Complementary Switching-Based Reconfigurable Strategy for Hotspot Mitigation in PV Modules

We have previously shown that the power output of red muscle from warm-acclimated scup is greatly reduced when the fish swim at low temperatures. This reduction occurs primarily because, despite the slowing of muscle relaxation rate at cold temperatures, warm-acclimated scup swim with the same tail-beat frequency and the same stimulation durations, thereby not affording the slower-relaxing muscle any extra time to relax. We hypothesize that power output during swimming could be increased if the stimulus duration were reduced or if the relaxation rate of the red muscle were increased during cold acclimation. Scup were acclimated to 10 degrees C (cold-acclimated) and 20 degrees C (warm-acclimated) for at least 6 weeks. Cold acclimation dramatically increased the ability of scup red muscle to produce power at 10 degrees C. Power output measured from cold-acclimated muscle bundles driven through in vivo conditions measured from cold-acclimated scup swimming at 10 degrees C (i.e. work loops) was generally much greater than that from warm-acclimated muscle driven through its respective in vivo conditions at 10 degrees C. The magnitude of the increase depended both on the anatomical location of the muscle and on swimming speed. Integrated over the length of the fish, the red musculature from cold-acclimated fish generated 2.7, 8.9 and 5.8 times more power than the red musculature from warm-acclimated fish while swimming at 30 cm s(-)(1), 40 cm s(-)(1) and 50 cm s(-)(1), respectively. Our analysis suggests that the cold-acclimated fish should be able to swim in excess of 40 cm s(-)(1) with just their red muscle whereas the warm-acclimated fish must recruit their pink muscle well below this speed. Because the red muscle is more aerobic than the pink muscle, cold acclimation may increase the sustained swimming speed at which scup perform their long seasonal migrations at cool temperatures. We then explored the underlying mechanisms for the increase in muscle power output in cold-acclimated fish. Contrary to our expectations, cold-acclimated muscle did not have a faster relaxation rate; instead, it had an approximately 50 % faster activation rate. Our work-loop studies showed that this faster activation rate, alone, can increase the mechanical power production during cyclical contractions to a surprising extent. By driving cold-acclimated muscle through warm- and cold-acclimated in vivo conditions, we were able to partition the improvement in power production associated with increased activation rate and the approximately 20 % reduction in the duration of electromyographic activity found in the accompanying study. Depending on the position and swimming speed, approximately 60 % of the increase in power output was due to the change in the red muscle's contractile properties (i.e. faster activation); the remainder was due to the shorter stimulus duty cycle of cold-acclimated scup. Thus, by both shortening the in vivo stimulation duration and speeding up the rate of muscle activation as part of cold-acclimation, scup achieve a very large increase in the power output of their red muscle during swimming at low temperature. This increase in power output probably results in an increase in muscle efficiency and, hence, a reduction in the energetic cost of swimming. This increase in power output also reduces reliance on the less aerobic and less fatigue-resistant pink muscle. Both these abilities may increase the swimming speed at which prolonged aerobic muscle activity can occur and thus reduce the travel time for the long seasonal migrations in which scup engage.

This study investigates the impact of shading on the performance of photovoltaic (PV) systems, a critical consideration for optimizing solar energy generation. Shading can occur due to various environmental factors, including nearby structures, vegetation, and atmospheric conditions, leading to significant reductions in energy output and overall system efficiency. Through a combination of experimental measurements and simulation modeling, we assessed how different shading scenarios affect the electrical performance of PV arrays. The findings reveal that even partial shading can cause substantial decreases in power generation, with shaded cells experiencing reverse biasing and increased thermal stress, resulting in potential hot spot formation. The analysis also highlights the importance of PV module configuration and orientation in mitigating shading effects. Additionally, the study highlights the functionality of bypass diodes in PV systems. By allowing current to bypass shaded or malfunctioning cells, these diodes help maintain optimal performance levels even when some cells are compromised. The analysis includes comparative assessments of PV systems with and without bypass diodes under identical shading conditions. Results demonstrate that systems equipped with bypass diodes exhibit significantly improved performance, including higher voltage and current outputs, thereby enhancing overall energy yield. This research underscores the necessity for site-specific evaluations during the design phase of PV installations to ensure maximum efficiency. The insights gained from this study contribute to a deeper understanding of shading dynamics in PV systems and provide practical recommendations for improving solar energy utilization. Ultimately, addressing shading challenges is essential for advancing the reliability and effectiveness of solar power as a sustainable energy solution. The findings deduce the importance of integrating bypass diodes in PV systems to mitigate the detrimental effects of shading, ultimately contributing to more effective utilization of solar energy resources.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Abdul Hadi Mohaimin, Kenneth Siok Kiam Yeo, Rafidah Petra; Thermoelectric cooling for solar PV. AIP Conference Proceedings 10 January 2023; 2643 (1): 040005. https://doi.org/10.1063/5.0111297 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Effects of changing partial cell shading on the electrical and thermal characteristics of crystalline silicon photovoltaic module

