Power Drop Research Articles

An Automatic PI Tuning Method for Photovoltaic Irrigation Systems Based on Voltage Perturbation Using Feedforward Input

This paper proposes a new automatic tuning method for the proportional-integral (PI) controllers of photovoltaic irrigation systems (PVIS) without the need for any other power source or batteries. It enables the optimisation of the values of the PI parameters (Kp and Ki) automatically, eliminating the requirement for skilled personnel during the installation phase of PVIS. This method is based on the system’s voltage response when a disturbance signal is introduced through the feedforward input of the PI controller. To automatically assess the response properties, two indicators are proposed: the total harmonic distortion (THD), used to evaluate the sine response, and the total square distortion (TSD), used to evaluate the square response. The results indicate that the tuning changes for different irradiance and temperature conditions due to the non-linearity of the system, obtaining the most conservative values at maximum irradiance and temperature. The robustness of the results of the new automatic tuning method to abrupt photovoltaic (PV) power fluctuations due to clouds passing over the PV generator has been experimentally tested and the results show that the obtained tuning values make the PVIS stable, even when PV power drops of 66% occur abruptly.

Optimization of power feedback control system for HCN interferometer on EAST Tokamak

The Hydrogen Cyanide (HCN) interferometer stands as an indispensable diagnostic tool, designated to measure the line-integrated electron density on the Experimental Advanced Superconducting Tokamak (EAST), thereby offering essential density feedback signals for EAST operation. The HCN laser used in the interferometer is a continuous glow discharge gas laser. However, owing to variations in external ambient temperature, the HCN laser exhibits output power instability. The current power automatic feedback control system for the HCN laser interferometer exhibits low actuator adjustment precision, thereby limiting its ability to achieve maximum output power. Moreover, the system may cause a temporary power drop to zero during adjustment, while EAST operation requires the HCN laser interferometer to maintain high power continuously. In order to solve the issues, this paper developed an innovative actuator that ingeniously amalgamates the virtues of piezoelectric ceramic and stepper motor. This novel actuator, demonstrating a broad adjustment range and high precision, is intended to replace the present one in the HCN interferometer power control system. While the stepper motor executes coarse adjustment, the piezoelectric ceramic enables precise adjustment, thus enhancing the adjustment accuracy of the automatic power control system to a sub-micrometer level and an adjustment range greater than 5 mm. Accurate determination of the regulator's adjustment direction can significantly improve the efficiency of adjustment. The slope of the laser output power peak decreases as it approaches the maximum value, and increases as it moves away from the maximum value. Therefore, this system replaces the original threshold algorithm with a slope algorithm. By correctly judging the adjustment direction, the efficiency of adjustment is improved. Furthermore, this algorithm can keep the output power stable on a power peak. There will be no instances of zero power output during the adjustment, allowing the power to remain stable above the set threshold for a long time. Currently, this system has been successfully applied to the HCN interferometer, and testing has found that the system can maintain stability for at least 16 hours. Furthermore, even when the laser output power was intentionally reduced to below the set threshold, the system was able to respond quickly and adjust the output, rapidly restoring it to above the predefined threshold. Multiple tests have shown the strong robustness of the system, indicating it meets the stringent demands of the EAST's complex environment.

Evaluation of the Performance of Polycrystalline and Monocrystalline PV Technologies in a Hot and Arid Region: An Experimental Analysis

In arid regions, the behavior of solar panels changes significantly compared to the datasheets provided by the manufacturer. Therefore, the objective of this study is to determine the performance of both polycrystalline and monocrystalline solar modules in an arid region characterized by a large potential for solar irradiation and high temperatures. The influence of environmental parameters, such as temperature and dust, on the output power of solar modules with different technologies (monocrystalline and polycrystalline) has been investigated. The Artificial Hummingbirds Algorithm (AHA) has been used to extract parameters for PV modules. As a result, it has been demonstrated that for high solar irradiation, the polycrystalline PV module experiences a smaller decrease in output power than the monocrystalline PV module as the module temperature increases. The percentage drop in output power is approximately 14% for the polycrystalline PV module and nearly 16% for the monocrystalline PV module. However, for low solar irradiation, it is advisable to use monocrystalline modules, as a 21% decrease in power was observed for polycrystalline modules compared to a 9% decrease for monocrystalline modules. Additionally, the monocrystalline PV module was more affected by dust than the polycrystalline PV module under high solar irradiation conditions, while under low incident solar radiation, the polycrystalline PV module was more affected by dust than the monocrystalline PV module. The power drop of the monocrystalline PV module was greater than that of the polycrystalline PV module for high solar radiation (>500 W/m2). Therefore, the advantage of this proposed work is to recommend the use of polycrystalline solar panels in regions characterized by high solar irradiation and high temperatures instead of monocrystalline solar panels, which are more efficient in regions worldwide characterized by low solar irradiation and low temperatures.

