Reflection Of Sunlight Research Articles

A Superhydrophobic Dual-Mode Film for Energy-Free Radiative Cooling and Solar Heating.

Traditional electric cooling in summer and coal heating in winter consume a huge amount of energy and lead to a greenhouse effect. Herein, we developed an energy-free dual-mode superhydrophobic film, which consists of a white side with porous coating of styrene-ethylene-butylene-styrene/SiO2 for radiative cooling and a black side with nanocomposite coating of carbon nanotubes/polydimethylsiloxane for solar heating. In the cooling mode with the white side, the film achieved a high sunlight reflection of 94% and a strong long-wave infrared emission of 92% in the range of 8–13 μm to contribute to a temperature drop of ∼11 °C. In the heating mode with the black side, the film achieved a high solar absorption of 98% to induce heating to raise the air temperature beneath by ΔT of ∼35.6 °C. Importantly, both sides of the film are superhydrophobic with a contact angle over 165° and a sliding angle near 0°, showing typical self-cleaning effects, which defend the surfaces from outdoor contamination, thus conducive to long-term cooling and heating. This dual-mode film shows great potential in outdoor applications as coverings for both cooling in hot summer and heating in winter without an energy input.

A hierarchically structured self-cleaning energy-free polymer film for daytime radiative cooling

Radiative cooling without using electricity represents an ideal green solution for air-conditioning. Despite exciting progress made so far, most of the radiative cooling materials are vulnerable to outdoor contamination, which leads to decreased performance. Herein, we fabricate a hierarchically structured PVDF/PDMS porous film which integrates strong sunlight reflectance (97%), high thermal-infrared emittance (96%) and robust superhydrophobicity (160.2°). The synergy of the effective solar reflection and thermal-infrared emission enables the film to yield a sub-ambient temperature drop of 12.3 °C under strong sunlight. More importantly, the superhydrophobicity keeps the film away from contamination by self-cleaning, maintaining well the radiative cooling performance for a long-term outdoor use. Additionally, the as-obtained film shows excellent chemical durability after exposure to different pH solutions and UV light irradiation. This work provides a new strategy to integrate self-cleaning with radiative cooling, showing great potential to advance energy-free cooling materials toward real-world applications.

A method of estimating the spatiotemporal distribution of reflected sunlight from glass curtain walls in high-rise business districts using street-view panoramas

• A novel method is proposed to estimate the spatiotemporal distribution of reflected sunlight. • A novel panoramic transformation algorithm to qualify sunlight reflection duration. • A new method to estimate time-specific reflection intensity from glass curtain walls. • The spatiotemporal distribution of reflection is affected by season, city morphology, and building characteristics . Obtaining the time and location of sunlight reflection within a street environment is important to improve the comfort and safety of public spaces. This paper proposes a method to estimate the spatiotemporal distribution of sunlight reflection within a street based on street-view data. First, the solar path on the panorama is plotted to obtain the potential orientation of the radiation source and the reflection on building facades. Next, the continuous time–date distribution of direct and reflected sunlight at a certain site is obtained by the panoramic projection transformation approach. The accumulative duration and time-series parameters of the reflected scenario are estimated by a matrix operation. By mapping the time-specific duration of the sunlight reflection scene, we can obtain the spatiotemporal distribution within the street network. We applied the proposed method to a case study in a high-rise business district and quantified the range, duration, and intensity of reflected sunlight in the surrounding area. Seasonal changes, city morphology, and facade orientation were found to be the factors affecting the distribution tendency of reflected sunlight. The risk detection, visualization, and quantification analysis results on sunlight reflection can provide a reference for city management, urban planning, and environmental evaluation.

