Formation Of Hot Spots Research Articles

From pollution to solutions: Insights into the sources, transport and management of plastic debris in pristine and urban rivers

River systems are important recipients of environmental plastic pollution and have become key pathways for the transfer of mismanaged waste from the land to the ocean. Understanding the sources and fate of plastic debris, including plastic litter (>5 mm) and microplastics (MPs) (<5 mm), entering different riverine systems is essential to mitigate the ongoing environmental plastic pollution crisis. We comprehensively investigated the plastic pollution in the catchments of two rivers in the Yangtze River basin: an urban river, the Suzhou section of the Beijing-Hangzhou Grand Canal (SZ); and a pristine rural river, the Jingmen section of the Hanjiang River (JM). The abundance of plastic pollutants in SZ was significantly higher than in JM: 0.430 ± 0.450 items/m3 and 0.003 ± 0.003 items/m3 of plastic litter in the water; 23.47 ± 25.53 n/m3 and 2.78 ± 1.55 n/m3 MPs in the water; and 218.82 ± 77.40 items/kg and 5.30 ± 1.99 items/kg of MPs in the sediment, respectively. Plastic litter and MPs were closely correlated in abundance and polymer composition. Overall, the polymer type, shape and color of MPs were dominant by polypropylene (42.5%), fragment (60.4%) and transparent (40.0%), respectively. Source tracing analysis revealed that packaging, shipping, and wastewater were the primary sources of plastic pollutants. The mantel analysis indicated that socio-economic and geospatial factors play crucial roles in driving the hotspot formation of plastic pollution in river networks. The composition of the MP communities differed significantly between the sediments and the overlying water. The urban riverbed sediments had a more pronounced pollutant ‘sink’ effect compared with the pristine rivers. These findings suggested that the modification of natural streams during urbanization may influence the transport and fate of plastic pollutants in them. Our results offer pivotal insights into effective preventive measures.

Integrating Fiber Sensing for Spatially Resolved Temperature Measurement in Fuel Cells

Fiber optic sensors integrated into fuel cell stacks have the potential to significantly enhance the temperature control and health monitoring of fuel cells. Inhomogeneous loading, both within individual cells and across different cells in a stack, leads to the formation of local hotspots that accelerate aging and degrade performance. This study investigates the behavior and feasibility of incorporating polyimide-coated optical fiber sensors into bipolar plates for precise and spatially resolved temperature monitoring. The sensor is successfully integrated into a single cell of a fuel cell stack, positioned on the bipolar plate in direct contact with the membrane. Pre-tests are conducted to thoroughly evaluate the technical properties of the fiber in relation to specific cell requirements. Additionally, a physical prototype featuring the sensor is developed and employed to validate its effectiveness under realistic operating conditions. The temperature measurement obtained via the fiber exhibits a continuous profile throughout the entire length, covering both the active area and distributor region of the cell. Throughout the entire 60 min test period, the measuring system provided continuous and uninterrupted temperature measurements, encompassing the start of the stack, the heating phase, the subsequent stable operating point, and the cooling phase. However, some technical challenges are identified, as mechanical pressure exerted on the fiber influences the measured temperature. While this work demonstrates promising results, further advancements are necessary to address inhomogeneous loading within fuel cells and hotspot mitigation. The precise monitoring of temperature distribution enables early detection of potential damage, facilitating timely interventions to improve the service life and overall performance of fuel cells.

Evaluation of PM2.5 spatio-temporal variability and hotspot formation using low-cost sensors across urban-rural landscape in lucknow, India

The high-resolution spatio-temporal monitoring through low-cost sensors (LCS) provides important insights into the dynamics of localized pollution patterns and in conceptualizing effective environmental management and public health interventions. We assessed the role of meteorology and local sources on spatially distributed PM2.5 pollutants measured from a unique urban-rural scaled network of LCS in Lucknow, India. The city-wide average PM2.5 annual cycle ranged between 29 ± 7 μg/m3 during the monsoon to 64 ± 30 μg/m3 during the rest of the year. During non-monsoon seasons, >60% of air mass trajectories indicated regional level transportations primarily from the north-western plains of the Indo-Gangetic basin, with peak weighted concentration weighted trajectory (WCWT, scale: 0–100) value estimated at >70. To analyze the impact of local sources, we designed a statistical classification method to divide each seasonal distribution into five incremental concentration groups ranging from no risk zone to hotspots. The hotspots were identified both within urban and rural regions with their average concentration measured as 23 μg/m3 and 26 μg/m3 higher than the rest of the regions in pre-monsoon (2 hotspots) and post-monsoon (4 hotspots) season, respectively. Further analysis shows that the nighttime concentrations were much higher in several locations (up to 40% in pre-monsoon and 54% in post-monsoon compared to their daytime levels), indicating the greater impact of local sources in the presence of low boundary layer height. A diurnal trend analysis along with conditional bivariate probability function (CBPF) was performed to interpret the characteristics and locations of the dominant sources. The study highlights the importance of a dense network of LCS to scale air quality monitoring in spatially heterogeneous environments and as a futuristic tool for PM2.5 exposure-based studies.

