High Solar Intensity Research Articles

Comparative study of different functionalized graphene-nanoplatelet aqueous nanofluids for solar energy applications

The optical properties of nanofluids are peculiar and interesting for a variety of applications. Among them, the high light extinction coefficient of nanofluids can be useful in linear parabolic concentrating solar systems, while their properties under high light irradiation intensities can be exploited for direct solar steam generation. The optical characterization of colloids, including the study of non-linear optical properties, is thus a needed step to design the use of such novel materials for solar energy exploitation. In this work, we analysed two different types of nanofluids, consisting of polycarboxylate chemically modified graphene nanoplatelets (P-GnP) and sulfonic acid-functionalized graphene nanoplatelets (S-GnP) dispersed in water, at three concentrations from 0.005 wt% to 0.05 wt%. Moderately stable nanofluids were achieved with favourable light extinction properties, as well as a non-linear optical behaviour under high input solar intensities.

The role of seasonality and photoperiod on the lethality of suicide attempts: A case-control study.

The risk factors related to suicidal behaviors are complex and not yet fully known. Several studies underline how suicide results from the combination of psycho-social, biological, cultural, and environmental factors. The aim of this study was to investigate the potential role of seasonality and photoperiod on high-lethality suicide attempts (HLSA) compared with low-lethality suicide attempts (LLSA) in a sample of psychiatric inpatients. After attempting suicide, subjects were admitted in the emergency/psychiatric ward of the IRCCS Ospedale Policlinico San Martino from 1st August 2013 to 31st July 2018. Socio-demographic and clinical characteristics were collected. The sample consisted of four hundred thirty-two individuals admitted for suicide attempt. One hundred thirty-three subjects (30.8%) of the sample committed a HLSA. The HLSA group peaked in the months with a higher sunlight exposure (June and July). Bivariate correlation analyses between seasonality/photoperiod in the whole sample and HLSA were positively associated with summer and highest solar intensity period. Data were limited to a single hospital, patients' seasonal environment, meteorological variables and psychological factors. In addition, the presence of acute life-events fostering the suicidal crisis has not been investigated. The current study provides a novel perspective on the questions surrounding the impact of seasonality and daylight exposure on lethality of suicide attempts. further studies are needed to provide deeper understandings on the delicate molecular network that links suicide behaviors, seasonality and daylight in order to develop more effective prevention and treatment strategies in the future.

Experimental investigation and numerical modelling on the performance assessments of evacuated U – Tube solar collector systems

In this paper, an experimental investigation for predicting the performance of evacuated U – tube solar collector is presented. A simplified numerical model is developed for predicting the working fluid outlet temperature of a single evacuated U – tube solar collector and also for the whole solar collector system. The model predictions are compared with the experimental data and noticed a good agreement exists between them. It is observed from the experimental and numerical analyses that evacuated U – tube solar collector manifolds connected in series provides higher temperature rise of working fluid at higher solar intensities and lower working fluid inlet temperatures and flow rates. The working fluid transition time in an evacuated U – tube solar collector is defined for analysing the time taken by a working fluid to attain a steady state condition. Based on experimental analysis, three empirical correlations for predicting working fluid transition time, energy efficiency and exergy efficiency are developed as the function of operating parameters and ambient temperature. Data predicted from these correlations match with the experimental data with maximum errors of ±12.7%, ±6.9% and ±7.8% for working fluid transition time, energy efficiency and exergy efficiency of an evacuated U – tube solar collector, respectively.

A comparative study of the decolorization capacity of the solar-assisted Fenton process using ferrioxalate and Al, Fe-bentonite catalysts in a parabolic trough reactor

Abstract In this work, the decolorization efficiency of Reactive Red 120 (RR120) synthetic solution using ferrioxalate (CuOFeB) and Al, Fe-bentonite (AlFeB) catalysts in the solar-assisted Fenton process was evaluated, as well as impact of H2O2 photolysis on the process efficiency.The photo-Fenton oxidation of dye has been investigated using a concentrating solar parabolic reactor with constant solar radiation of 550 W/m2 and 950 W/m2 for spring and summer periods, respectively. Experimental data has proved that photolysis of hydrogen peroxide has an important role in the process of decolorization, achieving a decolorization efficiency over 80.78% at pH 7. Under the optimal reaction conditions, both catalysts showed a good stability in the processes with dye removal over 90%. The mineralization efficiency depends on the intensity of the solar radiation, wherein ∼50% was achieved under the higher solar intensity. Comparing reaction rate it is important to note that the larger specific surface area of AlFeB (155.83 m2/g) makes him a superior catalyst and thus solar-assisted Fenton process with this catalyst fast and efficient. Based on the decolorization rate constants, the examined processes can be placed in the following order: AlFeB (950 W/m2) > AlFeB (550 W/m2) > CuOFeB (950 W/m2) > CuOFeB (550 W/m2). These findings are confirmed on real effluent, whereby a greater degree of decolorization (91.89%) and mineralization (43%) has been achieved with AlFeB catalyst compared to CuOFeB (30.09% and 15%) during the process.

