Increase In Cell Temperature Research Articles

Performance Analysis of Solar Photovoltaic (PV)-Thermoelectric (TEG) Hybrid Energy System for Electricity Generation

The solar spectrum responsible for PV operation comprises the ultra-violent, visible and invisible radiation. The increase in cell temperature due to the invisible radiation in the solar spectrum reduces the solar PV performance. This research investigated the performance of solar PV-TEG hybrid energy system for energy optimization in comparison with simple solar PV system. The solar PV-TEG hybrid energy system is one on which thermoelectric generators (TEG) were couple with PV module for conversion of the excess heat energy due to rise in cell temperature to electrical energy. The output parameters of both systems such as; short circuit currents open circuit voltages and PV cell temperature were measured with respect to incident solar radiation. The power production and efficiencies for the simple PV and hybrid PV-TEG systems were evaluated and compared, The results revealed that at maximum value of 920 W/m2 average hourly sun radiations, 57.9 W useful PV power input was simultaneously utilized by the simple PV and hybrid PV-TEG systems. The operating temperatures of the simple PV and the hybrid PV-TEG systems varies from 64.5°C to 58.9°C which is 9.94%, reduction. The simple PV and hybrid PV-TEG short circuit currents and open circuit voltages varies with values (17.8 to 20.13 V) and (0.56 to 0.57 A), which have increased by 1.78% and 14.1% respectively. However, with respective values 10.14 W and 11.58 W of power outputs an increase of 14.5 % was realized. These enable enhancing respective 17.5 % and 20 % energy efficiencies. The overall power output and efficiency of the hybrid PV-TEG energy system reported were 11.67 W and 20.2% which showed increased by 15.09 % and 15.43% respectively compared to the simple PV system. Moreover, the statistical analysis conducted reported quality of the measured results and inequality of the respective pairs of output values with P-values of 0.000 in each case. Therefore, integrating PV module with TEG enables reduction .......

Association of Dynamic Trajectories of Time-Series Data and Life-Threatening Mass Effect in Large Middle Cerebral Artery Stroke.

Life-threatening, space-occupying mass effect due to cerebral edema and/or hemorrhagic transformation is an early complication of patients with middle cerebral artery stroke. Little is known about longitudinal trajectories of laboratory and vital signs leading up to radiographic and clinical deterioration related to this mass effect. We curated a retrospective data set of 635 patients with large middle cerebral artery stroke totaling 95,463 data points for 10 longitudinal covariates and 40 time-independent covariates. We assessed trajectories of the 10 longitudinal variables during the 72h preceding three outcomes representative of life-threatening mass effect: midline shift ≥ 5mm, pineal gland shift (PGS) > 4mm, and decompressive hemicraniectomy (DHC). We used a "backward-looking" trajectory approach. Patients were aligned based on outcome occurrence time and the trajectory of each variable was assessed before that outcome by accounting for cases and noncases, adjusting for confounders. We evaluated longitudinal trajectories with Cox proportional time-dependent regression. Of 635 patients, 49.0% were female, and the mean age was 69years. Thirty five percent of patients had midline shift ≥ 5mm, 24.3% of patients had PGS > 4mm, and 10.7% of patients underwent DHC. Backward-looking trajectories showed mild increases in white blood cell count (10-11K/UL within 72h), temperature (up to half a degree within 24h), and sodium levels (1-3mEq/L within 24h) before the three outcomes of interest. We also observed a decrease in heart rate (75-65 beats per minute) 24h before DHC. We found a significant association between increased white blood cell count with PGS > 4mm (hazard ratio 1.05, p value 0.007). Longitudinal profiling adjusted for confounders demonstrated that white blood cell count, temperature, and sodium levels appear to increase before radiographic and clinical indicators of space-occupying mass effect. These findings will inform the development of multivariable dynamic risk models to aid prediction of life-threatening, space-occupying mass effect.

