Horizontal Light Research Articles

Self-Oscillations of Submerged Liquid Crystal Elastomer Beams Driven by Light and Self-Shadowing

Liquid Crystal Elastomers (LCEs) are responsive materials that undergo significant, reversible deformations when exposed to external stimuli such as light, heat, and humidity. Light actuation, in particular, offers versatile control over LCE properties, enabling complex deformations. A notable phenomenon in LCEs is self-oscillation under constant illumination. Understanding the physics underlying this dynamic response, and especially the role of interactions with a surrounding fluid medium, is still crucial for optimizing the performance of LCEs. In this study, we have developed a multi-physics fluid-structure interaction model to explore the self-oscillation phenomenon of immersed LCE beams exposed to light. We consider a beam clamped at one end, originally vertical, and exposed to horizontal light rays of constant intensity focused near the fixed edge. Illumination causes the beam to bend towards the light due to a temperature gradient. As the free end of the beam surpasses the horizontal line through the clamp, self-shadowing induces cooling, initiating the self-oscillation phenomenon. The negative feedback resulting from self-shadowing injects energy into the system, with sustained self-oscillations in spite of the energy dissipation in the surrounding fluid. Our investigation involves parametric studies exploring the impact of beam length and light intensity on the amplitude, frequency, and mode of oscillation. Our findings indicate that the self-oscillation initiates above a certain critical light intensity, which is length-dependent. Also, shorter lengths induce oscillations in the beam with the first mode of vibration, while increasing the length changes the elasticity property of the beam and triggers the second mode. Additionally, applying higher light intensity may trigger composite complex modes, while the frequency of oscillation increases with the intensity of the light if the mode of oscillation remains constant.

Plumes of Water Ice/Gas Mixtures Observed in the Lunar Polar Region

The presence of water condensation in the lunar polar region has been reported. However, the origin and amount of water remain unknown, and information on the migration mechanism of water is key for understanding the delivery of water to the Earth–Moon system. We herein report the first identification of the migration process observed as localized and condensed plumes of water ice/gas mixtures ejected from the lunar surface to space in the polar region based on spectral data derived by SELENE/Kaguya. We identified water and other volatile absorption in 10,200 spectra at the nonpermanent shadowed region during the nighttime when no illumination reached the lunar surface, while nearly horizontal solar light at these regions could illuminate the sky. Ray-tracing analyses suggested that the majority of the observed volatile signal did not come from the lunar surface but from the sky (space). The majority of the identified plumes were observed at or near the hydrogen distribution reported previously. Volatile materials were repeatedly identified in some locations and most of the plume events did not coincide with the major meteoroid streams. Rather, more signals were identified during the winter season in each pole. The timing, duration, location, and temperature simulations all suggest that impact events cannot be their main origin, but rather the volatile sublimation from the subsurface (∼10 cm depth). Overall, it was revealed that the lunar polar region is active in terms of volatile migration, which is significant for understanding water delivery to the Earth–Moon system.

Clinical characteristics and lateralization of the horizontal semicircular canal light cupula.

