Total Radiation Flux Research Articles

Bifacial Photovоltaic Sensor for Insolation Energy Resource Monitoring

Accurate and reliable measurements of the total solar radiation flux make it possible to evaluate the efficiency of using stand-alone photovaltaic systems in various meteorological conditions. These measurements allow more accurately predict in time the energy production volume, accumulator and capacitive storage devices parameters and the payback period. Research purpose was to study the possibility of creating a photoelectric sensor and a method of uninterrupted measurement based on this sensor which allows to measure total solar radiation flux including its direct, diffused and reflected components simultaneously. The photovaltaic sensor with bifacial photosensitivity was manufactured and applied, which is low-inertia comparing to traditional thermoelectric pyranometers, and its spectral sensitivity is quite close to the same parameter of photovoltaic power supply system. It creates the possibility to estimate the insolation level capable to be completely converted into electrical energy without an ineffective heat-generating long-wavelength part of the solar spectrum. A laboratory measuring stand was made to test the sensor's operability. Modeling and experiments’ the sensor parameters were carried out and confirmed its operability. The bifacial photosensitivity sensor allows to control simultaneously direct, diffused and reflected from the earth's surface components of solar radiation, what gives more complete information about the energy potential of the photovoltaic power supply system location.

Assessing the Influence of Urban Lights on Night Sky Brightness with a Smartphone

The darkness of the sky is a critical parameter for assessing the suitability of an astronomical site. Among various sources of light pollution, urban lights pose the most significant threat to ground-based optical astronomical and planetary observations. Quantitatively assessing the impact of urban lights with varying scales and fluxes is indispensable for selecting an ideal optical observation site. In order to quantitatively assess the changes in Night Sky Brightness (NSB) relative to the distance from urban areas and to establish a foundation for safeguarding the light environment at the newly developed Lenghu astronomical site on the Tibetan Plateau, we employed both a Sky Quality Meter and a pre-calibrated smartphone. These instruments were used to measure the NSB in the vicinity of two cities, Da Qaidam and Delingha, which vary in size and radiant flux, on the Tibetan Plateau. The findings indicate that the NSB around both cities decreases significantly as the distance from the city center increases, although the rate of decrease varies between the two locations. This decline can be effectively modeled using an exponential decay function. Notably, the influence of city lights on NSB becomes negligible at distances exceeding 30 km from Da Qaidam, while for Delingha, this distance extends to 50 km due to its larger city size and higher total radiant flux. The methodologies and results presented in this paper offer valuable insights for the selection of astronomical observation sites and the development of light pollution management policies.

Water Sterilization using Ultraviolet Light-Emitting Diodes

In order to provide adequate living conditions, it is crucial for each building to have access to essential utilities such as water, electricity, and sewage systems. In some regions, they may experience isolation, but they can still establish connections to distribution networks and fulfill basic living requirements. In such cases, local solutions like wells and septic tanks are implemented. The water sourced from these sources contains a multitude of viruses and bacteria that can have a detrimental effect on the health of anyone who consumes it. Numerous water filtration/sterilization options are available on the market, but they come with significant installation, maintenance, and operating expenses. The use of ultraviolet C (UVC) rays generated by mercury lamps for sterilization by irradiation is becoming increasingly popular due to its cost-effectiveness in terms of installation and maintenance. The main drawbacks of this technique are the high energy consumption and the potential danger of mercury exposure. This article describes the processes for designing, making, and testing two water filtration probes that use light-emitting diodes (LED) diodes to emit UVC rays. This solution lowers energy consumption eliminates the risk of mercury contamination, and leads to a decrease in maintenance costs, as the lifespan of diodes is longer than that of mercury vapor lamps. The two probes have LED diodes that emit at a wavelength of 275 nm, with a total radiant flux of 12 mW and 100 mW, respectively. Biological tests were carried out in the laboratory to assess the effects of these probes on an artificially contaminated water sample. The results obtained are satisfactory and comparable to those of sterilization devices with LED lamps.

