Maximum Daylight Research Articles

A new building envelope – increasing daylight and energy efficiency with water flow glazing

ABSTRACTBuilding industry is still chasing the dream of fully transparent glass facades. However, available technologies of today show severe contradictions to the main purpose of such fully glazed facades: on the one side, the clear and unobstructed view from the inside into the outside environment, on the other side enabling maximum daylight autonomy to the building users. The main reason is the inevitable requirement of solar protection to avoid solar heat gains and consequently high cooling capacities in buildings. Solar coatings, tinted glass, switchable windows and classic interior and exterior sun shading devices all have the same general effect: The quality of the views to the outside is reduced, the amount of available daylight decreases. The European Union has funded the project InDeWaG (Industrial Development of Water Flow Glazing Systems) within the framework of the European research program HORIZON 2020. During the research period of three and a half years the international consortium incorporating research institutes, industry and designers is developing a new insulation glass unit. In the cavity of this unit a water‐glycol mixture is circulating. Due to the spectral properties of water, it captures most of the infrared solar radiation: it is transparent to visible wavelengths of the sunlight but opaque to NIR wavelengths. Consequently, water flow glazing has the same natural light transmission as conventional glazing whilst reducing the heat transfer towards the interior space. Moreover, the water circulation allows to use, store or dissipate the energy captured by absorption of the waterfilled cavity.

Performance analysis of semitransparent photovoltaic module for skylights

The Semitransparent Photovoltaic (STPV) module could replace the glazing materials of the skylight in residential buildings, which minimizes the energy consumption in artificial lighting, heating, and cooling load of the building. In this study, the electrical, thermal and daylight performance of STPV skylights are investigated for actual outdoor environmental condition by installing it on the rooftop window of the experimental room at Kovilpatti (9°10′0″N, 77°52′0″E), Tamilnadu, India. The STPV modules are specially designed and fabricated for the skylight with specific PV cell coverage ratio (PVCCR) values are 0.62, 0.72, and 0.85. The various parameters are analysed such as power generation, electrical efficiency, module surface temperatures, solar heat gain, and reduction in cooling load, illuminance, daylight factor and CO2 mitigation by the STPV skylights. It is revealed that the maximum daylight factor of 4% and indoor illuminance of 850 lux is obtained in 0.62 PVCCR and reduction in cooling load due to the installation of PV skylight is calculated as 248 kWh/year during summer. On observation, it is found that the overall maximum energy saving potential is 450 kWh/year for 0.72 PVCCR, and its unit cost of the power generation is estimated as 0.0354 $/kWh.

Towards user centered building design: Identifying end-user lighting preferences via immersive virtual environments

Abstract In this paper, a systematic approach is presented to (1) collect end-user lighting-related behavior by using immersive virtual environments (IVEs) as an experimental tool, (2) integrate the collected data with building performance simulation (BPS) tools in order to translate behavioral information into quantitative measures (i.e., preferred lux level), and (3) incorporate user preference data for evaluating design alternatives with the objective of meeting end-user lighting preferences while reducing the building lighting-related energy consumption. To evaluate the applicability of this approach, 89 participants' lighting preferences, performance (reading speed and comprehension), personality traits, and environmental views were collected in IVEs. BPS tools were used to translate participants' lighting preferences into quantitative lux distributions, which were then used to evaluate alternative designs and make user-centered design decisions. The results of the experimental study show that participants preferred to have maximum simulated daylighting compared to electric lighting. Additionally, participants with some or maximum levels of simulated daylighting performed significantly better on the assigned reading and comprehension tasks than those that did not have any simulated daylighting available. Lastly, by collecting participant personality traits, it was observed that extroverts are significantly more likely to prefer maximum lighting (maximum electric lighting and simulated daylighting) compared to other people. To demonstrate how the collected data and results could be used during the design phase of buildings, as one example, a design case study is presented, in which the design of the same office space (as the experiment) is improved to meet participants' lighting preferences and increase the available simulated daylighting.

