Papers by Keyword: Illuminance

Abstract: Balancing thermal comfort and energy efficiency in buildings remains a key challenge. While HVAC systems regulate temperature directly, recent studies suggest that visual factors—such as horizontal illuminance and correlated color temperature (CCT)—can influence perceived thermal comfort through psychological mechanisms. This study examined how these visual factors affect thermal sensation and comfort in cooling environments (26–30°C). A controlled climate chamber experiment was conducted with 54 healthy female participants under varying air temperatures, illuminance levels (100–2900 lx), and CCTs (2800–5200 K). Mean skin temperature increased with air temperature but remained unaffected by variations in illuminance or CCT, indicating stable physiological responses to visual conditions. However, higher illuminance and CCT levels led to enhanced sensations of coolness, particularly at 30°C. Visual comfort also improved slightly with increasing illuminance, while CCT effects on comfort were modest and dependent on air temperature. These findings suggest that adjusting the visual environment can enhance thermal comfort without changing actual temperatures, supporting higher cooling setpoints (around 28°C) and contributing to energy-efficient building design.

Abstract: The majority of energy consumption in buildings is attributed to air conditioning and lighting systems. To address environmental concerns and reduce energy consumption, minimizing the energy usage associated with these systems is imperative. This study investigates the impact of LED lighting's illuminance and correlated color temperature changes on psychological evaluations in indoor settings. The research aims to contribute to sustainable building design by enhancing energy efficiency through lighting design. Furthermore, it aims to validate the Kruithof curve in LED lighting. The experiment, conducted in the summer of 2023, involved 17 female students experiencing various lighting conditions in a controlled environment. Illuminance levels ranged from 100 to 3000 lx, and color temperatures ranged from 2800 to 5200 K. Using a 7-point impression evaluation (SD method) with 20 pairs of adjectives, three factors ("Comfort," "Cleanliness," "Dynamism") were identified to explain variations in evaluations. A strong positive correlation was found between "Comfort" and color temperature. Comparison with Kruithof's experiment revealed different trends, with "Comfort" scores being positive at specific color temperatures above a certain illuminance level.

Abstract: In this study, the color difference thresholds of the human eye for textiles in a wide range of colors under high-illuminance conditions were examined. As the high-illuminance conditions, 2856 K-2000 lux and 6504 K-2000 lux, which are in the range of illumination conditions used in spaces that highlight products such as show windows, were used. It was observed that people cannot generally perceive color differences in textiles smaller than 4.29 ΔE*_ab. Also, the color difference threshold varied depending on the color center and lightness of the textiles observed. Color differences in red and blue colored textiles were easier to be perceived than other colored textiles, while those in yellow colored textiles were the hardest to be perceived. It was also found that people are generally better able to discriminate colors between dark textiles than between light textiles. Meanwhile, the correlated color temperature of the illuminant, that is, whether it was a warm-white (2856 K) illuminant or a cool-white (6504 K) illuminant, did not significantly affect people’s perception of color differences in textiles under high illuminance conditions.

Abstract: A lighting audit is an investigational process that measures conditions against standards to determine any lighting improvement measures. The objective of this study is to conduct a lighting audit to evaluate the level of existing lighting in the work environment of the academic faculty building. The lighting audit for the faculty buildings consists of a walk-through audit, lighting desktop work, field data measurement, and lighting analysis. The illuminance level cross-checks with the MS 1525:2019 and the lighting guideline from the Department of Safety and Health Malaysia. The illuminance analysis finding denotes most areas have violated the standards and are in overlit status. Few lighting conservation measures were proposed and prioritized the LED lighting installation. Economic analysis for retrofitting of LED lighting generates energy saving at 30%, a return on investment of two months, and about 6.60-tonne CO₂ emission reduction annually. The LED lighting installation shows attractive investment and has good potential at higher luminous efficacy around 40-256 Lm/Watt for the respective areas.

Abstract: To compute energy demand based on the reference years hourly averages of external variables are often generated in the smooth form. On the other hand, daylight should be evaluated in a shorter interval because human eyes perceive light in the moment of its occurrence. This study shows alternative to the description of annual daylight conditions based on statistic characteristics mean and median to create Daylight Standard Reference Year for Bratislava. Both methods are presented as contribution to the development of daylighting engineering. Authors are interested in lighting engineering to ensure satisfactory luminous environment at workplaces and in buildings for housing and recreation. Good daylighting in interiors is also related to the reduction of electricity consumption for lighting. This paper presents method for generation of daylight standard reference year DSRY based on one minute data measured at CIE IDMP stations. This reference year can be applied for evaluation of daylighting in the specific locality.

