Daylighting Controls Research Articles

A state-of-the-art artificial intelligent techniques in daylighting controller: models and performance

Lighting designers are always on the quest to develop a lighting control strategy that is aesthetically pleasing, comfortable, and energy-efficient. In an indoor context, electric lighting blended with daylighting controls forms a quintessential component for improving the occupant’s comfort and energy efficiency. Application of soft computing techniques, adaptive predictive control theory, machine learning, HDR photography, and wireless networking have facilitated recent advances in intelligent building automation systems. The evolution and revolution from the 19th to the 21st century in developing daylighting control schemes and their outcomes are investigated. This review summarizes the state-of-the-art artificial intelligence techniques in daylighting controllers to optimize the performance of conventional photosensor-based control and camera-based control in commercial buildings. The past, current, and future trends are investigated and analyzed to determine the key factors influencing the controller design. This article intends to serve as a comprehensive literature review that would aid in creating promising new concepts in daylighting controllers.

Application of luminous efficacies for daylight illuminance data generation in subtropical Hong Kong

PurposeDaylight plays a crucial role in the attainment of building energy savings. Harnessing daylight in building designs will require the need for daylight illuminance data. However, daylight illuminance data are scarce due to few measuring stations. Aside from being sparse, illuminance measuring stations can be expensive to set up, thus making the luminous efficacy model a better alternative. Hence, this study attempted to model horizontal luminous efficacies under the 15 Commission internationale de l'éclairage (CIE) standard skies. Therefrom, daylight illuminance was estimated from a proposed vertical luminous efficacy model.Design/methodology/approachMeasured solar irradiance, daylight illuminance and luminance distribution data were gathered from the local measuring station in Hong Kong. The luminance distribution data were used to classify the skies into the 15 CIE standard skies. Next, the solar irradiance and daylight data were used to derive the horizontal luminous efficacies under each standard sky. Furthermore, a vertical luminous efficacy model developed using the measured data was described, and this was used to predict vertical illuminance.FindingsIt was observed that Skies 1, 8 and 13 seem to be predominant in Hong Kong. Also, the result showed that constant luminous efficacies could be used for deriving illuminance data. Furthermore, horizontal luminous efficacy ranged from 40 to 190lm/W, indicating that daylight can provide sufficient visibility during working hours. The vertical luminous efficacy model proves to offer reasonable estimations of vertical illuminance data.Research limitations/implicationsFurther work needs to be done with more measured data to cover for spring seasons. The described model still needs to be fitted with different world climates to ascertain its universal applicability. The evaluations need to be done under obstructed sky conditions to cater for dense and clustered urban centres.Practical implicationsThe discussed luminous efficacy model could be used to derive illuminance data in the absence of measured daylight illuminance data, especially in the subtropical region. Also, the comparative advantage of daylight over artificial lighting was highlighted in this study.Originality/valueUnlike previous studies, this paper discusses the luminous efficacies of global, direct and diffuse components under the 15 CIE standard skies. Furthermore, the described luminous efficacy analysis provides an approach for deriving vertical and horizontal illuminance data. Such vertical data will be required for analysing building lighting requirements, sensible heat from electric lighting, and energy savings from daylighting controls. Also, the information on horizontal luminous efficacies will help evaluate solar roof and skylight designs.

A new tool and workflow for the simulation of the non-image forming effects of light

Other than supporting vision, light plays an important role in regulating human circadian rhythms through its non-image-forming (NIF) effects. Simulating potential NIF stimulation from daylight indoors, however, is a challenging task, requiring the continuous evaluation of luminous exposures at the eye, which are affected by changing sky's spectral power distributions at a location, time of day and year, and estimation of the sky patches’ contributions at a viewing position, which dynamically vary through a space. Existing multi-channel NIF simulations tools use measured or pre-computed spectral sky data. Yet, these are difficult to obtain with flexible spatio-temporal resolution. To address this challenge, and dynamically estimate a range of NIF metrics, we developed a tool and workflow based on 17 original Python-scripted Grasshopper components. This paper illustrates the design and development of the tool and workflow, also presenting an example of practical application to evaluate the yearly variations of potential NIF stimulation from an interior position or under an unobstructed sky. This is the first step to propose more robust building design and modelling concepts, beyond conventional visual comfort issues, and to adequately balance lighting energy use with occupants’ comprehensive needs, while connecting daylighting and electric lighting systems and controls within integrated solutions.

