Paleoenvironmental reconstructions on a (supra-)regional scale have gained attention in Quaternary sciences during the last decades. In terrestrial realms, loess deposits and especially ...intercalations of loess and buried soils, so called loess-paleosol sequences (LPS) are important archives to unravel the terrestrial response to e.g. climatic fluctuations and reconstruct paleoenvironments during the Pleistocene. The analysis of LPS requires the knowledge of several key factors, such as the distribution of the aeolian sediments, their location relative to (potential) source areas, the climate conditions that led to their emplacement and the topography of the sink area. These factors strongly influence the sedimentological and paleoenvironmental characteristics of LPS and show broad variations throughout Europe, leading to a distinct distribution pattern throughout the continent.
We present a new map of the distribution of aeolian sediments (mainly loess) and major potential source areas for Europe. The map was compiled combining geodata of different mapping approaches. Most of the used geodata stems from accurate national maps of 27 different countries. Problematic aspects such as different nomenclatures across administrative borders were carefully investigated and revised. The result is a seamless map, which comprises pedological, geological, and geomorphological data and can be used for paleoenvironmental and archeological studies and other applications.
We use the resulting map and data from key geomorphological cross-sections to discuss the various influences of geomorphology and paleoenvironment on the deposition and preservation of Late Pleistocene loess throughout Europe. We divided the loess areas into 6 main loess domains and 17 subdomains to understand and explain the factors controlling their distribution and characteristics. For the subdivision we used the following criteria: (1) influence of silt production areas, (2) affiliation to subcatchments, as rivers are very important regional silt transport agents, (3) occurrence of past periglacial activity with characteristic overprinting of the deposits. Additionally, the sediment distribution is combined with elevation data, to investigate the loess distribution statistically as well as visually.
Throughout Europe, the variations, and differences of the loess domains are the results of a complex interplay of changing paleoenvironmental conditions and related geomorphologic processes, controlling dust sources, transport, accumulation, preservation, pedogenesis, alongside erosional and reworking events. Climatic, paleoclimatic, and pedoclimatic gradients are on the continental scale an additional important factor, since there are e.g. latitudinal differences of permafrost and periglacial processes, an increase in continentality from west to east and in aridity from northwest to southeast and south, strongly affecting regional sedimentary and geomorphic dynamics.
We propose three main depositional regimes for loess formation in Europe: (1.) periglacial and tundra loess formation with periglacial processes and permafrost in the high latitude and mountainous regions; (2.) steppe and desert margin loess formation in the (semi-)arid regions; and (3.) loess and soil formation in temperate and subtropical regions. Loess deposits of (1.) and (2.) show coarser, sandier particle distributions towards the glacial and desert regions. In the humid areas (3.) forest vegetation limited dust production and accumulation, therefore, there is an increase in finer grain sizes due to an increase in weathering.
•New seamless loess map of Europe including related Late Pleistocene sediments•Review on European loess landscapes divided in six domains and 17 subdomains•Geomorphology of loess regions including 3D images of selected loess landscapes•New conceptual model of loess genesis in Europe•Paleoenvironmental variations determine spatial pattern of loess formation and domain subdivision
•The dust deposition rate first increased and then fell when the dust particle size increased.•The maximum deposition rates are 14.28%, 13.53%, 6.79% and 9.78% for different tilt angles.•The ...mechanisms of dust deposition on ground-mounted PV panels were studied.•The influences of dust deposition on PV efficiency were analyzed.
