Diffuse Sunlight Research Articles

Diffuse sunlight and cosmic rays: Missing pieces of the forest growth change attribution puzzle?

Forest growth changes have been a matter of intense research efforts since the 1980s. Owing to the variety of their environmental causes – mainly atmospheric CO2 increase, atmospheric N deposition, changes in temperature and water availability, and their interactions – their interpretation has remained challenging. Recent isolated researches suggest further effects of neglected environmental factors, namely changes in the diffuse fraction of light, more efficient to photosynthesis, and galactic cosmic rays (GCR), both emphasized in this Discussion paper. With growing awareness of GCR influence on global cloudiness (the cosmoclimatologic theory by H. Svensmark), GCR may thus cause trends in diffuse-light, and distinguishing between their direct/indirect influences on forest growth remains uncertain. This link between cosmic rays and diffuse sunlight also forms an alternative explanation to the geological evidence of a negative correlation between GCR and atmospheric CO2 concentration over the past 500 Myr. After a careful scrutiny of this literature and of key contributions in the field, we draw research options to progress further in this attribution. These include i) observational strategies intending to build on differences in the spatio-temporal dynamics of environmental growth factors, ranging from quasi-experiments to meta-analyses, ii) simulation strategies intending to quantify environmental factor's effects based on process-based ecosystem modelling, in a context where progresses for accounting for diffuse-light fraction are ongoing. Also, the hunt for tree-ring based proxies of GCR may offer the perspective of testing the GCR hypothesis on fully coupled forest growth samples.

Rapid detoxification of polluted water using ultrastable TiO2 encapsulated CsPbBr3 QDs in collected sunlight

The CsPbBr3 perovskite quantum dots (CPB PQDs) was prepared using the anti-solvent precipitation method in ambient air. The low water stability of CPB PQDs hinders photocatalytic applications, so colloidal CPB PQDs were encapsulated and protected with TiO2. The thickness of TiO2 encapsulation was controlled by immersing the same volume of CPB PQDs into different concentrations of Titanium (Ti) precursor. The optimum CPB/TiO2 composition degrades 78% Methylene Blue (MB) after 300 min under natural (diffuse) sunlight. Furthermore, the same photocatalyst detoxifies MB more than 99% after 50 min illumination of collected sunlight. This outstanding photocatalysis in collected sunlight is attributed to the improved rate of photoinduced charge carriers and their efficient separation due to favourable band alignment of CPB PQD with TiO2. This work provides a pathway to implement an efficient photocatalyst strategy for environmental remediation in outdoor conditions.

Factors affecting wavelength-resolved ultraviolet irradiance indoors and their impacts on indoor photochemistry.

We measured wavelength-resolved ultraviolet (UV) irradiance in multiple indoor environments and quantified the effects of variables such as light source, solar angles, cloud cover, window type, and electric light color temperature on indoor photon fluxes. The majority of the 77 windows and window samples investigated completely attenuated sunlight at wavelengths shorter than 320nm; despite variations among individual windows leading to differences in indoor HONO photolysis rate constants (JHONO ) and local hydroxyl radical (OH) concentrations of up to a factor of 50, wavelength-resolved transmittance was similar between windows in residential and non-residential buildings. We report mathematical relationships that predict indoor solar UV irradiance as a function of solar zenith angle, incident angle of sunlight on windows, and distance from windows and surfaces for direct and diffuse sunlight. Using these relationships, we predict elevated indoor steady-state OH concentrations (0.80-7.4×106 molec cm-3 ) under illumination by direct and diffuse sunlight and fluorescent tubes near windows or light sources. However, elevated OH concentrations at 1m from the source are only predicted under direct sunlight. We predict that reflections from indoor surfaces will have minor contributions to room-averaged indoor UV irradiance. These results may improve parameterization of indoor chemistry models.