Experimental and numerical study of thermal coupling on catalyst-coated membrane for proton exchange membrane water electrolyzer

During the long-term operation of proton exchange membrane water electrolyzers (PEMWEs), Formation of localized hotspots in the catalyst-coated membrane (CCM) will seriously threaten the safe and efficient operation of the electrolyzer. This paper adopts a combination of dynamic experiments and numerical simulation analysis, aiming to develop the in-situ characterization technology of the thermal characteristics as well as the theoretical analysis of the multiphysics field for the·PEMWE. Based on both experimental and theoretical results, it is concluded that: (1) The high current density leads to an extremely uneven temperature distribution on the surface of the CCM. High temperature difference (as high as 34.04 °C) and high local temperature (up to 98.08 °C) are observed; (2) 30–50% of the electrical energy during the electrolyzer is converted into heat, of which the polarization heat accounts for the major part, followed by proton-conductive Joule heat; (3) The accumulation of gas phase during the transfer process of gas-liquid two phases is the primary cause of the deterioration of heat transfer, which further leads to local overheating. This study provides an experimental and theoretical basis for the safe and efficient operation of proton exchange membrane water electrolysis technology.

Peripatric speciation within Torreya fargesii (Taxaceae) in the Hengduan Mountains inferred from multi-loci phylogeography

BackgroundThe Hengduan Mountains (HDM) are one of the major global biodiversity hotspots in the world. Several evolutionary scenarios, especially in-situ diversification, have been proposed to account for the high species richness of temperate plants. However, peripatric speciation, an important mode of allopatric speciation, has seldom been reported in this region.ResultsHere, two chloroplast DNA regions and 14 nuclear loci were sequenced for 112 individuals from 10 populations of Torreya fargesii var. fargesii and 63 individuals from 6 populations of T. fargesii var. yunnanensis. Population genetic analyses revealed that the two varieties are well differentiated genetically (FST, 0.5765) and have uneven genetic diversity (π, 0.00221 vs. 0.00073 on an average of nuclear loci). The gene genealogical relationship showed that T. fargesii var. yunnanensis is inferred as derived from T. fargesii var. fargesii, which was further supported by the coalescent simulations (DIYABC, fastsimcoal2 and IMa2). By the coalescent simulations, the divergence time (~ 2.50–3.65 Ma) and the weak gene flow between the two varieties were detected. The gene flow was asymmetrical and only occurred in later stages of divergence, which is caused by second contact due to the population expansion (~ 0.61 Ma) in T. fargesii var. fargesii. In addition, niche modeling indicated that the two varieties are differentiated geographically and ecologically and have unbalanced distribution range.ConclusionsOverall, T. fargesii var. fargesii is always parapatric with respect to T. fargesii var. yunnanensis, and the latter derived from the former in peripatry of the HDM following a colonization from central China during the late Pliocene. Our findings demonstrate that peripatric speciation following dispersal events may be an important evolutionary scenario for the formation of biodiversity hotspot of the HDM.

Theory of continental drift – causes of the motion. Outline of the theory

The theory of mantle convection currents as the cause of lithospheric plate movements has several major problems, including the absence of an adequate energy source. As shown in our previous contribution, an unbiased interpretation of geochemical data does not support the assumptions of a significant amount of radionuclides in the lower mantle or even in the core. It is our assertion that solar radiation is the primary energy source in the lithosphere. This energy is converted into mechanical energy via thermoelastic waves, even in depths with minimal temperature fluctuations. This has been confirmed by various methods of continuous stress measurement. The periodic and quasiperiodic thermoelastic reversible deformations, such as the circadian and annual cycles (including tidal periods), can also cause irreversible deformations due to the ratcheting mechanism. The 2D model showed that the strength limit is exceeded in 0.3 % of all diurnal cycles during the year. As a consequence, continents tend to extend while the oceanic lithosphere is pushed and overthrusted between continents. The middle-ocean ridges, similar to continental rifts, are filled by ascending magma which is one example of the ratcheting mechanism. The final plate movements are determined by the distribution of major continents and the overall westward drift of the lithosphere, which is slower for deep-rooted plates like the Indian one. Large asteroid impacts are important triggers (and possibly significant energy sources) of discrete events, like the formation of hotspots and large igneous provinces.

