Slat Angle Research Articles

Visibility Control for Supporting Workers using Blind-based Partitioning Devices

Open-plan offices encourage communication among office workers, but they also create distractions stemming from the movement, glances, and nearby conversations of co-workers. Partitions are often employed to mitigate these distractions, yet they struggle with achieving equilibrium between privacy and situational awareness. In this study, we propose a system of visibility control utilizing a blind-based partitioning device whose slat angles can be individually controlled. To demonstrate our system’s efficacy, we implemented a prototype of the device consisting of 48 controllable slats with servo motors, allowing visibility control of the front and both sides of the worker’s desk. Our accuracy test of the visibility control revealed that visibility from the user’s view can be controlled with an error of 6.4%. Subsequently, we conducted a user study that asked participants to design the shape of the partition under specific conditions of task and co-worker location. The results show that users want to change the partition shape according to the conditions and that using the device improves the subjective sense of task performance, comfort, concentration, and visual privacy in the video-summarizing tasks, but slightly reduces subjective comfort and concentration in the conversation tasks. These findings demonstrate a solid need for our system and established the usage guidelines.

Modeling a solar shading system that controls heat gain by using solar energy to change louver slat angles

In this study, we propose a model for a passive louver system that adjusts slat angles using solar heat energy. The model is structured in two stages: predicting the surface temperature of a solar collector plate and using this temperature to determine the slat angles. The system was installed and monitored in a building in Okinawa, Japan, to validate the model’s accuracy with field measurements. The validation showed that while the model accurately predicted the daily opening and closing times of the louvers, it faced limitations in minute-by-minute variations, making it less suitable for scenarios requiring instantaneous state evaluations, such as lighting environment assessments. Additionally, predicting the temperature for the double-skin façade was challenging and could affect overall model accuracy. Despite these issues, the model effectively achieved its primary goal of predicting annual energy consumption by accurately forecasting the daily opening and closing times of the louvers. The model’s fast computation speed and simplicity make it particularly suitable for annual energy simulations and easy to integrate with existing energy simulation programs. Further research is needed to enhance minute-by-minute reproducibility and integrate temperature predictions for double-skin façades, ensuring a comprehensive evaluation of both thermal and lighting environments.

Impact of Real-Time Blind Slat Angle Control on Reducing Total Energy Consumption of a Library Building Using an Optimized Artificial Neural Network Model: A Case Study of the Six Moroccan Thermal Zones

Abstract The prevalence of extensive glazed areas in contemporary buildings contributes significantly to solar radiation infiltration, elevating energy demands and causing discomfort for occupants. Window shading devices play a pivotal role in addressing this challenge. This paper presents the development and optimization of an artificial neural network (ANN) predictive model, designed to enable real-time control of slat angles by predicting total energy loads, specifically during summer (for cooling and lighting purposes). The refined model demonstrates high precision, achieving a normalized root mean square error (nRMSE) of approximately 1.72% and a correlation coefficient (R) of around 0.999, despite utilizing limited meteorological data. Key inputs for the model include solar radiation, solar altitude, and external temperature, with a particular focus on slat reflectivity. The study assesses the efficiency of three slat types based on their reflectivity: high (80%), medium (50%), and low (20%). Additionally, the research explores the impact of window-to-wall ratio (WWR) values on the control system's efficacy, revealing a positive correlation between higher WWR values and improved energy savings through ANN slat angle control. Furthermore, the study extends the applicability of the ANN model to the six thermal zones in Morocco, affirming its generalization across diverse environmental conditions.

Parametric Thermal Simulations of an Airflow-Screen Façade System

Energy-saving performance is required for building façades, and high-performance window systems, such as double-skin and airflow windows, are being considered as viable alternatives. However, those systems are costly owing to the increased number of glazing panes. Therefore, an airflow-screen façade system (AFS) that combines glazing, a blind, and a roller shade can be a viable solution. The design issues of AFS are the backflow to the indoor side and the effect of natural convection on indoor airflow when exhaust fans are not in use during holidays and at nighttime. However, only few studies exist on the annual thermal behavior of AFS. In this study, based on the thermal load calculation program NewHASP, a simulation model of AFS was built using a thermal node solar heat gain model and a ventilation network model. Sensitivity analysis of the maximum and annual thermal load were performed with the following parameters of the AFS: roller shade airtightness, glazing type, blind slat angle control system, window orientation, and exhaust fan air volume. The results of the sensitivity analysis indicate that the maximum and annual thermal loads were the most sensitive to were the direction the window faces and the airtightness of the roller shade.

