Reduce Lighting Energy Research Articles

Indoor Lighting Study: case of UDES’ Solar Smart House Bou-Ismail-Algeria

In the residential sector, the energy consumed for lighting represents an important amount of the total energy consumption in a typical house. In this paper, a lighting system in a solar smart house prototype in Bou-Ismail, Algeria, has been studied. This study focuses on the optimization of lighting and the energy consumption in the house, where the experimental and the simulation of the light distribution in the house was carried out using DIALux software. The purpose is to find the most suitable devices that are able to reduce lighting energy consumption and still ensure an optimal visual comfort inside the house. The obtained results show the efficiency of the proposed lighting system, where a reduction in energy consumption of 55.87% has been achieved.

Fuzzy Control Strategy of Tunnel Lighting Based on Input Parameter Optimization

The mismatch between illumination and traffic safety brightness in tunnels leads to much-wasted lighting energy and safety problems. Effective control of tunnel lighting can be achieved by lighting on demand and reducing lighting energy consumption. This paper uses the curve fitting and linear interpolation methods to optimize the luminance reduction factor K proposed in the Highway Tunnel Lighting Rules. It constructs a multi-zone division of traffic speed, traffic flow, and brightness outside the tunnel to obtain the K value under actual road conditions and to establish a fuzzy controller for dimming control. The simulation demonstrates that the proposed strategy can save about 37.38% of tunnel lighting compared to the graded lighting control strategy.

Reducing Lighting Energy Use in Controlled Agricultural Environments

Photometric simulations using both daylight and electric lighting were performed to compare the energy use of conventional high-pressure sodium (HPS) greenhouse lighting to that of light-emitting diode (LED) lighting. Photometric simulations of a hypothetical greenhouse were performed in three different geographic locations in the United States with widely different annual daylight availability: Albany, NY, Fairbanks, AK, and Phoenix, AZ. Simulation conditions included summer and winter, overcast and clear skies, and several lighting layouts and distributions. The analysis showed that, while maintaining the criteria levels of photosynthetic photon flux density, lighting energy savings were primarily attributable to increased LED source efficacy rather than HPS. Secondary energy savings were attributable to the ability to continuously dim LED lighting in response to daily and seasonal changes in daylight. Despite options for LED luminaires with a slim form factor, reduced crop shading compared with larger conventional HPS luminaires did not result in significant lighting energy savings.

Natural light transmittance of light-transmitting concrete (LTC) incorporated with optical fibres

This paper focused on investigating the light transmittance properties of light-transmitting concrete (LTC) under sunlight. Self-compacting concrete (SCC) and polymethylmethacrylate (PMMA) optical fibres with fibre diameter of 2 mm were used to fabricate LTC blocks. Since fibre spacing, LTC surface area, and light incidence angle are important factors which affect the light transmittance, but are rarely investigated in previous studies, the current study used fibre spacing of 15 mm, 18.75 mm, and 25 mm, and different LTC surface area, altered by placing one to six blocks together, to investigate the effects on light transmittance of LTC under sunlight. The light transmittance tests were conducted on a sunny day from 9 a.m. to 4p.m. A light meter was used to measure the intensity of light transmitted by the LTC. Fresh properties tests of SCC and compression tests on LTC were also conducted. The results show that LTC incorporated optical fibres had lower compressive strength compared to the control concrete block. The difference in fibre spacing has no significant effect on the compressive strength of LTC. The light transmittance of LTC with a spacing of 15 mm has the best light transmittance performance among the LTC blocks with different fibre spacing. The increment of light transmittance was approximately 24% to 28% near solar noon, when the LTC surface area increased from one block to six blocks regardless of the fibre spacing. It was found that the light transmittance declined drastically when the light incidence angle was beyond the acceptance angle. Further research is needed on LTC that takes into account the distance between the light meter and the LTC block to obtain a more comprehensive understanding of light transmittance before it is applied in building construction, with the aim to reduce light energy consumption.