Positional vertigo and nystagmus are the main symptoms and signs of dizziness, respectively. Despite the clinical utility of the supine roll test (SRT) and null point (NP) in diagnosing light cupula, a type of positional vertigo, there exists a notable gap in the literature concerning the comprehensive evaluation of lateralization values based on various nystagmus characteristics and the intensity of direction-changing positional nystagmus (DCPN) in the SRT, particularly in comparison to the NP. Additionally, limited data on abnormal canal paresis (CP) in light cupula patients underscores the need for further research with a larger patient population to elucidate this mechanism. This study aims to investigate the characteristics of positional nystagmus and lateralization of the horizontal semicircular canal (HSCC) light cupula, which is a type of positional vertigo and nystagmus that is poorly understood. Eighty-five patients (17 males, 68 females; mean age, 60.9 years) with light cupula were reviewed. We summarized the characteristics of spontaneous nystagmus and positional nystagmus, including supine positioning nystagmus, bow nystagmus, and lean nystagmus. Then, the side of the NP was identified as the affected side, and the values of the fast phase direction of the spontaneous nystagmus, supine positioning nystagmus, bow nystagmus, and lean nystagmus, as well as the intensity of the DCPN in the SRT, were used to diagnose the affected sides. Caloric testing was also performed for some patients. Light cupula was observed in 5.7% of the patients with positional nystagmus. The frequencies of supine positioning nystagmus (88.2%), bow nystagmus (90.6%), and lean nystagmus (83.5%) were higher than spontaneous nystagmus (61.2%) (p < 0.001). The second NP (NP2) (92.9%) and third NP (NP3) (83.5%) were readily detected, affecting the left and right sides in 38 and 47 patients, respectively. Lateralization through the fast phase directions of bow nystagmus and lean nystagmus did not significantly differ from that of NP (all p > 0.05). However, the accuracy rate of lateralization through the sides with more vigorous DCPN in the SRT was 63.5%, significantly lower than through NP (p < 0.001). Particularly in patients with supine positioning nystagmus (n = 75), the rate was only 58.7% (p < 0.001). However, the rate was 100% in patients without supine positioning nystagmus (n = 10). Among the 70 patients who underwent caloric testing, 37 had abnormal CP, and the sides of the reduced caloric reaction were ipsilateral to the affected sides of the light cupula in 83.8% of the patients. Besides utilizing the NP to determine the affected side, the fast phase direction of the bow nystagmus or lean nystagmus can also aid in identification. However, a simple comparison of the intensity of DCPN in SRT cannot provide accurate lateralization, especially in patients with supine positioning nystagmus. There is a high incidence of CP on the affected side of the light cupula.

Einstein’s special relativity applies a not recognized physical mistake leading to an absurd interpretation of the Michelson‐Morley experiment and absurd physics

Special relativity (SR) needs different speeds of light in the horizontal arm of the Michelson‐Morley interferometer to “explain” a constant speed of light in all inertial frames. To obtain equal speeds from the two different speeds of light (c−v) = [(1 ‐ v/c) × c] and (c + v) = [(1 + v/c) × c], Einstein mathematically accelerates the speed of the photons in the direction of Earth’s motion around the Sun from [(1 ‐ v/c) × c] to [(1 − v2/c2) × c], and in the opposite direction, Einstein decelerates the speed of the photons from [(1 + v/c) × c] to [(1 − v2/c2) × c]. Besides the fact that light cannot be accelerated or decelerated, a change of the speed of the photons in the inertial frame of the Sun would also change the speed c of photons on Earth, because in both inertial frames, the photons always move in horizontal light path of the Michelson‐Morley interferometer in the same direction. SR contradicts its own postulates: 1. SR contradicts the constant speed c of light on Earth; 2. SR contradicts the constant speed c of light in all inertial frames, respectively, in all frames of reference; 3. SR contradicts the principle of relativity. Einstein transformed photons into particles that are allowed to violate logical and physical laws but are not allowed to interact with gravity, so that they have to follow curved world lines. However, giving up logical and physical laws because of precise predictions of a physical theory means arguing pseudo-scientifically. Instead, a simple quantum physical explanation of gravity is presented.

Walking After Dark: A Sidewalk Illumination Case Study in Cedar City, UT

Sidewalks are an important part of public space, but they are becoming increasingly dangerous, especially at night. Therefore, it is important that sidewalks are adequately illuminated to meet the safety, comfort, and accessibility needs (i.e., provide high levels of pedestrian reassurance) to sidewalk users. The objective of this case study was to quantitatively measure and subsequently explore the spatial and statistical distributions of light intensities along the sidewalks that surround Southern Utah University in Cedar City, Utah. A secondary objective was to develop a set of “adequate lighting” guidelines (i.e., 5 to 10 lux) to help identify areas that could benefit from sidewalks lighting enhancements. A digital light meter was used to measure horizontal light intensity, in lux, at a systematic sample of 208 points along the sidewalks within the study area. Geographic coordinates were also collected for each sample observation to enable mapping and spatial analysis of the light intensity data. Results indicate 61% of the observations have lux values equal to zero (complete darkness), 13.4% met or exceeded the minimum guidelines, while 4.3% fell within the “adequate lighting” guidelines adopted by this case study. These results suggest that sidewalks are too dark in too many places to provide reassurance to sidewalk users in the study area. The mapping and spatial analysis results from this case study also provide information to support targeted visibility enhancements of sidewalks within the study area. KEY WORDS: Lighting; Optimum Illuminance; Luminometer; Sidewalks; Pedestrians; Safety; Security; Reassurance

Daylight performance of horizontal light pipe and shading systems in office room with bilateral opening

