Daylighting environments within higher educational buildings play an important role in students’ vision health and learning efficiency. Effective daylighting predictors can help architects and ...designers to create pleasant daylighting environments. This field study investigates the performance of commonly applied daylighting predictors in Nanjing. Illuminance and luminance data are measured on site. A hundred and thirteen subjective responses to visual comfort and lighting impressions are collected through an online survey. A lighting impression model composed by the affection component, the stimulation component, and the distribution component is suggested. According to the data analysis, general daylighting predictors present comparable performance to customized daylighting predictors with regard to estimations of subjective assessments. The four general daylighting predictors, horizontal illuminance, vertical illuminance, mean luminance of an entire scene, and mean luminance of the horizontal 40° band, are recommended to effectively predict individual probability of reporting daylight sufficiency, desiring to adjust lighting levels, and reporting degrees of daylighting stimulations.
•A field study integrating visual comfort and lighting impression was conducted.•A lighting impression model consisted of three components was obtained.•Four daylighting predictors and their logistic regression models were proposed.
•Transmitting lens-walled compound parabolic concentrator (TLWCPC) as skylight.•The smart daylighting control potential of TLWCPC was analyzed and validated.•The effects of the orientation direction ...and inclination angle were analyzed.•The annual smart daylighting control performance in five cities was investigated.
Regulation of solar transmission through windows offers the potential to reduce energy consumption in buildings. Recently, the daylighting control characteristic of optical concentrators have drawn considerable research attentions owing to their variable transmittance in response to sun motion. In this research, we aim to propose and validate a novel way to smartly regulate the indoor daylighting environment while generating renewable electricity generation at the same time through the concentrating photovoltaic/Daylighting (TLWCPC-PV/D) skylight. This research particularly focuses on the evaluation of smart daylighting control (SDC) performance of it. The optical model of the TLWCPC-PV/D skylight was built with using ray-tracing simulation technique, which is also validated by experiment results. Because of the variable optical concentration process, the TLWCPC shows obvious SDC characteristic: when –32°＜θ＜32°, average daylighting efficiency is 11.15% while when −43°≤θ ≤ –32° and 32°≤θ ≤ 43°, average daylighting efficiency is 58.89%. Five cities with different latitudes are selected to perform the yearly daylighting control analysis. The comparative results indicated that orientation direction has an essential impact on SDC characteristic of the TLWCPC-PV/D skylight and the system in the North-South orientation shows excellent SDC ability i.e. it shows larger daylighting efficiency during the early morning and later afternoon periods while maintains lower daylighting efficiency during the noon period. Compared with other complex and expensive energy-saving glasses, the TLWCPC-PV/D skylight smartly adjusts the solar transmission through the optical concentration process according to sun motion and offers a new strategy of easy fabrication and multi-energy use that opens avenues for both static solar concentrator design and SDC mechanism in energy-saving buildings.
A conceptual new window/glazing technology called POLarizer-FENestration (POLFEN) is presented. In 1935, Edwin Land's pioneering work on polarizers successfully developed a sheet polarizer that was ...used in various applications. Subsequently, polarizers were employed in windows to modulate daylight and reduce associated glare. Early prototype windows were circular in shape so that the polarizing filter could be rotated to modulate the daylight. However, compared to rectangular-shaped windows that are ubiquitous, circular windows are rare in buildings. Therefore, a new window/glazing technology, discussed in this paper, was developed that utilizes a polarizing film in a conventional rectangular or square window, arranged in the form of strips or a checker-grid over the window panes to modulate daylighting levels and control glare. In this new research, a working prototype of the glazing technology is developed and demonstrated including simulations using the Radiance daylighting simulation software. In the current work, two types of measurements were taken: photographs of the indoor luminous environment and illumination levels (Lux) at selective points on the work-plane both in a physical prototype as well as in the simulation model under two sky conditions: CIE clear sky with sun, and overcast sky. The results indicate that the new glazing technology resulting from this concept can effectively modulate daylighting levels, minimized associated glare to an acceptable level while maintaining a view to the outdoor environment. The technology can be classified as Variable Transmission Glazing (VTG), similar to Electrochromic (EC) glazing since it also offers a dynamic modulation of solar optical properties (Tvis).