Uncovering the Differential Growth of Microcystis aeruginosa Cultivated under Nitrate and Ammonium from a Photophysiological Perspective

Cyanobacteria have a relatively high affinity for NH4+, yet a NO3–-rich environment is comparatively conducive to their proliferation. To date, little information is available on why NO3–-N favors cyanobacterial biomass accumulation. This study investigated the dependence of biomass, nitrogen assimilation characteristics, and photophysiological performance of Microcystis aeruginosa on the forms of nitrogen supply, including NO3–-N-only, NH4+-N-only, and NO3–-N + NH4+-N. The results indicated that despite the retarded growth of M. aeruginosa, cells supplied with NO3–-N-only maintained a simultaneous promotion in the growth rate, nitrogen assimilation efficiency, and photosynthetic capacity, resulting in high biomass production. Cells supplied with NH4+-N-only and NO3–-N + NH4+-N were able to rapidly assimilate nitrogen during initial cell proliferation, showing a preferential use of NH4+-N and the inhibition of NO3– uptake by NH4+. However, growth repression occurred as cultivation time was prolonged when NH4+-N was excessively supplied, mainly due to PSII photodamage, intracellular redox imbalance, and increased electron energy accumulation. Thus, cells supplied with NH4+-N-only had to reduce light energy capture, increase photoprotection, and consume excess electrons to mitigate the damage. These findings are critical for improving our understanding of the role of different nitrogen forms in the regulation of cyanobacterial photophysiological performance and growth.

Optimization of top-floor rooms coupling cool roofs, natural ventilation and solar shading for residential buildings in hot-summer and warm-winter zones

The high building energy-saving potential of integrated passive technologies has drawn significant public attention. This paper combined field measurements and multi-objective optimization to reduce lighting and air conditioning (AC) energy by coupling cool roofs, natural ventilation (NV), and solar shading. Experimental measurements verified the cooling effects of cool roofs and NV based on thermal performance. The influences of cool roofs on heating and cooling energy were obtained. A building simulation model was validated by measurement data of thermal performance and AC energy use collected from a Guangzhou residential building. Energy-saving potentials under NV and daylight implemented strategies were then quantified. Compared to the black room without energy-saving strategies, daylight could reduce lighting energy by 3.3 kW h/(m2·yr), and AC energy use could be reduced by 4.7, 22.7 and 26.9 kW h/(m2·yr) in the black, blue and white rooms adopting NV, respectively. The roof albedo, roof insulation thickness and window-to-wall ratio notably impacted AC and lighting energy based on global sensitivity analysis. Optimal design schemes based on multi-objective optimization could reduce the top-floor room energy consumption by up to 52.3 kW h/(m2·yr).

A study on the energy saving of lighting through the development of integrated control of multifunctional shading system

Recently, interest in integrated shading and lighting control, which are building components, is increasing to reduce the energy used in buildings. However, the multi-functional shading system, which has recently been distributed, has a natural lighting function through ceiling reflection by introducing sunlight into the room, but it is difficult to control interworking with surrounding electric lighting and integrated control is impossible due to solar reflection or acquisition. In order to solve this problem, we intend to design and implement an integrated control system for multifunctional shading devices that affect the indoor light environment and thermal environment and are effective in reducing lighting energy. This study can reduce energy in buildings by controlling the temperature through an internally integrated control system for the inflow of sunlight into the room. In addition, integrated monitoring control is possible through real-time power and energy measurement and on-site sensor data management. As a result of this study, 34.5% of lighting energy could be saved through the study of the automated system of integrated control of multifunctional shading devices.

Assessment of the impacts of window-to-wall ratio and overhangs on building energy performance – Kabul, Afghanistan

Windows have the potential to save energy in a significant way. Therefore, the analysis and optimization of the Window-to-Wall Ratio (WWR) play an important role in improving energy efficiency in buildings. Windows are always beneficial to utilize daylight and reduce lighting energy demand. However, solar heat gain is advantageous during cold days and disadvantageous on hot days. As the configuration of the window areas varies according to the geographical location, the objective of this study is to evaluate the impact of WWR on the energy performance of buildings in the cold semi-arid climate of Kabul, Afghanistan. In this study, various energy simulations were conducted for three types of building shapes (Square, Rectangle, and “L”-Shape) to determine the most energy-efficient proportion of windows and overhang sizes in different cardinal directions. Based on the simulation results, windows on south façades have notable energy-saving potential in Kabul's climatic conditions. However, increasing the window size on north, east, and west façade leads to an increase in the total heating and cooling energy consumption. The optimal WWR of the south façade window for square, rectangular, and “L”-Shaped is 0.7, 0.55, and 0.55, respectively. Additionally, the findings indicate that overhangs in all orientations slightly affect the total energy demand as they only reduce cooling load. The study concludes that optimizing the windows on the south façade reduces energy demand by up to 8.13% if no windows are provided in other directions, while the total energy consumption rises by up to 36% as the WWR on the north, east, and west façades increase from 0 to 0.8.