Design optimization of smart glazing optical properties for office spaces

In this paper, a systematic analysis is presented to determine optimal optical properties of smart glazing to minimize energy demand for perimeter office spaces. The optimization analysis considers the impacts of design and operation conditions of commercial buildings including size and orientation of windows as well as the climate characteristics of the buildings. In addition, daylighting benefits are included in the analysis of smart glazing that can transition between clear and dark states as well as intermediate tint levels. The optimization analysis results confirm that smart glazing can provide substantial energy efficiency for office buildings when coupled with daylighting controls especially for cold climates and large windows. However, the analysis indicates that specific set of optical properties for both clear and dark states are required to achieve optimal energy efficiency benefits for smart glazing when applied to office spaces. Indeed, the presented analysis allows the identification of the optimal optical properties for smart glazing depending on several influencing factors including primarily the climate as well as the window size and orientation. Moreover, the magnitude of the annual energy savings achieved by the smart glazing depends largely on the optical properties of the static glazing type used as a reference. Using code-compliant static glazing as a reference, the energy savings incurred by smart glazing range from 1.2% to 13.3% depending on daylighting controls and climatic conditions.

BIM application for analyzing impacts of construction parameters on energy use and energy costs in buildings

Energy-saving solutions in buildings in Vietnam are a great concern for sustainable development nowadays. However, energy-efficient and cost-saving designs based on the integration of Building Information Modeling (BIM) and building energy analysis are still limited. This study aims to provide energy-efficient and cost-saving designs for buildings by performing the cloud-based building energy simulation. Particularly, the analysis of the impact of changing building parameters on energy consumption and energy cost was performed in this study. Considered building parameters includes building orientation, wall construction, window-to-wall ratio (WWR), lighting efficiency, daylighting and occupancy controls, and, heating ventilation, and air conditioning system. The findings of the study can facilitate building designers, building owners or investors can obtain the best solution for designing the buildings. The first contribution of the study, to provide an in-depth analysis of the impact of the building parameters of energy cost and energy consumption. The second contribution is to contribute to the domain knowledge promotion of the digital transformation in the construction industry.

Real-time daylight glare control using a low-cost, window-mounted HDRI sensor

The main limitation of existing daylight glare control strategies is their fundamental inability to efficiently identify the location, size and brightness of potential glare sources in real-time. This study presents a new daylight glare control framework, using a low-cost, window-mounted programmable High Dynamic Range Image (HDRI) sensor with a wide fisheye lens. With proper calibration, the sensor can accurately measure the luminance, size, and relative position of any exterior glare sources in real time, using per pixel analysis. We present a method to enable reliable solar-tracking and an efficient glare source positioning algorithm, which can also detect glare sources of small size but significant luminance (e.g., intense reflections from surroundings). Complications due to the occupant position relative to the sensor/source are also discussed. The HDRI-based glare control was implemented in a private office with automated roller shades and was also compared with two common glare controls under the same sky conditions. The experimental results showed that the HDRI-based glare control can continuously and fully protect from detected glare sources, maintaining visual comfort, whereas the other controls failed in certain instances or are over-conservative. This new framework is the first proposed solution to address direct and reflective glare in a straightforward and efficient way, and it can be used as an extra layer in existing daylighting controls for glare mitigation. This technology can be used in the future to fully replace photometer-based fenestration controls and additional sensors, as well as to learn occupant visual preferences associated with exterior conditions.

An assessment of the load modifying potential of model predictive controlled dynamic facades within the California context

California is making major strides towards meeting its greenhouse gas emission reduction goals with the transformation of its electrical grid to accommodate renewable generation, aggressive promotion of building energy efficiency, and increased emphasis on moving toward electrification of end uses (e.g., residential heating, etc.). As a result of this activity, the State is faced with significant challenges of systemwide resource adequacy, power quality and grid reliability that could be addressed in part with demand responsive (DR) load modifying strategies using controllable building technologies. Dynamic facades have the ability to potentially shift and shed loads at critical times of the day in combination with daylighting and HVAC controls. This study explores the technical potential of dynamic facades to support net load shape objectives. A model predictive controller (MPC) was designed based on reduced order thermal (Modelica) and window (Radiance) models. Using an automated workflow (involving JModelica.org and MPCPy), these models were converted and differentiated to formulate a non-linear optimization problem. A gradient-based, non-linear programming problem solver (IPOPT) was used to derive an optimal control strategy, then a post-optimization step was used to convert the solution to a discrete state for facade actuation. Continuous state modulation of the façade was also modeled. The performance of the MPC controller with and without activation of thermal mass was evaluated in a south-facing perimeter office zone with a three-zone electrochromic window for a clear sunny week during summer and winter periods in Oakland and Burbank, California. MPC strategies reduced total energy cost by 9–28% and critical coincident peak demand was reduced by up to 0.58 W/ft2-floor or 19–43% in the 4.6 m (15 ft) deep south zone on sunny summer days in Oakland compared to state-of-the-art heuristic control. Similar savings were achieved for the hotter, Burbank climate in Southern California. This outcome supports the argument that MPC control of dynamic facades can provide significant electricity cost reductions and net load management capabilities of benefit to both the building owner and evolving electrical grid.