•POLFEN, a concept of a new glazing technology utilizing linear polarizers, can be successfully employed in conventional window shapes (i.e., square or rectangular) to quickly and effectively modulate daylight and its associated glare.•POLFEN glazing technology can be classified as Variable Transmission Glazing (VTG), similar to Electrochromic (EC), as it offers variable transmission properties.•POLFEN glazing technology offers quick modulation of daylight and associated glare through mechanical actuation.•POLFEN modulates daylight and preserves the view of the outdoors.
The present research analyzes enhanced classroom daylighting utilization. The enhanced classroom daylighting incorporates a shed roof with an additional ceiling window, where the window-to-wall ratio ...is 41% on the north face and 56% on the south face. First, daylight factor and daily lighting, heating, and cooling loads were analyzed. In comparison with a typical classroom, an energy-savings effect and maximized energy-savings effect occurred. The result shows that enhanced classroom daylighting is expected to achieve 27% energy savings using daylighting. In addition, compared with the typical model, the energy savings in the enhanced classroom daylighting utilization model could be 10 points higher and is expected to increase by a higher illuminance setpoint. In the last section, a sensitivity study was performed to analyze the relationship between the system operation and the energy consumption ratio. With different ranges and setpoints, the enhanced daylighting utilization model shows a varying tendency with respect to the energy consumption ratio.
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•Parameters other than the suggested ones do not improve the simulation results.•Increasing the ambient bounces to more than 8 does not affect the accuracy of results.•The effect of ...disabling ambient accuracy (-aa = 0) in Radiance is nominal.•±0.1 change in reflectance factors significantly affects the accuracy.•Decreasing ambient bounces to less than 6 creates biased results.
Most of the new studies in Radiance rely on industry-accepted values for setting Radiance parameters. Although Radiance is validated against the analytical test cases of CIE 171:2006, there is no scientific basis for these settings. Therefore, the aim of this study is to assess the effect of Radiance parameters and model-related components on the accuracy of simulation results in Radiance by comparing field measurements and simulation results. This study uses a point by point illuminance comparison of simulation results and field measurements under an overcast sky with measured illuminance in HoneybeePlus version 0.0.04 which uses Radiance version 5.1. The accuracy is rechecked with three other measured illuminance levels at different times under the same sky. Furthermore, this study assesses the effect of simulation parameters and model settings on the accuracy of simulation results. Results show that the recommended Radiance settings for having accurate results are accurate enough with a bias below 15%. Setting ambient bounces to more than 8 and disabling interpolation by setting ambient accuracy to 0 does not significantly affect the simulation results. By disabling interpolation, Monte Carlo ray tracing provides accurate results for simple geometries. Moreover, ±0.1 difference in reflectance factors has a significant effect on the accuracy of results. This study makes a scientific basis for setting Radiance parameters and measuring reflectance factors in future studies. The outcome of this paper creates a validated model for future studies on shaders, light shelves, and related designable components that rely on daylight in general.
This study presents an investigation of circadian lighting potential for a fibre optics daylighting system (FODS) in a single office in Beijing, China. Research methods included the monitoring of ...FODS daylighting performance during a 11-month period, the indoor lighting simulations at the horizontal workplane and vertical planes using a single office model, and thus the theoretical calculations of circadian stimulus brought by the FODS. Key findings are as follows: There is a high possibility that a proper level of circadian light at a windowless workspace could be achieved through applying the FODS in northern China. With this FODS, the non-visual effect of lighting (circadian system entrainment) can be attained when a standard lighting requirement was met at the horizontal workplane based on occupants' visual performance in this office. Compared with typical artificial lighting systems, the FODS can deliver circadian light in a more efficient way. In addition, it can be found that the application of FODS system would benefit office workers in terms of both visual and non-visual aspects. It is the first study to investigate the non-visual performance of a fibre optics daylighting system.