Inactivation times from 290 to 315 nm UVB in sunlight for SARS coronaviruses CoV and CoV-2 using OMI satellite data for the sunlit Earth

UVB in sunlight, 290–315 nm, can inactivate SARS CoV and SARS CoV-2 viruses on surfaces and in the air. Laboratory exposure to ultraviolet irradiance in the UVC range inactivates many viruses and bacteria in times less than 30 min. Estimated UVB inactivation doses from sunlight in J/m2 are obtained from UVC measurements and radiative transfer calculations, weighted by a virus inactivation action spectrum, using OMI satellite atmospheric data for ozone, clouds, and aerosols. For SARS CoV, using an assumed UVC dose near the mid-range of measured values, D90 = 40 J/m2, 90% inactivation times T90 are estimated for exposure to midday 10:00–14:00 direct plus diffuse sunlight and for nearby locations in the shade (diffuse UVB only). For the assumed D90 = 40 J/m2 model applicable to SARS CoV viruses, calculated estimates show that near noon 11:00–13:00 clear-sky direct sunlight gives values of T90 < 90 min for mid-latitude sites between March and September and less than 60 min for many equatorial sites for 12 months of the year. Recent direct measurements of UVB sunlight inactivation of the SARS CoV-2 virus that causes COVID-19 show shorter T90 inactivation times less than 10 min depending on latitude, season, and hour. The equivalent UVC 254 nm D90 dose for SARS CoV-2 is estimated as 3.2 ± 0.7 J/m2 for viruses on a steel mesh surface and 6.5 ± 1.4 J/m2 for viruses in a growth medium. For SARS CoV-2 clear-sky T90 on a surface ranges from 4 min in the equatorial zone to less than 30 min in a geographic area forming a near circle with solar zenith angle < 60O centered on the subsolar point for local solar times from 09:00 to 15:00 h.

Secchi Disk Measurements in Turbid Water

AbstractIn the classical theory of the Secchi disk depth, diffuse sunlight falling on the disk is reflected back to the observer's eye along the most direct route, as a beam. The disappearance depth, ZSD, of the disk is then expected to vary inversely with the sum of the beam and diffuse attenuation coefficients: c + KD. Observations presented here show that, in the most turbid waters sampled, the Secchi disk is visible at greater depths (by a factor of up to 4) than predicted by this theory. In these conditions, the disk appears blurry, and it seems likely that some of the light reflected by the disk returns to the eye as diffuse light, photons being scattered one or more times on their journey from the disk surface to the observer. We have modified the theory of the Secchi disk in turbid water to allow for a mixture of beamed and diffuse light contributing to disk visibility. The modified theory corrects the under‐estimate of Secchi depths in turbid waters and gives good agreement with observations over a wide range of turbidity. The insight gained allows a more informed interpretation of Secchi disk measurements in turbid water.

A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches

AbstractA number of radiation modification approaches have been proposed to counteract anthropogenic warming by intentionally altering Earth's shortwave or longwave fluxes. While several previous studies have examined the climate effect of different radiation modification approaches, only a few have investigated the carbon cycle response. Our study examines the response of plant carbon uptake to four radiation modification approaches that are used to offset the global mean warming caused by a doubling of atmospheric CO2. Using the National Center for Atmospheric Research Community Earth System Model, we performed simulations that represent four idealized radiation modification options: solar constant reduction, sulfate aerosol increase (SAI), marine cloud brightening, and cirrus cloud thinning (CCT). Relative to the high CO2 state, all these approaches reduce gross primary production (GPP) and net primary production (NPP). In high latitudes, decrease in GPP is mainly due to the reduced plant growing season length, and in low latitudes, decrease in GPP is mainly caused by the enhanced nitrogen limitation due to surface cooling. The simulated GPP for sunlit leaves decreases for all approaches. Decrease in sunlit GPP is the largest for SAI which substantially decreases direct sunlight, and the smallest for CCT, which increases direct sunlight that reaches the land surface. GPP for shaded leaves increases in SAI associated with a substantial increase in surface diffuse sunlight, and decreases in all other cases. The combined effects of CO2 increase and radiation modification result in increases in primary production, indicating the dominant role of the CO2 fertilization effect on plant carbon uptake.