The dust deposition behaviours of ground-mounted solar photovoltaic (PV) panels and their effects on the PV efficiency were numerically investigated. The shear stress transport k-ω turbulence model with the inlet user-defined function profiles and the discrete particle model were used to predict the wind flow fields and the dust deposition rates of a PV panel. A grid independence study was conducted, and the mean pressure coefficient was validated with the related experimental data. The effects of the different dust particle diameters and the different tilt angles of the PV panels on the dust deposition characteristics were investigated carefully. The results showed the dust deposition rates of a PV panel were considerably affected by the different tilt angles. The dust deposition rates were considerably higher for the upward PV installations than for the downward ones. Moreover, the dust deposition rates were greater when the solar PV panel was more horizontal with the ground. The peak deposition rates were observed for the 150-μm dust particles for all of the tilted PV panel angles. The maximum deposition rates were 14.28%, 13.53%, 6.79% and 9.78% for the tilted PV panel angles of 25°, 40°, 140° and 155°, respectively. Moreover, the main deposition mechanisms of the solar PV panel were analysed and discussed for the different dust particle sizes and PV panel installation angles. Finally, an empirical model was developed for estimating the PV output reductions caused by the dust deposition for different tilt angles, which could be applied in practical engineering applications.
Photovoltaic (PV) panels' photoelectric conversion efficiency will decrease as dust deposition on their surface. An approach to dust removal on the PV panel's surface by longitudinal high-speed ...airflow was investigated to increase the output power. In this paper, commercial CFD software was used to numerically simulate the characteristics of dust removal by longitudinal high-speed airflow. The PV panels' output characteristic model under the action of dust removal by high-speed airflow is established by Simulink software, and the influence of high-speed airflow on the output characteristic is studied. Firstly, the dust removal mechanism of the PV panel under high-speed airflow is studied. Secondly, the impact of different tilt angles of the PV panel, dust particle size, airflow velocity, and blowing time on the dust removal effect of the PV panel surface were studied. The optimal airflow velocity and blowing time were obtained according to the airflow velocity and blowing time and their influence on the dust removal rate. Finally, the effect of high-speed airflow dust removal on PV power generation's efficiency and output characteristics is studied. The findings demonstrate that as the tilt angle increases, so does the dust removal rate increases continuously. In addition, the rate at which dust is removed increases with airflow velocity and blowing time. When the tilt angle is 30°, the best airflow velocity of dust removal is 5 m/s, and the best blowing time is 8 s. When the tilt angle is 45°, the best airflow velocity of dust removal is 10 m/s, and the best blowing time is 5 s. With the increase in airflow velocity and blowing time, the output power of PV panels continues to increase. When the airflow velocity is 10 m/s, and the blowing time is 5 s, 7.5 s, 12.5 s, and 15 s, the maximum output power after dust removal is increased by 15.44 %, 23.05 %, 23.38 %, and 23.39 %. This paper's research results can guide the design of the practical engineering application of longitudinal blowing high-speed airflow in the dust removal of PV panels.
•A dust removal method based on longitudinal high-speed airflow on the surface of PV panels.•Dust removal under the action of longitudinal high-speed airflow is simulated by CFD.•The effect of high-speed airflow dust removal on the output power is studied.
Dust deposition density and particle size impact on PV module energy utilization was investigated. Module A was clean, and modules B, C and D were dusted with deposition densities of 6.94 g/m2, ...13.88 g/m2, and 20.83 g/m2, respectively. Test-1 and test-2 were carried out with steel slag dust particles with a size of 61 μm and 109 μm, respectively. The decrease in energetic efficiency comparing module A was 2.45%, 3.99% and 5.9% for the B, C and D modules in test-1, respectively. In test-2, the decrease in energetic efficiency was 1.77%, 2.77%, 3.63% for modules B, C, and D. In test-1, the exergy efficiency of modules B, C, and D declined by 2.67%, 4.3%, 6.62%. In test-2, the exergy efficiency fell by 1.94%, 2.84%, 4.19% for modules B, C and D, respectively. The annual exergy destruction cost was calculated to be $49.97, $51.48, $52.42, and $53.78 for modules A, B, C, and D, respectively. For test-2, the corresponding values were $48.13, $49.2, $49.66, and $50.4 for modules A, B, C, and D, respectively. The decrease in energetic and exergetic efficiency was lowered by the particle size increase. The decrease in energetic and exergetic efficiency was raised by increased deposition density.