A Study on Daylight Performance Evaluation in Primary School Classrooms

From the early beginning of construction in history, priority of using daylight has played an active role in the settlement decision, building shape and façade design. Today, the necessity of conscious consumption has become an accepted fact due to the depletion of energy resources. For this reason, the effective use of daylight and reducing lighting energy consumption have become one of the most important goals of today's architecture. 
 The purpose of the natural lighting system is providing sufficient daylight to the target area, considering the visual comfort conditions. Nowadays, for the architectural design of buildings, the use of passive systems is primarily preferred in terms of energy efficiency. The use of natural lighting as a passive system, minimizing building lighting energy requirements and creating the desired visual environment should be prioritized in terms of providing visual comfort. In educational buildings, it is vital to design a lighting system in which daylight is used effectively in order to meet the visual needs of the instructors and students and to minimize the usage of lighting energy. Within the scope of the TS EN 17037 standard, which was developed for daylight assessment in buildings and approved by CEN on 29.07.2018 and lastly updated on 02.03.2022, the criteria for daylight assessment is handled under 4 headings: daylight provision, view out, exposure to sunlight and protection from glare. For each criteria specified in indoor daylight assessment, three grades are defined as 'minimum, medium and high'.
 In this study, the criterion of providing daylight in educational buildings was examined in accordance with the TS EN 17037 standard. With the study, it is aimed to develop an approach to determine the optimum values ​​of the parameters of direction, obstacle presence and transparency ratio in the context of providing sufficient daylight in the primary classroom design. Investigated building type is the primary school building classroom, which was created in optimum dimensions according to the characteristics of primary education classrooms defined in the ‘Educational Buildings Minimum Design Standards Guide’ published by the Ministry of National Education. It is aimed to evaluate and develop the criteria given in the ‘Educational Buildings Minimum Design Standards Guide’ according to the TS EN 17037 standard, which defines daylight performance in Turkey. The classroom model discussed within the scope of the study has been modeled with the Rhino program according to the alternative transparency rates and obstacle situations; In the simulation, the Climate Studio plugin, which was developed for the calculation of dynamic evaluation parameters, was used. The area handled by using evaluation methods according to the 17037 standard included in the software was evaluated in terms of annual daylight performance. The availability of target illuminance levels in half of the daylight hours throughout the year was calculated using the daylight autonomy method, and the climatic data of the province of Istanbul were used as a representative in the calculations. The results obtained were evaluated according to the TS EN 17037 Daylight Standard, and the scenarios created were classified as 'minimum, medium and high' according to the availability of daylight. According to this classification, optimum transparency ratio, window direction and obstacle conditions conditions for the city of Istanbul in primary school classroom design are discussed. The optimal transparency ratios for each aspect are discussed. The minimum transparency ratio values ​​given in the ‘Educational Buildings Minimum Design Standards Guide’ were compared with the optimum transparency ratios obtained.
 
 
 Keywords: Daylight Performance, TS EN 17037, Primary school classrooms, Window Design

Factors influencing the state of blinds and lights in primary schools: Behavioural models and opportunities to improve children's visual environment

The state of blinds and lights affects children's visual environment and comfort, however, there is a significant gap in research on the factors leading to the operation of blinds and lights in primary school classrooms. This study identifies and categorises the main drivers of operations on blinds and lights and investigates optimal light levels for children in primary schools. The study collected measurements of environmental variables, observations of operations on blinds and lights using forms and time-lapse cameras and visual sensation questionnaires in 31 naturally ventilated classrooms in the UK for one year. Results suggest that operations on blinds and lights are influenced by a range of contextual, occupant-related and building-related factors. Behavioural models of blind and light operation in primary schools are developed using the data collected. With regards to children's visual comfort, in the current study, at 730 lux, 80% of the children were satisfied with the light level in their classroom. The findings and models presented in this study could be used by designers of schools to achieve more visually comfortable classrooms. For example, the results suggest that vertical blinds rather than roller blinds may be a better design choice for classrooms as their slats can be adjusted to control direct sunlight but also allow ventilation. The research concludes with a range of strategies for managing the visual environment through operations on blinds to both reduce lighting energy consumption, as well as increase the quality of the visual environment thereby improving school children's health and productivity.