A novel electrical approach to protect PV modules under various partial shading situations

Objective: To investigate the effect of ultrasonic parameter settings on maximum temperatures in the drilling site and penetration time and determine the most suitable parameters for efficient and safe robot-based ultrasonic bone drilling in spinal surgery. Methods: Five adult bovine thoracic and lumbar vertebrae specimens (T10-L6) were cut into 10 mm thick slices. A total of 50 slices were obtained. Among them, 30 and 20 slices were used for cancellous bone experiments and cortical bone experiments, respectively. In the cancellous bone experiment, the slices were randomly divided into three groups, corresponding to different feed rates of 0.8 mm/s, 1.6 mm/s, and 2.4 mm/s, respectively, with 10 slices in each group. The cancellous part of each slice was drilled 9 times with different output powers from 20% (48 W) to 100% (120 W). In the cortical bone experiment, the slices were randomly assigned into two groups, corresponding to a different feed rate (0.8 mm/s and 1.6 mm/s). Drilling was performed on the cortical part of each slice 4 times with different output power, which increased from 70% (84W) to 100% (120 W). All experiments were conducted at room temperature of 25 ℃. Maximum temperature and penetration time were recorded. The maximum grinding temperature and penetration time of cancellous bone and cortical bone under different output power and feed rate were compared. Results: At the same feed rate, the maximum temperature of the cancellous bone decreased as output power increased. There were statistically significant differences in the maximum temperature between the output powers of 120 W and 24 W under different feed rates(61.2 ℃±9.4 ℃ vs 70.9 ℃±5.7 ℃, 59.2 ℃±7.1 ℃ vs 69.5 ℃±10.7 ℃, 55.5 ℃±5.5 ℃ vs 69.2 ℃±9.3 ℃, all P<0.05). At the premise of the same output power, there was no significant difference in the maximum temperature among different feed rates (all P>0.05). At the feed rate of 0.8 mm/s, the maximum temperature of cortical bone decreased as the output power increased. The maximum temperature at the output power of 120 W was significantly lower than that of 84 W (P=0.048). However, at the feed rate of 1.6 mm/s, the maximum temperature could not be significantly lowered by the increase in output power (P>0.05). Under the same output power, the maximum temperature at the feed rate of 1.6 mm/s were all significantly lower than those of 0.8 mm/s (all P<0.05). The penetration time of cancellous bone did not decrease significantly with the increase in the output power (all P>0.05) while it decreased significantly as the feed rate increased (all P<0.05). Regarding cortical bone at the feed rate of 0.8 mm/s, the increase in output power could not shorten the penetration time (P>0.05); at the feed rate of 1.6 mm/s, the penetration time at the output power of 120 W was significantly shorter than that of 96 W (P=0.008). With the same output power, the penetration time at the feed rate of 1.6 mm/s were significantly shorter than those at 0.8 mm/s (all P<0.05). There was no statistical difference in the penetration failure rate among different feed rates with the same output power (all P>0.05). The penetration failure rate was 0 when the output power of cancellous bone was 48 W and above and the output power of cortical bone were 108 W and 120 W. Conclusions: The maximum temperature of vertebral cancellous bone and the cortical bone is primarily influenced by the output power and the feed rate, respectively; the penetration time of cancellous bone and the cortical bone is affected by the feed rate and both of feed rate and output power, respectively. The most suitable parameters are output power of 120 W and feed rate of 2.4 mm/s for cancellous bone and output power of 120 W and feed rate of 1.6 mm/s for cortical bone.

Partial shading across solar cells can cause large reverse voltages and reduce the maximum generated output power. The effects of shading can be mitigated via the use of bypass diodes across the shaded cells. The impact of using bypass diodes on the solar cell performance under shading has been studied at a module level using MATLAB. Algorithms have been designed to study the effects of non-overlapping bypass diode configuration in a randomly shaded solar module and results have been compared with modules devoid of bypass diodes. I-V and P-V curves have been plotted and maximum peak power is tracked for severe to intermediate levels of shading patterns.

Partial shading among the photovoltaic modules is the most commonly observed scenario that can permanently damage the modules by creating mismatch among cells, hotspot, and unexpected losses in the system. Basically, modules are provided with bypass diodes for prevention from destructive effect of the hotspot. Bypass diodes configuration plays a crucial role in the operation and performance of the modules during shading. In this paper, the sensitivity of PV modules with no bypass diode, grouped bypass diodes, overlapped bypass diodes, and single bypass diodes during partial shading is investigated. The investigation is carried out in the MATLAB/Simulink environment for a module under various cell-level shadings. The comparison is done using power generation, losses, efficiency, and number of peaks analysis. It is found that the performance and characteristics of the modules are highly susceptible to the bypass diodes configurations and nature of shading.KeywordsPhotovoltaic (PV)Bypass diodesHotspotMismatch lossPartial shadingPower generation