Tracking-free adaptive contact concentration photovoltaics

Adaptive Contact Concentration Photovoltaics (ACCPV) is outlined as a scheme to access CPV efficiency improvements without mechanical tracking. This could allow CPV to play a role in applications where maintenance-free reliability and compact size are essential requirements. Conversion efficiency enhancement using sunlight concentration in multi-junction or potentially single junction solar cells due to the well-known increase in the Shockley-Quessar limit are enabled by replacing a tracking system with an array of switchable electrodes. Cell electrodes are segmented and are connected employing a switching system that adapts to sunlight conditions. Unlike CPV systems, the ACCPV concept allows for effective operation in diffuse sunlight conditions. System losses that must be considered in order to determine whether a net benefit for ACCPV exists for a given solar cell type include optical losses, series resistance losses, and Auger losses. The ACCPV concept is clearly presented and relevant system losses are discussed. A 3% absolute increase in triple junction cell efficiency is projected.

Design and testing of highly transparent concentrator photovoltaic modules for efficient dual‐land‐use applications

AbstractTwo types of highly transparent concentrator photovoltaic (CPV) modules that separately utilize direct sunlight and diffuse sunlight for efficient dual‐land‐use applications were designed and tested. The type A module, comprising a typical‐scale CPV lens and solar cells, has a completely direct‐diffuse‐separated design for power generation and other solar applications. On the other hand, the type B module, consisting of a microscale CPV lens and solar cells, was designed to increase the amount of direct sunlight transmitted based on an intentional reduction in the ratio of the lens aperture area to the module aperture area. In experiments, both modules exhibit higher electricity yields and module‐transmitted irradiances (MTIs) than those of a conventional partially transparent flat photovoltaic module with 17% efficiency Si solar cells. Furthermore, the modules show direct normal irradiance‐based efficiencies of 26.7% (type A) and 18.5% (type B) while simultaneously showing MTI‐to‐global normal irradiance ratios of 15.3%‐63.7% (type A) and 38.0%‐63.8% (type B) under various irradiance conditions. Thus, an irradiance of at least 160 W/m2 under the modules can be achieved even when they are arrayed without gaps (at a ground coverage ratio = 1).

Hydrogels as an Emerging Material Platform for Solar Water Purification.

Growing concern over water scarcity leads to increased research interest in advanced water purification technologies. Solar water purification, which uses solar energy to separate water and impurities through vaporization, enables the utilization of sustainable energy and potential freshwater resources to alleviate water scarcity. However, the essential process of solar water evaporationto remove impurities is energy intensive. Insufficient solar absorption and thermal loss limited the vapor generation rate and, thus, lowered the purified water yield. Diffuse natural sunlight cannot satisfy the intrinsic energy demand for rapid water vaporization. Therefore, developing new material platforms that can simultaneously provide high solar absorption, effective energy utilization, and low energy demand for water vaporization to achieve highly efficient solar water purification under natural sunlight is anticipated. In this Account, we review our recent progress on hydrogel-based evaporators for solar water purification in terms of material selection, molecular engineering, and structural design. First, we introduce the unique water state in hydrogels consisting of free, intermediate, and bound water, of which intermediate water has a reduced energy demand for water evaporation. Then, we describe the design principles of hydrogel-based solar evaporators, where the polymeric networks are tailored to regulate the water state. The water state in hydrogels defines the vaporization behavior of water. Thus, the polymer networks of hydrogels can be architected to tune the water state and, hence, to further reduce the evaporation enthalpy of water. Armed with fundamental gelation chemistry, we discuss synthetic strategies of hydrogels for efficient vapor generation. By incorporating solar absorbers with hydrophilic polymer networks, solar energy is harvested and converted to heat energy, which can be in situ utilized to power the vaporization of contained water in the molecular meshes, and the solar absorbers having strong interaction with hydrogels guide the formation of microstructure to reduce the energy loss and ensure adequate water transport of evaporative water. Regulating the vaporizing fronts, engineering the surfaceof hydrogels has been focused to favor the evaporationof waterto further enhance the solar-to-vapor efficiency. By using hydrophilic polymers as building blocks, the hydrogel-based solar evaporators have also been endowed with multiple functionalities, such as antifouling, permselectivity, and thermal responsiveness, to improve water collection andpurification abilities. Taking advantages of these merits, hydrogels have emerged as apromising materials platform to enable efficient solar water purification under natural sunlight. This Account serves to promote future efforts toward practical purification systems using hydrogel-based solar evaporators to mitigate water scarcity by improving their performance, scalability, stability, and sustainability.