The role of silicon in plant under normal conditions and stress

The paper is a review view data on the role of silicon (Si) in the physiology of higher taxa plants; data on the synthesis and localization of Si in cells, as well as its participation in the mechanisms of tolerance and plasticity of plants under the influence of adverse environmental conditions. The unique physical properties of silicon are described, which explain its bioactivity as a regulator of absorption and reflection of sunlight, as well as a regulator of photosynthesis. The role of silicon in the regulation of water balance and transpiration of plants, in the protection of plant cells for the action of biotic and abiotic stresses by including protective mechanisms at the level of the organs, tissue and cell are shown. Recent studies have shown some homology of aquaporin proteins and silicon transporters. Particular attention is paid to the effect of silicon on the expression of genes involved in the synthesis of osmotic substances and secondary metabolites with protective properties. The study confirms that the conceptual basis for the protection and preservation of flora from abiotic and biotic stresses may be the preservation and reproduction of species characterized by increased silicon uptake and accumulation of this ion in plant organs. Thus, the obtained data indicate the prospects of further studies of silicon participation in plant adaptation to adverse changes upon environmental factors in natural ecosystems or agrocoenosis with modern conditions of increasing anthropogenic pressure and forecast of global climate change.

Hierarchically Designed Three-Dimensional Composite Structure on a Cellulose-Based Solar Steam Generator.

The emerging water purification technology represented by solar water evaporation has developed rapidly in recent years and is widely used in seawater desalination. However, the high reflectivity of sunlight and low efficiency of photothermal conversion greatly hinder its application prospects. In this paper, the hierarchical structure of the film was designed and optimized by the addition of carbon materials in the process of bacterial cellulose culture. A cellulose-based composite film material with a microporous structure was obtained, which can improve the photothermal evaporation rate and photothermal conversion efficiency from the structural principle to improve the stability of floating on the water. Bacterial cellulose (BC) as a three-dimensional carrier was combined with one-dimensional and two-dimensional (1D/2D) compounds of carbon nanotubes (CNT) and reduced graphene oxide (RGO) to form composite films for solar evaporation. By the addition of CNT-RGO (21.8 wt %), the composite showed prominent photothermal evaporation rate and photothermal conversion efficiency properties. Through in situ culture of BC, not only a tight structure can be obtained but also the surface of BC contains a large number of hydroxyl groups, which have many active sites to load photothermal materials. BC nanofibers, CNT, and RGO cooperate to form a porous network structure, which provides continuous double channels for the rapid transmission of water molecules and light paths, so as to form an excellent photothermal layer. The photothermal conversion efficiency is 90.2%, and the photothermal evaporation rate is 1.85 kg m-2 h-1 to achieve efficient solar interface evaporation. This is a high level of photothermal properties in a cellulose-based solar steam generator. The superior photothermal performance of this hybrid film possesses scalability and desalination ability.

Volcanic Climate Warming Through Radiative and Dynamical Feedbacks of SO2 Emissions

AbstractVolcanic flood basalt eruptions have been linked to or are contemporaneous with major climate disruptions, ocean anoxic events, and mass extinctions throughout at least the last 400 M years of Earth's history. Previous studies and recent history have shown that volcanically‐driven climate cooling can occur through reflection of sunlight by H2SO4 aerosols, while longer‐term climate warming can occur via CO2 emissions. We use the Goddard Earth Observing System Chemistry‐Climate Model to simulate a 4‐year duration volcanic SO2 emission of the scale of the Wapshilla Ridge member of the Columbia River Basalt eruption. Brief cooling from H2SO4 aerosols is outweighed by dynamically and radiatively driven warming of the climate through a three orders of magnitude increase in stratospheric H2O vapor.

Towards a standard approach for annual energy production of concentrator-based building-integrated photovoltaics

A form of building-integrated photovoltaics, luminescent solar concentrators are devices used to enhance solar cell output per unit area through red-shifted, concentrated internal reflection of sunlight. Luminescent solar concentrators have shown promise, but they have yet to achieve commercial success. At present, it is prohibitively difficult for architects and solar engineers to assess their annual energy production and subsequently conceptualize their economic potential. To bridge this gap, this paper provides an approach for annual performance evaluation of luminescent solar concentrators that parallels conventional processes used internationally for existing photovoltaic projects and solar development proposals. The approach starts by following conventional processes to evaluate the plane-of-array irradiance. Then, two metrics are introduced to evaluate the effective irradiance incident on solar cells within an LSC: 1) LSC optical efficiency is employed to determine the proportion of light reaching solar cells relative to the exposed surface; 2) LSC spectral mismatch factor is defined to represent the impact of spectral differences due to absorption and luminescent emission within an LSC. These metrics have never been employed in such a context before. With their addition, the process to produce LSC energy estimates becomes analogous to the conventional process to produce estimates for solar panels. The proposed approach is first validated against the commercial software, PVsyst. Then, case studies in Albany, NY and Phoenix, AZ are conducted to present energy estimates (at the maximum power point) for solar panels, and both planar and wedge-shaped luminescent solar concentrators when mounted vertically on a southern facing surface.