New gas radiation model of high accuracy based on the principle of weighted sum of gray gases

The standard WSGG (Weighted Sum of Gray Gases) model is very fast and simple but can lead to relatively high discrepancies in the computation of the radiative heat transfer. A new model of high accuracy relying on the principle of the WSGG model is proposed. Contrary to the standard WSGG model, the pressure absorption coefficient depends here weakly on the temperature while the weighting factor is not predefined by a mathematical function. Mathematical properties on the model parameters are obtained and we show that all the model parameters can be determined from only one of them. This last is reconstructed with an efficient inverse algorithm from the total radiative heat source data computed with the LBL method using HITEMP 2010. We propose an efficient method to find good initial guesses (of the model parameters) leading to the best accuracy of the model. It is shown, on 17 selected 1D cases representative of the combustion of CO2H2O mixtures, that the maximum relative errors on the radiative heat source for the new model (based on 6 gray gases) does not exceed 3.5% (for these 17 cases) whereas for the standard WSGG model, these errors vary up to 14.5% (five cases have errors higher than 10.0% and nine cases have errors between 5.0% and 10.0%). The accuracy of the total radiative heat flux is also greatly enhanced with the new model. We also show that the present model is robust and can be used in 3D geometry.

Lab-scale tubular LED UV reactor for continuous photocatalysis

Photocatalytic water treatment is considered a promising technique to prevent micropollutants from entering the environment. However, no off-the-shelf UV reactors on lab scale are available to study new processes and photocatalysts. In this study, we present a tubular UV reactor equipped with 30 UV-LEDs, emitting UV light at 367 nm and a total radiant flux of 42W. The UV reactor has an irradiated length of 300 mm and can host any transparent chemical reactor on the inside with a maximum diameter of 28 mm. The device is optimized for lab experiments with total dimensions of just 334 mm x 193 mm x 172 mm. Besides water treatment, a broad range of other photochemical and photocatalytic experiments can be performed with the reactor. Two identical UV reactors have been built and are successfully used for photocatalytic water treatment experiments. The degradation of methylene blue with TiO2 as photocatalyst was studied to validate the UV reactor. Furthermore, photocatalytic and hybrid processes were conducted in the UV reactor to degrade a broad range of pharmaceutical micropollutants.

Analyzing the impact of various factors on leaf surface temperature based on a new tree-scale canopy energy balance model

Trees are one of the effective ways to regulate the microclimate, while the environmental parameters influence their transpiration rate. These complex processes manifest at the macro scale through leaf surface temperature (LST). Therefore, the key to studying the influence of trees on the microclimate is to calculate the LST. In this paper, we propose a new tree-scale canopy energy balance (CEB) model related to tree canopy height based on the big-leaf model to calculate the LST and analyze the influence of various factors on both LST and each sub-term of CEB. The results indicate that air temperature and solar radiation have a greater effect on LST than relative humidity on it. When the total solar radiation flux remains constant, air parameters primarily affect the latent heat flux of trees through the vapor pressure deficit between leaves and the air. The transpiration rate of trees is influenced not only by air parameters, but also by stomatal resistance. Solar radiation can directly determine the magnitude of the net radiation flux in the CEB, while its influence on latent heat flux is insignificant. Under high solar radiation flux conditions, an increase in wind speed can mitigate the rise of LST.

Математическое моделирование прогноза урожайности сельскохозяйственных культур на основе данных полевого мониторинга и дистанционного зондирования

A mathematical model for forecasting crop yields based on field monitoring data and remote sensing of the Earth has been constructed. The model includes the following main values: vegetation indices NDVI, total solar radiation flux at the lower boundary of the atmosphere, efficiency of using photosynthetically active solar radiation, biomass respiration costs. After the parameterization of the mathematical model using observational data, the number of uncertain (calibration) coefficients of the model decreases from 8 to 2. These coefficients are determined by the method of successive approximations when comparing the results of calculations with observational data on the yield of a particular agricultural crop (ACC) in a given field. It is shown that the values of these coefficients strongly depend on the choice of optimal conditions for the growth of ACC. To reduce the yield forecast error, an approach based on the numerical integration of the total energy flux density by methods of the second and fourth orders of accuracy is proposed. When using numerical integration methods of a high order of accuracy, the yield forecast error decreases on average by 20% compared to the widely used model for calculating biomass growth, which has the first order of accuracy.