Physical Activity of Patients with COPD from Regions with Different Climatic Variations

ABSTRACTSeasonal changes in physical activity in daily life (PADL) of patients with Chronic Obstructive Pulmonary Disease (COPD) living in regions of the world with contrasting (i.e., mild or marked) weather variations have not been yet investigated. We aimed to quantify PADL and compare its variability caused by seasonality in patients with COPD who live in world regions with different summer-winter climatic variations (i.e. Londrina, Brazil and Leuven, Belgium). In a longitudinal, prospective and observational study, patients with COPD from Brazil and Belgium wore the SenseWear Armband for 7 days in summer and 7 days in winter. Active time (≥2METs) was the primary outcome. PADL data were matched day-by-day with weather information. Regarding the two assessment moments, median (min;max) temperatures were 11 (−5.5;27.2)°C in Leuven and 21 (7;27)°C in Londrina. Patients in Brazil (n = 19, 69 ± 7 years, FEV1 47 ± 15%pred) and Belgium (n = 18, 69 ± 6 years, FEV1 50 ± 15%pred) decreased their active time in winter compared to summer (p < 0.05), and this reduction was more pronounced in Brazil (p = 0.01, between group). Mean, minimum and maximum temperature, daylight duration and relative humidity were significantly related to active time. Patients with COPD decrease their PADL in winter even in a region with milder climatic variation.

Lights, building, action: Impact of default lighting settings on occupant behaviour

Occupant behaviour and their interactions with building systems could significantly influence energy consumption in buildings. Studies suggest “default setting” techniques could be used as intervention strategies as people's preferences are dramatically influenced by minor variations in settings. With the goal to reduce lighting-related energy consumption, we studied the effects of default lighting settings on occupants' rate of lighting adjustments in a single occupancy office space. Through the use of immersive virtual environments, we analysed 160 participants' data in a virtual office space. Based on the results, people are significantly more likely to keep the lighting settings if the default condition had some or maximum daylighting available. Additionally, the participants reading speed and comprehension were respectively faster and more accurate in conditions where simulated daylight was available. By using default settings, we can influence occupant behaviour towards more energy efficient choices in their daily interactions with building's lighting and shading systems.

Model-based shading and lighting controls considering visual comfort and energy use

Dynamic facades with high performance glazing and shading systems have the potential to balance daylighting needs, comfort and energy use, when integrated with lighting and thermal system controls. This paper presents the development and implementation of model-based control (MBC) algorithms for shading and lighting operation, aiming at minimizing lighting energy use while satisfying glare constraints. A fast and reliable lighting-glare model was used to compute real-time interior lighting conditions, lighting energy use and daylight glare probability, for predetermined shade positions (10% increments) at each control time step, based on the readings of two sensors on each building facade. Three visual comfort criteria (DGP, vertical and work plane illuminance) were embedded and compared in the real-time shading control logic, which selects the highest shade position (maximum daylight utilization) that satisfies the visual comfort criteria at each time step. The approach is similar to an optimization scheme for discrete shade positions, using visual comfort constraints as a priority, but here it is applied efficiently with a semi-analytical model in real-time control.The developed MBC strategies were successfully demonstrated in office spaces, controlling shades and electric lighting in real-time, using simple sensor readings as inputs. An innovative, variable control interval logic was also developed and implemented, resulting in reduced shading operation without sacrificing the benefits, creating less disturbance for occupants and extending equipment life. Finally, the developed MBC strategies were evaluated using annual simulation, in terms of frequency of shade movements, annual percentage of working hours with risk of glare, lighting energy use, and fraction of outside view.

Window design in architecture: Analysis of energy savings for lighting and visual comfort in residential spaces

Window design is decisive in providing appropriate visual comfort for occupants and sufficient energy savings in electric lighting. In daylighting, visual comfort is dependent on the maximum daylight autonomy. Moreover, energy consumption in electric lighting relies on daylight autonomy. The aim of this research is to quantify these metrics in a residential room for different window models and analyze the results obtained. The surface reflectance and the geometry of the window are variable. DaySim 3.2 lighting program provides the simulations of the room model according to different orientations and weather conditions. Following the trials, it was concluded that daylight autonomy is proportional to the glass surface and reflectance of surfaces at the back of the room, while its influence near the façade is negligible. However, energy consumption does not depend on window shape. It is also concluded that windows located higher up result in higher illuminance at the back of the room than those in centered locations. The conclusions of this research are contrasted with the analysis of daylight metrics for different locations and orientations of the window.