Tempering of water storage tank temperature in hot climates regions using earth water heat exchanger

In hot climate regions, outdoor domestic water tank is directly exposed to high solar intensity in addition to hot summer wind stream. The storage water temperature increases above 50 °C. In order to overcome this problem, time dependent analysis of cylindrical domestic storage water tank that exposed to high solar radiation is performed. The analysis includes energy balance for the water tank as well as to an earth water heat exchanger used to reduce the water temperature in summer months. The governing equations are solved numerically using fourth order Runge-Kutta method. It is found that using earth water heat exchanger reduces the water temperature by about 16 °C. A comparison of the numerical results with experimental data showed a good agreement.

Degradation in perovskite solar cells stored under different environmental conditions

Investigations carried out on the degradation of perovskite solar cells (PSCs) stored in different open air environmental conditions are reported here. The solar cells were stored in the open in the dark inside the laboratory (relative humidity 47 ± 5%, temperature 23 ± 4 °C), under compact fluorescent lamp (CFL) illumination (irradiance 10 mW cm2, relative humidity 47 ± 5%, temperature 23 ± 4 °C) and under natural sunlight outside the laboratory. In the outdoor storage situation the surrounding conditions varied from time to time and the environmental conditions during the day (irradiance 100 mW/cm2, relative humidity ~18%, temperature ~45 °C at noon) were entirely different from those at night (irradiance 0 mW/cm2, relative humidity ~66%, temperature ~16 °C at midnight). The photovoltaic parameters were measured from time to time inside the laboratory as per the International Summit on Organic Photovoltaic Stability (ISOS) protocols. All the photovoltaic parameters, such as short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), of the solar cells stored outdoors decayed more rapidly than those stored under CFL or in the dark. The solar cells stored in the dark exhibited maximum stability. While the encapsulated solar cells stored outdoors were completely dead after about 560 h, the solar cells stored under CFL illumination retained >60% of their initial efficiency even after 1100 h. However, the solar cells stored in the dark and tested up to ~1100 h did not show any degradation in PCE but on the contrary exhibited slight improvement, and this improvement was mainly because of improvement in their Voc. Rapid degradation in the open air outside the laboratory under direct sunlight compared with the dark and CFL storage has been attributed to high temperature during the day, high humidity at night, high solar illumination intensity and the presence of ultra-violet and infra-red radiation in incident solar light. Under CFL storage the top Ag electrode decomposed and reacted with the active layer. The decomposition and reaction of Ag electrode was accelerated in the outdoor conditions under direct sunlight. These results suggest that Ag is a good electrode material for efficient PSCs but is not good for their long term stability.

High‐Performance Large‐Scale Solar Steam Generation with Nanolayers of Reusable Biomimetic Nanoparticles

The harvesting of solar radiation for steam generation has drawn wide attention as a future sustainable technology for the renewable production of clean water worldwide. Here, a new super‐dark metasurface of 200 nm thickness is presented, which reaches a solar thermal efficiency of 87% when exposed to an intensity of only 2.3 sun, maintaining a stable efficiency of 90% at higher solar intensities. The metasurface is composed of extremely robust nanoparticles, which are up to 98% recyclable and can be produced on massively large scales by wet chemistry. By employing such reusable nanoparticles on an area of 1 m2, 1.2 kg of seawater can be purified within only 1 h under natural sunshine. With such excellent performances, this nanomaterial can open new applications of high‐performance solar steam.

Techno-economic and environmental analysis of an integrated standalone hybrid solar hydrogen system to supply CCHP loads of a greenhouse in Iran

ABSTRACTThe techno-economic and environmental performance of hybrid solar hydrogen energy systems was investigated to provide combined cooling, heating and power (CCHP) demands of a standalone greenhouse in Iran to achieve sustainable agriculture based on an optimization procedure. From the environmental point of view, by deploying hybrid energy systems, 83%, to 100% of emissions can be avoided. Also a sensitivity analysis was performed on the hybrid energy systems in order to study the effect of major parameter variation on the systems justification. It was concluded that hybrid solar systems are economically competitive with conventional systems, for high solar intensity locations with high diesel fuel prices and decreased prices for PV and hydrogen storage technology.