Occupant seating optimization to reduce lighting energy consumption and improve comfort

occupant presence and behavior are non-negligible factors affecting building energy consumption. It should be emphasized: guaranteed building core functions is a prerequisite for energy saving. This paper proposes a method that can minimize building energy consumption and improve occupant comfort. Through monitoring the entry and exit of a 24-person office, occupant presence is obtained. And the difference in comfort of occupants is investigated and analyzed. The occupant is moved to a seat that is more thermally comfortable. Then occupants with a high degree of overlap in-room time are gathered in the same lighting area to reduce lighting energy consumption. Through the multi-objective optimization model, the lighting energy consumption is reduced by 16.2%, and the overall indoor comfort is slightly improved.

Integrating Daylighting with Task-Ambient Lighting for Enhanced Energy Savings in Office Spaces

Daylighting has been widely studied as a fundamental aspect of spatial illumination and energy efficient façade design. Effective installation and control of shading devices diminishes the adverse effects of prevailing climatic conditions on building envelope performance and reduces resultant lighting and cooling energy consumption. Task-ambient lighting as a free-standing approach has also been proven to reduce lighting energy consumption compared with typical general ambient lighting. This study estimates the energy saving potential of integrating daylighting through fixed external horizontal shading slats with task lighting. Spot measurements were taken in a test room to validate a daylight calculation program. Full year indoor work plane daylight simulations were performed for office spaces of different floor areas and varying window to wall ratios. Indoor daylight quality was assessed using the Useful Daylight Illuminance metric and three different task lighting schemes explored. Lighting energy savings of 10% to 90% were estimated under the three schemes in comparison to similar office spaces with common unshaded heat reflective glazing.

Multi-objective optimization of daylight performance and thermal comfort in classrooms with light-shelves: Case studies in Tehran and Sari, Iran

In educational buildings, an efficient daylight design has significant influences on student’s visual comfort, well-being and productivity while it offers significant benefits for reducing lighting energy consumption. Besides visual discomfort, the excess of daylight entry to space will cause disadvantages, including building overheat. Therefore, it is essential to define the optimal design for daylight control devices. In previous studies, daylight performance of light-shelf as a window-attached daylight control device has been studied. This paper aims to investigate the effect of sky cloudiness on the optimum light-shelf properties defined for typical classrooms. In addition, the optimum properties of the light-shelf for classrooms in two cities have been defined, which had not been addressed in Iran’s national codes and guidelines. The methodology used is based on three steps: daylight optimization of light-shelf parameters, thermal comfort analysis for selected solutions, and choosing the best option. Four parameters of light-shelf, including height, length of the exterior part, length, and angle of inner part, have been considered as variables. Using Octopus optimization algorithm in Rhinoceros, Grasshopper simulation tool, a multi-objective algorithm has been applied to find the optimum combination of the parameters based on daylight performance indicators. Thermal comfort analysis has been conducted for selected solutions with optimized light shelves using Openstudio. The results indicated that applying light-shelf in Tehran with less sky cloudiness is more effective than Sari in terms of providing both daylight and thermal comfort, especially for cases with more window to wall ratio (WWR). Sari, the case with lower WWR, does not necessarily have less Annual Solar Exposure, even with an optimized light-shelf. Hence choosing the best option without comparing daylight metrics for optimized solutions of various WWR is misleading. According to the results, although the best options are different in the cities as the effect of sky cloud cover, the optimum light-shelf properties are the same in light-shelf height, exterior, and interior length, while the pivot angles vary. There is also a relation between rotation angle and daylight availability regarding WWR in each city. Considering daylight and comfort issues, WWR for the best option in Tehran is greater than Sari. The study results provide useful information for designers for choosing the optimal properties of light shelves and the best option for design in the two mentioned cities.