A low-cost stereo-fisheye camera sensor for daylighting and glare control

This study presents the development of a window-attached, low-cost fisheye-stereo camera sensor system for reliable daylighting controls in buildings. The stereovision sensor composed of two cameras can measure 3-D position and luminance of any exterior bright sources after photometric and geometric calibration. Also, by applying a neutral density sensor on one of the cameras and substituting the overflown pixels of the luminance map, a complete luminance map with a wide dynamic range can be retrieved. The new sensor exhibited promising results in validation of 3-D positioning and luminance acquisition, and can be used for real-time glare source detection, location and intensity measurements.

Shading and day-lighting controls energy savings in offices with fully-Glazed façades in hot climates

Shading devices installed on windows are designed to reduce solar radiation transmission into the space by absorbing and reflecting radiation rays. This study investigates the effect of shading and day-lighting controls when applied on fully-glazed facades on the annual energy savings in hot climates. For this reason, a dynamic simulation model of a space containing brise soleil and venetian blinds added to the façade exterior surface was developed on EnergyPlus and validated experimentally for office spaces located in Doha, Qatar. Comparison between the experimental and simulation models showed maximum discrepancies of 11.8% and 13.5% in surface temperature and peak space thermal load, respectively.Upon validation, the simulation model was used to evaluate the annual energy savings associated with the use of shading devices on both south and north-oriented façades in Qatar. For the south-oriented façade, brise soleil and fixed blinds with 90° with the vertical were found to save 18.6% and 20.6% of the space energy demands respectively, while mitigating glare risks. As for the north façade, the addition of brise soleil and blinds saves 7.7% and 9.1% of the space total energy demands respectively and removes all risks associated with glare. The adoption of a shading control for the blind angle and day-lighting control for the electric lights was found to save 26.1% of the space total energy without compromising the comfortable glare limit. This control strategy allows the occupants to benefit from the fully-glazed façade while still upholding the indoor space requirements in terms of outdoor visual comfort and day-lighting entrance.

High-Performance Buildings 구현을 위한 신기술 연구 동향 및 에너지 절감 효과 평가

Purpose: The purpose of this study is to analyze the energy performance by applying new technologies for passive and active control. Method: We selected new technologies for passive and active control which are based on formal study by analyzing technology applied to the High-Performance Buildings in various countries. Also, we analyzed energy saving potential for each technologies by breakdown the result of the energy saving rates in detail. Result: For the wall and roof insulating methods, preceding studies showed that up to 21% energy could be saved by improving roof insulation and applying proper outside insulation compared to non-insulation. For the windows and glazing system, preceding studies showed that Low-E glazing system could save up to 11% energy compared to single glazing system. Studies about solar and daylighting controls revealed that effective daylighting dimming control could save 13% of energy compared to uncontrolled situation. Studies on DOAS (Dedicated Outdoor Air System) showed that about 23% energy could be saved compared to standard VAV system. Studies on the active chilled beam showed that about 25% energy could be saved compared to standard VAV system and studies of applying UFAD (Under Floor Air Distribution) could consume 31% less energy than applying overhead system.

Balancing daylight, glare, and energy-efficiency goals: An evaluation of exterior coplanar shading systems using complex fenestration modeling tools

Exterior shades are the most effective way to control solar load in buildings. Twelve different coplanar shades with different geometry, material properties, and cut-off angles were investigated for two California climates: the moderate San Francisco Bay Area climate and a hot and dry Southern California climate. The presented results distinguish themselves from other simulation studies by a newly developed method that combines three research-grade software programs (Radiance, EnergyPlus, and Window 7) to calculate heat transfer, daylight, and glare resulting from optically-complex fenestration systems more accurately. Simulations were run for a case with constant electric lighting and a case with daylighting controls for a prototypical, internal load dominated office building.In the case of daylighting controls, the choice of slat angle and solar cut-off angle of a fixed exterior slat shading system is non trivial. An optimum slat angle was identified for the considered cases. Material properties (e.g., solar and visible reflectance) did not affect energy use if constant electric lighting was assumed, but they did have a significant influence on energy use intensity (EUI) when daylighting controls were assumed. Energy use increased substantially when an additional interior shade was used for glare control.