Coronal bright point statistics

Context. The corona of the Sun is the part of the solar atmosphere with temperatures of over one million Kelvin, which needs to be heated internally in order to exist. This heating mechanism remains a mystery; we see large magnetically active regions in the photosphere lead to strong extreme UV (EUV) emission in the corona. On much smaller scales (on the order of tens of Mm), there are bipolar and multipolar regions that can be associated with evenly sized coronal bright points (CBPs). Aims. Our aim was to study the properties of CBPs in a statistical sense and to use continuous data from the SDO spacecraft, which makes it possible to track CBPs over their whole lifetime. Furthermore, we tested various rotation-speed profiles for CBPs in order to find out if the lower corona is co-rotating with the photosphere. Then we compiled a database with about 346 CBPs together with information of their sizes, shapes, appearance and disappearance, and their visibility in the EUV channels of the AIA instrument. We want to verify our methods with similar previous studies. Methods. We used the high-cadence data of the largest continuous SDO observation interval in 2015 to employ an automated tracking algorithm for CBPs. Some of the information (e.g., the total lifetime, the characteristic shape, and the magnetic polarities below the CBPs) still requires human interaction. Results. In this work we present statistics on fundamental properties of CBPs along with some comparison tables that relate, for example, the CBP lifetime with their shape. CBPs that are visible in all AIA channels simultaneously seem to be brighter in total and also have a stronger heating, and hence a higher total radiation flux. We compared the EUV emission visibility in different AIA channels with the CBP’s shape and lifetime. From the tracking algorithm we confirm a strict co-rotation of the CBPs with the photospheric differential rotation. Conclusions. The tracked CBPs have a typical lifetime of about 1–6 h, while the hottest and brightest ones seem to exist for significantly longer time, up to 24 h. Furthermore, the merging of two CBPs seems not to have an influence on the overall size of the persisting CBP. Finally, fainter and cooler CBPs tend to have only weaker magnetic polarities, which clearly supports a coronal bright point heating mechanism based on magnetic energy dissipation.

Optical Modelling of a Linear Fresnel Concentrator for the Development of a Spectral Splitting Concentrating Photovoltaic Thermal Receiver

Concentrating photovoltaic thermal (CPVT) solar collectors can be regarded as a promising technology, as they are capable of providing renewable electricity and industrial heat simultaneously. The development of a novel CPVT receiver for a linear Fresnel concentrator requires detailed knowledge about the optical performance of the utilised mirror field. Therefore, this paper presents a generic optical model for such concentrating solar systems. The model was developed in MATLAB™ and calculates the sun’s position depending on the location, date and time. The subsequent geometrical computation of each mirror stripe angle is the basis for the detailed consideration of internal shading mechanisms that are typical for Fresnel mirror concentrators. Furthermore, the cosine losses are determined separately for each mirror. The outcomes of the developed model comprise the optical performance parameters of the considered Fresnel mirror field, such as the geometric efficiency, resulting irradiance in the receiver input plane, expected width of the focus image, concentration factor and total radiant flux impinging the receiver. Due to the chosen design of the model, its application is not limited to a particular kind of Fresnel concentrator. By contrast, all geometric parameters, such as the number of mirrors, the dimensions of the mirrors and the receiver, among others, can be freely adjusted.

Traceability of Total Spectral Radiant Flux (TSRF) Scale Using Spectral Irradiance and Total Luminous Flux Scale at CSIR-NPL, India

Traceability of Total Spectral Radiant Flux (TSRF) Scale Using Spectral Irradiance and Total Luminous Flux Scale at CSIR-NPL, India

A wide-band based weighted-sum-of-gray-gases model for participating media: Application to [formula omitted]-[formula omitted] mixtures with or without soot