Parametric control of multiple blinds to enhance daylighting performance in the dome building: Case study of a mosque building in Saudi Arabia

Clerestory windows encircling the dome are a common feature in mosque architecture. They serve the purpose of allowing daylight to penetrate the spacious interior from all directions through smaller windows compared to side-lit windows. However, maintaining the required uniform daylighting coverage throughout the day in buildings with different directions remains a challenge. The integration of advanced daylighting systems with dome geometry, coupled with parametric control, can significantly enhance daylighting performance. In this research, a novel approach and simplified integrated method for parametrically controlling a multiple blinds system with incremental slat angle in a mosque dome's drum are developed, whereby the blinds in each direction respond independently and parametrically to the sun's movement. Parametrically controlled blinds are installed on the windows around the mosque’s dome to maximize the utilization of daylight while preventing direct penetration of solar radiation. Then, the daylighting performance of parametrically controlled multiple blinds was compared to that of conventional blinds and unshaded windows in a typical Mosque in Saudi Arabia during the noon prayer time. The study found that the parametrically controlled blinds can dramatically enhance the daylight coverage inside the mosque from around 38% to 88% for an illuminance range of 150–500 lx, while protecting users from direct sunlight. Promisingly, the system revealed that it can protect worshippers from direct sunlight, minimize potential glare and provide visual comfort.

Daylighting performance assessment of a split louver with parametrically incremental slat angles: Effect of slat shapes and PV glass transmittance

Advanced shading systems, including light redirecting systems, may cause undesirable glare and affect the quality of the transmitted daylight. Therefore, it is important to integrate different building components, such as shading and glazing, to comprehensively assess daylighting performance and ensure a comfortable, luminous environment. This study proposes an advanced daylighting design based on a parametrically controlled split louver with reflective slats to redirect sunlight onto a ceiling and integrated PV glazing to control the illuminance levels. A special contoured slat design (retro shape) was evaluated and compared to different slat shapes (flat, curved, and oval) of the upper section. In addition, the effect of the PV glass transmittance (30 %, 50 %, and 70 %) on the daylighting performance was investigated. The daylight analysis was performed using Grasshopper software as a parametric tool to predict the daylighting performance through advanced dynamic metrics including Useful Daylight Illuminance (UDI), Daylight Glare Probability (DGP), and Illuminance Uniformity (Uo). It is found that the retro-shaped slat design can significantly improve the daylight distribution and level without using the common blind system for more than 90 % of the work plane area within the recommended acceptable UDI range (150 ∼ 750 lx) for a longer period of the day (including the early morning and late afternoon). Furthermore, retro-shaped slats can improve the Uo throughout the space to achieve the recommended level (0.70), while PV glazing can reduce the risk of daylight glare.

Investigation on overall energy performance of a novel multi-functional PV/T window

PV windows are considered to be a promising building-integrated PV technology due to their excellent electrical, daylighting and thermal performance. However, the shading of the PV cells increases the heating load in winter and the high temperature of PV cells exacerbates the cooling load in summer. Moreover, a significant portion of the heat absorbed by the PV modules is usually wasted. To address these issues, this paper proposed a multi-functional PV/T window. This system could recover the heat on PV cells for producing warm air in winter and hot water in other seasons. As a result, the proposed system can realize the combined PV/T utilization of solar energy and reduce the seasonal thermal needs of the building. First, the mathematical model of the proposed window was developed and validated. Next, the developed model was integrated into building energy software to evaluate the overall energy performance of the proposed window in four different cities of Yangtze River region: Shanghai, Nanjing, Wuhan, and Chongqing in China. These cities experience the subtropical humid climate (Cfa in the Köppen-Geiger classification) and belong to the zones with medium global horizontal irradiation. The sensitivity analysis revealed that the optimal slat angles are between 0o and 40o, while the optimal orientation angles range from 30o to 60o. Selecting low-iron glass as the inner glass resulted in the lowest overall energy consumption. By adopting the MFPV/T window, the annual operation cost of the studied case could be reduced by 34% (6.4 $/m2), 36% (7.0 $/m2), 28% (5.7 $/m2), and 16% (2.9 $/m2) in these four cites, respectively. Additionally, the annual CO2 emissions could be curtailed by 53.5, 58.5, 47, and 22.3 kg/m2, respectively.