Energy Optimisation in Office Buildings Through Daylighting Design for Climatic Conditions of Central India

This paper is based on the premise that energy optimisation is possible in office buildings through design of daylighting. The motivation for the study was born of the fact that in India, among all building typologies, commercial buildings consume the maximum energy. This energy consumption is mainly for cooling of the building and lighting the interior spaces. Cooling and lighting up spaces generates heat in and around the building, which again increases the cooling load. Out of the total electrical energy required in the building, around 20-40% is used for lighting purposes. Despite availability of daylight during the working hours, artificial lighting is used in offices that have huge internal spaces with large spans. This paper aims at understanding the factors related to daylight penetration into office building in different situations and developing guidelines for achieving maximum daylight penetration in large spaces.

Analysis of Various Opening Configurations of a Second-Generation Virtual Natural Lighting Solutions Prototype

ABSTRACTTo address the absence of natural light in working spaces, virtual natural lighting solutions (VNLS) can be promising. VNLS are systems that artificially provide lighting as well as a realistic outside view with properties comparable to those of real windows and skylights. This article discusses the evaluation and analysis of various opening configurations of a second-generation VNLS prototype, which features an array of light emitting diode (LED) tiles coupled with a line of linear LED fixtures with adjustable color temperatures that provide direct light. Simulation using Radiance was performed and validated with the measurement results. Various possibilities of placing the prototypes inside the test room were investigated in Radiance to determine the effect on space availability and visual comfort. Based on the comparison of seven configurations of two prototypes with equal total opening size, it was found that nearly all configurations tested yielded a space availability of 100% with a criterion of 200 lx and where space availability is defined as the percentage of points on a horizontal grid that meet or exceed the target illuminance. Taking 300 lx as the criterion, two openings on each short wall facing each other (configuration 2) and four openings on a long wall (configuration 5) yielded space availabilities of more than 90%. Taking 500 lx as the criterion, configurations 2 and 5 yielded space availabilities between 25% and 50%. The highest uniformity (Emin/Eavg) was achieved under configuration 2 (0.59), whereas the maximum daylight glare probability (DGP) values under all configurations were between 0.25 and 0.30. Our simulation results suggest that the space availability in a private office can be optimized by placing a VNLS prototype on each short wall facing each other or by placing two on a long wall.

The influence of shading control strategies on the visual comfort and energy demand of office buildings

A lighting control strategy using daylighting is important to reduce energy consumption, and to provide occupants with visual comfort. The objective of this research is to evaluate visual comfort and building energy demand, and suggest lighting and shading control strategies for visual comfort and building energy savings. This research intends to achieve visual comfort and energy savings in an office building, by means of visual environmental control, and focuses on a quantitative criterion (illuminance), and a qualitative criterion (glare index) in daylighting. We used HDR images captured in real scene and simulation (DIVA-for-Rhino) for glare evaluation. The measured data from the mock-up room and the scale model were compared, to validate the simulation tool. Vertical eye illuminance (Ev) is recommended for the glare index, in place of the DGI or DGP. To prevent disturbing glare and to secure maximum daylight, control strategies of lighting and shading are suggested, related to the Ev value. In addition, the EnergyPlus program was used for calculation of the annual energy consumption. Building energy consumption is presented according to three building orientations, and 10 control strategies of lighting and shading. If there is no need to consider glare, a blind slat angle of 0° or dynamic shading is better in winter, regardless of the building orientation. In summer, a blind slat angle of 30° (static angle) or dynamic shading is suitable for an energy efficient and anti-glare control strategy.