The presence of participating gases and soot in combustion processes often makes the thermal radiation the main mechanism of heat transfer due to the elevated temperatures involved. The accurate solution of the radiative transfer equation (RTE) through the line-by-line (LBL) integration in engineering applications is in general still impracticable due to the high computational effort required to account for the millions of spectral lines that characterize the absorption coefficient of a gas. Global spectral models, such as the weighted-sum-of-gray-gases (WSGG) model, are attempts to replace the LBL integration with low computational cost and satisfactory accuracy. In the present study, an improvement of the WSGG model through a partition of the spectrum is proposed. The spectrum is divided into a set of ranges in which the standard methodology of the WSGG model is applied to determine the gray gases coefficients in these bands. This is the central aspect of what is named here a wide-band based WSGG (WBW) model, which consists firstly of determining the emittance of each band from the HITEMP 2010 database, then obtaining the pressure-absorption coefficients and the temperature-dependent coefficients. The total radiative heat flux and radiative heat source are obtained by the summation of the contribution of each band individually. For soot, a gray gas approach is considered for each band via Planck-mean absorption coefficients. A set of 1D problems consisting of two infinite parallel black walls, filled with a non-isothermal and non-homogeneous gaseous mixture of water vapor, carbon dioxide and soot, is solved. The results show that, especially in cases where the thermal radiation of soot is dominant, the maximum deviations obtained with the proposed method in relation to the LBL solution reduce by almost three times compared to other global WSGG models in the literature, in addition to decreasing by 40% the number of equations that need to be solved.

The probability distribution of absorbed direct, diffuse, and scattered radiation in plant canopies with varying structure

When applied to plant canopies, classical radiation theory for a turbid medium yields relatively simple expressions for average fluxes of absorbed radiation within an arbitrary volume of vegetation. However, due to the effects of shading and leaf angle, these averaging volumes usually contain a continuous distribution of leaf-level radiative fluxes ranging from full sun to full shade. These distributions are obscured within turbid media models and are thus usually not considered directly unless a computationally expensive leaf-resolving model is used. Consideration of the full probability distribution of absorbed radiative fluxes can yield valuable information about interactions between plant structure and function, not only for radiative fluxes but also for fluxes of radiation-dependent biophysical processes such as photosynthesis. This work presents the theoretical derivation of probability distributions of absorbed direct, diffuse, scattered, and total radiative fluxes for homogeneous canopies with varying structure. The theory is verified against predictions of a three-dimensional leaf-resolving model, and used to explore the impacts of canopy structure on the distribution of absorbed radiation.

Анализ особенностей расчета характеристик фонового излучения при решении задач лазерной локации в инфракрасном диапазоне спектра

The article considers the proposed method for calculating the background radiation characteristics when solving problems of laser location in the infrared range of the spectrum. The process of laser ranging in the infrared range is described for the case of an extended homogeneous background, which is characterized by emissivity and absolute temperature. Expressions for the diffusely reflected laser and intrinsic thermal reduced fluxes of background radiation are derived. The calculation of the reduced flux of diffusely reflected laser radiation was carried out taking into account the features of the main schemes for constructing laser location systems (LLS). An expression is obtained for the total background radiation flux, which takes into account the effect of diffusely reflected probing laser radiation and the intrinsic thermal radiation of the underlying surface. Graphs of dependences of background radiation fluxes for several typical values of the laser location system internal characteristics (power of the laser radiation source, design parameters of the receiving optical system) and external conditions (absolute temperature and emissivity of the underlying background surface) are presented. Taking into account the dependence graphs of background fluxes, the limiting values of the design parameters of laser location systems and external conditions were determined, under which the value of the intrinsic thermal reduced radiation flux significantly prevails over the value of the diffusely reflected laser reduced radiation flux

Experimental study of fire plume temperature and radiant heat flux of a horizontal jet flame impinging a wall

Jet fire usually appears in natural gas fuel production and transportation due to uncontrolled fuel leakage. Jet fire can impinge on equipment surface or a passive firewall to make the fire plume temperature and the radiant heat flux complex. Experiments of a horizontal jet flame impinging a wall under various fuel initial velocity and nozzle-wall spacing were carried out. Results show the changing relationship between the amount of oxygen required and the actual amount of oxygen results in the different temperature distribution of fire plume on the wall surface. A new dimensionless number is proposed to determine the maximum rising temperature of fire plume on the wall surface. The fire plume volume and the distance between a certain position and fire plume within the viewing angle range of the radiometer, as two important factors, can explain the trend of radiant heat flux well. A virtual total radiant heat flux Qv,tr received by a core area of the horizontal jet fire impinging the wall is estimated. Qv,tr firstly increases, and then decreases with Zn-w increasing. Increasing fire plume volume and increasing distance between the wall and the fire plume have the opposite effect on controlling Qv,tr together.