Performance of photovoltaic cells in photovoltaic thermal (PVT) modules

Integrating cooling systems with photovoltaic (PV) modules represents a very important aspect of keeping modules within acceptable operating temperatures. The objective of this study is to analyse the performance of each series-connected PV cell in photovoltaic thermal (PVT) modules. The importance of this analysis is due to the consideration of the variable operating temperature values of the PV cells, resulting in a different performance of each PV cell. The PVT modules are cooled with water serving as both a heat sink and a solar heat collector. This enhances the electrical efficiency value of the PVT modules by preventing them from elevated temperature values, while the recovered thermal energy can be utilised to increase the overall PV effectiveness. The new consideration in this study over the existing ones is the temperature distribution of each PV cell is applied for the calculation of the current voltage characteristics of the PV modules, which makes the analysis more accurate. The variance in the temperature values is a result of the temperature gradient of the fluid flowing through the pipes where the heat exchange differs in the flow direction. The potential of this study becomes more important for countries of high ambient temperatures and high solar intensity.

Experimental Study on Enhancing the Productivity of Solar Still Using Locally Available Material as a Storage Medium

This experimental study focuses on the effect of pebbles as an energy storage medium on the performance of a solar distillation system. Two single basin solar stills are fabricated with an effective area of 0.5 m2, the glass cover was tilted at 10° with respect to the horizontal. The experiments on the still were carried out under the same climatic conditions for two different modes of operations, (1) conventional still and (2) modified still (pebbles as storage medium). From the study, it could be concluded that (1) the productivity of solar still is increases 9.5 % when pebbles are used as storage medium (2) the maximum amount of heat losses occurs in the solar still is the combined effect of radiation and convection heat transfer from glass to ambient (3) pebbles have the potentiality to store the heat during high solar intensity period and to release the stored energy to water when the solar intensity is low.

Zr-doped TiO2 supported on delaminated clay materials for solar photocatalytic treatment of emerging pollutants

Solar light-active Zr-doped TiO2 nanoparticles were successfully immobilized on delaminated clay materials by a one-step sol-gel route. Fixing the amount of TiO2 at 65wt.%, this work studies the influence of Zr loading (up to 2%) on the photocatalytic activity of the resulting Zr-doped TiO2/clay materials. The structural characterization demonstrates that all samples were formed by a delaminated clay with nanostructured anatase assembled on its surface. The Zr dopant was successfully incorporated into the anatase lattice, resulting in a slight deformation of the anatase crystal and the reduction of the band gap. These materials exhibit high surface area with a disordered mesoporous structure formed by TiO2 particles (15–20nm) supported on a delaminated clay. They were tested in the solar photodegradation of antipyrine, usually used as an analgesic drug and selected as an example of emerging pollutant. High degradation rates have been obtained at low antipyrine concentrations and high solar irradiation intensities with the Zr-doped TiO2/clay catalyst, more effective than the undoped one. This work demonstrates the potential application of the synthesis method for preparing novel and efficient solar-light photocatalysts based on metal-doped anatase and a delaminated clay.

The Martian atmospheric ion escape rate dependence on solar wind and solar EUV conditions: 1. Seven years of Mars Express observations

More than 7 years of ion flux measurements in the energy range 10 eV–15 keV have allowed the ASPERA-3/IMA (Analyzer of Space Plasmas and Energetic Ions/Ion Mass Analyzer) instrument on Mars Express to collect a large database of ion measurements in the Mars environment, over a wide range of upstream solar wind (density and velocity) and radiation (solar EUV intensity) conditions. We investigate the influence of these parameters on the Martian atmospheric ion escape rate by integrating IMA heavy ion flux measurements taken in the Martian tail at similar (binned) solar wind density (nsw), velocity (vsw), and solar EUV intensity (IEUV) conditions. For the same solar wind velocity and EUV intensity ranges (vsw and Is constrained), we find a statistically significant decrease of up to a factor of 3 in the atmospheric ion escape rate with increased average solar wind density (5.6 × 1024s−1 to 1.9 × 1024s−1 for 0.4 cm−3 and 1.4 cm−3, respectively). For low solar wind density (0.1–0.5 cm−3) and low EUV intensity, the escape rate increases with increasing solar wind velocity from 2.4 × 1024s−1 to 5.6 × 1024s−1. During high solar EUV intensities the escape fluxes are highly variable, leading to large uncertainties in the estimated escape rates; however, a statistically significant increase in the escape rate is found between low/high EUV for similar solar wind conditions. Empirical-analytical models for atmospheric escape are developed by fitting calculated escape rates to all sufficiently sampled upstream conditions.