Optimizing the control of Venetian blinds with artificial neural networks to achieve energy savings and visual comfort

Solar shading devices, such as Venetian blinds, are effective in controlling heat and light gain in buildings. This study focuses on developing an Artificial Neural Network (ANN) to automate the management of Venetian blinds in order to find a balance between energy savings and visual comfort. Typically, automatic control strategies rely on cut-off angles or maintaining appropriate indoor illuminance. However, finding the optimal trade-off between solar gain and daylight is challenging, particularly in regions with temperate or tropical climates. To this end, this paper proposes a novel approach to identify the best slat arrangement. The optimal angle is determined by simulating all possible slat angles using EnergyPlus and selecting the one that maximizes an objective function. The ANN is trained to recognize this angle as a function of variables that can be easily measured in situ. The resulting building’s behavior is tested on EnergyPlus using the output provided by the ANN. The results demonstrate that the target angle can be identified with high reliability, even for windows with different orientation and in other cities. The energy savings for heating/cooling are up to 37.7 %/38.7 %. The UDI200-800 increases by up to 38.5 % at the expense of a slight increase in lighting consumptions (13.5 %).

Energy performance assessment of venetian blinds in south-oriented residential spaces in hot arid desert climates

Purpose Window shading has always been an effective technique to control the access of solar radiation; however, inappropriate selection of the shading technique, location and optical properties may lead to an increase in energy consumed for cooling and artificial lighting. Venetian blinds (VBs) are a type of adjustable shading devices that can be installed to the interior, exterior or in between glass panes of a window and that can be easily implemented in both new and existing buildings. This study aims to investigate the impact of three VB parameters: slat angle, reflectivity and location on the overall energy consumption of a residential space with a south-facing facade under the hot arid desert climate of Saudi Arabia’s capital, Riyadh. For the purpose of globalizing the findings, the same investigations were applied for two other cities of similar climates: Cairo, Egypt, and Arizona, the USA. Design/methodology/approach A test room was modelled for energy simulation, with a 20% window-to-wall ratio. A VB was assigned with alternatives of being located to the indoor, outdoor or in between double glass panes. High, medium and low reflectivity values were applied at each location at slat angle alternatives of 15°, 30°, 45°, 60°, 75° and 90°. Findings Results showed VB performance across slat angles, where up to 20.1% energy savings were achieved by mid-pane high reflectivity VBs in Riyadh, while the value exceeded 30% in case of being externally located. A similar performance pattern occurred in the other two cities of hot arid desert climates: Cairo and Arizona. Research limitations/implications The study is limited to VBs at a fixed position, with no upward movement for partial or full openness conditions. The effect of blind control and operation on performance, such as the amount and duration of openness/closure of the blind and changes in slat angle across time, in addition to VB automation, shall be investigated in a future study. Practical implications The better understanding of VB energy performance achieved would enhance a more rational selection of VBs, which would benefit the construction industry as it would assist designers, real estate developer companies, as well as end-users in the decision-making process and help to realize energy-efficient solutions in residential buildings. VB production entities would also benefit by manufacturing and promoting for energy-efficient products. Originality/value In this study, a matrix of combinations of three VB parameters was developed, and the effect of these combinations on the overall energy consumption of both artificial lighting and heating, ventilation and air conditioning (HVAC) systems was evaluated and compared to identify the combinations of higher efficiency. The literature showed that these three parameters were hardly investigated in a combined form and hardly assessed by considering the overall energy consumed by both artificial lighting and HVAC.

