Lighting Energy Consumption Research Articles

Semi-Transparent PV and Double-Glazed Windows for Heat Reduction and Electricity Generation: A Study for Office Buildings in Tropical Climate

This research aims to develop a methodology for the evaluation of the potential energy saving and energy generation of semi-transparent PV and double-glazed window in Indonesia office buildings. The evaluation is based on Comsol software. The heat transfer equations for the inside the enclosure between the glass have been constructed according to the natural convection equation. The simulations were accomplished for four orientations from January until December and compared to a single-glazed window. The results show that it is possible to reduce the energy consumption for artificial lighting and air-conditioning using appropriate control systems and furthermore to generate electricity using semi-transparent photovoltaic panels in windows. The use of semi-transparent PV and double-glazed window has proven to be more effective in reducing heat transfer in buildings and generate electricity. East-facing double-glazed windows produce the most electricity, approximately 341 kWh.

Coupled optical-thermal-electrical modelling of translucent photovoltaic curtain wall considering indoor lighting

The thermal, optical and electrical properties of PV curtain walls are coupled, and the results obtained from a single calculation model are biased. Therefore, the development of a coupled thermal-optical-electrical performance model for crystalline silicon PV curtain walls is essential for their thermal-optical-electrical performance analysis. In this paper, light harvesting calculation models, heat transfer calculation models and power generation calculation models are developed based on the structural characteristics of translucent crystalline silicon photovoltaic curtain walls, and the coupled calculation models are developed using the linkage between some input and output parameters and the parameters of the calculation process. An experimental platform for translucent crystalline silicon photovoltaic curtain walls was built and the performance parameters of light, heat transfer and power generation of photovoltaic curtain walls and ordinary curtain walls were calculated according to the experimental conditions. The coupled model is then used to analyse the thermal, optical and electrical performance of buildings with translucent PV curtain walls with different PV module distribution methods and comprehensive energy consumption under the five thermal zones, and the best solution is given for the PV module distribution methods of translucent PV curtain walls in each of the five thermal zones based on the results of the light and comprehensive energy consumption studies.

Performance evaluation of a light shelf with a folding reflector (LSFR) to improve daylighting performance

Recently, light shelves have been in the spotlight as a solution to the increasing lighting energy consumption in buildings, and various studies have confirmed their effectiveness. However, there is a lack of research on light shelves that operate according to the solar azimuth. To address this, this study proposes a light shelf with a folding reflector (LSFR) that operates in alignment according to the solar azimuth and validates its effectiveness through a testbed. The key findings are as follows. (1) The proposed LSFR is divided into three modules and becomes an inclined plane by moving the modules at both ends. Moreover, combined with light shelf angle control, the LSFR enables control over the direction of daylight inflow through light shelf reflection. (2) This study determines the optimal angle for a flat light shelf with angle control, highlighting the need to adjust the angle based on the external environment to enhance daylighting efficiency. (3) Upon implementing the optimal specifications, the LSFR reduces lighting energy consumption by an average of 49.5% and enhances the indoor uniformity ratio by 20.1% compared with Case 2 (flat light shelf with angle control). Particularly, the LSFR achieved a satisfactory 300 lx illumination without using additional lighting under the environmental conditions set in this study, which demonstrates the effectiveness of Case 3.

Semi-experimental investigation on the energy performance of photovoltaic double skin façade with different façade materials

The photovoltaic double skin façade (PV-DSF) is a cutting-edge building envelope renowned for its dynamic nature and power generation capabilities, which attracts substantial scientific attention. However, the current lack of experimental support makes it challenging to draw definitive conclusions about the influence of façade material. This study aims to address this gap by investigating the energy performance of PV-DSF with different façade materials, thereby establishing an empirical foundation for its optimization. In this regard, the full-size comparison experiments on PV-DSF with 20/40% photovoltaic (PV) glass as external façade and laminated/double glass as internal glass were conducted in Harbin, China. The EnergyPlus software is adopted for the simulation of lighting energy consumption. The results indicate that PV-DSF with 40% PV outperforms that with 20% PV, leading to significant reductions in total energy consumption in both summer (22.73%) and winter (16.84%). The double glass can prevent 0.49 MJ of total heat gain in summer, which is accompanied by a marginal 0.03 MJ increase in winter energy consumption. In total, for optimal annual performance, 40% PV and double glass are recommended as the façades of PV-DSF. The results of this investigation can provide an experimental foundation for PV-DSF optimization in sustainable building design.