Joint blind and light control for lighting energy reduction while satisfying light level and anti-glare requirements

This paper presents a joint blind and light control scheme for lighting energy optimization in a lighting control system. The proposed scheme utilizes the maximum available daylight without any glare and reduces lighting energy consumption while satisfying the user’s light level requirements. The optimal blind tilt angle that transmits the maximum available daylight without any glare is computed based on the sun’s altitude and the window ’s orientation, and an optimization problem is formulated that minimizes the required artificial lighting energy to satisfy the user’s lighting requirements. The simulation results show that, relative to conventional lighting control schemes, the proposed scheme achieves improvements in lighting energy consumption while satisfying the anti-glare and user’s light level requirements.

Structural Assessment of a Transparent Wall Panel with Load-Bearing Backup Framing and Polycarbonate Sheathing for Residential Construction

AbstractA new type of wall system for use in light-frame construction has recently been developed at Penn State University to allow for maximum daylighting and the use of glazing integrated photovoltaics to generate electricity. One structural option of the proposed wall system employs structural steel tubing to form the gravity load-bearing frame and polycarbonate sheets to perform the sheathing function. The exterior skin of the wall consists of a glazing system, which includes aluminum framing and glass panes that incorporate photovoltaics. Preliminary structural tests are presented to show the gravity load carrying capacity of the steel framing and in-plane lateral load carrying capacity of the polycarbonate sheathing. Similar tests were also carried out on conventional wood-frame panels to serve as benchmarks for evaluation of the proposed system. This paper mainly focuses on the structural system and provides a summary of the structural test results, which show that the proposed system can provide g...

Effects on sustainability of various skylight systems in buildings with an atrium

PurposeThe purpose of this study is to compare the natural lighting performance of roof skylight systems in buildings with atriums and to compare the sustainability and energy efficiency of several roof skylight systems for educational buildings with atriums.Design/methodology/approachFive roof skylight systems previously assessed in another study were adapted for simulation. In order to determine the effects of each skylight system on natural lighting, all the physical data of the building to be studied were recorded and entered into a computer.FindingsThe results of the study showed that roof skylight systems should be designed both to limit light during periods of maximum daylight to avoid such problems as glare, flare, and so on; and to direct light indoors as fully as possible during periods of limited daylight. In this regard, the “Moving Sunshade Double Layer” roof system showed better performance than the other four roof skylight systems.Research limitations/implicationsIn subsequent studies, roof systems appropriate for natural lighting should be studied for other plan types, hospitals, public buildings and so on. Moreover, real structures in which direct environment measurements can be taken could be used for obtaining data, instead of simulations.Practical implicationsUse of the roof system suggested by the research will minimize lighting and air conditioning costs, and enhance building sustainability.Originality/valueThis study explores methods of taking advantage of natural lighting indoors through the use of roof skylight systems, and identifies the most appropriate, sustainable and energy efficient roof skylight system for education buildings having an atrium.

Opinion: Daylighting prescriptions: Keep taking the pills?

The role that daylight evaluation plays in the design process has acquired a new impetus as the need to demonstrate compliance with various ‘performance indicators’ becomes ever more pressing. Two of the most used rating systems are BREEAM and LEED which originated in the UK and US respectively, though they are both used world-wide. Until recently, the majority of codes worldwide were founded on the daylight factor. First proposed in the UK in the early 1900s, and formalised into building standards over fifty years ago, the daylight factor is simply the ratio of internal illuminance to unobstructed horizontal illuminance under standard CIE overcast sky conditions (usually expressed as a percentage). One of the key standards documents for daylight in buildings is British Standard 8206-2 ‘‘Lighting for buildings - Part 2: Code of practice for daylighting’’, and many guidelines refer to that. BS 8206-2 recommends that ‘‘the average daylight factor should be at least 2%’’. A slightly more exacting recommendation has featured in LEED: ‘‘75% of all critical visual task occupied space must achieve a Daylight Factor of 2%’’. Since maximum daylight factor values are rarely specified, the prescription of minimum daylight factor values in the majority of guidelines has inevitably led to a perception that ‘more is better’. The Carbon Trust have recommended ‘‘not less than 4%, preferably 6%’’ daylight factor. And one can find statements such as the following in various good practice guidelines for schools: ‘‘Maximise daylight factor to improve student performance (5% or more)’’. Compliance ‘chasing’ is now a major driver in building design and expert daylight designers rarely have any input. Fundamental design parameters that have enormous consequences for overall building performance are being selected on the basis of daylight factor evaluations - a climate and orientation insensitive metric that takes no account of sun. Consequently, the elusive balance between good daylight provision and effective solar control is often not achieved. Among the problems discovered in a detailed review by the Commission for Architecture and the Built Environment (CABE) of forty proposed designs for schools across England were classrooms which are too dark or prone to overheating on sunny afternoons. Extending the basis of the daylight factor approach by incremental means has proved problematic. Recent ‘clear sky’ options in LEED and ASHRAE provide no guidance on normalising the sky output, a significant omission since absolute values are now the