ПОРІВНЯЛЬНИЙ АНАЛІЗ ЕФЕКТИВНОСТІ РОБОТИ СОНЯЧНОЇ ЕНЕРГЕТИКИ У ПРОВІДНИХ КРАЇНАХ СВІТУ

It has been performed a comparative analysis of solar power efficiency in individual regions and leading countries across the world and in Ukraine. It is estimated that amongst some regions the leadership belongs to European countries due to continuance development of solar energy, lessons learned in course of solar facilities operation and implementation of state-of-the-art machinery and equipment. The leader of solar power efficiency is Spain. Its dominant positions are determined by high solar intensity in comparison with other European countries and the current legal requirements obliging owners of new facilities to install certain amount of solar inverters during construction. It should be mentioned that such the approach allows minimizing line losses while transmission of electricity since major part of electricity produced is consumed by the producer itself. It is confirmed that solar power efficiency in Ukraine is at the mean European level that is largely due to solar power plants location in the southern regions of the country with higher solar radiation intensity and use of up-to-date equipment. It is recommended to divide further investigation into two separate directions, one of which is a comparison study of operation efficiency for large solar plants and another one is an analysis of operation of small solar facilities mounted on building roofs and walls.

A Chemical Analysis of Airborne Particulates at the near Coast Site, Ul-jin Geun Gyungbook

East Asia is characterized by anthropogenic emissions resulting from the large population and fast economic growth of this region. Since the prevailing wind is westerly and northwesterly, emissions from Ul-jin can be expected to contribute to acidic deposition increase in downwind direction. Aerosols collected at the near coast site, Uljin geun, gyungbook and were analyzed for NH4 +, Mg2+, Na+, Ca2+, Cl-, SO4 2-, and NO3 - from Aug. 2012 to Feb. 2013. The seasonal averaged aerosol concentration showed the highest potassium and calcium ion in winter and the highest ammonium ion due to a meadow and high solar intensity in summer. Sodium and chloride ion showed the same ratio all seasons and sulfate and nitrate species showed the maximum value in winter Chemical components of aerosols collected at the near coast site, Uljin geun, gyungbook were lower by 16 to 73% than those collected at other similar environment site such as kanghwa, yangyang. Comparing air quality data at the near coast site, Uljin geun, gyungbook, There was found that Uljin coast site is less influenced by the sea salts(potassium, magnesium, calcium) and nss-SO4 2- percentage is 3~13% higher than similar condition site.

First step into space: performance and morphological evolution of P3HT:PCBM bulk heterojunction solar cells [corrected] under AM0 illumination.

P3HT (poly(3-hexylthiophene-2,5-diyl)):PC61BM ([6,6]-phenyl-C61 butyric acid methyl ester) bulk heterojunction solar cells are fabricated and characterized as a function of solar intensity, temperature, and aging at vacuum conditions under illumination with AM0 illumination for testing potential use in space applications. The evolution of the inner film morphology is probed with grazing incidence X-ray scattering techniques and correlated with the evolution of the efficiency during aging. Grazing incidence wide-angle X-ray scattering shows almost no change of the crystalline structure of the P3HT:PCBM films due to aging. In contrast, the morphological evolution on the mesoscale extracted from grazing incidence small-angle X-ray scattering can explain the observed decay of the overall efficiency. The behavior at high solar intensities as well as elevated temperatures suggests that organic solar cells have high potential for space applications in the future.

Vegetation Placement for Summer Built Surface Temperature Moderation in an Urban Microclimate

Urban vegetation can mitigate increases in summer air temperature by reducing the solar gain received by buildings. To quantify the temperature-moderating influence of city trees and vine-covered buildings, a total of 13 pairs of temperature loggers were installed on the surfaces of eight buildings in downtown Toronto, Canada, for 6 months during the summer of 2008. One logger in each pair was shaded by vegetation while the other measured built surface temperature in full sunlight. We investigated the temperature-moderating benefits of solitary mature trees, clusters of trees, and perennial vines using a linear-mixed model and a multiple regression analysis of degree hour difference. We then assessed the temperature-moderating effect of leaf area, plant size and proximity to building, and plant location relative to solar path. During a period of high solar intensity, we measured an average temperature differential of 11.7 °C, with as many as 10-12 h of sustained cooler built surface temperatures. Vegetation on the west-facing aspect of built structures provided the greatest temperature moderation, with maximum benefit (peak temperature difference) occurring late in the afternoon. Large mature trees growing within 5 m of buildings showed the greatest ability to moderate built surface temperature, with those growing in clusters delivering limited additional benefit compared with isolated trees. Perennial vines proved as effective as trees at moderating rise in built surface temperature to the south and west sides of buildings, providing an attractive alternative to shade trees where soil volume and space are limited.