CFD Analysis of Cross-Ventilation in Buildings with External Louvers: Impact of Slat Angles

CFD Analysis of Cross-Ventilation in Buildings with External Louvers: Impact of Slat Angles

Effect of interior venetian blinds on natural convective heat exchange at a full-scale window glazing

• The setting of the louver enhances the convection heat transfer from the window. • The space of the louver from the window has a great influence on the heat transfer. • Differences in louver angles result in up to 45% difference in heat transfer. • Differences in flow types will result in a deviation of 70% in the heat transfer. • Correlations are proposed for the convective heat transfer from the louvered surface. The indoor venetian blinds are commonly used to block the solar radiation, which will also have an impact on the convective heat transfer from windows. The existing research on this phenomenon is almost based on reduced-scale experiments or simulations, which do not reflect the natural convection of actual windows. In this work, the natural convection near a full-scale window when louver close to the window ( n ≤ 10 mm) is firstly investigated by CFD simulation. Research indicates that the convective heat transfer from the full-scale window will be enhanced when the louver is closer to the window. The cause for the increased heat transfer is not only related to the thermal bridge effect of the aluminum louvers, but also to the type of flow near the window. Three different flow types will be generated along the window surface with venetian blinds during our simulation, which are named as Duct-directed flow (DDF), Transition flow (TF) and Louver-directed flow (LDF). The difference between the flow types will result in a discrepancy of approximately 70% in the convective heat transfer from the window. In addition, the influence of the slat angle φ , space from slats to window n and temperature difference between air and window Δ T on flow development and convective heat transfer has been investigated in this study. The correlation obtained from this work allows to accurately calculate the convective heat transfer from the full-scale window covered with venetian blinds, and the average error of the correlation is within 8.2%.

Multi-objective optimization of Venetian blinds in office buildings to reduce electricity consumption and improve visual and thermal comfort by NSGA-II

Because the building sector has become a huge energy consumer, providing useful approaches can help tackle this important issue. Windows are an important component of a building since most of the natural light inside the building is provided by passing this component. Improper design of windows and their associated components, such as shadings, overheats the space and increases energy consumption, and on the other hand, disturbs the visual and thermal comfort of the building's occupants. The present paper aims to present a new approach for multi-objective optimization of the architectural specifications and control parameters of a smart shadow curtain. The use of this proposed approach leads to a significant reduction in building energy consumption and improved thermal and visual comfort. Energy-related simulations are performed through EnergyPlus software. Afterward, 21 design variables including control strategies and setpoints, location and orientation of shading, slat dimensions and material specifications, as well as hourly slat angle are considered in JEPLUS software. These simulations are conducted in four geographical directions over seasonal and annual periods for the city of Tehran, Iran. JEPLUS + EA software is employed to perform sensitivity analysis on the outputs of JEPLUS software and data optimization. Morris sensitivity analysis is implemented to investigate the effects of input variables on the objective functions. The NSGA-II algorithm is then applied to optimize the data to extract the optimal points on a Pareto front. The optimization results indicate that the external blind performs better than the internal blind and also the smaller the angle of the blind slat is, the better the visual comfort is but increases the electricity consumption for lighting. A comparison of the results of multi-objective optimization of controlled blind characteristics with initial values demonstrates that based on geographical directions, the total energy consumption of the entire building decreases by a range of 40–50 % per year, while visual comfort and thermal comfort are improved by ranges of 70–100 % and 10–40 %, respectively.

Numerical investigation of fire in the cavity of naturally ventilated double skin façade with venetian blinds

Double skin façades (DSFs), offer great views, architectural aesthetics, and energy savings. Yet, in a fire event the glass façade breaks leading to risks to human life and firefighting difficulties. Shading devices incorporated to prevent unfavourable heat gains to reduce cooling load though offer energy savings potentially present other challenges in firefighting and occupants’ evacuation. In this study, Fire Dynamic Simulator (FDS) was used to numerically investigate the spread of a 5 MW HRR polyurethane GM27 fire in a multi-storey double skin façade building with Venetian blinds placed in its cavity. The blinds were positioned 0.4 m away from the internal glazing, middle of the cavity and 0.4 m away from the external glazing respectively. In each blind position the slat angle was opened at 0°, 45°, 90° and 135° respectively. The results show peak inner glazing surface temperature ranged between 283°C to 840°C depending on the thermocouple position, the Venetian blind position and slat opening angle. Without Venetian blinds, peak inner glazing surface temperatures ranged between 468°C to 614°C. In all cases except when the slat angle was 0° and the blind was positioned closer to the outer glazing, the inner glazing surface temperature from the closest thermocouple (TC 14) above the fire room exceeded 600°C, the glass breakage temperature threshold. Overall, the Venetian blind position and slat opening angle influenced the spread of fire. Venetian blind combustibility and flammability were not considered and therefore recommended for future studies. Practical Application: Our manuscript helps to develop new thinking on mitigation of fire risks in buildings for architects, engineers and designers when incorporating Venetian blinds in Double Skin Façades (DSFs).