Daylighting implementation in the building can reduce building energy use. Previous research about Horizontal Light Pipe and shading systems in the Tropics examined daylighting strategies in a room with a unilateral opening, which receives daylight through a window in one wall. The bilateral openings from two adjacent side windows have the potential to improve daylight distribution and have yet to be discussed in previous research. This research evaluates the daylight level and distribution of HLP and shading systems in a room with a bilateral opening from two adjacent windows. The research method is experimental with simulation using IES-VE (Integrated Environment Solution-Virtual Environment) as a tool. The Daylight Factor (DF) and Uniformity Daylight Factor (UDF) of a room with bilateral openings from two adjacent windows were compared with a room with bilateral openings, HLP, and shading systems. The results indicate that integrating HLP and shading systems in an office room with two adjacent side windows decreases the average Daylight Factor (DF) by 48.74%, bringing the average DF fulfilling the recommended DF level for the office room. HLP and shading systems improve the Uniformity Daylight Factor and percentage of sensor points with DF 2-5%, as high as 56% and 67.38%, sequentially.

The impact of aspect ratio of buildings implementing Horizontal light pipe and shading systems on daylight performance

ABSTRACT Deep-plan buildings limit daylight use in spaces far from the building perimeter, leading to uneven daylight distribution. Integrating a Horizontal Light Pipe (HLP) as an optical daylighting system, reflective light shelves, and blinds as shading systems can reduce excessive daylight levels at the perimeter area of a building and improve daylight uniformity. Earlier investigations of HLP daylight performance concentrated on fixed building geometries, but few studies focused on the building aspect ratio, one of the design variables of building geometry that greatly influences daylight performance. This study aims to investigate the impact of the aspect ratio of buildings implementing HLP and shading systems on daylight performance. The research method was experimental, using IES-VE simulation as a tool. The daylight factor (DF), uniformity daylight factor (UDF), and useful daylight illuminance (UDI) of various aspect ratios and depths of office buildings implementing HLP and shading systems were analyzed. The results show that increasing the building aspect ratio from 1:1 to 2.1:1 sequentially increased the average DF and UDF values by 18.47% and 17.2%, respectively. Improving the building aspect ratio from 1:1 to 2.1:1 along the east-west axis improved the UDI by 3%, whereas the north-south axis decreased it by 10.2%.

Investigation of the Efficacy of Horizontal Hollow Light Tubes for Energy Conservation in Illuminating Buildings

This study investigates the properties of light transmission and distribution, examining how incident light angles impact illuminance distribution and daylight factor. Light tubes are acknowledged as promising tools to enhance lighting conditions and reduce energy consumption in building design. The study involved installing horizontal hollow light tubes, each measuring 0.5 m in length and 0.30 m in diameter, on a wooden test model. A 20-watt LED lamp was employed as the light source, and an illuminance meter recorded the values at various horizontal and elevation angles. The study’s assessment included calculating the average illuminance and daylight factor to obtain light transmission efficiency and energy-saving potential. The findings revealed that both aluminum alloy and zinc alloy tubes experienced a decrease in illuminance as incident elevation angles increased, with the most effective light transmission occurring at a horizontal angle of 90°. Notably, the aluminum alloy tube outperformed the zinc alloy tube, demonstrating more than a 15% increase in light transmission efficiency. Furthermore, the daylight factor values from both types of tubes aligned with established standards for residential and office activities, underscoring their potential as energy-efficient lighting solutions for spaces lacking natural light or with limited illumination.

Detection of Mooney faces is robust to image asymmetries produced by illumination.

Face detection relies on the visual features that are shared across different faces. An important component of the basic spatial configuration of a face is symmetry around the vertical midline. Although human faces are structurally symmetrical, they can be asymmetrical in an image due to the direction of lighting or the position of the face. In the experiments presented here, we examined how face detection from simple contrast patterns that occur across the face is affected by the image asymmetries associated with variations in the horizontal lighting direction. We presented observers with two-tone images of faces (Mooney faces) that isolated the unique pattern of contrast in the shading and shadows on a face, illuminated from a wide range of horizontal directions. In two experiments, we found that face detection is surprisingly robust to these lighting changes, with sensitivity in discriminating between face and non-face patterns reduced only at the most extreme lighting directions. This tolerance to changes in the horizontal lighting direction depended partly on the orientation of the face, vertical lighting direction, and contrast polarity. Our results provide insight into how contrast cues produced by shading and shadows occurring across the facial surface are utilized by the visual system to detect human faces.