WEATHER FACTORS AFFECTING CANOPY ORIENTATION OF MAIZE IN THE RAINFOREST OF SOUTHWESTERN NIGERIA

Despite the wide recognition of plant architecture as a key factor for optimum productivity in most crops, factors affecting maize (Zea mays L.) crop configurationis poorly understood and often neglected in the rainforest ecologies of sub-Saharan Africa. The present study provides an analysis of the weather factorsaffecting canopy architecture of maize in the rainforest of sw Nigeria. Five maize varieties were planted weekly from March to November of 2016 and 2017 in randomized complete block experiments at the Obafemi Awolowo University Teaching & Research Farm (OAU T&RF). Data were collected on upper and lower leaf angle (LAUpper and LALower), and leaf orientation values (LOVUpper and LOVLower) which served as indices for canopy architecture.Weather data were obtained from the automatic weather station located on the farm. ANOVA revealed that environment had significant effects on canopy architecture andgrain yield (P = 0.01; R2 ≥ 80 %). Correlation and regression analyses showed thatsoil moisture, soil temperature, and solar radiation greatly affected canopy configuration (P ≤ 0.01), particularly LA and LOV. Sequential path analyses confirmed that soil moisture for LA, and soil temperature for LOV, were the most important weather factors directlyinfluencing canopy architecture in maize. Leaf angle was directly influenced by soil moisture and indirectly byair relative humidy and rainfall, while LOV was directly influenced by soil temperature and solar radiation, and indirectly by air relative humidity, heat unit, total radiation, rainfall, and soil heat flux.

Measurement of color, photometry and electrical parameters of street light LEDs

This paper presents the procedure to evaluate the performance parameters of street light LEDs i.e. color, photometry, and electrical characteristics such as voltage, current, power, and power factor using a standard Sphere Spectroradiometer. The integrating Sphere 1.5 Meter measures total radiant flux (W/nm), from which total Luminous flux and color quantities are obtained at different levels of the supply voltage. There are three street light LEDs tested experimentally with the Spectroradiometer for different voltage levels for flux and power output. The simulated spectrum test reports give values of parameters such as color, photometry, and electrical quantities. At the later stage, the performance of LED is compared with the conventional incandescent lamp. The simulated spectral, as well as experimental results, have shown the superiority of LED street light over an incandescent lamp.

The Role of Heat Flux in an Idealised Firebreak Built in Surface and Crown Fires

The disruptions to wildland fires, such as firebreaks, roads and rivers, can limit the spread of wildfire propagating through surface or crown fire. A large forest can be separated into different zones by carefully constructing firebreaks through modification of vegetation in firebreak regions. However, the wildland fire behaviour can be unpredictable due to the presence of either wind- or buoyancy-driven flow in the fire. In this study, we aim to test the efficacy of an idealised firebreak constructed by unburned vegetation. The physics-based large eddy simulation (LES) simulation is conducted using Wildland–urban interface Fire Dynamic Simulator (WFDS). We have carefully chosen different wind velocities with low to high values, 2.5~12.5 m/s, so the different fire behaviours can be studied. The behaviour of surface fire is studied by Australian grassland vegetation, while the crown fire is represented by placing cone-shaped trees with grass underneath. With varying velocity and vegetation, four values of firebreak widths (Lc), ranging from 5~20 m, is tested for successful break distance needed for the firebreak. For each failure or successful firebreak width, we have assessed the characteristics of fire intensity, mechanism of heat transfer, heat flux, and surface temperature. It was found that with the inclusion of forest trees, the heat release rate (HRR) increased substantially due to greater amount of fuel involved. The non-dimensional Byram’s convective number (NC) was calculated, which justifies simulated heat flux and fire characteristics. For each case, HRR, total heat fluxes, total preheat flux, total preheat radiation and convective heat flux, surface temperature and fire propagation mode are presented in the details. Some threshold heat flux was observed on the far side of the firebreak and further studies are needed to identify them conclusively.