Optimization Control Strategy for Transition Season Blinds Balancing Daylighting, Thermal Discomfort, and Energy Efficiency

Natural lighting in office buildings is often affected by excessive solar heat gain and discomfort glare, and the transitional seasons are no exception. Therefore, addressing the issue of natural lighting in buildings has always been a challenge in developing shading control strategies. This study designed a model-based calculation method for shading blind control indicators. The method combines existing physical models for sky conditions, solar radiation, heat transfer, thermal comfort, glare, and illuminance calculations and incorporates modifications and additions. Additionally, an equivalent energy-saving model for shading was established. A shading blind control strategy balancing indoor light and the thermal environment with energy savings during transitional seasons was proposed. In transitional seasons, this method can eliminate 100% of glare, reduce discomfort illuminance duration by 81.3% and heat discomfort duration by 87.5% and save 81.3% of lighting energy consumption when air conditioning is used. By comparing the simulation results of an office building in Xi’an with the results obtained from this calculation method, the absolute error percentage was found to be 6.83%, verifying the reliability of the calculation method. Finally, the proposed control strategy was compared with common methods such as no blinds, end-angle control, and fixed-angle control to evaluate its performance in terms of daylighting, thermal comfort, and energy savings. The results showed that the control strategy proposed in this study has significant advantages with respect to various performance indicators.

Evaluation of Design Parameters for Daylighting Performance in Secondary School Classrooms Based on Field Measurements and Physical Simulations: A Case Study of Secondary School Classrooms in Guangzhou

The quality of natural lighting within secondary school classrooms can significantly affect the physical and mental well-being of both teachers and students. While numerous studies have explored various aspects of daylighting performance and its related factors, there is no universal standard for predicting and optimizing daylighting performance from a design perspective. In this study, a method was developed that combines measurements and simulations to enhance the design parameters associated with daylighting performance. This approach facilitates the determination of precise ranges for multiple design parameters and allows for the efficient attainment of optimal daylighting performance. Daylight glare probability (DGP), point-in-time illuminance (PIT), daylight factor (DF), and lighting energy consumption were simulated based on existing control parameters of operational classrooms. The simulation results were then validated using field measurements. Genetic algorithms (GAs) were employed to optimize the control parameters, yielding a set of optimal solutions for improving daylight performance. The differences between daylighting performance indicators corresponding to the optimal solution set and those of the basic model were compared to test the performance of the optimized parameters. The proposed method is a robust process for optimizing daylight design parameters based on GAs, which not only enhances daylighting performance but also offers scientifically grounded guidelines for the design phase. It is a valuable framework for creating healthier and more productive educational environments within secondary school classrooms.

Parametric design of photovoltaic louver integrated shading devices for west facade windows of office buildings in central China

ABSTRACT In order to improve the shading performance and power generation effect of Photovoltaic shading integrated devices (PVSDs) on the west facade of buildings in China, a multi-objective optimization design method is proposed in this paper. Taking a west-facing office building in Zhengzhou, Henan Province, as an example, a parametric model of photovoltaic (PV) louvers for windows on the west facade is established, and parametric design research is carried out on the energy-saving potential of PV louver shading systems. Based on the optimization objectives of power generation of PV louvers, indoor thermal discomfort hours, building cooling load and lighting energy consumption, the performance of the west facade office with PVSD under different design strategies was simulated, and the optimal design strategy was determined according to the preference of decision makers. Compared with the basic type without a non-shading model, the indoor lighting energy consumption of the optimized west facade PVSD is slightly increased. However, overall performance is improved, with a 35% reduction in cooling load, a decrease of 804.59 kWh in total energy consumption, and a shortened summer thermal discomfort time of 404 hours. The power generation of PV louvers can replace 46% of the total energy consumption of the room. The results show that the installation of PVSD on the west facade window is important for alleviating the overheating inside the room and improving the energy-saving and power generation potential of the room.

Cash for Coolers or Sustainable Lighting? Assessing Different Components of a Large-Scale Energy Efficiency Program in Mexico

In one of the largest demand-side energy efficiency programs at the time, the Mexican government supported more than 11 million, mostly low-income households in replacing their old light bulbs and appliances with more efficient models. Previous evaluations of this program focused exclusively on appliances, which made up almost 90 per cent of the total program cost, and found modest benefits in terms of energy savings. This study compares the respective effects of replacing light bulbs and appliances simultaneously in a single econometric framework, using data from nationally representative household surveys and a difference-in-differences approach which exploits geographical variation in treatment intensities. Despite using different sources and types of data, our results for the appliances replacement intervention are largely in line with the estimates of previous studies. In addition, we find that the impact on energy consumption (proxied by the amount paid for electricity) of replacing light bulbs was of comparable magnitude as that of replacing appliances, although the average cost per participating household was much smaller. Overall, our results suggest that low-cost investments that help poor households reduce their energy consumption for lighting can have high returns on energy efficiency in the residential sector.