Daylight Performance of Integrated Horizontal Light Pipe with Shading Devices (Validation) for High-Rise Building in Tropical Climate

Daylight is known to bring benefits to human in terms of productivity, psychology, and physiology. The emergence of deep plan layout in high-rise hinders the utilisation of the abundance daylight available in tropical climate. This brings challenges to ensure a uniform distribution in the interior room. This study focuses on the software validation of the integration of a horizontal light pipe (LP) and shading devices (SD) to illuminate the deep plan where the former provides daylight in the deepest portion of the room while the latter helps to shade the excessive daylight at the window opening. The shading devices that have been chosen are overhang, light shelf, and blinds. The computer simulation, Integrated Environment Solution: Virtual Environment (IESVE), is being validated with physical model experiment with a scale of 1:10. The experiment was conducted in an open carpark in Universiti Sains Malaysia, Penang, Malaysia from 9am to 3pm for two days. The validation was done using graph comparison, Pearson Correlation, relative root mean square error (RRMSE), and relative mean bias error (RMBE). The results shows that the daylight ratio (DR) from the software has positive relationship with the experiment data. Hence, the software can be used to further simulate various integration of LP and SD.

Discrimination of facial identity based on simple contrast patterns generated by shading and shadows

The pattern of shadows and shading across a face is determined partly by face shape and may therefore provide a cue for facial recognition. In this study, we measured the ability of human observers to discriminate facial identity based simply on the coarse pattern of contrast produced by the interaction between facial geometry and lighting direction. We used highly realistic 3D models of human heads to create images of faces illuminated from different horizontal and vertical directions, which were then converted to two-tone images (‘Mooney faces’) to isolate the coarse pattern of contrast. Participants were presented with pairs of two-tone faces and judged whether it was the same person in both images. Participants could discriminate facial identity based on the minimal cues within the two-tone images, though sensitivity depended on the horizontal and vertical lighting direction. Performance on the Mooney recognition task correlated with general facial recognition ability, though the role of face-specific processing in this relationship was not significant. Our results demonstrate that shading information in the form of simple contrast cues is sufficient for discriminating facial identity, and support the idea that visual processing is somewhat optimised for overhead lighting – here, in the relatively high-level context of face identity recognition.

P‐174: The causes and improvement of the waterfall in Mini/MicroLED Displays

The display product using Mini/MicroLED backlight, in the case of using the PWM dimming method, with the OC (open cell, OC) of the 4‐mask process, there will be a significant change in the horizontal light and dark band under the low gray level, which is called the waterfall phenomenon in the industry. In this paper, the causes of the waterfall phenomenon are analyzed and studied, and three methods of improving the waterfall are proposed. Experimental tests were carried out on the module of 34‐inch 1152 partition, and the display effect before and after the improvement was compared, and the effectiveness of the proposed method was verified.

Validation of IES-VE for Assessing Daylight Performance of Building Implementing Horizontal Light Pipe and Shading Systems in the Tropics

Abstract. Various daylight simulation tools, which are rapidly developed, become a reliable way for simulating the complex daylighting environment. Empirical validation of the daylight simulation tool is essential in determining its reliability, especially in simulating light transport and shading system in the Tropics. Distinct from previous research, the validation involves Horizontal Light Pipe (HLP), a side window with shading systems in different room aspect ratios and orientations. This study aims to validate the simulation results of Integrated Environmental Solutions-Virtual Environment (IES-VE) Radiance IES with the measurement results of physical scaled models for evaluating HLP, light shelves, and blinds' daylight performance under intermediate and overcast sky conditions. Two physical scaled models 1:10 represent office rooms with HLP and shading systems with different room aspect ratios were constructed. Daylight Factor (DF) and Daylight Ratio (DF) of physical scaled model measurement and IES-VE simulation were compared. The results showed that under intermediate and overcast sky conditions, the Pearson correlation between simulation and measurement results using DR and DF was strong, significant, and positive, as high as 0.84 and 0.80, respectively. The Mean Bias Error between simulation and measurement results under intermediate and overcast sky conditions were -12% and -7.7%, respectively. IES-VE is reliable to evaluate the HLP and shading systems' daylight performance with different room orientations in the Tropics.