Three-dimensional observations of the electric field distribution of variable frequency microwaves, and scaling-up organic syntheses

Variable Frequency Microwave (VFM) radiation provides a solution to the inhomogeneity of the electric field in the cavity, which has long led to a decline in the reliability of microwave chemical data and its industrial utilization. Herein, we report in-situ three-dimensional experimental measurements of the electric field’s uniform distribution of VFMs within a multimode cavity under high power conditions, and their subsequent comparison to Fixed Frequency Microwaves (FFM) that could only be assessed earlier through theoretical analysis. We also examine the consequences of changes in VFM irradiation conditions and elucidate the threshold at which VFM irradiation might prove beneficial in syntheses. With an ultimate focus on the use of VFM microwave radiation toward industrial applications, we carried out an effective synthesis of 4-methylbyphenyl (4-MBP) in the presence of palladium (the catalyst) supported on activated carbon particulates (Pd/AC), and revisited two principal objectives: (a) the effective suppression of discharge phenomena (formation of hot spots), and (b) synthesis scale-up using a 5-fold increase in sample quantity and a 7.5-fold larger reactor size (diameter) than otherwise used in earlier studies.

Template-confined assembly of Ag nanocubes: An approach to fabricate SERS substrate with good performance

Surface-enhanced Raman scattering (SERS) is an important analytical technique. Its detection sensitivity and reproducibility depend on the density and distribution of SERS hotspots. Self-assembly is an efficient method to produce of SERS substrates due to its easy accessibility. However, the assembled defects can hardly be avoided on large area, which could lower the density and uniformity of the hotspots, leading to poor SERS performance. Herein, we report a method to reduce the defects by taking a patterned substrate as template to confine the assembly of Ag nanocubes. The template was prepared based on the combination of photo lithography and self-assembly. Confined by the template, the Ag nanocubes were assembled closely in each dots of the pattern. The limit of detection (LOD) is down to 3.42 × 10−17 M and the enhanced factor (EF) is up to 3.44 × 1010 on the prepared substrate for detecting rhodamine 6G (R6G). In addition, the relative standard deviation (RSD) of the different substrates is 8.75 %. The assembled Ag nanocubes exhibits high sensitivity and reproducibility as SERS substrate, which are contributed by the formation of high-density and uniform hotspots. The prepared substrate can be used for detecting trace amounts of melamine in milk with LOD of 2.06 × 10−7 M and RSD of 6.91 %, so the substrate is applicable for analyzing various analytes.

Mechanism of Hotspot Formation in Energetic Materials Under Mild Impact Loading

Mechanism of Hotspot Formation in Energetic Materials Under Mild Impact Loading

Formation of hot spots at end-on pre-compressed isochoric fuels for fast ignition

It is crucial to form a hot spot that can drive a self-heating nuclear burn propagation into the surrounding cold fuel in ignition process of laser fusion. In this paper, we discuss the formation of a hemispherical hot spot located at the edge of an end-on precompressed isochoric fuel instead of a central spherical hot spot surrounded by cold fuel in a corona plasma shell. This configuration leads to a new energy loss mechanism named hot spot collapse, which originates from mass loss of the hot spot through the interface with the vacuum. A semi-analytical model is proposed including α particle induced burning, hot spot collapse and other energy loss processes. Then a modified ignition criterion is derived. The results show that the competition between the hot spot collapse and the burn propagation is crucial in the formation of the hot spot. The formation of such a hot spot at end-on precompressed isochoric fuels would require a somewhat higher initial temperature of Th=9 keV for a hot spot with an initial areal density ρd=0.6gcm−2 . Simulations are performed with a 3D hybrid particle-in-cell/fluid code for the heating process by fast electrons and a 3D radiation hydrodynamics code for the burning process. Simulation results agree with the model. Our optimized result shows a 10 ps heating laser pulse with an energy as low as 39 kJ can lead to a fast ignition in the ideal case. This study provides an effective reference for design and evaluation of experiments planned for fast ignition schemes.