Optimal Design of Tilted Building Envelope Considering Air Conditioning Energy Demand, Daylight Utilization and Glare Protection—Case Study

An important energy-saving method to optimize building envelope design is the integration of local climate characteristics. This study attempts to find sloped facade configurations to balance air conditioning energy demand and daylight utilization for four directions in an area with a hot climate. Tilt angle dependence of the air conditioning energy demand, useful daylight illuminance (UDI) and daylight glare index (DGI) are selected to investigate the acceptance thresholds of the tilt angle. The final facade’s configuration is achieved by employing the graphical optimization method. An acceptable solution that balances better daylight performance and less energy consumption by air conditioning is developed. Due to the considered city being located in a low-latitude area with great daylight availability as well as a fully dimmable light control strategy, unbearable glare reduction can be achieved by benefiting from the sloped facades, without necessarily sacrificing much usable daylight. Meanwhile, there is no obvious increase in the demand for lighting energy consumption, and a good outward view is preserved. The sloped rather than vertical facade provides natural solar shading to the east-, south- and west-oriented windows while allowing low-angle winter solar heat to warm the building space. Tilt angles between 35°and 40° are preferred for the east facade, and smaller tilt angles of between 30°and 35° are recommended for the south facade. Larger tilt angles of between 40°and 45° are preferred for the west facade. However, the north-facing facade’s outward tilt would cause an undesirable increase in air conditioning energy demand. The annual air conditioning energy demand of the east-, south- and west-facing space is found to separately decrease by 7.1%, 7.3% and 9.9%, respectively, benefiting from the sloped facades.

Optimising augmented reality projector light output to balance art conservation, colour quality and energy consumption

Light absorbed by sensitive artwork may cause irreversible damage. Optimising the spectral power distribution of light sources to minimise absorbed light can reduce damage while maintaining the colour appearance of the artwork. Previous absorption-minimisation studies used optimisation methods without comparing their performance. Here, three-channel LED-augmented reality projector spectra were optimised for 24 colour samples using a brute-force (BF) and multi-objective genetic algorithm (MOGA). The BF search and MOGA performed similarly in achieving optimal results, reducing both light absorption and energy consumption by almost half. However, MOGA was 2.5 times faster than BF in finding optimal solutions. The results indicate that an LED RGB projector can be used to illuminate museum artefacts to reduce light absorption and energy consumption, with the caveat of perceptible colour shifts in some of the colour samples. Future research will investigate observers’ subjective evaluations of artwork under optimised lighting.

GA-BP based daylight prediction and sensor placement in residential areas

This paper conducts a comprehensive analysis of the light environment in different areas of residential houses located in Beijing’s Guangyuanli neighborhood. The main objective of this study is to assess the contribution of natural daylight to residential illuminance, with the aim of providing a foundation for reducing energy consumption and enhancing light comfort. While previous research predominantly focused on sensor deployment in single scenes such as offices and classrooms, these approaches are inadequate for multi-scene analysis of daylight in residential areas. Moreover, traditional deployment methods can negatively impact the quality of life and everyday living experience. To overcome these limitations, a prediction model is developed to estimate ceiling and window illuminance, as well as work surface illuminance in various scenes within residential buildings. The Dialux software is employed for data simulation, and a GA-optimized BP neural network is utilized to train the model, establishing the mapping relationship between input variables and corresponding illuminance outputs. By inputting sensor values from different scenarios into the model, the predicted daylight illuminance values can be obtained. This predictive approach facilitates the evaluation of light comfort and energy consumption reduction in different functional areas of residential buildings.

Daylight and energy performance of side lighting systems in an office room in a subtropical climate

In office buildings, daylight is an important natural resource, as it is profusely available during occupied hours. However, its use can increase energy consumption for air conditioning. Therefore, combining this resource with side lighting systems and promoting its integration with electric lighting is essential to obtain an energy balance. This paper aims to analyze daylight performance and the energy consumption for lighting and air conditioning considering four types of glazing, four orientations, from window-to-wall ratios varying between 40% to 100% for bare and shaded window models in an office room located in a subtropical city in southern Brazil. The methodology was based on Useful Daylight Illuminance levels of 500 to 2,500 lx, Daylight Autonomy levels of 500 lx, and total energy consumption through simulation in DesignBuilder software. The results showed that L13 glazing is not recommended for bare and shaded windows, regardless of window orientation. M76 presented the best performance for energy consumption for West shaded windows. For the West, shading is necessary irrespective of the glazing type (except L13, whose best performance is for bare windows) from WWR 50%. M76 and M52 had the lowest total energy consumption. The findings of this study add to an understanding of the energy savings and lighting performance of different types of glazing, combined with window apertures, and solar orientations for a subtropical climate. Furthermore, the study shows that the choice of glazing depends not only on the presence of shading but also on the orientation and WWR, without a linear behavior.