Analysis of End-Use Impact of Daylighting and Glare Controls for Private Office Spaces

ABSTRACTEarly design phase decisions are critically important to reduce a building’s energy needs. Building orientation and exterior aesthetics which drive window sizes and types are often made by architects and owners prior to daylighting or sustainability consultant’s involvement. Because designs can be difficult, if not impossible, to change as the design process proceeds the need to inform design decisions has lead to the development of a simplified calculation method capable of predicting annual lighting, cooling, and heating loads in a private office design with minimal input based on various design parameters. The method correlations have been produced for four US cities of varying climates to confirm the regression approach is transferable. An example design using these equations calculated to within 4% to 8% of detailed building energy simulation results. One significant benefit of the developed calculation method is its ability to evaluate the three main energy consumption sources’ impact provides a quick and complete assessment of the consequences of early design decisions.

Angular selective window systems: Assessment of technical potential for energy savings

Static angular selective shading systems block direct sunlight and admit daylight within a specific range of incident solar angles. The objective of this study is to quantify their potential to reduce energy use and peak demand in commercial buildings using state-of-the art whole-building computer simulation software that allows accurate modeling of the behavior of optically-complex fenestration systems such as angular selective systems. Three commercial systems were evaluated: a micro-perforated screen, a tubular shading structure, and an expanded metal mesh. This evaluation was performed through computer simulation for multiple climates (Chicago, Illinois and Houston, Texas), window-to-wall ratios (0.15–0.60), building codes (ASHRAE 90.1-2004 and 2010) and lighting control configurations (with and without). The modeling of the optical complexity of the systems took advantage of the development of state-of-the-art versions of the EnergyPlus, Radiance and Window simulation tools. Results show significant reductions in perimeter zone energy use; the best system reached 28% and 47% savings, respectively, without and with daylighting controls (ASHRAE 90.1-2004, south facade, Chicago, WWR=0.45). Angular selectivity and thermal conductance of the angle-selective layer, as well as spectral selectivity of low-emissivity coatings, were identified as factors with significant impact on performance.

Data analysis and stochastic modeling of lighting energy use in large office buildings in China

Lighting consumes about 20% to 40% of the total electricity use in large office buildings in China. Commonly in building simulations, static time schedules for typical weekdays, weekends and holidays are assumed to represent the dynamics of lighting energy use in buildings. This approach does not address the stochastic nature of lighting energy use, which can be influenced by occupant behavior in buildings. This study analyzes the main characteristics of lighting energy use over various timescales, based on the statistical analysis of measured lighting energy use data from 15 large office buildings in Beijing and Hong Kong. It was found that in these large office buildings, the 24-hourly variation in lighting energy use was mainly driven by the schedules of the building occupants. Outdoor illuminance levels had little impact on lighting energy use due to the lack of automatic daylighting controls (an effective retrofit measure to reduce lighting energy use) and the relatively small perimeter area exposed to natural daylight. A stochastic lighting energy use model for large office buildings was further developed to represent diverse occupant activities, at six different time periods throughout a day, and also the annual distribution of lighting power across these periods. The model was verified using measured lighting energy use from the 15 buildings. The developed stochastic lighting model can generate more accurate lighting schedules for use in building energy simulations, improving the simulation accuracy of lighting energy use in real buildings.

Design Optimization of Energy Efficient Office Buildings in Tunisia

Optimal and cost-effective energy efficiency design and operation options are evaluated for office buildings in Tunisia. In the analysis, several design and operation features are considered including orientation, window location and size, high performance glazing types, wall and roof insulation levels, energy efficient lighting systems, daylighting controls, temperature settings, and energy efficient heating and cooling systems. First, the results of the optimization results from a sequential search technique are compared against those obtained by a more time consuming brute-force optimization approach. Then, the optimal design features for a prototypical office building are determined for selected locations in Tunisia. The optimization results indicate that utilizing daylighting controls, energy efficient lighting fixtures, and low-e double glazing, and roof insulation are required energy efficiency measures to design high energy performance office buildings throughout climatic zones in Tunisia. In particular, it is found that implementing these measures can cost-effectively reduce the annual energy use by 50% compared to the current design practices of office buildings in Tunisia.