Productivity correlated to photobiochemical performance of Chlorella mass cultures grown outdoors in thin-layer cascades

This work aims to: (1) correlate photochemical activity and productivity, (2) characterize the flow pattern of culture layers and (3) determine a range of biomass densities for high productivity of the freshwater microalga Chlorella spp., grown outdoors in thin-layer cascade units. Biomass density, irradiance inside culture, pigment content and productivity were measured in the microalgae cultures. Chlorophyll-fluorescence quenching was monitored in situ (using saturation-pulse method) to estimate photochemical activities. Photobiochemical activities and growth parameters were studied in cultures of biomass density between 1 and 47 g L(-1). Fluorescence measurements showed that diluted cultures (1-2 g DW L(-1)) experienced significant photostress due to inhibition of electron transport in the PSII complex. The highest photochemical activities were achieved in cultures of 6.5-12.5 g DW L(-1), which gave a maximum daylight productivity of up to 55 g dry biomass m(-2) day(-1). A midday depression of maximum PSII photochemical yield (F (v)/F (m)) of 20-30% compared with morning values in these cultures proved to be compatible with well-performing cultures. Lower or higher depression of F (v)/F (m) indicated low-light acclimated or photo-inhibited cultures, respectively. A hydrodynamic model of the culture demonstrated highly turbulent flow allowing rapid light/dark cycles (with frequency of 0.5 s(-1)) which possibly match the turnover of the photosynthetic apparatus. These results are important from a biotechnological point of view for optimisation of growth of outdoor microalgae mass cultures under various climatic conditions.

Ergonomic and Economic Daylight for Workplaces in Iran

Even today lighting design of buildings is too often solely based on task illuminance levels with little consideration of the importance of the light distribution for the appearance and visual appeal of the lit spaces. In respect to no available information or calculation models on illuminance in Iran, equations proposed by Illuminating Engineering Society of North America in 2000 were adopted to calculate illuminance on the south facing vertical surfaces. Generally 315 times measurements were taken at three measuring stations over 15 days at one hour intervals between 12 July and 1 August 2007 from 9:00 a.m. to 3:00 p.m. to confirm calculated data. Mean respective values of measured and calculated illuminance exceed 33.59 and 33.27 KLx. Measured illuminance in each standard time at three stations exhibited a better agreement with calculated illuminance by IESNA equations in correspondent daylight times (related in 1 h later) rather than those calculated for the same standard times. A regression model with a good linear correlation (R2 = 0.806) was developed between measured and calculated values of south facing vertical illuminance. Economic and ergonomic daylight found to be 46.5 and 17.8 KLx, respectively. The maximum Daylight Autonomy for maintaining average internal illuminance of 500Lx, also maximum useful daylight illuminance to achieve internal illuminance in range of 100-2000 Lx found to be more than 55% of working year in Iran.

Evaluation of plasma ACTH, α-melanocyte–stimulating hormone, and insulin concentrations during various photoperiods in clinically normal horses and ponies and those with pituitary pars intermedia dysfunction