Use of Botanicals Plant for Stored Grain Pest Management: A Critical Review

The current paper has been studied to understand the significance of various plant products (botanicals) against storage insect pests of seeds and grains. Grain storage is critical in agriculture for the next generation and food security. Insect pests are economically relevant among the several biotic and abiotic elements that impact the fate of grains during storage because they cause significant loss. The expanding demands of the world's growing population can be met by lowering or eradicating the insect pest population while storing. The most damaging storage insect pests are Sitotroga cerealella, Sitophilus sp., Rhyzopertha Dominica, Trogoderma granarium, Tribolium sp., Callosobruchus sp., and others. Insect damage includes the ingestion of seed, exuviae debris, webbing, and cadavers, rendering the grain unfit for human consumption and reducing both quality and quantity. They manipulated the storage environment, resulting in the formation of hotspots that are conducive to the spread of storage fungi and other dangerous microflora. Conventionally, we use synthetic pesticides to manage various insect pests that are hazardous to the environment and ecosystem in a variety of ways, including the elimination of natural enemies, insect resistance and resurgence, making soil, water, and air sick, and having residual effects that cause various disorders or diseases in animals and humans. Botanicals such as neem (Azadirachta indica), Bach (Acorus calamus), phoolakri (Lantana camara), draik (Melia azadarach), kali mirch (Piper nigrum), and basuti (Adhatoda zeylanica) are biodegradable, non-residual, equally effective, and widely available etc. may show to be a superior solution for controlling insect pests, particularly storage pests, without impacting grain or seed quality or harming our ecology or environment. Thus, botanicals can be used alone or in conjunction with IPM to manage insect pests.

Study on the electrochemical effect of ZnO addition on flash sintering of 3 mol% yttria stabilized zirconia

Flash Sintering has shown tremendous promise in reducing the sintering time and temperature. However, significant heterogeneity in densification and microstructure was observed in the flash-sintered sample due to hotspot formation and electrochemical effects (electrochemical blackening). In this work, we have varied the extent of electrochemical reaction by (0.75-3 mol%) ZnO addition during flash sintering of 3 mol% yttria-stabilized Zirconia (3YSZ). A substantial increase in grain size was observed throughout with an increase in dopant concentration. With the addition of 0.75 mol% ZnO dopant in 3YSZ, a significant improvement in densification and a significant reduction in the presence of cracks were observed. The extent of electrochemical blackening was seen to be increasing with the increase in dopant concentration. The blackened phase was found to be distorted tetragonal Zirconia by Raman analysis. The ZnO doped 3YSZ showed ionic to electronic transition in conduction during flash sintering likely due to electrochemical effects.

Evidence of trapping and electrothermal effects in vertical junctionless nanowire transistors

Understanding trap dynamics and formation of localized temperature hot-spots due to self-heating is crucial for the design optimization of emerging vertical junctionless nanowire transistors (VNWFET). This work investigates the operation of an 18 nm VNWFET technology, for the first time, leveraging pulsed current–voltage measurements. Results indicate increased trap activity as well as electrothermal effects with increasing pulse width. Multiphysics simulations are then used to provide a deeper insight into the nanoscale transport of the VNWFETs. We then incorporated these effects into the SPICE-compatible VNWFET compact model and further investigated the behaviors of trapping and electrothermal effects in basic logic circuits based on the compact model simulation.

Sequestration and export of microplastics in urban river sediments

In rivers, riverbeds are considered to have dual properties as a short-term sink and a source of further mobilization for microplastics. To better understand the sources, storage, and fate of microplastics in river systems, this study quantified the formation of microplastic hotspots in riverbeds and seasonal variations in microplastic inventories in riverbeds, especially for small-sized microplastics (<330 µm), with a fluorescence-based protocol. This study provides first-hand measured evidence for the sequestration of microplastics in the riverbed under low-flow conditions and its export from the riverbed under high-flow conditions. The results show that riverbeds in urban areas are still hotspots for microplastic pollution and that high inputs of urban microplastics control microplastic load in its downstream areas. Seasonal rainfall exported 34.86 % (equivalent to 4.34 × 1011 items/8.57 t) of microplastic pollution from the riverbed, and its removal capacity may be related to the rainfall intensity. Wider riverbeds are conducive to the formation of microplastic hotspots due to the flow slow down. Most importantly, rainfall-driven scouring of the riverbed can enhance the pollution of small-sized microplastics in the riverbed, especially the smallest-size microplastics (<100 µm). Therefore, this study not only contributes reliable information about the sequestration and export of microplastics in the riverbed, but also provides a possible mechanism to explain the lack of small-sized microplastics (<330 µm) in the ocean.

