential for investigation into the interaction of light with man. According to present knowledge, two different spectral sensitivities of the visible irradiance are relevant: (1) the spectral luminous efficiency function for vision and (2) the action spectrum for melatonin suppression, also used for other non-visual biological effects. We developed a device called LuxBlick to measure and record both quantities. It consists of two light sensors that are fixed on the wearer's head, and a control unit and data recording mini-computer worn in a bag around the waist. Real-time data are accessible to those wearing the device. Suitable to be worn in everyday life, the parts at the head are of low mass at the head and inconspicuous. [ABSTRACT FROM AUTHOR]

The colour rendering index was introduced at a time when a second generation of fluorescent lamps was being brought onto the market. Today a new generation of light sources based on LED technology is becoming available, so it is opportune to consider whether the colour rendering index is applicable to these relatively new sources. In the present work a series of visual colour rendering investigations are described and their correlation with the current method of calculating colour rendering index as well as with possible updates of the calculation method is evaluated. Visual experiments have shown that the CIE Test Method is not a good predictor of visual perception. A method based on calculating colour differences using the CIECAM02 colour appearance model provides better correlation between visual and calculated colour rendering values. [ABSTRACT FROM AUTHOR]

The near visual acuity (400 mm distance) of 27 children aged 10‐11 years old was measured by a licensed optometrist under two common fluorescent lamps of CCT 3600 K and 5500 K. Acuities were measured for three lighting conditions, either both lamps providing equal task luminance or a condition where the task and room luminance from the 5500 K lamps was set 50% lower. For the equal luminance condition, the results showed visual acuity was significantly better (P<0.001) under the higher CCT lamp with 24 of 27 children having better acuity. Paired t-tests comparing the lower luminance condition showed significantly less acuity for the 5500 K lamps at the lower luminance, but no significant difference between the 3600 K lamps at the higher luminance compared with the 5500 K lamps at the lower luminance. [ABSTRACT FROM AUTHOR]

This paper compares the different visual objectives that have been used in side-by-side matching experiments. In tests, two different fluorescent lamps were compared in juxtaposed booths by a series of observers. It was found that: (i) there was no significant difference in illuminance ratio when matching the booths according to six different visual objectives including equal brightness, equal clarity and equal pleasantness; and (ii) the matched condition was not predicted by illuminance based on V(λ). The data exhibited the error associated with the application of dimming previously noted by Fotios. [ABSTRACT FROM AUTHOR]

Screw-based dimmable compact fluorescent lamps (SD-CFLs) are promoted as alternatives to incandescent lamps. This paper investigates the performance of SD-CFLs over their dimming range--including luminous flux output, colorimetric quantities, and electrical characteristics--and compares these data against the performance of incandescent lamps. The performance of SD-CFLs differs from that of the incandescent lamps they are meant to replace in several important ways, including their colour appearance, colour rendering properties, and dimming range. These and other attributes that might inhibit the widespread application of current SD-CFLs are discussed. [ABSTRACT FROM AUTHOR]

The paper presents a comprehensive analysis dealing with the behaviour and economics of electronic compact fluorescent lamps. The economic analysis, based on the results of the test concerning the lifetime and the lamp lumen maintenance factor of electronic compact fluorescent lamps, and conducted using the cost-discount method, showed an obvious advantage for lamps of this type compared with incandescent ones. The strategic importance of the mass use of electronic compact fluorescent lamps, as well as serious power quality implications it can cause to the network, are explained in detail. Possible solutions of this problem are also presented. [ABSTRACT FROM AUTHOR]

The high frequency (HF) electronic ballast has been replacing the conventional magnetic ballast for operating fluorescent lamps. It has the advantage of low energy consumption, running the lamps free from stroboscopic effects, low noise production, being light weight and allowing the lamps to be dimmed. This study shows that for a cellular office at the perimeter of a building lit by a dimmable HF electronic ballast lighting, about 40% of the lighting energy could be saved under Hong Kong's daylight conditions. A saving of 40% at the perimeter amounts to an overall lighting energy saving of about 10% if the perimeter area is about one quarter of the total floor area. Lighting energy normally accounts for about 30% of the total energy consumption for office buildings. For a shallow plan office building, the amount of saving using a daylight linked system could be significant. [ABSTRACT FROM AUTHOR]

The author discusses the views of British Prime Minister Harold Macmillan regarding wind of change and its connection to the field of lighting. Topics discussed include the dramatic changes in lighting technology, the emergence of fluorescent lamps, and the increasing use of solid state lighting due to the enhancement of people's knowledge about visual system function.