To measure plasma ACTH, alpha-melanocyte-stimulating hormone (aloha-MSH), and insulin concentrations during various photoperiods between February and October in horses and ponies with and without pituitary pars intermedia dysfunction (PPID). Cohort study. 13 clinically normal (control) ponies, 14 clinically normal (control) horses, 7 ponies with PPID, and 8 horses with PPID. Blood samples were collected from February through October during 8 photoperiods: 1, February 13 through March 2; 2, April 4 through 6; 3, June 19 through 22; 4, August 6 through 7; 5, August 14 through 17; 6, September 4 through 6; 7, September 26 through 28; and 8, October 16 through 18. Plasma ACTH, alpha-MSH, and insulin concentrations at each photoperiod were compared among groups. Log ACTH concentration was increased during photoperiod 4 through 8, compared with photoperiod 1 through 3, in all groups. In photoperiod 3 through 7, log ACTH concentrations were higher in horses and ponies with PPID, compared with values for control horses and ponies. alpha-Melanocyte-stimulating hormone (log and raw value) concentration was higher in photoperiod 2 through 8, compared with photoperiod 1, in control horses and ponies. In horses and ponies with PPID, log alpha-MSH concentration was higher in photoperiod 3 through 8, and alpha-MSH concentration was higher in photoperiod 4 through 8, compared with photoperiod 1. In control horses and ponies, plasma insulin concentration was lower in photoperiod 3 than in photoperiod 1. Plasma alpha-MSH and ACTH concentrations increased as daylight decreased from summer solstice (maximum daylight hours) to 12 hours of daylight.

Identifying the Relationships Between Urban Water Consumption and Weather Variables in Seoul, Korea

As anthropogenic climate change threatens the reliability of urban water supplies, it is essential to build understanding of the relationships between weather and water consumption. We used daily and monthly data from 2002 to 2007 to conduct a statistical analysis of how seasonal water use in Seoul, South Korea is affected by weather variables. The Pearson, Kendall, and Spearman tests indicated that all weather variables were significantly correlated with per capita water use at most timescales, with mean, minimum, and maximum temperatures and daylight length positively correlated, and precipitation, wind speed, relative humidity, and cloud cover showing an inverse relation with water use. Once the influence of maximum temperature is controlled, water consumption is only significantly associated with wind speed and daylight length, as indicated by the partial correlation coefficient values. Ordinary least square (OLS) regression models explain between 39 and 61% of the variance in seasonal water use, indicating that approximately one-third to two-thirds of the variation is due to weather variables alone. Daily water consumption in July increases up to 4 liters per person with a one degree increase in maximum temperature. Significant improvement of the modeling of seasonal water use was achieved by developing autoregressive integrated moving average (ARIMA) models, which account for autocorrelation in the time series and explain up to 66% of the variance in water use. Our results indicate that weather plays a significant role in determining water consumption in Seoul, and that has important implications for management of urban water resources under potential future climate change.

Interactions between louvers and ceiling geometry for maximum daylighting performance

The impact of ceiling geometries on the performance of louvers was investigated using physical model experiments and Radiance simulations. Two performance indicators, the illuminance level and its distribution uniformity, were used to assess daylighting performance in a room located in a subtropical climate region. It was found that the performance of the louvers can be improved by changing the ceiling geometry. The illuminance level increased in the rear of the room, and decreased in the front—near the window—compared to rooms having horizontal ceilings. Radiance results were found to be in good agreement with physical model data obtained under a clear sky and high solar radiation. Louvers' daylighting performance was reduced by tilting the louvers downward. The best ceiling shape was found to be one that is chamfered in the front and rear of the room.

Equations for estimating global solar radiation in data sparse regions

The knowledge of the amount of solar radiation in an area/region is very essential in the field of Solar Energy Physics. In this work two equations are put forward for estimating global solar radiation from common climate variables in data sparse regions. The first is the Hargreaves equation, R s=0.16 R a T d 0.5 where R a is the extraterrestrial solar radiation and T d is the temperature difference (maximum minus minimum), while the second is the Angstrom equation, R s= R a(0.28+0.39n/N) where n and N are the measured sunshine hours and the maximum daylight duration respectively. The global solar radiation estimated by the two equations for three sites, Owerri (5°28′N, 7°2′E), Umudike (5°29′N, 7°33′E) and Ilorin (8°32′N, 4°46′E), located in different climate zones of in Nigeria, West Africa, are in agreement with those of earlier workers and that from Photovoltaic Geographic Information System (PVGIS) project. The implication of this in solar photovoltaic applications has been stressed.