Design and performance investigation of a novel double-skin ventilated window integrated with air-purifying blind

The blind is an effective device for controlling solar heat gain through the window. However, the usage of it exists the issues of overheating in summer and low heat gain in winter. Meanwhile, formaldehyde is a common indoor gaseous pollutant in buildings. Here, we proposed a novel double-skin ventilated window integrated with air-purifying blind, which could improve the overheating issue in summer and the solar thermal efficiency in winter while realize formaldehyde degradation at the same time. Then the system heat and mass transfer model was developed and verified, the impacts of various parameter on system performance were analyzed. Finally, the performance comparison of the double-skin ventilated window with air-purifying blind and shading blind applied in Hefei was performed. Main results were: (1) The model had the high accuracy in terms of thermal transfer, optical behavior and air purification. (2) The optimal slat angle and position of blind applied in winter and summer were 20° and 50o, 0.3 m and 0.7 m, respectively. (3) Compared with shading blind, the double-skin ventilated window with air-purifying blind could improve the thermal and visual comfort, and the saved thermal energy was 23.9 kWh/m2 in winter and 78.8 kWh/m2 in summer.

A Study on Daylighting Performance of Split Louver with Simplified Parametric Control

A split louver consists of two sections with their slat angles to be adjusted separately for glare protection and redirection of sunlight, respectively. The upper section works in conjunction with the lower section to enhance daylight availability and uniformity throughout the year. The study aims to improve the daylighting performance of the split louver by applying a simplified parametric control, which predetermines the angle difference between adjacent slats in the upper section for a chosen solar altitude and then keeps this difference fixed during operation. The slats in the upper section can be changed parametrically using the Grasshopper to reflect daylight onto the ceiling and then illuminate the rear zone of a space. The lower section of the split louver can control the daylight in the front space area and may affect the amount of light in the back. The performance indicator in evaluating the proposed split louver design for the chosen typical days is the percentage coverage of the work plane area for the illuminance range of 150~750 lux, which was achieved up to 100% in some cases. The proposed split louver with the simplified parametric control has the potential to provide relatively consistent and distributed daylight coverage of the floor area and a glare-free environment.

Louver and window position effect on cross-ventilation in a generic isolated building: A CFD approach

Natural ventilation has been used to increase indoor air quality, remove pollutants, and remove heat absorbed in the building structure. Some architectural features such as wind-catcher systems are used to induce airflow into buildings, and openings equipped with louvers are employed to reduce solar daylight while allowing natural ventilation. Earlier studies on ventilated louvers and wind-catchers have shown the impact of the louvers’ opening positions and slat angles. However, their combination with each other has been less studied. This paper presents CFD simulations of cross-ventilation in a generic isolated building integrated with a one-sided roof-top wind-catcher and the outlet opening, both equipped with louvers for three different window opening positions. The isothermal 3D steady RANS equations were solved with the Standard k- ε method. The CFD simulations with CFX software were validated with the wind-tunnel experiments. The results show that the lowest dimensionless wind velocities inside the building were observed for the arrangement “Down” for both cases with and without louvers. In contrast, the highest air exchange efficiency and dimensionless wind velocities inside the building were measured for the arrangement “Up” for the case with louvers. This research can be considered as an architectural strategy to improve indoor natural cross-ventilation.

Advanced control strategy to maximize view and control discomforting glare: a complex adaptive façade

ABSTRACT Increasing demands for full-glazed façades have motivated designers/researchers to propose advanced control strategies for dynamic shading systems to mitigate the negative impacts of excessive sunlight penetration into interior spaces. Nevertheless, in line with the latter, outside view is commonly obstructed as a result of utilizing conventional shading systems including Venetian blinds. This is primarily the consequence of conventional systems’ lack of flexibility to respond appropriately to occupants’ requirements and the sun's changing orientation. This paper presents the virtual prototype development of a Multi-layer blind system through a brute-force algorithm. It emphasizes proposing a customizable and affordable complex shading system with advanced control strategies for multiple building typologies. The research intends to improve visual comfort (daylight and glare) and maximize unblocked window view in a single office room located in Tehran. Furthermore, the control system was developed based on a combination of the cut-off and a glare protection control strategy. Concerning the cut-off control system, the slat angles change to block direct sun radiations, and then, if needed, the position of the front slat, named ‘View slat’, changes to avoid discomforting glare. In conclusion, the proposed prototype could improve daylight performance by up to 44% and maximize unobstructed outdoor view by approximately 47% in an almost glare-free zone. Finally, the usage of swarm intelligence could significantly improve the performance of the proposed prototype by determining which blind and how they should respond to environmental changes and occupants’ requirements.