Dust accumulation on photovoltaic (PV) modules is responsible for the reduction in solar radiation received and/or transmitted, hence, decreases the efficiency of the PV cells. To enhance the ...performance of PV modules, the nature and the structure of dust should be evaluated. This paper investigates the seasonal variability of dust and PV soiling losses over 4 months (15 weeks, over the summer of 2018) in a soiling station deployed at the American University of Sharjah, UAE. A custom-made setup was employed to collect the dust samples on glass sheets. This will provide a better understanding of the soil deposition rates and composition. The accumulated dust was characterized for its morphological and elemental properties. The dust samples were directly collected from the panels mounted outdoor in the desert environment. Various characterization techniques were performed to determine the dust samples’ composition. The results showed that the dust particles are mostly rich in carbon, oxygen, calcium, silicon, thus indicating the presence of silica and calcite. UV–Vis results showed a decrease in transmittance of 30% after 15 weeks of soiling. This results of this work are essential for the development of proper self-cleaning techniques for PV modules deployed in Sharjah.
•The dust accumulation rate of 0.7 mg/week was recorded at 25°.•A decrease in transmittance of about 30% after 15 weeks of soiling was reported.•High oxygen and carbon content were reported in the dust samples.•The results reported here provide a basis to develop a proper cleaning technique.
With increasingly refined and complex usage scenarios, the use of purely superhydrophobic surfaces/interfaces has become increasingly limited. Flexible and stretchable superhydrophobic surface with ...self-cleaning fine-dust deposition function is gaining popularity, but their low-cost fabrication faces multiple challenges. Herein, a flexible superhydrophobic surface was fabricated using chewing gum and SiO2, while being can be shapeable, stretchable, self-healable, and reusable. The apparent contact angle (APCA) increases along with the dosage of SiO2 increase, the apparent contact angle (APCA) reaches to the maximum of 156 ± 5°, and the sliding angle (SA) reaches 3 ± 2° at the dosage of SiO2 1.0 g, the adhesive force reaches to minimum of 0.034 mN. The study demonstrated that this composite material exhibits self-cleaning fine-dust deposition surface properties by simply pasting it onto different surfaces of metals, fabrics, paper, and plastics. The chewing gum/SiO2 material shows robust resistance to sandpaper abrasion, tape-peeling, finger wiping, and solutions with different pH values. This material can be used on metals, fabrics, paper, and plastics for a myriad of self-cleaning fine-dust deposition applications.
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The topic of soiling of photovoltaic module (PV) and concentrated solar power (CSP) collectors has recently gained increasing attention due to its impact on solar power production, especially in arid ...and semi-arid areas with high concentrations of airborne dust. Soiling describes the deposition of dust and other contaminants on surfaces, reducing solar irradiation by absorbing or reflecting the sunlight, causing energy yield losses which can exceed 1% per day. The amount of soiling is influenced by complex interactions of many factors which can vary significantly from site to site.
In this study we provide a detailed overview of macroscopic and microscopic factors influencing soiling. This includes a global analysis of key parameters including airborne dust concentrations, dust characteristics (mineral composition, size distribution), and particle deposition rates. A theoretical model for relevant particle adhesion and removal forces is presented to achieve a microscopic understanding of wind cleaning effects. Further, it was found that dew occurs frequently on PV modules in many soiling affected areas and that this can significantly increase particle adhesion. Therefore, a detailed analysis and model of the dew-driven soiling mechanisms of cementation, particle caking, and capillary aging are given on the basis of microstructural material and dust characterization of outdoor exposed glass samples. Furthermore, we study the complex interplay and dynamics of different environmental parameters (relative humidity, ambient and module temperature, airborne dust concentration, wind speed) and their correlation to dust accumulation, and provide explanations with the help of the developed models. Overall the study aims to provide a useful, in-depth but also global overview and fundamental understanding of soiling processes on PV modules down to the microscale, which could be used to develop appropriate soiling mitigation strategies.
•Overview of microscopic and macroscopic parameters influencing soiling.•Worldwide review of dust properties, concentrations and soiling rates.•Theoretical model for particle adhesion and removal forces relevant for soiling.•Microstructural analysis and model of dew-driven mechanisms increasing adhesion.•Analysis of dynamics of environmental parameters and correlation with soiling rates.
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