Impact of dust particles on the output power of photovoltaic modules in Calabar, Cross River State

During the dry season, dust particles on photovoltaic modules (PV modules) are a regular occurrence in Calabar, Cross River State. This dusty condition or environment is caused by the migration of dust particles from the Sahara region via the east-west wind. The concentration of dust on PV modules has an impact on the overall performance of solar energy systems. This research looks into the effect of dust particles on the output power of solar modules. This investigation was carried out by subjecting 80-watt monocrystalline PV modules to an outdoor experiment and analyzing the changes in current and voltage from the control and dusty PV modules with a digital multimeter. Other environmental factors such as relative humidity, ambient temperature, and solar radiation were also measured with a hygrometer, thermometer, and solar power meter respectively. Appropriate formulars were employed to calculate output power and efficiency. Dust particles on the surface of PV modules dramatically reduces the quantity of sunlight that penetrate the panel by 21.10%, resulting in a drop in the system's overall output power. The study emphasizes on the importance of frequent cleaning and maintenance of PV systems.

Numerical investigation of a thermoelectric generator system with embedded sickle-shaped fins

To enhance the utilization efficiency of exhaust gas in thermoelectric generator (TEG) systems, a polygonal heat exchanger with embedded sickle-shaped fins was proposed in this study. A coupled fluid-thermal-electric multiphysics numerical model was developed to analyze the impact of different fin variables on system performance. Subsequently, the established model was validated on a test bench. The results indicate that embedded sickle fins significantly improve the TEG performance. Higher fins enhance the system's output power and temperature uniformity, albeit with increased pressure drop. Conversely, elongated linear fins and increased arc fin radius decrease pressure drop but reduce its output power. Additionally, increasing the end angle of the arc improves temperature uniformity with minimal effect on output power and pressure drop. Moreover, the TEG system exhibits optimal performance when the linear fin length is 180 mm, the height is 45 mm, the radius of arc fins is 305 mm and the end angle is 8°. At the inlet air temperature of 600 K and the velocity of 40 m/s, the TEG output power, temperature uniformity coefficient and pressure drop for this configuration are 116.59 W, 0.99 and 845 Pa, respectively. This work contributes a theoretical reference for the structural optimization of low-backpressure TEG systems in future automotive exhaust applications.

Ultraviolet-light–dark cycle analysis of degradation in perovskite solar cells

The stability of perovskite solar cells must be evaluated under realistic outdoor conditions, such as light–dark cycles, because their reversible performance changes under such conditions. Therefore, in this study, we performed light–dark cycle analysis of lead halide perovskite solar cells under ultraviolet (UV) light irradiation to evaluate their metastability and UV degradation. The power drop under UV irradiation was recovered after storing the cells in dark because of ion-migration effects. Furthermore, the energy yield during 6 h of UV irradiation reduced slightly during the light–dark cycles, similar to the reduction in energy yield observed under a white-light-light-emitting diode. This change in energy yield indicates that the power drop observed after 6 h of UV irradiation cannot be attributed to UV-induced degradation of the perovskite used in this study. Our findings show that light–dark cycle analyses are effective for distinguishing between metastability and UV-induced material degradation.