Indoor Illumination of Terpenes and Bleach Emissions Leads to Particle Formation and Growth.

Application of chlorine bleach solution (major component sodium hypochlorite, NaOCl) in indoor environments leads to the emission of gaseous hypochlorous acid (HOCl) and chlorine (Cl2), both of which are strong oxidants. In contrast to the outdoor atmosphere, where mixing ratios of HOCl and Cl2 tend to be low (10s-100s of ppt), indoor HOCl and Cl2 can reach high levels during cleaning activities (100s of ppb or higher). HOCl and Cl2 may react with unsaturated organic compounds on indoor surfaces and in indoor air. In this study, we studied the reaction of limonene, one of the most common indoor volatile organic compounds (VOCs) arising from use of cleaning products, fragrance, and air fresheners, with HOCl and Cl2 in an environmental chamber. A dark reaction was observed between limonene and HOCl/Cl2 leading to gas-phase reaction products that were investigated using proton transfer reaction mass spectrometry (PTR-MS). With subsequent exposure to indoor fluorescent lights or diffuse sunlight through a nearby window, a substantial mass loading of secondary particles were formed with an averaged mass yield of 40% relative to the amount of limonene consumed. Aerosol mass spectrometry (AMS) measurements indicate a large contribution of particulate chlorine species. Electrospray ionization mass spectrometry (ESI-MS) analysis of filter-collected particles indicates the formation of high molecular weight products. This is the first study of the oxidation of limonene with HOCl and Cl2, and it illustrates the potential for particle formation to occur with indoor lighting during the use of common cleaning products.

Estimating below-canopy light regimes using airborne laser scanning: An application to plant community analysis.

Light is a key driver of forest biodiversity and functioning. Light regimes beneath tree canopies are mainly driven by the solar angle, topography, and vegetation structure, whose three‐dimensional complexity creates heterogeneous light conditions that are challenging to quantify, especially across large areas. Remotely sensed canopy structure data from airborne laser scanning (ALS) provide outstanding opportunities for advancement in this respect. We used ALS point clouds and a digital terrain model to produce hemispherical photographs from which we derived indices of nondirectional diffuse skylight and direct sunlight reaching the understory. We validated our approach by comparing the performance of these indices, as well as canopy closure (CCl) and canopy cover (CCo), for explaining the light conditions experienced by forest plant communities, as indicated by the Landolt indicator values for light (L light) from 43 vegetation surveys along an elevational gradient. We applied variation partitioning to analyze how the independent and joint statistical effects of light, macroclimate, and soil on the spatial variation in plant species composition (i.e., turnover, Simpson dissimilarity, β SIM) depend on light approximation methodology. Diffuse light explained L light best, followed by direct light, CCl and CCo (R2 = .31, .23, .22, and .22, respectively). The combination of diffuse and direct light improved the model performance for β SIM compared with CCl and CCo (R2 = .30, .27 and .24, respectively). The independent effect of macroclimate on β SIM dropped from an R 2 of .15 to .10 when diffuse light and direct light were included. The ALS methods presented here outperform conventional approximations of below‐canopy light conditions, which can now efficiently be quantified along entire horizontal and vertical forest gradients, even in topographically complex environments such as mountains. The effect of macroclimate on forest plant communities is prone to be overestimated if local light regimes and associated microclimates are not accurately accounted for.