Improve Lighting Balance Performance and Energy Consumption by Using Kinetic Adaptive Skin for Office Space in Cairo, Egypt

Improve Lighting Balance Performance and Energy Consumption by Using Kinetic Adaptive Skin for Office Space in Cairo, Egypt

Parametric Design and Genetic Algorithm Optimization of a Natural Light Stereoscopic Cultivation Frame

Vertical farming (VF) is an emerging cultivation frame that maximizes total plant production. However, the high energy-consuming artificial light sources for plants growing in the lower and middle layers significantly affect the sustainability of the current VF systems. To address the challenges of supplementary lighting energy consumption, this study explored and optimized the structural design of cultivation frames in VF using parametric modeling, a light simulation platform, and a genetic algorithm. The optimal structure was stereoscopic, including four groups of cultivation trough units in the lower layer, two groups in the middle layer, and one group in the upper layer, with a layer height of 685 mm and a spacing of 350 mm between the cultivation trough units. A field experiment demonstrated lettuce in the middle and lower layers yielded 82.9% to 92.6% in the upper layer. The proposed natural light stereoscopic cultivation frame (NLSCF) for VF was demonstrated to be feasible through simulations and on-site lettuce cultivation experiments without supplementary lighting. These findings confirmed that the NLSCF could effectively reduce the energy consumption of supplemental lighting with the ensure of lettuce’s regular growth. Moreover, the designing processes of the cultivation frame may elucidate further research on the enhancement of the sustainability and efficiency of VF systems.

BIM-Based Building Performance Simulation Analysis: A Multi-Parameter-Driven Approach to Building Energy Efficiency and Carbon Reduction

Global warming and other environmental problems are increasing the demand for high-performance buildings. The development of high-performance computers and building information models has a significant impact on buildings’ energy simulation. High-performance building design needs to comprehensively consider geography, climate, material, cost and other factors which is a highly complex multidisciplinary research problem. Therefore, it is urgent to use advanced modeling and simulation technology to realize it, involving Building Information Modelling (BIM), parametric design and cloud platform. Comprehensive simulation of building performance refers to a multidisciplinary collaborative design, and the correlation between research objects and parameters should be achieved by complex programming design. This study integrates BIM, computer, cloud computing and other technologies to simulate BIM-based building energy consumption performance. Based on project information, geometry information and physical properties exhibited by materials stored in BIM model, the energy analysis model is created. Revit–Dynamo API functions are employed to generate a novel BIM model in Revit after automatically changing and transferring user-defined parameters. BIM energy consumption model is converted into Green Building eXtended Markup Language (GBXML) file and uploaded to Green Building Studio (GBS) cloud server. The optimal project solution is yielded by retrieving the energy consumption simulation results of BIM models with a range of parameters. The case study shows that building volume, glass material, window-wall ratio and window height have significant influence on energy consumption targets of buildings. In hot-summer and cold-winter areas, the total energy consumption of glass materials with high insulation and reflection coefficient is small. The window size slightly impacts the annual lighting energy consumption, but it has significant influence on the annual air conditioning energy consumption, with a maximum increase of about 22%. Finally, the application advantages and limitations of the framework in high-performance building design and its application prospects in energy-saving building design are discussed.

Dynamic Illumination Method for Rural Highway Intersections with Traffic Flow Changes

The conflicts between vehicles and vulnerable road users are frequent at rural highway intersections. Improving lighting conditions at intersections can significantly reduce the likelihood of nighttime accidents. This study aims to develop a dynamic illumination method for rural highway intersections with traffic flow changes. First, the safety design principles of a lighting scheme were formulated for minimum illuminance, vehicle speed, and traffic risk at intersections. In addition, a traffic risk quantification model for intersections was developed with illuminance and traffic flow parameters as inputs, incorporating gap acceptance theory and the braking safety distance model. Second, combining safety design principles and a traffic risk quantification model, a calculation method for optimal illuminance at intersections was designed with minimum illuminance as the optimization objective, and considering the risk at intersections not exceeding the safety threshold as the constraint. Finally, a case study was conducted in a simulated environment. Evaluation results demonstrate that limiting the maximum nighttime vehicle speed at intersections to 50 km/h can maximize the energy-saving rate of the lighting system while ensuring traffic safety and transport efficiency. The advantage of the method is that it can calculate the safe lighting scheme for highway intersections without any historic accident data and save lighting energy consumption. It increases the feasibility of promoting lighting facilities at rural highway intersections.