Monitored lighting energy savings from dimmable lighting controls in The New York Times Headquarters Building

Digital addressable, dimmable lighting controls were introduced to the US market in the early 2000s with the promise of energy savings while allowing greater flexibility than their analog counterpart. The New York Times Company installed this emerging technology, after thorough pre-procurement testing, in their new building in New York, NY. Four years after full occupancy (2007), the owner agreed to participate in post-occupancy monitoring of the lighting system to verify actual performance. Annual lighting energy savings from daylighting, setpoint tuning and occupancy controls were determined for the daylit, open-plan office areas on three typical floors (6th, 11th, and 20th) of the 51-story tower. Energy savings were calculated from data recorded by the lighting control system, after calibration through independent energy consumption measurements. Savings from dimming controls (daylighting and setpoint tuning) were 12.6kWh/m2yr for the daylit spaces on the three floors overall, or 20%, relative to ASHRAE 90.1-2007. Against the prescriptive code in effect at the time of the building's construction (ASHRAE 90.1-2001), savings were 21.0kWh/m2yr or 28%. Annual lighting energy use with all lighting control strategies was 33.9kWh/m2yr in the daylit, open plan zones on average for the three floors. A simple payback analysis was conducted.

U.S. energy savings potential from dynamic daylighting control glazings

Daylighting controls have the potential to reduce the substantial amount of electricity consumed for lighting in commercial buildings. Material science research is now pursuing the development of a dynamic prismatic optical element (dPOE) window coating that can continuously readjust incoming light to maximize the performance and energy savings available from daylighting controls. This study estimates the technical potential for energy savings available from vertical daylighting strategies and explores additional savings that may be available if current dPOE research culminates in a successful market-ready product. Radiance daylight simulations are conducted with a multi-shape prismatic window coating. Simulated lighting energy savings are then applied to perimeter floorspace estimates generated from U.S. commercial building stock data. Results indicate that fully functional dPOE coatings, when paired with conventional vertical daylight strategies, have the potential to reduce energy use associated with U.S. commercial electric lighting demand by as much as 930TBtu. This reduction in electric lighting demand represents an approximately 85% increase in the energy savings estimated from implementing conventional vertical daylight strategies alone. Results presented in this study provide insight into energy and cost performance targets for dPOE coatings, which can help accelerate the development process and establish a successful new daylighting technology.

Towards low-energy retail warehouse building

Retail warehouse buildings consume a growing proportion of the energy used within Australia and they have potential to be designed much more efficiently. This article outlines the results of modelling reductions in the energy consumption for a retail warehouse building in the Sydney, Australia climate. The design evaluated in this research consumes 73% less energy than does the base-case building, resulting in a significant reduction in on-going costs and in greenhouse gas emissions that are associated with the operation of this building. Techniques for reducing the total energy consumed by the building were explored using the simulation software, DesignBuilder and EnergyPlus. It was found that energy required for lighting, which is approximately 69% of the total energy consumed in the base-case model, could be dramatically reduced by introducing daylight through a sawtooth roof, in conjunction with efficient T5 fluorescent lighting and automatic daylighting controls. Other savings were made by adding insulation to the building, using natural ventilation and selective glazing to limit heat transfers into and out of the building.

Development of an optimal daylighting controller

A new lighting and daylighting control strategy is modeled and evaluated against conventional lighting and daylighting controls. The new lighting and daylighting control strategy can be incorporated in an energy management and control system (EMCS) to operate and control lighting fixtures in any indoor space. The new daylighting control can also be modeled and integrated in detailed building energy simulation tools. Through a validation analysis, it was found that the new control strategy provides more energy savings than conventional daylighting controls. Moreover, the validation analysis has indicated that existing daylighting control simulation analysis tools could overestimate lighting energy savings associated with daylighting controls. Moreover, it was also found that if calculated solar and illuminance data are used instead of measured solar radiation data, the errors in predicting lighting energy use when daylighting controls are utilized can be significant.

Energy performance regression models for office buildings with daylighting controls

Sensitivity analysis is performed to observe the response of the system when a given design parameter is changed. It is important to know the relationships between the input parameters and output results such that appropriate design variables can be selected to achieve the optimum building energy performance. This paper studies the sensitivity of energy performance and establishes regression models for office buildings with daylighting designs in Hong Kong. The building energy simulation computer program, namely EnergyPlus, was used to generate data for the analysis. The important input design parameters affecting the daylighting schemes were identified and analysed in terms of annual building electricity expenditures and peak electrical demands. Four building envelope design parameters, namely, window-to-wall ratio, light transmittance of windows, projection ratio of overhang, and projection ratio of side-fins were found to correlate well with the predicted incremental electricity use (IEU) and incremental peak electricity use (IPEU). Both linear and non-linear multiple regression techniques were used to develop regression models and energy equations for the predictions of IEU and IPEU. Statistical results show that such models and equations can be used to evaluate the energy performance of various building envelope design schemes for building with daylighting controls during the early design stage.