Effects of Light Component and Water Stress on Photosynthesis of Amazon Rainforests During the 2015/2016 El Niño Drought

AbstractWhether enhanced sunshine increases photosynthesis in Amazon rainforests during drought is unclear. Here we used a light component‐based two‐leaf‐photosynthesis model, driven with climate data and satellite vegetation data, to inspect the controlling mechanisms among climate factors on gross primary production (GPP) during the 2015/2016 El Niño drought event. We found that simulated GPP and Moderate Resolution Imaging Spectroradiometer enhanced vegetation index indicated an Amazonian “browning” and not a “green up” during the 2015/2016 El Niño year relative to the 2011–2014 interval. The result shows that, along with intensified sunlight, diffuse sunlight and diffuse fraction as well as canopy light use efficiency decreased, which further produced a decreased potential GPP* (determined by light components and leaf area index of shaded and sunlit leaves). The decreased GPP* and drought‐induced water stress jointly reduced canopy photosynthesis of Amazon rainforests during the 2015/2016 drought. The light component variations caused a reduction in GPP but with a magnitude inferior to the GPP reduction from water stress. These findings suggest that intensified sunlight did not enhance photosynthesis of Amazon rainforests and highlight the important role of light components in interannual and seasonal variations of photosynthesis in Amazon rainforests.

Nitrogen-doped carbon nanodots/PMMA nanocomposites for solar cells applications

Carbon Nanodots (CNDs) are a novel class of nanocarbons that consist of discrete, quasi-spherical nanoparticles with sizes below 10 nm. Besides, due to their low cost, environmentally friendly and low toxicity, CNDs could substitute traditional semiconductor quantum dots (QDs), generally top luminescent materials, but usually made of heavy metals. A very interesting property of CNDs is their tunable emission, characterized by multi-fluorescence colors under varied excitation wavelengths. Photoluminescent CNDs properties give them potential applications in areas such as biomedicine, bioimaging, catalysis, optoelectronics and solar concentrators. Luminescent solar concentrators (LSC) are usually thin plates or sheets made of transparent polymers, such as poly(methyl methacrylate) (PMMA), doped with photoluminescent species. Direct and diffuse incident sunlight is absorbed by these species and the emitted visible light is guided through the polymer to be collected by attached solar cells, increasing their efficiency. CNDs are promising candidates as luminescent doping species for PMMA in preparing hybrid materials, which could be an advantageous and innovative alternative for solar cells applications. In this work, highly fluorescent nitrogen-doped CNDs (NCNDs) were prepared following a simple and controllable synthetic approach under microwave irradiation (MW). Arginine and ethylenediamine were used as carbon and nitrogen precursors and water as reaction medium. The MW parameters were optimized (240°C, 26 bar, 200 W, 180 sec) to obtain the desired properties of the final material, in terms of optical performance. Nanocomposites of NCNDs/PMMA were prepared by solution blending, with 0.1 wt.% and 0.01 wt.% of NCNDs, followed by film casting. The down conversion fluorescence behavior of NCNDs and NCND/PMMA nanocomposites were characterized by Photoluminescence spectroscopy. A broad emission peak at 356 nm was observed for the NCNDs when excited at 300 nm and the fluorescence peaks shift from 356 to 474 nm as excitation varies from 300 to 420 nm. On the other hand, the fluorescence of the NCNDs in the PMMA matrix showed significant broad emission at around 450 nm when excited between 300 and 320 nm.

Eco‐Friendly, High‐Loading Luminescent Solar Concentrators with Concurrently Enhanced Optical Density and Quantum Yields While Without Sacrificing Edge‐Emission Efficiency

A luminescent solar concentrator (LSC) consists of loaded luminophores and a waveguide that can concentrate direct and diffuse sunlight, which is a crucial ingredient for developing solar glasses. In general, the loading concentration in LSCs is strongly restricted (typically &lt;1 wt.%) to mitigate concentration‐induced quenching (CIQ), reabsorption losses, and aggregation‐induced scattering (AIS). However, this will induce transmission losses in particular for thin‐film LSCs. To address all aforementioned issues, large‐Stoke‐shift LSCs with different loadings are simply prepared based on thiolated gold nanoclusters (GSH‐AuNCs) dispersed in the polyvinylpyrrolidone (PVP) matrix. In contrast to conventional luminophores with a severe CIQ effect, photoluminescence quantum yields (PL‐QYs) can be significantly enhanced up to ≈25% (from 0.5 to 1%) even under high loading of ≈26 wt.%. Such PL‐QY enhancement is attributed to the synergistic effects of the suppression of non‐radiative relaxation and enhancement of radiative decay processes due to surface ligand‐matrix coordination. In addition, our high‐loading LSCs also exhibit excellent optical quality and film uniformity without introducing noticeable AIS effects. Thanks to those unique properties, eco‐friendly LSCs with high optical density can still hold a high edge‐emission efficiency of ≈70% due to minimal reabsorption and scattering losses, yielding an external quantum efficiency of ≈15% at the wavelength of 400 nm.