Assessment of solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers in Malaysian tropical latitude

In this paper, the solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers were assessed. The KT solar radiation model was coded in the MATLAB-based environment to compute the monthly solar radiation values. Seven-year data of monthly average daily solar radiation on a horizontal surface in Bangi, Malaysia (latitude = 3°N) were adopted as input in the simulation programme and the results were compared with the local optimum tilt angle at solar noon and other solar radiation model. The contour mappings of solar irradiation at various orientations in 12 months were presented. Results showed that the surface tilted ≤20° could intercept a relatively high solar intensity, which was less sensitive to the variation of azimuths with average solar insolation deviation of 11.82 %. The monthly optimum tilt angle altered throughout the year, ranging from −24° (in equator direction) to +22° (in north direction). The estimated annual optimum slope, 1.4° facing to the equator, was close to local latitude. Based on the seasonal analysis, the north-facing surface was able to intercept higher daily average solar radiation energy compared to south-facing plane. The optimum angles for seasonal south- and north-facing surfaces were found to be 14.4° and 14.8°, respectively, with a tolerable slope deviation of ±5° from the optimal values in the present work.

Experimental and theoretical analysis of solar still with glass basin

A single-slope solar still with a basin size of 1 × 1 × 0.2 m3 has been fabricated with glass of 6 mm thickness. The glass basin consists of two compartments, upper and lower compartments. The lower compartment (heating zone) has glass strips and the upper compartment (evaporating zone) has a hole through which the water comes in from the lower compartment. The performance of the still is compared by placing ethylene glycol and zinc nitrate solutions and heat storage materials like sand and wax were kept in between the glass strips. Aluminum cubes and sponges were also made to float in the upper compartment. The results illustrate that the still with corrugated sheet was more productive. The theoretical evaluation was also made. Then the still was modeled using gambit and fluent for high and low solar intensities. Thermal analysis using fluent overlaps with the experimental and theoretical production rates.

Studies on Wastewater Treatment Using Solar Photocatalysis in Oman

The demand for water in Sultanate of Oman is rapidly growing due to fast urbanization as well population growth. Oman depends on ground water and its limited rainfall for around 65% of its water supplies with desalinated water making up the remaining 35%. Oman is considered to be water stress country with an average annual rainfall of 100 mm and it is also predicted that water demand exceeds renewable sources by 25% due to decline in water levels and saline intrusion in coastal aquifers. In addition to the natural water resources available much emphasis is also given for desalination, municipal and oil produced treated water for the countrys requirement. Many techniques are used for treatment of pollutants in wastewater; solar photocatalysis is one such technique that is gaining popularity in the recent past. Oman is blessed with highest solar intensity in the world and hence the focus is on harnessing solar energy for various purposes including in wastewater treatment. This paper discusses the research output on the performance of solar photocatalysis wastewater treatment in Oman.

Assessment of solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers in Malaysian tropical latitude

In this paper, the solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers were assessed. The KT solar radiation model was coded in the MATLAB-based environment to compute the monthly solar radiation values. Seven years data of monthly average daily solar radiation on a horizontal surface in Bangi, Malaysia (latitude = 3° N) was adopted as input in the simulation programme, and the results were compared with the local optimum tilt angle at solar noon and other solar radiation model. The contour mappings of solar irradiation at various orientations in 12 months were presented. Results showed that the surface tilted at ≤20° could intercept a relatively high solar intensity, which was less sensitive to the variation of azimuths with average insolation deviation of 11.82%. The monthly optimum tilt angle altered throughout the year, ranging from -24° (in equator direction) to +22° (in north direction). The estimated annual optimum slope, 1.4° facing to the equator, was close to local latitude. Based on the seasonal analysis, the north-facing surface was able to intercept higher daily average solar radiation energy compared to south-facing plane. The optimum angles for seasonal south- and north-facing surfaces were found to be 14.4° and 14.8°, respectively, with a tolerable slope deviation of ±5° from the optimal values in the present work.