Simulation-assisted data-driven method for glare control with automated shading systems in office buildings

An automated shading system is expected to effectively prevent visual discomfort associated with glare while providing adequate daylight penetration. However, the concept of visual comfort has not been well integrated into existing commercial shading systems, leaving potential for visual discomfort and resulting in occupants’ dissatisfaction. Meanwhile, advanced methods in the academic literature are not always suitable for industrial applications due to problems associated with intensive real-time computation or privacy concerns. This research aims to address this gap by developing a simulation-assisted data-driven method for glare control with automated shades. The proposed strategy utilizes data from pre-simulated daylight analyses to develop glare predictive models using machine learning algorithms. With real-time solar irradiance measurements and the sun position as the input variables to feed the predictive models, the control algorithm can predict the glare condition and set the shades to an appropriate position that maximizes daylight ingress without causing glare. The presented method was verified using climate-based simulation to adjust the slat angle of automated venetian blinds in an office building. Its performance was compared to that of the conventional cut-off angle control for glare elimination, lighting use savings, and view access. The results showed that the proposed strategy was able to prevent 86.5%–96.9% of the glare and potentially reduce lighting energy use by 80.8% while the cut-off control only resulted in 28.9% glare elimination and 67.6% lighting energy savings. The presented method also allowed for unobstructed view more frequently, outperforming the cut-off angle control in all the examined categories.

A case study of lighting retrofit to improve building energy efficiency and lighting quality by using luminaires with nano optical coating

Lighting retrofit is a common technique to reduce lighting energy use and to improve lighting quality. It is usually performed by replacing the lamps in the existing luminaires with more efficient lamps. Despite the high potential to enhance lighting performance by improving other parts of the luminaires such as reflectors, lighting retrofits usually keep their designs unchanged and focus on the change of the lamps. In this case study, an alternative lighting retrofit method - the replacement of reflectors using a nano optical coating - was tested in a typical office in Hong Kong. The case study used a luminaire with a highly reflective nano optical coating. The pre- and post-retrofit illuminance level, illuminance uniformity, glare and lighting energy use were measured. The results show that the use of the nano optical coating enables the reduction of light tubes in the office and thus the lighting energy consumption without lowering the lighting quality. The lighting retrofit enhances the illuminance uniformity in the office by 14.6% while keeping the illuminance level and discomfort glare within the satisfactory level. It also lowers the lighting energy use of the office by 37.5%.

The negative impact of skylights on light-irresponsive historical sites within archaeological museums: A case study

Most historical sites in archaeological museums have an inorganic origin. According to the specifications prescribed in CIE 157: 2004, these inorganic collections are light-insensitive and can be preserved in an environment without any light restrictions. Roof skylights are therefore widely used in archaeological museums in China to provide natural lighting and reduce lighting energy consumption. However, many of the historical sites in these archaeological museums are not preserved as well as expected due to their unique soil-air coupled preservation environment and the transmission of sometimes intense sunlight into the relic preservation area. This research takes Chengdu Jiangnan Pavilion Street Site Museum as a case study to evaluate the influence of skylights and direct sunlight on historical sites within archaeological museums. An integrated analysis of the negative impact of skylights on historical sites was implemented by comparing the preservation environment in illuminated and non-illuminated areas. The results show that the light intensity at the illuminated area is more than 100 times at the non-illuminated area, the intense sunlight not only induces severe environmental fluctuations where the maximum daily change in temperature and RH reach 9.7 °C and 24%, respectively, but, under the damp conditions at this site, also accelerates salt accumulation at the site surface and stimulates moss growth. Strong sunlight through a skylight can result in deterioration even of light-insensitive historical sites within archaeological museums, and so skylights in archaeological museums should be rationally designed to avoid sunlight directly hitting the surface of historical sites housed within them.

Energy savings and daylighting evaluation of dynamic venetian blinds and lighting through full-scale experimental testing

Commercial buildings consume around 20% of the total energy utilized in the U.S. The use of shading devices in buildings has the potential to reduce building energy consumption while also providing a more desirable indoor environment for building occupants. Similarly, lighting device controls help reduce lighting energy consumption as well as internal loads. However, there is lack of full-scale experimental testing of integrated dynamic shading and lighting controls. This study presents full-scale experimental testing data to quantify these energy and daylighting impacts. Testing was performed utilizing two different control strategies, in three different orientations under three different types of sky conditions. The shading device was also used in conjunction with two different types of glazing. An average of 25.4% cooling energy savings and 48.5% lighting energy savings was achieved. Visual discomfort evaluated using Simplified Daylight Glare Probability was prevented more than 85% of time during occupied hours. Improvement in daylight levels evaluated using Useful Daylight Illuminance was also achieved. Finally, analysis of the relationship between the illuminance level measured at the work plane and a ceiling illuminance sensor is performed to translate the real-world applicability of shading device controls.