Increasing the data transfer rate leads to the use of spectrally efficient types of amplitude-phase modulation, characterized by high values of the peak factor. For energy-efficient amplification of such signals, it is promising to use transmitters built using the Envelope Elimination and Restoration (EER) method. Purpose: further development of methods for using switching operating modes of active elements, taking into account the current state of the element base, increased capabilities of digital signal processing and computer modeling of various transmitter units operation. Development of requirements for the characteristics of EER transmitter units, based on a given level of intermodulation distortions and out-of-band oscillations and development of EER transmitter structural diagram with the possibility of subsequent increase in output power. Methods: an analysis of the requirements for individual units is carried out, taking into account the possibility of their combined influence. Results: a structural diagram of 250 ... 300 W HF range EER transmitter has been developed with the possibility of subsequent increase in the transmitter output power. Variants of implementing output power adjustments have been proposed and requirements for the transmitter exciter characteristics have been developed. Practical relevance: the implementation of the developed recommendations will ensure the fulfillment of requirements for permissible intermodulation distortions of the amplified signal and the permissible level of out-of-band oscillations.

Design and optimization of the radial inflow turbogenerator for organic Rankine cycle system based on the Genetic Algorithm

In order to understand how partial shading at the cell level affects modules normal operation, a standard monocrystalline silicon PV module, divided in three equivalent cell strings by bypass diodes, was submitted to several shading fractions ranging between 10% and 100% of a solar cell area. The modules were characterized by thermal imaging using a thermal camera and I-V curves were also obtained. A loss in the current produced in the string containing the shaded cell was verified. Such current loss increases with the shaded area, plummeting the electrical power produced by the module by one third for larger shading fractions. For all the shadings tested, a significant and non-uniform increase of temperature of the shaded cell was detected. For shaded fractions of 50% and 70%, the temperature differences between the shaded cell and the rest of the module were as high as 36.6 °C and 56.9 °C respectively.

The main converter of mechanical wind energy into electricity in wind turbines is an electric generator. Typically, such systems use synchronous generators with permanent magnets on the rotor. The main disadvantage of this design is the complexity or the impossibility of adjusting the output parameters of the generator: voltage, power, etc. Known methods and tools aimed at solving this problem relate to cases where the wind speed is constant, ie constant. In real conditions, the nature of the wind is changeable. The average annual wind speed for Ukraine varies between ≈ 5-6 m / s. The current value of wind speed depends on weather conditions, time of day and season. Accordingly, the nature of the output power of the generator will be variable. In this paper, the authors evaluate the effectiveness of the correction of the output power of the generator of the multiplier wind turbine at discrete and random values of wind speed. The main power unit of this study is a magnetoelectric synchronous generator with two-sided arrangement of magnets on the rotor and with axial magnetic flux. To solve this goal, a numerical simulation mathematical model of the system was developed, consisting of a multiplier-free wind turbine and a magnetoelectric synchronous generator with two-way arrangement of magnets on the rotor and with axial magnetic flux in the MATLAB-Simulink software package. The developed simulation model takes into account the change of the output parameters of the generator when the wind speed changes and vice versa, the system in which the change of the initial state of the generator leads to a change in the parameters of the rotor of the wind turbine. The variability and discreteness of wind speed is realized in the MATLAB-Simulink system by generating signals, the values of which at certain points in time are a random variable distributed according to the normal (Gaussian) law with predetermined parameters. Using the developed mathematical model, numerous simulation experiments were performed, which investigated the efficiency of correction of the output power of the studied system when connecting static capacitors to the armature winding of the generator and when applying current to the additional winding of the magnetoelectric generator. When connecting an additional magnetizing capacitance ≈30 μF to the generator terminals, there is an increase in output power by ≈5-10%. When the voltage is applied to the excitation winding Uf = 8 V, there is an increase in the output power of the generator ≈30-40% than without regulation. Therefore, it is a more efficient way to correct the output power of the magnetoelectric generator. The developed mathematical model can be used in further research to synthesize the control law of the additional winding of the magnetoelectric generator for the most efficient conversion of mechanical wind energy into electrical energy.

Increase in operating temperature of photovoltaic (PV) cells decreases its conversion efficiency and power output. In the present study, numerical simulations were carried out to find the proper design of diffuser so as to get uniform distribution of air along with the PV panel. Uniform distribution of air plays a vital role in decreasing thermal stresses which reduces the formation of hot spots, and ultimately it increases the life of the PV panel. The CFD results show that the new design of diffuser with three inner deflector plates and curved side walls maintain uniformity of air at inlet of PV panel. The experimental study with new diffuser indicates a significant reduction in the surface temperature of PV panel which results in increase in power output and efficiency.

Output performance analysis and power optimization of different configurations half-cell modules under partial shading

The ouput power of solar panel that decreased due to shading has been improved using bypass diode method. The placement of bypass diodes increased the output current and power. New peaks and maximum powerpoints on the current-svoltage characteristics and power-voltage characteristics were observed. Without bypass diodes, the maximum output power was only around 50 W. After placing bypass diodes, the first peak around 115 W and second peak around 150 W appeared at voltage of around 31 V and 40 V, respectively.