Operational Detection of Sun Glints in DSCOVR EPIC Images

Satellite images often feature sun glints caused by the specular reflection of sunlight from water surfaces or from horizontally oriented ice crystals occurring in clouds. Such glints can prevent accurate retrievals of atmospheric and surface properties using existing algorithms, but the glints can also be used to infer more about the glint-causing objects—for example about the microphysical properties and radiative effects of ice clouds. This paper introduces the recently released operational glint product of the Earth Polychromatic Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) spacecraft. Most importantly, the paper describes the algorithm used for generating the key component of the new product: a glint mask indicating the presence of sun glint caused by the specular reflection of sunlight from ice clouds and smooth water surfaces. After describing the glint detection algorithm and glint product, the paper shows some examples of the detected glints and discusses some basic statistics of the glint population in a yearlong dataset of EPIC images. These statistics provide insights into the performance of glint detection and point toward possibilities for using the glint product to gain scientific insights about ice clouds and water surfaces.

중적외선 센서 위성 영상의 상온 온도 정보 추출 가능성 및 정확도

It was common knowledge in textbooks that images acquired using mid-infrared ray were not suitable for measuring temperature near room temperature. But a recent satellite image using a mid-infrared sensor show the possibility that the result measured using the mid-infrared sensor can also measure the temperature near room temperature. In this paper, the possibility and accuracy of extraction room temperature information from satellite images with mid-infrared sensors are reviewed. The mid-infrared satellite image reviewed in this paper showed the temperature of room temperature well, and regarding the reliability as an absolute value of the measured temperature, the effect of the heat transfer amount due to the direct reflection of sunlight on the surface and the effect of the infrared absorption amount absorbed in the atmosphere can be seen as a relatively small or constant value. However, the problem of uncertainty in the radiation coefficient due to physical properties, which is the limit of the non-contact thermometer, remained a problem to be solved.

Transparent radiative cooling films containing poly(methylmethacrylate), silica, and silver

Window is the least energy-efficient part of buildings or cars; however radiative cooling, as an efficient energy-zero technology, is rarely used in window films of buildings or cars. Therefore, we in this work fabricated a transparent dual-layer film for daytime radiative cooling, which contained a layer of polymethyl methacrylate (PMMA) uniformly mixed with modified silica nanoparticles (SiO2 NPs) and a layer of silver. The dispersion of the modified SiO2 NPs in PMMA was notably improved through in-site grafting PMMA, which resulted in a high transparency of the radiative cooling film even at a high filling fraction of SiO2 (20 wt%). Owing to the strong broadband IR absorbance/emittance (εAW = 94.3%) and high sunlight reflectance (ρ ≈ 50%), the dual-layer film possessed a high cooling capacity and could achieve an average temperature drop of 1.4 °C than pure PMMA film in the daytime outdoor cooling measurement. In the simulated automotive cooling test, the dual-layer film cooled the interior space up to 6 °C below ambient temperature during peak solar hours. The excellent optical property and cooling capability exhibit a promising application of building and car windows for cooling their interior spaces.

Improving displacement measurement accuracy by compensating for camera motion and thermal effect on camera sensor

Displacement measurement is a major concept in the daily maintenance and failure assessment of engineering structures. Vision-based systems offer a cost-effective, simple alternative for non-contact displacement measurement. However, its measurement is challenging because of the errors induced by camera instability (thermal effects on camera sensor and camera motion). Researchers have tried to compensate for the errors induced by camera instability in displacement calculation methods by placing fixed objects in the background. However, remotely-located objects in the background cannot fully allow for camera rotations. Supplementary sensors can be employed to measure the camera motion in six degrees of freedom (6-DOF), although this method is unable to compensate for thermal effects on camera sensor. This paper presents a dual-view system that can compensate for the camera instability by using a camera, a beam splitter, a convex lens, and a photomask. The beam splitter and convex lens enable the camera to capture dual-view data and measure the instability of the system by using the photomask. In laboratory tests, the Root Mean Squared Error (RMSE) of the displacements measured by the proposed system did not exceed 0.05 mm under the conditions of drastic temperature variations and strong winds. Outdoor tests showed that the reflection of sunlight on the objects will seriously affect the practical performance of the proposed system, and a robust localization method for the photomask is necessary. The measurement scheme design for the track structure vibration of high-speed railways proved the acceptable engineering practicability and installation flexibility of the dual-view system.