Renewable energy storage using hydrogen produced from seawater membrane-less electrolysis powered by triboelectric nanogenerators

Utilization of widely available seawater for hydrogen generation using robust electrolysis methods can provide sustainable solutions to energy carriers. Sea waves at the same time provide abundant renewable energy that can produce the electricity required for seawater electrolysis. This work presents a novel design for a self-powered hydrogen generation based on membrane-less seawater electrolysis integrated with spring-assisted spherical triboelectric nanogenerators. To streamline fabrication and minimize maintenance expenses, water electrolysis is conducted in a membrane-less electrochemical cell reactor. Employing a mathematical model, the system's performance is analyzed across different catalysts, electrolytes, and operational temperatures. The modeling outcomes indicate that elevating the cell's temperature can lower the necessary potential, enhancing overall electrochemical cell efficiency and decreasing capacitor charging duration. The voltage required for the cell to reach 100 mA cm−2 in the seawater decreases from 2.4 V to 1.9 V as the cell temperature increase from 25 °C to 70 °C. This is due to the decline in the hydrogen and oxygen evolution reaction overpotentials for NPNNS and Ti supported PtPd from 351 mV to 246 mV and 568 mV–394 mV, respectively. Furthermore, increase in the temperature results in an additional 19 % improvement in cell efficiency from 78 % to 97 % and producing hydrogen per cycle during electrolysis of seawater increase from 0.015 μmole to 0.020 μmole.

Performance prediction of a novel solar power tower system based on spectral beam splitting

Photovoltaic technology is currently the most widely used solar generation technology in engineering. The particular spectral response band of PV cells cannot convert all solar radiation into electricity. Meanwhile, some radiation will become heat, leading to an increase in cell temperature and a decrease in the conversion efficiency of photovoltaic cells. Spectral splitting technology is an effective technology to improve electrical generation efficiency and can achieve full spectrum utilization of solar energy. The current work involved (1) proposing a novel solar power tower comprehensive utilization system based on spectral splitting; (2) developing a spectral splitting thin film configuration by using the Needle method whose transmittance is higher than 90% against the band range of 510 nm-1, 020 nm; (3) setting up a spectral splitting PV panel whose cover glass is coated the developed film, and replacing the heliostat of SPT system by using such spectral splitting PV panels; (4) predicting the electrical power generation of the spectral splitting-based tower type concentrating solar power system. The results demonstrate that the power generation efficiency of the proposed system is 5.5% and 3.46% higher than PV power generation and SPT systems respectively.

Distribution of relaxation times used for analyzing the electrochemical impedance spectroscopy of polymer electrolyte membrane fuel cell

In this paper, a 25 cm2 polymer electrolyte membrane single cell is prepared by ultrasonic spraying coating method. The polarization curves and Electrochemical Impedance Spectroscopies (EIS) data of this cell are collected under different conditions, such as cell temperature, humidity, back pressure and pure O2. EIS data are analyzed by Distribution of Relaxation Time (DRT), and some results are concluded: (i) with the increase of current density, the Oxygen Reduction Reaction (ORR) time constant became lower, and the ORR reaction resistance and oxygen diffusion resistance both increases. (ii) With the increase of back pressure, the DRT peak assigned to oxygen diffusion process in cathode moves to low frequencies, the peak area decreases simultaneously. (iii) the proportion of the ORR polarization resistance gradually increases from 77 % to 84 % with the cell temperature increase from 65 °C to 80 °C. (iv) With the increase of humidity, the performance of the cell is decreased. (v) The oxygen diffusion resistance is negligible in pure oxygen working condition analyzed by DRT method.

Simulation and validation of the performance of a polycrystalline photovoltaic module

The performance of a solar module is described by its Current-Voltage (I-V) and Power-Voltage (P-V) curves, it is therefore necessary to generate these curves in order to validate the parameters of the module namely Short Circuit Current, Open Circuit Voltage, Maximum Power, Current and Voltage at Maximum Power Points, Fill Factor, and Efficiency. This study highlights two methods of generating I-V and P-V curves from a 30W sunshine (AP-PM-30) module. The methods include a computer simulation using MATLAB/Simulink software and an experimental procedure at different values of Irradiance and cell temperature. Findings from this study show that an increase in irradiance at constant cell temperature of the solar module results to significant increase in the current produced but slight increase in voltage. Consequently, the power output of the solar module also increases, while increase in cell temperature at constant irradiance decreases the voltage but slightly increases the current produced by the module but power output decreases. Therefore, these explain the influence of irradiance and cell temperature on the performance of a photovoltaic module.