Methods to measure the radiant flux of light-emitting diodes

To measure the radiant flux of light-emitting diodes, sphere integration, goniophotometric, and pulsed methods have been considered. A convenient method to calculate the radiant flux using the indicatrix of radiant intensity and an integrating sphere design to measure the total radiant flux of light-emitting diodes with a wide angular distribution of radiation have been proposed. Moreover, the calibration of measurement equipment has been considered. The proposed methods and measurement tools help enable the measurement of the radiant flux of light-emitting diodes in the range of 1 mW to tens of watts. The measurement results are compared using different methods. A method to estimate the absolute measurement error is proposed.

Postharvest temperature and light treatments induce anthocyanin accumulation in peel of ‘Akihime’ plum (Prunus salicina Lindl.) via transcription factor PsMYB10.1

Anthocyanin accumulation is responsible for red pigmentation in plum peel and affected by light and temperature. We investigated the effects of temperature and LED light (400−800 nm, with following red: green: blue ratio 20.9: 75.7: 3.4 respectively) with total radiant flux adjusted at 150 mol m−2 s−1 on anthocyanin accumulation in postharvest ‘Akihime’ plum peel and found that 20 °C/light could induce anthocyanin concentration and therefore improve red coloration. However, no significant anthocyanin accumulation was detected in the peel of plums treated with 30 °C or under dark conditions. RNA-Seq and qRT-PCR analysis showed that the transcript levels of anthocyanin accumulation-related genes, including phenylalanine ammonialyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumaroyl:CoA-ligase (4CL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) and glutathione S-transferase (GST) in the peel were upregulated by 20 °C/light treatment. Transcription factors differentially regulated by temperature and light were identified. A homolog of peach anthocyanin MYB activator, namely PsMYB10.1, was lowly expressed in the peel of unpigmented fruit but significantly upregulated by 20 °C/light treatment. The function of PsMYB10.1 was verified by transient overexpression in Nicotiana tabacum leaves, resulting in strong anthocyanin accumulation when co-infiltrated with PsbHLH3. Dual luciferase assays further showed that PsMYB10.1 activated the promoters of the anthocyanin biosynthetic genes PsANS, PsUFGT and PsGST. These results suggest that appropriate temperature and light regimes at postharvest can induce anthocyanin accumulation in the peel of ‘Akihime’ plum by activating the expression of the positive regulator PsMYB10.1 and consequently the genes involved in biosynthesis and transportation of anthocyanin.

Spectral radiative energy and exergy analysis of oxy-fuel gaseous media in one-dimensional furnace cases

In this study, the spectral radiation characteristics of gaseous media during oxy-fuel combustion are investigated using the heat transfer method from the perspective of energy quality and utilization. Based on the gas radiation model and radiation thermodynamic theory, the effects of different parameters on the spectral radiation proportion and total radiation flux are investigated in one-dimensional furnace cases, including the temperature, pressure, and molar ratio. Based on the results of radiative energy and exergy, a model was established to predict the spectral radiative exergy characteristics of gas flame in furnace. It is found that temperature is the dominant influencing factor. At a flame average temperature of 1600 K, the proportion of spectral radiation in the waveband of 0–2 μm accounts for 26.8%. The high-temperature and short-wavelength spectral radiation has a high exergy-to-energy ratio. Increases in the total pressure and molar ratio increase the total radiative energy, exergy, and short-wavelength radiation ratio, whereas the total pressure has less effect when the pressure is greater than 5 bar. The proposed model for predicting radiative exergy has an error of only about 1% within the flame temperature range. This study provides a reference for future research on the frequency-splitting cascade utilization and management of radiation energy in fuel combustion.