EFFICIENT USE OF ELECTRIC ENERGY WHEN OPERATING A BALL MILL WITH A CONSTANT ROTATION SPEED

Link for citation: Zakamaldin A.A., Perevoshchikov F.V., Shilin A.A. Efficient use of electric energy when operating a ball mill with a constant rotation speed. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 9, рр. 115-127. In Rus. The relevance. Ball mills are widely used in industry for grinding bulk materials, as well as in the last stages of ore crushing, where the required optimal particle sizes are achieved for enrichment. Although ball mills have a relatively simple design and cover extensive research, the industry is still struggling with the very low energy efficiency of the grinding process. As the retrofitting heavy equipment is the costliest approach, process optimization through control system is the most suitable for energy consumption reduction. As a rule, the feed rate is the main control variable for a mill with a constant rotation speed. Due to insufficient information content, outdated methods of analysis and control of the internal dynamics of the mill, control systems keep the target value of feed rate at a deliberately low level in order not to overload the mill. This article provides an explanation of how, in such a case, an increase in mill feed rate could affect the energy efficiency of grinding. The main aim: study of energy efficient modes of operation of stations; verification of models and confirmation of experimental data: the relationship between door loading and power consumption indicators; construction of buildings for energy efficient control of ball towers. Objects: the process of grinding in a ball tower with a constant rotation speed. Methods: mathematical description of the behavior of the electromechanical part of a machine that consumes current and works on a load in the form of spherical furniture; simulation modeling of the operation of the door electric drive; statistical analysis of production indicators. Results. The paper demonstrate the tendency to increase electricity consumption with a decrease in feed rate and vice versa, respectively for ball mills with a synchronous drive of 2500 kW based on modeling and experimental data. Increase in feed rate in the range of 10–40 t/h, there is a drop in active power by 0,48–1,57 %. The values of the specific power consumption of ~5–8 kWh/t during the grinding of apatite ore were obtained. An increase in productivity by 5 t/h on average leads to a decrease in the specific power consumption by 0,12 kWh/t. It is necessary to increase productivity in the operation of ball mills only after integrating measuring instruments into the control system of the mill, which allow an accurate assessment of the state of loading of the mill drum.

Numerical study on a coaxial geothermal exchanger equipped with a new inner tube: Entropy generation, thermodynamic irreversibility analysis and exergy efficiency performance evaluation

This paper focuses on the effect of inner tube fitted with CSF of different widths (H = 5–11 mm), thicknesses (W = 1.5–9 mm) and pitches (P = 50–200 mm) on the entropy generation, thermodynamic irreversibility and exergy efficiency performance of CGHE and gives the direction of improvement of CSF geometric parameters. A performance evaluation chart of exergy efficiency was also established to evaluate the exergy efficiency of each working condition. The results show that the assembly of CSF on the inner tube of the CGHE can effectively reduce the heat transfer entropy generation rate S˙gen,h, lowest 67.9% lower than that of the smooth inner tube, but the friction entropy generation rate S˙gen,f is significantly higher, highest being 10.33 times higher than that of the smooth inner tube. Increasing the width H and thickness and decreasing the pitch P both increase the entropy generation rate, but changes in width and thickness have a small effect on entropy, while changes in pitch P have a large effect on entropy, and their W˙loss follow the same pattern of variation as S˙gen. From Be and Ns it is clear that 99% is frictionally irreversible when Re > 30000, and frictional entropy generation is minimized at Re < 15000. When evaluated in terms of heat transfer improvement number NH, the direction of improvement of the CSF geometry parameters should be to increase the width H, thickness W and pitch P. In terms of exergy efficiency, the exergy efficiency for all cases results in greater than smooth inner tube coaxial GHE for the same pumping power and pressure drop conditions, but deterioration occurs for the same mass flow rate.

Optimized fuzzy proportional integral controller for improving output power stability of active hydrogen recovery 10-kW PEM fuel cell system

In conventional PEM fuel cell systems with active hydrogen recovery, a significant drop in the output power occurs during hydrogen purging. In the present study, this problem is addressed through oxygen and hydrogen flow control strategies based on a proportional integral (PI) controller, fuzzy PI controller, and optimized fuzzy PI controller, respectively. When the optimized fuzzy PI controller is applied to the hydrogen supply side, the output power increases to 9112 W, corresponding to an improvement of 16.82%. In addition, when the controller is applied to both the hydrogen supply side and the oxygen supply side, representing an efficiency improvement of 15.62%. Overall, the results show that the proposed fuzzy PI controller improves both the stability and the fuel efficiency of the considered 10-kW PEM fuel cell system.