Dynamic insights of carbon management and performance enhancement approaches in biogas-fueled solid oxide fuel cells: A computational exploration

The solid oxide fuel cell (SOFC) is drastically affected by carbon deposition when exposed to hydrocarbon fuels such as biogas. Ensuring sustainable energy production requires long-term operation free from carbon formation. In this study, a transient computational fluid dynamics numerical model was developed to analyze the effects of carbon deposition when utilizing biogas as fuel. In addition to validating the model with experimental results, including polarization and stability curves and gas composition within the cell were also compared for the first time, revealing good agreement. Initially, a comparison was made between biogas and coal gasification fuel gas (CGFG) to study the impact of gas composition. Namely, biogas showed a higher power density than the CGFG but an unstable operation, decreasing the cell voltage by 43% at 750 °C and constant current density of 0.2 A cm−2 over 40 h. Additionally, while the rise in applied current density showed no significant impact on the carbon formation rate, increasing cell temperature and current density amplified the power reduction rate. Moreover, potential approaches for regulating the rate of carbon formation were investigated. Namely, N2 (mole fraction = 50%), CO2 (CO2:CH4 = 2), and steam injection (steam: CH4 = 1) led to a cell voltage decline of 12%, 1%, and 3%, respectively. In addition, an anode thickness growth could improve power generation and enhance the cell operation stability so that cell voltage degradation of 8% resulted in 0.8 mm thickness of the anode.

Numerical study on using multichannel tube and PCM for improving thermal and electrical performance of a photovoltaic module

The electrical efficiency of a crystalline silicon module drops with increasing cell temperature. Phase change material (PCM) was commonly used to perform the thermal management of a PV module, while its poor thermal conductivity may act as a barrier to wide application. In the current study, an innovation design that utilizes excellent heat storage capacity (HSC) of PCM and high thermal conductivity of multichannel tube is introduced into a PV module (MPCM-PV). Computational Fluid Dynamics (CFD) modeling of the MPCM-PV together with experimental validation was conducted. It was determined that the established model can predict the performance of the MPCM-PV at reasonable accuracy. The effect of the structural and physical parameters on the operating performance of the MPCM-PV module was analyzed. The electric energy production was increased by 4.75 % when the number of channels was increased from 1 to 5. Additionally, the rectangular-shape channel rather than triangular shape was more beneficial for the MPCM-PV temperature reduction. Further, it was found that the low melting point and large HSC of PCM lead to the higher electric energy production. The electrical energy increments of 1.71 % and 0.32 % were respectively achieved when the HSC was increased from 240 kJ/kg to 560 kJ/kg and the melting temperature was decreased from 44 °C to 38 °C. The sensitive analysis suggested that the channel shape and the HSC have the most significant impact on electric energy production. These findings provide insight into the design the MPCM-PV system and can guide the development of efficient PV system.

Performance evaluation of a GaSb thermophotovoltaic converter

In recent years, Gallium Antimonide (GaSb), which has smallest bandgap among III-V semiconductors family, became the subject of extensive investigations in the field of thermophotovoltaic (TPV) converters, because of the recent improvements in optoelectronic technology. This paper describes an analytical process used to evaluate the performance of a GaSb TPV converter under different levels of illumination, taking account of the photons with energy below the cells bandgap by considering the cell’s reflectance to this fraction of incident radiation. The results show that a radiator temperature near 2200 K is most advantageous and a reflectance of 0.98 is necessary for below-bandgap irradiations to obtain conversion efficiency greater than 28%, at 300 K cell temperature. This efficiency will decrease as the cell temperature increase. The obtained results are found to be in good agreement with the available data.

Floating Photovoltaic Performance Evaluation Using Novel Cooling System Case Study

Photovoltaic panels nowadays are considered one of the most important methods for generating electricity directly from the sun as a green energy resource. The photovoltaic cells convert about 20% of solar energy to electric power, and the rest is converted to heat that increases the cells temperature. The photovoltaic performance decreases by about 0.4%–0.5% for each 1°C increase in cell temperature. This article studies the effect of using a novel cooling design to cool floating photovoltaic panels with natural cold water from natural sources. ANSYS has been used to conduct a series of simulations under different boundary conditions like solar radiation, ambient temperature, and cooling water temperature at Duhok Dam Reservoir, KRI. The results of the proposed cooling module showed a significant increase in efficiency (1.26%–2.49%) and power performance (17.76–36.81W) and a significant increase in power (6.43%–14.89%) compared to the non-cooled module. Thus, using an active cooling method for floating panels could be a typical option to boost the output of the solar panels. The results of this research have outperformed other research, with a power increase rate of about 14.1%.