Comparative photosynthetic responses of Norway spruce and Scots pine seedlings to prolonged water deficiency

Stressors of different natures, including drought stress, substantially compromise the ability of plants to effectively and safely utilize light energy. We investigated the influence of water stress on the photosynthetic processes in Picea abies and Pinus sylvestris, two species with contrasting drought sensitivities. Spruce and pine seedlings were exposed to polyethylene glycol 6000-induced water deficits of different intensities and durations. The maintenance of photosystem I (PSI) oxidation in spruce required increased photosynthetic control and led to the increased reduction of the plastoquinone pool, which was not the case in pine seedlings. As a result of increased excitation pressure, photosystem II (PSII) inactivation was observed in spruce plants, whereas in pine, the decreased PSII photochemistry was likely due to sustained non-photochemical quenching. Downregulation of PSII photochemistry and maintenance of PSI in an oxidized state were linked with the prevention of oxidative stress, even under severe water deficit. The decreased photosynthetic pigment content and photosynthetic gene expression suggested the coordinated downregulation of photosynthetic apparatus components under water stress to reduce light energy absorption. In summary, the observed adaptative mechanisms of pine and spruce to water stress may be similar to the well-studied adaptative mechanisms to winter stress, which may indicate the universality of protective mechanisms under various stresses in conifers.

Simulation analysis of natural lighting of residential buildings in Xi'an, China

The optimized design of natural lighting for residential buildings can greatly reduce lighting energy consumption and improve indoor environmental quality as well as the physical and mental health of residents. Through the DIALux simulation analysis, this paper analyses the importance of natural lighting factors in the Xi'an residential area and analyses factors such as latitude, date, window position, building aspect ratio, building height and window area. The study found that the winter solstice (December 22) is the most unfavourable day for residential lighting in Xi'an. Considering architectural beauty, building energy savings and natural lighting, the winter solstice is an effective time to calculate the window area of residential buildings in Xi'an. The higher the latitude is, the larger the window area required for the house. From April to August, the influence of latitude on window area is small; from January to April and from August to December, latitude has a greater influence on window area. This paper establishes a regression equation for residential window area in Xi'an and provides calculation tools for architects to use when designing residential windows that provides a reference for the design of residential windows at the same latitude (33° north latitude). Intelligent control strategies are put forward on natural lighting in residential buildings for working class families in this paper. An APP on smart phones is developed to realize the intelligent control of curtains. In accordance with family daily routine, the opening width of curtains is controlled automatically based on room functions and exterior illuminance, through which interior illuminance can be adjusted, indoor environmental quality can be improved and energy consumption of HVAC system can be reduced.

Optimizing windows for enhancing daylighting performance and energy saving

Using sustainable architecture design strategies specifically daylighting could reduce lighting energy that have an indirect impact on the HVAC energy requirements especially in cooling-dominated buildings in hot climate. As a result of the interactions between lighting and HVAC, the aims of this paper were to reduce the energy consumption by having the balance between beneficial natural light and excessive solar heat and therefore reducing the energy consumption and to have an easy guideline for the architecture to help in increasing the sustainable building designs in Egypt. This paper utilized simulation techniques for identifying the most efficient glazing with a good WWR and a correct daylight autonomy by dominating the thermal heat gain and reducing cooling load yet as energy consumption.Performance predictions and simulations will facilitate in distinguishing ways for reducing energy consumption and up building performance by rigorous analysis method and that is what's this analysis methodology is about. The implementation of the simulation process is carries out using Rhinoceros 3D modeling which supports DIVA for rhino as a simulation engine to space with southern orientation in Alexandria, Egypt.The outcome of this analysis is needless to say selecting the right glazing kind could be a Brobdingnagian issue of reducing energy.