Highly sensitive SERS platform on isotropic ionic liquid-based liposome

An ionic liquid (IL)-based liposome, consisting of an imidazolyl head and two undecene tails (N, Ń-bis(10-undecenyl)-2-methylimidazolium bromide, [MimV11, V11]Br), was prepared through self-assembly and used as a carrier to create an isotropic surface-enhanced Raman scattering (SERS) platform. The bridging of IL terminals was employed to enable the co-assembly in both hotspot formation and the induced localization of analytes. Specifically, gold nanoparticles (Au NPs) were grown and stabilized on the surface using the anion exchangeability and coordination effect of IL. Besides, the confinement effect of the isotropic surface spatially arranges the Au NPs in an array-like pattern, which not only facilitates the formation of hotspot-rich planes but also provides a uniform electrostatic driving force for molecular loading. This contributes to the improvements in detection sensitivity and reproducibility of the SERS signal. On this basis, the co-assembled platform presented an ideal enhancement factor (3.04 × 107) and a low detection limit (10-12 M) for methyl orange (MO). Additionally, the detection performance, adsorption orientation, and their influencing factors were investigated. The results showed that the adsorption of MO on the liposome exhibited two typical orientations, lying-type, and standing-type. It was mainly regulated by the resonance structures of MO and the steric effect of the SERS substrate. The isotropic co-assembly strategy achieves ultrasensitive trace detection and draws a fascinating application prospect for this hotspot-motivated and hot region-located SERS detection mode.

A multiscale 3D hotspot-rich nanostructured substrate for biomolecular detection of SARS-CoV-2

The current fabrication methods of surface-enhanced Raman scattering (SERS) chips used for biological detection mostly require antibodies conjugated on nanostructured metals or additionally connected to a reporter, which leads to complicated fabrication processes and increases the cost of these chips. More importantly, only a single-layer (2D) signal source is generated on the substrate of the chip, resulting in poor sensitivity. Herein, we constructed a single-component, multiscale, three-dimensional SERS (M3D-SERS) substrate from silver nanowires (AgNWs) packing. According to our results, the Raman enhancement effect of the M3D-SERS substrate was related to the degree of AgNWs stacking along the z axis. In addition, the light source-dependent plasmonic partition and hotspot formation of the M3D-SERS substrate were evaluated by the finite integration technique to prove that M3D-SERS offers advantages, with isotropic localized surface plasmon resonance as well as homogeneous hotspot distribution, for SERS over its 1D and 2D counterparts. Experimentally, the optimal construction of the M3D-SERS chip was explored and established based on the Raman signal enhancement of bovine serum albumin, and consequently, the efficiency of the M3D-SERS chip in detecting SARS-CoV-2-related biomolecules was investigated based on the detection superiority to biomolecules. This study demonstrates a simple, label-free, pre-treatment-free potential biosensor technology that can be used in healthcare units. Furthermore, in combination with a suitable laser light source, this technology can be applied for efficient detection in point-of-care tests with a handheld spectrometer.

Fast Tracking of Maximum Power in a Shaded Photovoltaic System Using Ali Baba and the Forty Thieves (AFT) Algorithm

Photovoltaic (PV) generation systems that are partially shaded have a non-linear operating curve that is highly dependent on temperature and irradiance conditions. Shading from surrounding objects like clouds, trees, and buildings creates partial shading conditions (PSC) that can cause hot spot formation on PV panels. To prevent this, bypass diodes are installed in parallel across each panel, resulting in a global maximum power point (GMPP) and multiple local maximum power points (LMPPs) on the power-voltage (P-V) curve. Traditional methods for maximum power point tracking (MPPT), such as perturb and observe (P&amp;O) and incremental conductance (INC), converge for LMPPs on the P-V curve, but metaheuristic algorithms can track the GMPP effectively. This paper proposes a new, efficient, and robust GMPP tracking technique based on a nature-inspired algorithm called Ali Baba and the Forty Thieves (AFT). Utilizing the AFT algorithm for MPPT in PV systems has several novel features and advantages, including its adaptability, exploration-exploitation balance, simplicity, efficiency, and innovative approach. These characteristics make AFT a promising choice for enhancing the efficiency of PV systems under varied circumstances. The performance of the proposed method in tracking the GMPP is evaluated using a simulation model under MATLAB/Simulink environment, the achieved simulation results are compared to particle swarm optimization (PSO). The proposed method is also tested in real-time using the Hardware-in-the-loop (HIL) emulator to validate the achieved simulation results. The findings indicate that the proposed AFT-based GMPP tracking method performs better under complex partial irradiance conditions than PSO.