Occupant behaviour and the potential of automating lighting control in terms of energy consumption – is there a link for residential buildings?

The implementation of occupancy-controlled and daylighting-dimmed lighting systems has an impact on the energy consumption of residential buildings. The BAC factor method of EN ISO 52120-1 estimates that 8% of the lighting energy can be saved compared to conventional manual control. However, it is assumed that their ability to potentially lower the lighting energy consumption is strongly related to external factors, such as the extent of daylight entrance and the behaviour of the inhabitants. By means of simulations in EnergyPlus, the performances of automated and manual lighting control are compared for an apartment and semi-detached building located in Brussels (Belgium) with variation in the occupant behaviour and orientation.It appears that an automated lighting control including 0-100% dimmer reduces the lighting energy demand for all investigated cases with savings up to 38.4%, whereas a similar control without dimmer does not necessarily reduce the lighting electricity demand. However, the results show a considerable variation, making prediction methods as the BAC factor method highly inaccurate. The actual relative energy performance depends on the automation system, type of building, orientation and occupant behaviour (i.e. number of inhabitants and occupancy rate). Hereby, the number of inhabitants has the most considerable impact on the relative energy performances with differences up to 50%, while the occupancy rate shows a significant correlation, especially for low numbers of inhabitants.

A study of patient-centered, energy-efficient lighting design for hospital wards

As one of the most critical areas in a hospital building, the rationalization of the lighting environment is crucial for both patients and healthcare workers. This paper presents findings from field research and questionnaire interviews conducted in the Taiyuan ward, which reveal several issues with the current lighting setup, including low illuminance value, poor light uniformity, color temperature not meeting standard requirements, inappropriate selection and arrangement of light sources, and high proportion of lighting energy consumption. By analyzing factors influencing the humane and energy-saving aspects of the ward lighting environment, we explore a comparative simulation of the window-to-wall ratio and the form of shading inside the windows in the natural lighting system of the wards. Additionally, we consider the selection, placement, and control methods of lamps and lanterns for the artificial lighting system. Based on these findings, we propose a method for designing the light environment of hospital wards that accounts for both humane and energy-saving aspects, providing a technical means for optimizing the ward's lighting environment.

Study on Improving the Energy Efficiency of a Building: Utilization of Daylight through Solar Film Sheets

Daylight can contribute to substantial reductions in the energy consumed by artificial lighting applications. However, issues such as visual comfort, illumination intensity, and availability represent major issues when daylight is relied upon to illuminate buildings. There are many technologies that are used to control received sunlight and minimize its side effects. The placement of solar film sheets on window glass is a common and popular method utilized in many buildings to minimize electric lighting energy consumption without causing undue visual discomfort to occupants. To examine the practicality of this application and its effect on room lighting, a modern office was selected in which to conduct this field study. Two measures were used to evaluate this technique: firstly, field measurements and their comparison to the specified standard illumination levels; and secondly, a short-form questionnaire survey conducted to obtain occupants’ opinions of the office lighting. Actual measurements were conducted in the selected office spaces, with and without applying solar control film coating on the window glass. Indoor luminance levels and lighting comfort were systematically recorded and analyzed. The findings of this study show that using a solar film with a visible light transmittance of 50% can achieve savings in energy consumption of up to 33% if utilized as part of an integrated lighting system.

Optimal design method for electrochromic window split-pane configuration to enhance building energy efficiency

Electrochromic (EC) windows can prevent glare by adjusting their tinting state, but the tinted EC glass will affect the use of daylight in the room, resulting in the increase of lighting energy consumption. Splitting the EC window into several panes and tinting only a portion of them can effectively mitigate the conflict between glare prevention and the usage of daylight. However, there is a lack of design methods for EC window split pane configurations to realize further lighting energy-saving potential. To address this problem, this study proposed an optimal design method for EC window split pane configuration. This method is based on the glare calculation model and aims to obtain the minimum tinted area hours (TAH) of the EC window. Taking a south-facing EC window office building in Beijing as a case study, the effectiveness of the proposed design method was investigated by simulation. Results show the proposed design method identified the most energy-efficient and comfortable split panes scheme. By combining with the split-pane glare control method, 95.3% of intolerable glare was prevented, and a useful daylight illumination index of 73.3% was achieved. It also significantly improved building energy efficiency, saving 29.8% of lighting energy consumption compared to whole window design scheme. This study provides a promising design methodology for the high-performance application of EC windows in buildings.