INFRAREDESIGN® as a Way of Individualizing and Protecting the Textile and High Fashion Design

Textile dyeing today includes the observation and creation of graphics, pictures and drawings for two light spectra: visible and near-infrared. In our work, we have developed systems of twin colorants - colors which are the same in the visible spectrum and different in the NIR region. Measurements of light absorbance at 1000 nm (Z) were introduced, since at this wavelength many cameras recognize the intensity of the reflection of daytime sunlight. The planned dyeing of unique clothing that gives extremely different information in the VIS (V) and NIR (Z) spectrum is proposed. In this work, the embedding of a unique hand drawing for the NIR spectrum into a complex computer graphic for the visible spectrum is demonstrated. Dyeing is done with colorants in conventional inkjet printing by producing the planned graphic form Z in the NIR spectrum, invisible to the naked eye. The final product is individualized in its form and protected; it can be detected and its two different states recognized only with dual ZRGB cameras.

The light’s in my eyes: optical modeling demonstrates wind is more important than sea surface-reflected sunlight for foraging herons

Multiple lineages of birds have independently evolved foraging strategies that involve catching aquatic prey by striking at them through the water’s surface. Diurnal, visual predators that hunt across the air-water interface encounter several visual challenges, including sun glint, or reflection of sunlight by the water surface. Intense sun glint is common at the air-water interface, and it obscures visual cues from submerged prey. Visually-hunting, cross-media predators must therefore solve the problem of glint to hunt effectively. One obvious solution is to turn away from the sun, which would result in reduction of glint effects. However, turning too far will cast shadows over prey, causing them to flee. Therefore, we hypothesized that foraging herons would orient away from, but not directly opposite to the sun. Our ability to understand how predators achieve a solution to glint is limited by our ability to quantify the amount of glint that free-living predators are actually exposed to under different light conditions. Herons (Ardea spp.) are a good model system for answering questions about cross-media hunting because they are conspicuous, widely distributed, and forage throughout a variety of aquatic habitats, on a variety of submerged prey. To test our hypothesis, we employed radiative transfer modeling of water surface reflectance, drawn from optical oceanography, in a novel context to estimate the visual exposure to glint of free-living, actively foraging herons. We found evidence that Ardea spp. do not use body orientation to compensate for sun glint while foraging and therefore they must have some other, not yet understood, means of compensation, either anatomical or behavioral. Instead of facing away from the sun, herons tended to adjust their position to face into the wind at higher wind speeds. We suggest that radiative transfer modeling is a promising tool for elucidating the ecology and evolution of air-to-water foraging systems.

Investigating the Importance of Tunnel Lighting and its Role in Reducing Traffic Accidents

Traffic safety is a major concern worldwide. Road accidents are the ninth leading cause of death in the world. Tunnel accidents are less common than road accidents. However, the severity of the accidents is more severe. One of the key factors in preventing accidents in road tunnels is proper lighting system. Failure to pay attention to this issue causes the phenomenon of black hole when approaching the tunnel, visual mismatch inside the tunnel and the phenomenon of glowing hole when leaving the tunnel. The creation of these factors has increased the risk potential at the entrance and exit of the tunnel up to 4 times the middle area of the tunnel. At the entrance to the tunnel, the reflection of sunlight from the surroundings and the lack of sufficient light usually cause some vision problems. It may lead to drivers' eyes not adapting to changing the brightness level at the tunnel entrance, thus increasing the risk of road accidents in this area. The aim of this study was to evaluate the lighting safety in very long road tunnels based on the visual adaptation of drivers in the tunnels. In this paper, first, generalities about tunnel safety are stated and using the CIE88-2004 standard, the required luminosity in the threshold, transition, interior and exit areas of the tunnel is designed. Finally, solutions are proposed to increase the safety of tunnels.