Enhancing the Performance of Human Motion Energy Harvesting through Optimal Smoothing Capacity in the Rectifier

Energy harvesting offers a promising solution for powering a growing variety of low-power electronics; however, harnessing energy from human motion, with its irregular and low-frequency bursts of power, presents conversion challenges. As rectification is a common part of it, this study investigates the influence of smoothing capacitor values on rectifier output for short, intermittent signals. We propose an analytical model that identifies an optimal smoothing capacity for the full-bridge rectifier, considering harvester internal resistance, frequency, and load resistance and leading to the highest average output voltage after rectification. The model was validated with detailed computer simulations; furthermore, a similar effect was revealed on a voltage multiplier circuit as well. Experimental measurements demonstrate that deviating from the optimal smoothing capacity results in up to 10% decrease in rectified RMS voltage, leading to significant drops in output power in specific energy harvesting systems. A real-world experiment with a human motion energy harvester further confirmed the findings in a naturally varying generation environment.

A TCN-Based Hybrid Forecasting Framework for Hours-Ahead Utility-Scale PV Forecasting

This paper presents a Temporal Convolutional Network (TCN) based hybrid PV forecasting framework for enhancing hours-ahead utility-scale PV forecasting. The hybrid framework consists of two forecasting models: a physics-based trend forecasting (TF) model and a data-driven fluctuation forecasting (FF) model. Three TCNs are integrated in the framework for: i) blending the inputs from different Numerical Weather Prediction sources for the TF model to achieve superior performance on forecasting hourly PV profiles, ii) capturing spatial-temporal correlations between detector sites and the target site in the FF model to achieve more accurate forecast of intrahour PV power drops, and iii) reconciling TF and FF results to obtain coherent hours-ahead PV forecast with both hourly trends and intra-hour fluctuations well preserved. To automatically identify the most contributive neighboring sites for forming a detector network, a scenario-based correlation analysis method is developed, which significantly improves the capability of the FF model on capturing large power fluctuations caused by cloud movements. The framework is developed, tested, and validated using actual PV data collected from 95 PV farms in North Carolina. Simulation results show that the performance of 6 hours ahead PV power forecasting is improved by 20% -30% compared with state-of-the-art methods.

Comparative Study of Thermodynamic Performance and System Characteristics of Solid Oxide Fuel Cell System with Three Different Fuels

The global demand for hydrogen is increasing as the global warming problem emerges. Hydrogen, which does not produce air pollutants, is attracting attention in various fields such as transportation and power generation. However, there are drawbacks in storing and transporting hydrogen in its own form. Hydrogen must be stored in the form of low-temperature and high-pressure liquefied hydrogen, which requires a lot of energy, and transportation costs are also high due to the low mass energy density of hydrogen. Therefore, there is a need to store and transport hydrogen in different forms, and a means to convert and use these different forms of hydrogen is needed.Solid oxide fuel cell (SOFC) is one of the energy conversion devices capable of using various types of hydrogen with high efficiency. Due to the high operating temperature of SOFC, fuel can receive adequate heat for reforming process from high temperature SOFC exhaust gas. Therefore, SOFC can use various types of fuels, such as methane and ammonia.Due to the fuel flexibility of SOFC, many SOFC system study using various fuels have been conducted. However, the SOFC operating conditions and system layout used in each study are all different. Also, most of studies lacked parasitic power consideration due to the pressure drop in system components. These limitations make it difficult to compare each SOFC system and find out effect of fuel on SOFC system.In this study, a quantitative comparison of SOFC using three different fuels, methane, ammonia, and hydrogen, was conducted. Thermodynamic models of a SOFC stack and balance of plant components developed from the previous study are used for the system simulations. Two system layouts, non-recirculation, and anode recirculation were chosen, and thermodynamic feasibility test was conducted based on T-Q diagram analysis at heat exchanger and reformer. With these system layouts, thermodynamic performance of the system and the design characteristics of the system components were compared. Boundary conditions, such as SOFC operating temperature, air and fuel utilization remains the same to compare each system result quantitatively. Also, most of design variables of system components are fixed to find out the effect of fuel on system components.Among three non-recirculation systems, ammonia fed non-recirculation system showed the highest electrical efficiency, while methane fed anode recirculation system showed the highest electrical efficiency among the anode recirculation systems. With the anode recirculation, SOFC power drop occurs due to the lower hydrogen concentration in the SOFC. However, fuel input drop due to anode recirculation is greater than the SOFC power drop, which positively affects system performance. But parasitic power is also increased due to recycle blower and higher mass flow rate of anode recirculation flow. In the case of ammonia fueled system, this increase in parasitic power leads to decrease in electrical efficiency.In this study, there are many constraints in operating conditions and BoPs designs to compare each system with different fuel. Therefore, operating conditions and BoPs designs are not optimized, so each system performance for each fuel may increase with appropriate system design. This optimization will be done in further study. Figure 1