How to Design the eHMI of AVs for Urgent Warning to Other Drivers with Limited Visibility?

The importance of an external interaction interface (eHMI) has grown in recent years. Most eHMI concepts focus on communicating autonomous vehicle (AV)'s yielding intention to pedestrians at a crossing. However, according to previous studies, pedestrians at a crossing rely mainly on the vehicle's movement information (implicit communication) rather than information from eHMIs (explicit communication). This paper has the purpose of proposing a specific use case in which the eHMI of future AVs could play an indispensable role in the safety of other road users (ORUs). Often VRUs cannot see the traffic flow due to a series of parked or stopped vehicles, which is a frequent cause of fatal traffic collision accidents. Drivers may also not be able to see approaching pedestrians or other cars from the side for the same reason. In this paper, the impact of an eHMI is tested from the perspective of drivers with limited visibility when a jaywalker steps into the road. A combination of colors, shapes, and information levels is presented on an eHMI. We show that our proposed eHMI design, in the deadlock scenario of a jaywalker and a driver who both lack visibility, significantly reduced the reaction time compared to when there was no eHMI. In the experiment, the willingness to stop, varying from 0 to 5, was measured from the driver's perspective. The results showed that most users felt uncertainty and did not move quickly when seeing the light band color alone. Textual information on the eHMI was significantly more effective in providing an urgent warning of this specific scenario than vertical and horizontal light bands with color without text. In addition, red color, blinking rapidly above 3 Hz, and egocentric messages were also necessary to reduce the PRT(perception response time). By using text-added eHMI (Vertical + Text eHMI), the mean time to achieve a score above 4 for willingness to stop was 2.113 s faster than when there was no eHMI. It was 2.571 s faster than the time until the slider of the participants reached the maximum level for willingness to stop. This is a meaningful amount of difference when considering a PRT of 2.5 s, which is the Korean road design standard. As eHMIs tend to be applied for smarter mobility, it is expected that they will be more effective in preventing accidents if the eHMI is standardized in autonomous driving level 2 to 3 vehicles driven by humans before fully autonomous driving becomes a reality.

P‐10.12: The causes and improvement of the waterfall in Mini/MicroLED Displays

The display product using Mini/MicroLED backlight, in the case of using the PWM dimming method, with the OC (open cell, OC) of the 4-mask process, there will be a significant change in the horizontal light and dark band under the low gray level, which is called the waterfall phenomenon in the industry. In this paper, the causes of the waterfall phenomenon are analyzed and studied, and three methods of improving the waterfall are proposed. Experimental tests were carried out on the module of 34-inch 1152 partition, and the display effect before and after the improvement was compared, and the effectiveness of the proposed method was verified.

Solutions for Horizontal light and Dark Lines Issue of Z-zig pixel arrangement Liquid Crystal Display

Solutions for Horizontal light and Dark Lines Issue of Z-zig pixel arrangement Liquid Crystal Display

Efficient sunlight harvesting with combined system of large Fresnel lens segmented mirror reflectors and compound parabolic concentrator without tracking sun for indoor daylight illumination

Sunlight is a great substitute for indoor artificial lighting during the daytime but still isn't so viable because of the cost of fiber-based daylighting system and its efficiency. In this paper, we report the design and development of a cost-effective non-mechanical tracking-based solar concentration system using a combination of a large Fresnel lens, segmented mirrors, and segmented compound parabolic concentrator (SCPC) for indoor daylighting application. This system presents the three-stage collection of sunlight by means of extending the collection aperture vertically while keeping the horizontal area same. First one is the concentrated light from the Fresnel lens, the second one is the direct sunlight incident onto the CPC and the third one is the direct sunlight reflected from the segmented mirrors onto the CPC. Hence the light transported through this system is adequate for illumination purposes inside the room. The manufacturing of ideal CPCs through the moulding process is both expensive and complex, and it necessitates extreme precision. Therefore, a cost-effective and efficient segmented CPC is designed and developed using a highly reflecting mirror-polished aluminum sheet which works well compared to the ideal CPC. To transport concentrated sunlight inside the room a highly reflecting horizontal light pipe is designed and developed. The collimated light at the output is challenging therefore, we have coupled inverted CPC at the exit of segmented CPC in the system. Further, to guide sunlight deep into the rooms we have coupled the entire system with a rectangular light pipe. An efficient diffuser is coupled at the end of the rectangular light pipe to illuminate the room uniformly. Various optical parameters such as illuminance, color rendering index (CRI), and correlated color temperature (CCT) values are analyzed from the result obtained which shows that the system can efficiently transport sunlight deep inside the room throughout the day. Therefore, the proposed system is very much helpful for the sustainable development of a country.