Simulation-based analysis of luminous environment of OLED lighting-integrated blinds for PV–OLED blind systems

Photovoltaic (PV) blinds generate power and control the sunlight entering the rooms. The control of PV blinds to maximize the power generation is disadvantageous to the indoor lighting environment as it blocks daylight. This study developed a PV–OLED blind system with an organic light-emitting diode (OLED) lighting panel attached to the back of a PV blind slat. It maximizes PV power generation, supplements indoor illuminance, and enables easy installation because it is an integrated device. A simulation modeling method of OLED, a surface-type lighting that rotates according to the blind angle, was developed and verified using measurement values. In order to apply the surface-type lighting form, a method of applying several luminous intensity distribution data files was used where we divided the height and width of one OLED lighting panel. As the number of height divisions increased, the coincidence rate with the measured values of the simulation results tended to increase. Using the proposed modeling method, the indoor illuminance distributions according to the installation position of the OLED lighting panel and the control angle of the slat were analyzed. When the slat angle was close to 60°, the influence of OLED was the greatest, and the influence of daylight decreased as the slat angle was decreased. As the slat angle increased, insufficient daylight could be compensated with an OLED lighting panel. As the OLED lighting panel was installed in the lower part of the blinds, the uniformity ratio decreased, and the average illuminance increased.

Design Optimisation of Fixed and Adaptive Shading Devices on Four Façade Orientations of a High-Rise Office Building in the Tropics

Optimisation of shading devices in buildings is a broadly investigated topic; however, most studies only focus on a single façade orientation, since the observed buildings are typically located in high latitude regions. However, in tropical regions, optimisation of all façade orientations is required due to the relatively high solar radiation and long sunshine duration. While adaptive shading devices are a promising solution, they are not without disadvantages, and as such a combination of adaptive shading devices and a fixed shading device shall be considered. This research therefore aims to design the optimum internal shading devices on four façade orientations of a high-rise office building in a tropical city, considering fixed and adaptive shading design options, and to determine the impact on annual daylight performance using computational modelling and simulation. The simulation is carried out under: (1) fixed design option, focusing on the numbers and width of slats; and (2) adaptive design option, focusing on the slat angle on various conditions. It is found that both sDA300/50% and ASE1000,250 are only influenced by the orientation. Under the fixed design option, the sDA300/50% and ASE1000,250 targets can be achieved only on the north and south façades, and accordingly the adaptive design option shall be implemented on the east and west façades. Overall, this study contributes to knowledge regarding the optimisation of shading devices in high-rise buildings in the tropics, considering the daylight admission from the four cardinal orientations.

Laboratory testing of a high efficiency light redirection system

Automated daylight redirecting slat technologies are designed to divert sunlight into the living space. They have a distinct advantage in that they can be retracted and extended, and slat angles can be adjusted according to the solar geometry and sky conditions. This study aimed to explore the geometric and photometric properties of a novel high-efficiency light redirection system (LRS). The LRS prototypes were installed in the clerestory window in the south-facing window testbed office and monitored under real sun and sky conditions. Workplane illuminance, daylight delivery efficiency (DDE) and visual comfort were evaluated. A number of simulation studies were conducted to evaluate the LRS and compare the results to the laboratory tests. The study shows that the specular properties of the slats provided significantly higher work plane illuminance and DDE. All systems showed an acceptable discomfort glare, or daylight glare probability (DGP) lower than 0.35. The comparison of the laboratory test and computer simulation was conducted using a Radiance tool. The results show that, for specular slats, the mkillum method with plastic material provided accurate work plane illuminance compared to the measurement. All simulated DGP shows accurate results compared to the laboratory test.