A Filtered Sun Sensor for Solar Tracking in HCPV and CSP Systems

Tracking systems with stringent performance are required to take advantage of solar energy produced through the use of high concentration photovolatics and concentrating solar power technologies. Closed-loop tracking systems use measurements provided by a sun sensor, which picks up direct and diffuse sunlight. High levels of diffuse sunlight produce increased levels of measurement noise at the output of the sensor, which in turn limits the maximal achievable gains in the closed-loop controller and consequently the tracking performance deteriorates. The goal of this paper is to present the advantages of equipping a four-quadrant photodiode sun sensor with infrared and linear polarizing optical filters. Experimental results show that these filters reduce the effect of diffuse radiation and allow increasing the performance of sun tracking systems regardless of the type of controller used in the solar tracker. Tracking experiments are presented under indoor and outdoor conditions employing algorithms currently used in solar trackers, including proportional-integral (PI), and proportional-integral-derivative (PID) controllers, and a recently proposed cascade control law. In all the cases, the best performance is obtained with the sun sensor equipped with an infrared filter. Experiments show that an infrared optical filter reduces the filtered mean squared tracking error up to 75% under artificial light conditions and 90% under direct sunlight.

Design and Evaluation of a III–V/Si Partial CPV Module for Maximization of Power Generation per Unit Module Area

This paper describes the design and evaluation of a III–V/Si partial concentrator photovoltaic (CPV) module with a stacked structure comprising a highly transparent CPV module and a Si cell, which aims to maximize the power generation from global normal irradiation (GNI) by harvesting not only direct, but diffuse sunlight as well. The module structure was designed by considering the optical and heat transfer characteristics, and its performance was evaluated by outdoor and indoor tests using a prototype submodule with a geometrical concentration ratio of 100×. The submodule achieves diffuse sunlight transmission of over 80%, thus generating more power from diffuse sunlight. Under clear-sky condition, the submodule with a single-sided Si cell exhibits the maximum GNI-based module efficiency of 30.7%. The submodule with a bifacial Si cell further improves the power generation and tolerance to tracking error angle for various sunlight conditions.

Calibration of Raman Lidar Water Vapor Mixing Ratio Measurements Using Zenithal Measurements of Diffuse Sunlight and a Radiative Transfer Model

Among the different techniques available for measuring the atmospheric water vapor content, Raman lidars stand out as accurate instruments providing detailed profiles with high temporal and altitude resolution. Their principle is based on obtaining the range-resolved ratio of the lidar signals corresponding to Raman returns from water vapor and nitrogen molecules, which is proportional to the water vapor mixing ratio. To do this, it is necessary to determine a calibration factor, specific of each lidar instrument. A method for obtaining this parameter, based on zenith measurements of diffuse sunlight, on Raman scattering models and on simulations, using a radiative transfer model, to estimate sky radiances at the wavelengths of interest, has been applied to the lidar system of Universitat Politecnica de Catalunya (UPC; Technical University of Catalonia, Barcelona, Spain). A set of calibrations, performed between 2016 and 2017, has permitted assessing the calibration procedure and analyzing the stability of the calibration factor in the UPC instrument. Results show that although the calibration factor can remain stable for long periods of time, it can suffer sudden variations that make indispensable to implement a convenient and reliable procedure to perform regular calibrations. We show that the method, which can be applied to any lidar with water vapor and nitrogen Raman channels, can completely dispense with radiosonde data. The calibration method is validated by comparison with simultaneous radiosonde water vapor measurements. Limitations of radiosondes for validating—and eventually calibrating—water vapor Raman lidars have been revealed.