Absurd: Einstein’s special relativity (SR) causes an inconstant speed of light, claiming to explain the consequences of a constant speed c

Einstein was led astray by a physically incorrect calculation by Michelson and Morley in the context of the Michelson‐Morley experiment. For the light beam in the horizontal light path, their calculation yields the claim that [(1 − v/c) × c] + [(1 + v/c) × c] = 2[(1 − v2/c2) × c]. This is incorrect and mathematically increases the horizontal light path 2d 0 by the factor [(1 + v2/c2)], which Einstein’s theory of special relativity corrects by introducing the time dilation factor γ and the length contraction factor 1/γ. When we calculate correctly, the mathematical increase in the length of horizontal light path no longer happens and Einstein’s mathematical corrections of the horizontal light path imply an inconstancy of the speed of light. This means that Einstein’s special relativity is just a mathematical correction of a physical calculation error, not a true physical theory, and it was thus pure chance that Einstein found the physically real kinematic time dilation factor γ. The null result of the Michelson‐Morley experiment, along with the kinematic and gravitational time dilation, must instead be explained by a constant value for the speed c of light with respect to the gravitational potentials of predominant gravitational fields, resulting from the principles of minimum energy and energy conservation. On this basis, it becomes possible to predict so-called general relativistic phenomena, e.g., the precession of Mercury’s perihelion or the phenomena observed in the binary pulsar PSR B1913 + 16, just by applying Kepler’s second law and simple quantum physical considerations. [R. G. Ziefle, Phys. Essays 33, 99 (2020)].

Daylighting Performance of Integrated Venetian Blinds with Horizontal Light Pipe System for Deep Plan High-Rise Office in Tropical Climate

A substantial amount of daylight is received by tropical countries like Malaysia. There are advantages and disadvantages to using this renewable resource in a high-rise office building. Such buildings' deep plan spaces make it difficult to create a uniform daylight distribution across the space. A solution for this issue is the usage of an integrated Venetian blind (VB) with a horizontal light pipe (LP). Using an overcast and intermediate sky in South orientation, seven (7) distinct types of VB angle configurations were simulated using the Integrated Environment Solution Virtual Environment (IESVE) to evaluate how well they performed in daylight with an integrated LP. The findings demonstrated that the daylight uniformity throughout the room was improved by the integration of the VB and LP systems. When compared to a room with only a LP installed, VB with 0o and -15o angles had the best performance. The combination of LP and VB allowed for the shading of the front portion of the space and at the same time, illuminating the rear portion of the space. The results of this study encourage building designers to utilise the integrated VB and LP in the deep open-plan high-rise office building and reduce the use of non-renewable energy resources.

Illumination and Lighting Energy Use in an Office Room with a Horizontal Light Pipe: Field Study at a High Latitude

This paper describes a field study of the illumination and lighting energy use in a full-scale test office in a building located in southern Norway. Natural light is provided to the office via southwest-oriented windows and a horizontal light pipe (HLP) with a daylight entrance facing the south. The study is a full-scale field study, and it is a continuation of the recently published study addressing a scale model and a theoretical model. The novelty of this study is a custom-made reflector for the HLP’s daylight distribution to preserve the features of natural light noted as the primary human association with daylight. The main research aim was to determine if the daylighting level in the back of the office was improved as a consequence of the daylighting provision from the HLP compared to a reference situation without a HLP, as well as whether the lighting energy use for the electric lighting system that was supposed to provide the recommended light level was reduced. This study includes monitoring of the outdoor and indoor illuminance levels as well as the energy consumption of the luminaires throughout the study’s test period and a corresponding reference period. The recorded data were used to test hypothesis applying inferential statistical analyses. In conclusion, this paper reports an increased daylight level on the working area in the rear part of the office of approximately 200 to 300 lx during clear and sunny days at equinox. The increased daylight level on the working area near the window of approximately 50 lx was also recorded. These findings have important implications for energy balance in the Zero Energy Buildings (ZEB) and the ‘peak load’ for energy consumption.