•Investigation of Circadian Light potential of FODS in a single office in Beijing.•A 11-month monitoring of FODS in terms of daylighting performance in a lab.•Analysis of computational simulation and theoretical calculation for Circadian Stimulus.•Identification of a high potential of the FODS to achieve circadian entrainment.
•The design and performance comparison of a novel use of the concentrator to achieve the multifunction of the electricity generation and daylighting;.•The prototype of the concentrators are ...manufactured and the outdoor overall concentrating photovoltaic/daylighting experiment system was built;.•Optical performance of the concentrator was analyzed through the ray-tracing simulation and indoor experiment under the solar simulator;.•The actual transmittance of the system was investigated through the outdoor experiment under different sky conditions.
This paper aims to validate an efficient way to use the low-concentration ratio concentrator for the building integrated concentrating photovoltaic/daylighting system, which is able to collect maximum solar energy for the renewable electricity generation and provide the function of daylighting. A 2-D static concentrator has been designed by leaving the lower portion of the outer parabolas near the base area uncoated to form the “daylighting window”, which is named as CPVD (indicating that the concentrator is for the concentrating photovoltaic/daylighting system), while the concentrator with the same structure but can only achieve the onefold function of the electricity generation is named as CPV. In order to address the interaction effects between the concentrating PV performance and daylighting performance, the overall detail comparison is made for the CPVD module and CPV module through the ray-tracing simulation and experimental characterization. It's found that CPVD and CPV have similar optical performance (indicated by concentrating PV performance, optical efficiency, opto-electric gain and flux distribution on the receiver etc.) at various incidence angles, which validates that setting the “daylighting window” have no native effects on the optical performance of the concentrator. At last, in order to quantify the beneficial harvest for the daylighting, the conducive lighting transmittance through the “daylighting window” under two different sky conditions: clear and overcast sky conditions are investigated through the outdoor experiments. The outdoor concentrating photovoltaic/daylighting experiment test rig is built and the transmittance of the CPVD is measured under two different sky conditions. Under the clear sky condition, the daily average transmittance of the CPVD is measured to be 8.73% which is pretty much consistent with the ray-tracing simulation results. Under the overcast sky condition, the transmittance value is lower, the daily average value of which is 7.11%.
The hybrid photovoltaic-daylighting window system has aroused more and more attention in recent years, because of its higher solar energy utilization ratio and better adaptability to building's ...energy consumption. In this area, the concentrator-PV type glazing technology is an important branch that smartly adopts the optical concentrators to realize the efficient use of solar energy for renewable electricity generation and daylighting at the same time. A novel transmitting lens-walled compound parabolic concentrator (TLWCPC) is designed, which is able to achieve the function of daylighting without decreasing its optical efficiency. Based on the TLWCPC, the TLWCPC-Photovoltaic/Daylighting (TLWCPC-PV/D) system is designed. Considering that the sun rays for daylighting will experience complex optical transmission processes in the concentrator, the proportion and amount of the diffuse solar irradiance have significant impacts on the overall daylighting performance of the concentrator-type PV glazing systems in both daylighting energy level and distribution uniformity. In order to address this issue, in this research, the ray-tracing simulation model for the TLWCPC-PV/D system installed on the roof of a typical office room is developed and the experimental results under sunny and overcast weather conditions are used to validate the accuracy and confidence of it. The validated ray-tracing model is then used to evaluate the effects of the proportion of the diffuse solar irradiance with the total solar irradiance set at a constant value on the overall daylighting performance of the TLWCPC-PV/D system at different incidence angles. It is found through the simulation results that at different incidence angles, the daylighting energy levels on the analysis grid show obvious decreasing trends with the increase of the proportion of the diffuse solar irradiance via different rates but the distribution uniformity of them is enhanced significantly. Finally, two actual tested weather profiles on either date with different proportions of the diffuse solar irradiance are selected to make the daily energy performance analysis for the TLWCPC-PV/D system, which further emphasizes the effects of the diffuse solar irradiance on the concentrating solar systems.