Improved YOLO Based Detection Algorithm for Floating Debris in Waterway.

Various floating debris in the waterway can be used as one kind of visual index to measure the water quality. The traditional image processing method is difficult to meet the requirements of real-time monitoring of floating debris in the waterway due to the complexity of the environment, such as reflection of sunlight, obstacles of water plants, a large difference between the near and far target scale, and so on. To address these issues, an improved YOLOv5s (FMA-YOLOv5s) algorithm by adding a feature map attention (FMA) layer at the end of the backbone is proposed. The mosaic data augmentation is applied to enhance the detection effect of small targets in training. A data expansion method is introduced to expand the training dataset from 1920 to 4800, which fuses the labeled target objects extracted from the original training dataset and the background images of the clean river surface in the actual scene. The comparisons of accuracy and rapidity of six models of this algorithm are completed. The experiment proves that it meets the standards of real-time object detection.

Cutting through the noise on negative emissions

Cutting through the noise on negative emissions

Considering the effect of optical attenuation on photon-enhanced thermionic emission converter of the practical structure

Abstract Photon-enhanced thermionic emission (PETE) is a new type of solar cell. The existing papers on PETE research do not consider the structure of actual PETE devices; in practical PETE structure, the original incident light intensity is attenuated by the window layer and the buffer layer (include anode in reflection PETE devices). In this paper, according to two kinds of the common structure of PETE device, the influence of transmission and reflection of sunlight on the conversion efficiency of PETE device is analyzed. Using a light-trapping structure on the cathode of the PETE device is a valid method to reduce the reflection of the incident light. The calculation results show that the optical attenuation has a great influence on the actual photon flux received by the cathode effective layer. Under the condition of reasonable operation of the device, the efficiency of PETE can be improved by reducing the size of the material, improving the light transmittance of the buffer layer and window layer, and using the light-trapping structure.

A dynamic vertical shading optimisation to improve view, visual comfort and operational energy

PurposeThe aim of this paper is to present a parametric design method to generate optimum adaptive facades regarding occupants' comfort and building energy criteria. According to the literature review, the following questions have arisen to address the research gaps: Is it possible to have the outside view throughout the whole year without discomfort glare by utilising adaptive solar facades (ASFs)? How can architects integrate both view quality and quantity into ASF design? What is the impact of dynamic vertical shading systems mounted on south facades on the outside view, occupants' visual comfort and operational energy? How can we evaluate the view quantity through multi-layer shading systems?Design/methodology/approachIn recent years, there is a surge in demand for fully glazed buildings, motivating both architects and scholars to explore novel ideas for designing adaptive solar facades. Nevertheless, the view performance of such systems has not been fully explored especially when it comes to the effect of dynamic vertical shading systems mounted on south facades. This fact clarifies the need to conduct more research in this field by taking into account the window view and natural light. Consequently, a simulation research is carried out to investigate the impact of a dynamic shading system with three vertical slats used on the south facade of a single office room located in Tehran, on both view quality and quantity, visual comfort and operational energy. The research attempts to reach a balance between the occupant's requirements and building energy criteria through a multi-objective optimisation. The distinctive feature of the proposed method is generating some optimum shading which could only cover the essential parts of the window area. It was detected from the simulation results that the usage of a dynamic vertical shading system with multi slats for south facades compared to common Venetian blinds can firstly, provide four times more view quantity. Secondly, the view quality is significantly improved through enabling occupants to enjoy the sky layer the entire year. Finally, twice more operational energy can be saved while more natural light can enter the indoor environment without glare. The final outcome of this research contributes toward designing high-performance adaptive solar facades.FindingsThis paper proposes a new metric to evaluate the view quantity through a multi-layer shading system. The proposed method makes it clear that the usage of dynamic vertical shading systems with multi-layers mounted on south facades can bring many benefits to both occupants and building energy criteria. The proposed method could (1) provide four times more view quantity; (2) improve view quality by enabling occupants to watch the sky layer throughout the whole year; (3) slash the operational energy by twice; (4) keep the daylight glare probability (DGP) value in the imperceptible range.Research limitations/implicationsThe research limitations that should be acknowledged are ignoring the impact of the adjacent building on sunlight reflection, which could cause discomfort glare issues. Another point regarding the limitations of the proposed optimisation method is the impact of vertical shading systems on users' visual interests. A field study ought to be conducted to determine which one could provide the more desirable outside view: a vertical or horizontal the view. Research on the view performance of ASFs, especially their impact on the quality of view, is sorely lacking.Originality/valueThis paper (1) analyses the performance of dynamic vertical shadings on south facades; (2) evaluates outside view through multi-layer shading systems; and (3) integrates both view quality and quantity into designing adaptive solar facades.