A roadmap to estimating agricultural ammonia volatilization over Europe using satellite observations and simulation data

Abstract. Ammonia (NH3) is one of the most important gases emitted from agricultural practices. It affects air quality and the overall climate and is in turn influenced by long-term climate trends as well as by short-term fluctuations in local and regional meteorology. Previous studies have established the capability of the Infrared Atmospheric Sounding Interferometer (IASI) series of instruments, aboard the Metop satellites, to measure ammonia from space since 2007. In this study, we explore the interactions between atmospheric ammonia, land and meteorological variability, and long-term climate trends in Europe. We investigate the emission potential (Γsoil) of ammonia from the soil, which describes the soil–atmosphere ammonia exchange. Γsoil is generally calculated in-field or in laboratory experiments; here, and for the first time, we investigate a method which assesses it remotely using satellite data, reanalysis data products, and model simulations. We focus on ammonia emission potential in March 2011, which marks the start of growing season in Europe. Our results show that Γsoil ranges from 2 × 103 to 9.5 × 104 (dimensionless) in fertilized cropland, such as in the North European Plain, and is of the order of 10–102 in a non-fertilized soil (e.g., forest and grassland). These results agree with in-field measurements from the literature, suggesting that our method can be used in other seasons and regions in the world. However, some improvements are needed in the determination of mass transfer coefficient k (m s−1), which is a crucial parameter to derive Γsoil. Using a climate model, we estimate the expected increase in ammonia columns by the end of the century based on the increase in skin temperature (Tskin), under two different climate scenarios. Ammonia columns are projected to increase by up to 50 %, particularly in eastern Europe, under the SSP2-4.5 scenario and might even double (increase of 100 %) under the SSP5-8.5 scenario. The increase in skin temperature is responsible for a formation of new hotspots of ammonia in Belarus, Ukraine, Hungary, Moldova, parts of Romania, and Switzerland.

Resonance in radio frequency sheath admittance and enhanced impurity emission near the ion cyclotron frequency

Ion cyclotron resonance heating (ICRH) is of considerable interest among all auxiliary heating techniques, because it transfers power directly to ions, targets the high-density core, and involves the cheapest radio-frequency (RF) components. During ICRH operation, RF sheaths form on the ICRH antenna itself, nearby hardware, and far-field surfaces. These sheaths are associated with large hot-spot formation and impurity emissions. This work presents high-resolution numerical modelling of RF sheaths in nuclear fusion scenarios using hPIC2, a Debye-scale particle-in-cell code. The modelling reveals a new RF sheath phenomenon which occurs when the RF is resonant with a species ion cyclotron frequency or harmonic in an oblique magnetic field. This resonance of the RF sheath causes modifications of the energy-angle distributions of the ions impacting on the walls, with consequent increase in wall impurity emission. Due to the 1/R scaling of the magnetic field in a tokamak, such cases are possible on divertor or vacuum chamber surfaces, depending on the geometry of the tokamak and the RF heating scenario. A simple physics interpretation using a driven damped harmonic oscillator is proposed, where the ion sheath transit time plays the role of damping the RF sheath admittance. Critically, the resonance leads to increased ion heat flux at the wall as well as increased physical sputtering, despite a lack of increase in RF rectified sheath potential.

Attenuation of hotspot phenomenon in PV systems

ABSTRACT PV waste management is a looming problem and a growing concern for environmental engineers and energy policymakers, as the early PV installations are approaching their end-of-life. Hence, improvement of PV reliability and prevention of early failures has now become more important than ever. Notably, the formation of hotspots in PV cells under partial shading and other mismatch conditions remains a dominant cause of early failures in PV modules. In this study, we undertake an experimental investigation to assess the effectiveness of the extant bypass mechanism in preventing hotspot formation in PV modules. The findings reveal several limitations associated with the conventional bypass approach. Although the bypass diode partially fulfills its intended purpose within a string array configuration, its effectiveness is entirely compromised when connected in the configuration of real-world installations, such as in a series-parallel (SP) array. The hotspot temperature in the SP array increased up to 70.7°C under partial shading conditions at the operating point (i.e., at MPP), whereas no hotspot was created (below 46.1°C) in a string array, except in the single-cell shading scenario. To make the bypass circuits effective, in the present work, a novel bypass strategy is proposed.