FIM: A fatigued-injured muscle model based on the sliding filament theory

Skeletal muscle modeling has a vital role in movement studies and the development of therapeutic approaches. In the current study, a Huxley-based model for skeletal muscle is proposed, which demonstrates the impact of impairments in muscle characteristics. This model focuses on three identified ions: H+, inorganic phosphate Pi, and Ca2+. Modifications are made to actin-myosin attachment and detachment rates to study the effects of H+ and Pi. Additionally, an activation coefficient is included to represent the role of calcium ions interacting with troponin, highlighting the importance of Ca2+. It is found that maximum isometric muscle force decreases by 9.5% due to a reduction in pH from 7.4 to 6.5 and by 47.5% in case of the combination of a reduction in pH and an increase of Pi concentration up to 30 mM, respectively. Then the force decline caused by a fall in the active calcium ions is studied. When only 15% of the total calcium in the myofibrillar space is able to interact with troponin, up to 80% force drop is anticipated by the model. The proposed fatigued-injured muscle model is useful to study the effect of various shortening velocities and initial muscle-tendon lengths on muscle force; in addition, the benefits of the model go beyond predicting the force in different conditions as it can also predict muscle stiffness and power. The power and stiffness decrease by 40% and 6.5%, respectively, due to the pH reduction, and the simultaneous accumulation of H+ and Pi leads to a 50% and 18% drop in power and stiffness.

Numerical simulation of flow channel geometries optimization for the planar solid oxide electrolysis cell

In a solid oxide electrolysis cell (SOEC), the flow channel design influences the gas distribution, mass transfer, temperature distribution, and electrochemical properties significantly. This study evaluates the overall performance of SOECs with rectangular, triangular, trapezoidal, and semicircular flow channels and examines the effect of the geometry of the flow channel cross-section on the electrolysis process, gas flow, and material distribution. The trapezoidal flow channel shows the best electrochemical performance, but requires a high power and high pressure drop; the triangular flow channel has the most uniform gas velocity and distribution; and the semicircular flow channel shows the maximum gas velocity. The trapezoidal shape is found to be the optimal shape. Sensitivity analysis of the SOEC with the trapezoidal flow channel indicates that increasing the operating temperature improves the electrochemical performance, and reducing the inlet gas's steam volume fraction increases the gas conversion rate and decreases the electrolysis voltage.

Automatic Electrical System Fault Diagnosis Using a Fuzzy Inference System and Wavelet Transform

Electrical systems consist of varied components that are used for power distribution, supply, and transfer. During transmission, component failures occur as a result of signal interruptions and peak utilization. Therefore, fault diagnosis should be performed to prevent fluctuations in the power distribution. This article proposes a fluctuation-reducing fault diagnosis method (FRFDM) for use in power distribution networks. The designed method employs fuzzy linear inferences to identify fluctuations in electrical signals that occur due to peak load demand and signal interruptions. The fuzzy process identifies the fluctuations in electrical signals that occur during distribution intervals. The linear relationship between two peak wavelets throughout the intervals are verified across successive distribution phases. In this paper, non-recurrent validation for these fluctuations is considered based on the limits found between the power drop and failure. This modification is used for preventing surge-based faults due to external signals. The inference process hinders the distribution of new devices and re-assigns them based on availability and the peak load experienced. Therefore, the device from which the inference outputs are taken is non-linear, and the frequently employed wavelet transforms are recommended for replacement or diagnosis. This method improves the fault detection process and ensures minimal distribution failures.