Effects of Day/Night Factor on the Detection Performance of FY4A Lightning Mapping Imager in Hainan, China

In this study, the effect of day/night factor on the detection performance of the FY4A lightning mapping imager (LMI) is evaluated using the Bayesian theorem, and by comparing it to the measurements made by a ground-based low-frequency magnetic field lightning location system. Both the datasets were collected in the summers of 2019–2020 in Hainan, China. The results show that for the observed summer thunderstorms in Hainan, the daytime detection efficiencies of LMI (DELMI) were 20.41~35.53% lower than the nighttime DELMI. Compared to other space-based lightning sensors (lightning imaging sensors/optical transient detectors (LIS/OTD) and geostationary lightning mapper (GLM)), the detection performance of LMI is more significantly influenced by the day/night factor. The DELMI rapidly dropped within about four hours after sunrise while it increased before sunset. For the storms that formed at night and lasted for an entire day, the DELMI remained relatively low during the daytime, even as the thunderstorms intensified. The poor detection performance of LMI during daytime is probably because of the sunlight reflection by clouds and atmosphere, which results in larger background radiative energy density (RED) than that at night. During night, LMI captured the lightning signals well with low RED (8.38~10.63 μJ sr−1 m−2 nm−1). However, during daytime, signals with RED less than 77.12 μJ sr−1 m−2 nm−1 were filtered, thus lightning groups could rarely be identified by LMI, except those with extremely high RED. Due to the limitations of the Bayesian theorem, the obtained DE in this study was “relative” DE rather than “absolute” DE. To obtain the absolute DE of LMI, the total lightning density is necessary but can hardly be measured. Nonetheless, the results shown here clearly indicate the strong impact of day/night factor on the detection performance of LMI, and can be used to improve the design and post-processing method of LMI.

A Combined Method for an Exhaustive Investigation of the Anidolic Ceiling Effect on Improving Indoor Office Daylight Quality: an Approach Based on HDR Photography and Subjective Evaluations

Lighting quality in office environments is a broad concept that must be taken into account in the design stage to deliver comfortable spaces to reduce workers' stress. Indeed, daylight should be sufficient to perform visual tasks while avoiding excessive brightness, high contrast, or intense sunlight reflections that can cause discomfort glare. This research aims to test the Anidolic Integrated Ceiling (AIC) performance in creating a visually comfortable space by reducing the probability of glare. A combined method was adopted for investigating the influence of the building orientation and the workers' view directions in the different moments of the day in the winter season. Data collection was performed in an experimental environment, i.e., a physical scale model of 1:4 under real sky conditions. Three variables were: (i) the viewer's positions (parallel and face to the window), (ii) the façade orientation, (iii) the time of the day (morning and afternoon). To investigate the correlation between the simulated environment and the subjective comfort, we collected the following data in parallel: illuminance level, Daylight Glare Probability Index (DGIP), Luminance Contrast Ratios (LCR) for assessing the daylighting environments, and people reactions to the lighting setting to evaluate the perceived discomfort glare. The findings indicate that the Anidolic system's performance differs according to the occupant's orientation and her\his visual direction. The performance of the north façade of the case study application in Biskra, Algeria, was the best one. Indeed, the AIC system allows a harmonious luminance distribution without creating discomfort glare. Glare assessment shows that glare is perceived imperceptible in the lateral view (less than 0.30) and varies between imperceptible and perceptible in the parallel view (LCR values between 1:1 and 1:29). The questionnaire results show that the subjects were more satisfied with the luminous atmosphere of the lateral view than the parallel view where people more likely perceived discomfort. The statistical analysis shows that participants' perceptions of contrast and sensitivity to glare have a strong relationship with DGIP and LCR (0.000) and no correlation with illuminance and LCR.