•The ray-tracing simulation model for the TLWCPC-PV/D module was built considering the diffuse solar irradiance.•The simulation model was validated using the experimental results under different weather conditions.•The effects of the diffuse solar irradiance on the daylighting performance of the TLWCPC-PV/D window were analyzed.•The daily energy performance analysis was performed for the TLWCPC-PV/D window.
•Presenting an optical fiber based hybrid solar lighting system for indoor illumination.•Combining the features of optical fiber daylighting and photovoltaic power generation.•Designing a secondary ...light concentrator to improve illuminance uniformity and avoid PPMA overheating.•Verifying technical feasibility by fabricated prototype during a whole day test.•Conducting cost analysis and comparing with three conventional lighting systems.
Optical fiber solar lighting systems are an appealing approach for illumination applications with the aim of reducing energy consumption and greenhouse gas emissions from artificial lighting. This study presented the design, construction and assessment of an optical fiber based hybrid solar lighting system for illumination of interior spaces. The proposed system combines the features of optical fiber daylighting technology and photovoltaic power generation technology. Specifically, a secondary light concentrator was designed to improve the uniformity of flux distribution and solve the overheating problem of PMMA fibers. The technical feasibility of the hybrid solar lighting system was validated using the fabricated prototype in a 5 m2 darkroom during a whole day test. Experimental results showed that, an average illuminance of 105 lx at a distance of 2 m from the end of optical fiber bundle was achieved, saving 316.82 kWh and reducing 251.24 kg carbon dioxide emissions every year in the studied case. Finally, cost analysis of the proposed hybrid solar lighting system was carried out and compared with three conventional lighting systems. The total payback period of the hybrid solar lighting system was 3.7 years and further reduced to 1.7 years in mass production. In the studied case, the hybrid solar lighting system was economically competitive after 2 years and 12 years of operation in comparison with a 100 W incandescent bulb lighting system and a 30 W T8 fluorescent lamp lighting system, respectively.
•A novel Concentrating PV/DC system is proposed for building application.•The concept of combining daylighting and PV system is presented.•Indoor experiment is conducted to validate the optical ...model.•The actual performance analysis of the CPV/DC system under real weather conditions is presented.•The CPV/DC system can be optimized for different building rooftop designs.
A wide range of developed and commercially available daylighting systems have been reported, however, they have just a single function, so they require an extra complex component to adjust daylighting intensity to create a better visual-comfort interior environment seasonally. Thus, in this paper, a novel concentrating photovoltaic/daylighting control system based on the lens-walled compound parabolic concentrator which is made by the transparent material is proposed. It combines both PV and daylighting control for green building design. At noon, when the incidence angle is small and the solar radiation is strong, the majority of the solar radiation can be collected by the PV cell for electricity generation and the remaining solar radiation will act as the daylighting source. In the morning or evening, when the incidence angle is large and the solar radiation is weak, the majority of the solar radiation will pass into the building for daylighting while the remaining solar radiation will be collected by the PV cell for electricity generation. An optical model was built for the ray-tracing simulation by using the commercial software Lighttools®. The prototype of the lens-walled compound parabolic concentrator was manufactured and assembled for the indoor experiment to validate the optical model. To prove the feasibility of the system, the optical and electrical performance of the proposed concentrating photovoltaic/daylighting control system are derived from the simulation and experimental results, and the actual all-day daylighting performance of it is investigated through the software simulation. The simulation and experimental results indicate good electrical and daylighting performance of the concentrating photovoltaic/daylighting control system, and the proposed concentrating photovoltaic/daylighting control system suits all kinds building rooftop designs with different inclination angles, which proves it a wide scope of application.