Power losses in PV arrays of field-aged modules

Most of studies are focused mainly on performance degradation analysis of solar cell or categorizing PV failure modes concerning solely climate or cell-technology. However, the impact of degradation modules on output power of PV arrays remains somewhat unclear and has not been reported so far. Therefore, main task of the present work is to get a general view of mismatch effect on PV arrays output for aged panels. Photovoltaic current-voltage characteristics of the 10 individual modules at Research Unit in Renewable Energies in Saharan Medium were measured and recorded. Measurements are based on the analysis of mismatch losses due to series and parallel connection of aged PV modules. Degradation data and the analysis of the I-V characteristics indicate that the tested modules have suffered in the hot desert. Both of visual and electrical degradation data reaffirm the direct relation between observed physical degradation and output power drop. Results and analysis of the I-V characteristics and degradation data indicate that Power losses in crystalline PV modules are also due to mismatch in the I-V characteristics of these modules. The paper provides many findings that can be beneficial in further studies on design of aged PV array and development of a crystalline silicon PV module and can enable the manufacturers to prevent premature failure in desert climates.

Photobiomodulation does not improve anaerobic performance in well-trained cyclists.

To determine if photobiomodulation (PBM) has ergogenic effects on the anaerobic performance of well-trained cyclists. Fifteen healthy male road or mountain bike cyclists participated in this randomized, double-blinded, placebo-controlled, crossover study. Athletes were randomly assigned to receive photobiomodulation (630nm, 4.6J/cm2, 6J per point, 16 points, PBM session) or placebo intervention (PLA session) in the first session. The athletes then performed a 30-s Wingate test to determine mean and peak average power, relative power, mean and peak velocity, mean and peak RPM, fatigue index, total distance, time to peak power, explosive strength, and power drop. After 48h, athletes returned to the laboratory for the crossover intervention. The repeated-measures ANOVA test followed by Bonferroni post hoc test or Friedman test with Dunn's post hoc test (p < 0.05), and Cohen's d statistic were used for comparisons. Performance in the Wingate test was not significantly different (p > 0.05) between PBM and PLA sessions for any variable. Only a small effect size was detected for time to peak power (-0.40; 1.11 to 0.31) and explosive strength (0.38; -0.34 to 1.09). We conclude that irradiation with red light, under a low energy density, does not promote ergogenic effects on the anaerobic performance of cycling athletes.

Associations among anesthesia-induced brain biomarkers during surgery, preoperative exposure to cancer therapeutics, and clinical outcomes.