Abstract: Building performance simulation is traditionally used to support the building design process. However, it can also be used during building operation phase by providing relevant data to building automation systems. We refer to monitoring and metering data generated by computational simulation (virtual) models as data from virtual sensors. Virtual sensors, if reliably and effectively incorporated, can expand the reach of real sensors. A continuous supply of virtual sensor data can support near real-time representation of both primary environmental variables (e.g., air temperature, relative humidity) as well as complex performance indicators (e.g., thermal comfort indices, visual glare). Such information, especially in large multi-zone buildings, would be otherwise expensive to obtain from real sensors due to high capital costs of the sensors, their installation, networking, and maintenance. Virtual sensors can increase the resolution of sensory information, as they imply little monetary expenditures and are not limited in view of numbers and location.Conventional building energy simulation uses a model of the building and creates boundary conditions using historic weather data and predefined schedules for lighting and equipment load. This method is suitable for evaluation of building designs but not suitable for monitoring and control processes during building operation phase, as such processes usually require actual real-time information regarding boundary conditions. Thus, capability to automatically update simulation model's boundary conditions in real-time using monitored data is required. Toward this end, a supervisory software application is developed, in Java programming language, to implement and illustrate the concept of virtual sensors using Radiance simulation program. This application creates virtual illuminance sensors in Radiance model and then automates the process of regularly updating simulation model's external and internal boundary conditions (solar irradiance, state of electrical lighting elements) by using real-time monitored data from on-site weather station and building management system (BMS). As a result, the simulation kernel can continuously generate virtual sensor readings that can be utilized by building monitoring and/or control systems. This paper discusses the general architecture of the application, to further illustrate the concept of virtual sensors. Moreover, it discusses the accuracy of virtual illuminance sensors by comparing their output with monitored illuminance data in realistic test scenarios.

Abstract: This paper deals with influence of surface shape on light absorption. The study was performed on polyvinylchloride samples with different grooves. It was investigated the influence of shape, width, depth and number of grooves on light absorption. The investigated material samples were produced on CNC milling machine. Experimental measurements of light absorbance were performed under diffuse daylight on the basis of illuminance ratio. Different factors, that have influence on light absorption, are evaluated in the conclusion of this work. It was found that the lowest light absorbance was obtained in case of the smooth polyvinylchloride sample. The material machining causes multiple reflections of light from groove surfaces. For this reason the light absorbance of the groove surfaces is higher compared to the smooth material sample.

Abstract: In order to investigate the influence of the light source with different illuminance and color temperature on the observers’ visual performance, five kinds of light sources were selected, named LED1, LED2, LED3, LED4 and Fluorescent, which have different illuminance or color temperature. 3 series of visual experiments, such as the ‘find out’ experiment, compared experiment, dose experiment were designed.13 observers were organized to carry out the experiment in the given time in turn. The reading rate, accuracy , index of mental capacity (IMC) and visual comfortable level score were analyzed, the results indicated that the light source with the lower color temperature and medium illuminance has the best visual performance and comfortable visual feel.

Abstract: The artificial lighting level and visual comfort of drivers for a high-speed train cab are evaluated by using computer simulation technology. The simulation model is established first, and then some lighting quality indexes, such as illuminance, illuminance uniformity and glare, are analyzed based on related design standards. Considering the effects of environmental lighting on drivers physiology and psychology, the analysis on environmental psychology for driver of the cab are conducted also. The evaluation method proposed in the paper is significant for improving artificial lighting design of high-speed train cab.

Abstract: This paper deals with the problem of light pollution and its potential impact on human body. Loss of darkness during the night has a negative effect on the environment, animals, plants and humans. Concerning humans, the light during the night can lead to desynchronization of circadian rhythms with subsequent lower production of sleeping hormone called melatonin. In addition to the negative impact on organisms, there is also economical effect of wastage of lighting during the night. Pollution caused by the occurrence of light during the night is relatively new term, which has been perceived very roughly so far. That is probably the reason, why Slovak legislation deals with this problem very roughly. Some limitation levels of illuminance of billboards were stated, but the legislation doesn ́t deal with the effect of the occurrence of higly influential light during the night on people at their homes.