FORMULASI KRIM TABIR SURYA EKSTRAK BUAH PARIJOTO (Medinilla speciosa Blume) DAN UJI NILAI SPF SECARA IN VITRO

Sunscreen preparations are cosmetic preparations used as a protection to reduce the impact of sun exposure whose formulations contain active ingredients to absorb or diffuse sunlight, especially in areas of ultraviolet and infrared wave emissions. One of the potential natural ingredients for a sunscreen is parijoto fruit (Medinilla speciosa Blume). It contains flavonoid compounds that are able to prevent the harmful effects of UV rays. The objective of this research is to find out the formula of sunscreen cream of parijoto extract that meets the good physical quality of cream and to find out the result of SPF value test of parijoto fruit extract as sunscreen cream preparation in Vitro. The design of the study was experimental research conducted in the laboratory. The sample used in this research was parijoto made into thick extract by maceration method. Further, the viscous extract obtained was made to be a sunscreen cream and then tested either its physical evaluation or calculation of SPF value. The results of this study indicate that the preparation of sunscreen cream of parijoto fruit extract included in the extra protection category with the value is 6.66 and can be made into the good and stable preparations. The sunscreen cream of parijoto fruit extract has good physical properties and also has activity as UV protection in vitro.

Design Criteria for Micro-Optical Tandem Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) harness light generated by luminophores embedded in a light-trapping waveguide to concentrate onto smaller cells. LSCs can absorb both direct and diffuse sunlight, and thus can operate as flat plate receivers at a fixed tilt and with a conventional module form factor. However, current LSCs experience significant power loss through parasitic luminophore absorption and incomplete light trapping by the optical waveguide. Here, we introduce a tandem LSC device architecture that overcomes both of these limitations, consisting of a poly(lauryl methacrylate) polymer layer with embedded cadmium selenide core, cadmium sulfide shell (CdSe/CdS) quantum dot (QD) luminophores and an InGaP microcell array, which serves as high bandgap absorbers on the top of a conventional Si photovoltaic. We investigate the design space for a tandem LSC, using experimentally measured performance parameters for key components, including the InGaP microcell array, CdSe/CdS QDs, and spectrally selective waveguide filters. Using a Monte Carlo ray-tracing model, we compute the power conversion efficiency for a tandem LSC module with these components to be 29.4% under partially diffuse illumination conditions. These results indicate that a tandem LSC-on-Si architecture could significantly improve upon the efficiency of a conventional Si photovoltaic cell.

Modeling and analyses of energy performances of photovoltaic greenhouses with sun-tracking functionality

Dynamic photovoltaic (PV) greenhouses integrate sustainable energy generation with plant cultivation, offering more possibilities of energy production and microclimate control by adjusting the sun-tracking angles. Previous studies on PV greenhouses barely paid attention to the PV partial shading effects, and rarely recorded the performance across the full range of rotation angles. In this study, we first build computer simulation models of typical greenhouses with high-density (1/2 roof area) and low-density (1/3 and 1/4 roof area) PV layouts. Then four special sun-tracking positions are found in the model of equivalent global irradiance, which is defined as the quotient of the total input power divided by the area of PV module under partial diffuse shadows. Simulation models are also built in terms of PV modules and interior irradiance. Simulations are conducted using the climate data of Delft, the Netherlands (52.01°N,4.36°E). Results show that high-density PVs under no-shading sun tracking generate 6.91% more energy than that under conventional (quasi-perpendicular) sun-tracking. Meanwhile, no-shading sun tracking allows more diffuse sunlight to enter the greenhouse mounted with high-density PV panels, resulting in 10.96% and 10.68% improvement on the annual average global irradiance and uniformity on the target plane compared to the fixed PV panels in the closed position. Regarding low-density PV layouts, which barely suffer from partial shading problems, quasi-perpendicular sun tracking improves the annual energy generation by 7.40% relative to the closed position. However, the average global irradiance reaches the minimum in this position because more sunlight is blocked by PVs. Meanwhile, the average uniformity of global irradiance reveals good (but not the best) performance, resulting in up to 9.80% (1/3 coverage) and 4.70% (1/4 coverage) improvement respectively compared to the closed position. The proposed methods and simulation results provide guidelines for the initial design and daily operation of PV greenhouses, aiming to balance the PV power generation and food production.