12095 Background: Cognitive impairment represents a key concern in oncology, as issues with memory and concentration can be a debilitating side effect of cancer and its treatment. Prior work demonstrates that the power of the alpha wave, a pattern of electroencephalographic (EEG) signals in the brain in patients under general anesthesia, correlates with cognitive function. In this study, we sought to investigate the associations among anesthesia-induced alpha power, preoperative exposure to cancer therapeutics, and clinical outcomes in a large cohort of patients undergoing surgery. Methods: We analyzed intra-operative EEG recordings of a retrospective cohort of patients with and without cancer who underwent surgery with general anesthesia at a single institution between 4/2016 - 12/2019. We used multivariable regression models (adjusted for age, sex, history of dementia) to determine associations of cancer-related covariates with patients’ alpha power (measured in decibels [dB]), and to determine associations of alpha power with clinical outcomes, such as hospital length of stay, discharge location, hospital readmission, and survival. Results: Among 1,084 total patients included in this study, 377 (35%) had a preoperative diagnosis of cancer. The most common cancer diagnoses were breast (87, 23% of those with cancer), gastrointestinal (85, 23%), genitourinary (73, 19%), and lung (47, 12%). We found that a cancer diagnosis alone was not associated with alpha power (-0.015 dB, p = 0.95). However, among patients with cancer, receiving chemotherapy within 3 months before surgery was associated with a 1.6dB drop in alpha power (p &lt; 0.001). By comparison, having a preoperative diagnosis of dementia was associated with a drop of 2.86dB (p &lt; 0.001). Decreased alpha power was associated with longer hospital stays (1.03 times longer per dB drop, p &lt; 0.001), higher rates of discharge to a rehab facility (odds ratio [OR] = 1.22 per dB drop, p &lt; 0.001), and higher mortality (hazard ratio = 1.085 per dB drop, p &lt; 0.001). We found no association between alpha power and 30-day readmission (OR = 1.04, p = 0.24). Conclusions: In this large cohort of patients undergoing surgery, we found that alpha power correlated with several important clinical outcomes, and that recent receipt of chemotherapy was associated with a decrease in alpha power. Of note, the observed drop of 1.6 dB among those with recent chemotherapy is roughly equivalent to aging 10-15 years, while a diagnosis of dementia was associated with a nearly 3dB drop in alpha power. As evidence suggests that alpha power corresponds with patients’ cognitive function, our findings highlight the need to prospectively monitor and track longitudinal alpha power in patients receiving cancer treatment to determine if early detection of changes in alpha power may predict for future treatment-related cognitive decline.

Simulation based analysis of the partial shading at different locations on polycrystalline PV array

Photovoltaic (PV) technologies have definite environmental advantages over other power generation techniques. No matter many technologies are used, PV power generation emits no emissions. Solar cells and PV modules are produced using a variety of manufacturing techniques, and as with any energy source or product, there are no dangers to the environment, human health, and safety associated with these processes. Like any other device, even PV cells and modules go under degradation due numerous reasons. Shading is one such mode of degradations which directly impact the output of a PV system. Along with that the output power drastically get impacted. There is a drop in the output power and the electrical characteristics gets distorted. During shading condition the characteristics curves,Power - Voltage and Current-Voltage curve are seen with unusual peaks which is the exact reason for the presence of shading in the module. The paper presents the various impact on the curves which confirm the presence of power loss due to shading.

Effects of Varying Volume Fractions of SiO2 and Al2O3 on the Performance of Concentrated Photovoltaic System

Highly concentrated triple-junction solar cells (HCTJSCs) are cells that have diverse applications for power generation. Their electrical efficiency is almost 45%, which may be increased to 50% by the end of the year 2030. Despite their overwhelming ability to generate power, their efficiency is lower when utilized in a concentrated manner, which introduces a high-temperature surge, leading to a sudden drop in output power. In this study, the efficiency of a 10 mm × 10 mm multijunction solar cell (MJSC) was increased to almost 42% under the climatic conditions in Lahore, Pakistan. Active cooling was selected, where SiO2–water- and Al2O3–water-based nanofluids with varying volume fractions, ranging from 5% to 15% by volume, were used with a 0.001 kg/s mass flow rate. In addition, two- and three-layer microchannel heat sinks (MCHSs) with squared microchannels were designed to perform thermal management. Regarding the concentration ratio, 1500 suns were considered for 15 August at noon, with 805 W/m2 and 110 W/m2 direct and indirect radiation, respectively. A complete model including a triple-junction solar cell and allied assemblies was modeled in Solidworks software, followed by temperature profile generation in steady-state thermal analyses (SSTA). Thereafter, a coupling of SSTA and Ansys Fluent was made, in combination with the thermal management of the entire model, where the temperature of the TJSC was found to be 991 °C without active cooling, resulting in a decrease in electrical output. At 0.001 kg/s, the optimum average surface temperature (44.5 °C), electrical efficiency (41.97%), and temperature uniformity (16.47 °C) were achieved in the of MJSC with SiO2–water nanofluid with three layers of MCHS at a 15% volume fraction. Furthermore, the average outlet temperature of the Al2O3–water nanofluid at all volume fractions was high, between 29.53 °C and 31.83 °C, using the two-layer configuration. For the three-layer arrangement, the input and output temperatures of the working fluid were found to be the same at 25 °C.