COOLING OF CONCENTRATED PHOTOVOLTAICS WITH PHASE CHANGE MATERIAL AND FINS

The increase in cell temperature with increased irradiance is probably the most significant disadvantage of using photovoltaic with reflector modules. In this study, a developed Phase Change Material system was integrated into the rear section of a concentrating Photovoltaic system to limit its temperature rise. The heat transmission of the concentrating photovoltaic with a phase change material system was investigated using an experimental method and a numerical method. The temperature distribution was simulated numerically using ANSYS 2021 three-dimensions model. Three cases were studied: one without wax, one with wax, and one with wax and fins. The results displayed convergence between the experimental results and the numerical results. The effect of using phase change materials on performance and efficiency of concentrated photovoltaic cells, the amount of temperature reduction through the wax melting period for concentration with paraffin wax and concentration photovoltaic with fin and paraffin wax by 2.8 °C and 6 °C, respectively, as well as an enhancement in efficiency of photovoltaic at the noon time of cases by 1.807% and 3.182% related to the reference photovoltaic. The outcomes also demonstrated that using fins aids in the distribution of temperatures, resulting in regular melting of wax in comparison to wax without fins.

Photovoltaic backside cooling using the space inside a conventional frame (IPCOSY)

Inefficiencies present in solar cells result in most of the absorbed energy being converted into heat, causing an increase in cell temperature, which leads to a further reduction in efficiency. Various cooling technologies can be found in the literature; however, these all come with their own challenges. In this research, we have designed a Photovoltaic (PV) panel that incorporates backside water cooling by creating a water chamber in the empty space inside the Aluminium frame. This panel was termed IPCoSy (Innovative Photovoltaic Cooling System). It was tested against a conventional cooling system that allowed water to drain when the cooling is switched off and a non-cooled control panel, and the results show that, even without any flow, a daily energy gain of about 3% is possible. When a controlled flow was introduced, gains of up to 10% were achieved. These gains can be further increased when IPCoSy is installed in ideal scenarios such as reverse osmosis plants, floating PV installations, or areas requiring water heating. Therefore, this research presents a new photovoltaic panel incorporating a water chamber designed for hot climate conditions.

Potential application of electrical performance enhancement methods in PV/T module

Hybrid photovoltaic/thermal (PV/T) modules have been proposed to generate more electricity and heat, which can improve the solar energy conversion efficiency per unit area. However, the photovoltaic (PV) efficiency of PV/T modules decreases as the PV cell temperature increases, which significantly affects the solar energy conversion efficiency of PV/T modules. Here, four temperature profiles (uniform, single-Gaussian, double-Gaussian, multi-Gaussian) are proposed on the PV cell surface by adjusting the heat transfer arrangement for the PV cell cooling duct in the PV/T module. Compared with the uniform temperature profile, the multi-Gaussian temperature profile PV cell efficiency increased by 1.292%; the single-Gaussian temperature profile PV cell efficiency decreased by 4.308%. The results show that for PV cells in the PV/T module, different temperature profiles lead to great differences in electrical performance, and a nonuniform temperature profile can be set to improve their electrical performance.

Experimental study to optimize the thermal performance of Li-ion cell using active and passive cooling techniques

Lithium Ion (Li-ion) batteries have been utilized generally in electrical vehicles and different applications because of their no memory effect, high specific energy, high energy density, and high efficiency. However, these batteries generate a large amount of heat when they are charged and discharged at a higher C-rate which eventually leads them toward thermal runaway. To extend the lifespan, effectiveness, and capacity of Li-ion batteries, a suitable Battery Thermal Management System (BTMS) is necessary. In this research work, the effect of active and passive cooling techniques (i.e., natural convection cooling, forced cooling, and phase change material (PCM) cooling) are studied on the charging and discharging of Li-ion cell at higher C-rate. Lauric acid is used as Organic PCM for cooling of single cell and its thermophysical properties are obtained using differential scanning calorimetry (DSC). In the absence of natural convection cooling, experimental findings demonstrated that the highest cell temperature during discharging at 3C, 2C, and 1C was 69 °C, 60 °C, and 38.7 °C respectively. The maximum increase in cell temperature using natural convection cooling, forced cooling, and PCM cooling is 39.9 °C, 20.1 °C, and 20.8 °C as compared to the absence of natural convection at 3C discharge rate. The PCM cooling has shown a temperature reduction of 7.2 %, 25.3 % and 31 % as compared to lack of natural convection using a discharge rate of 1C, 2C, and 3C. Experimental results proved that PCM cooling was most effective and capable of controlling the cell temperature without any external power and assisting the Li-ion cells to operate within a safe temperature range.

Comparative Experimental Investigation on Front Cooling for Tempered Glass Photovoltaic Thermal System

ABSTRACT Photovoltaic (PV) technology that converts solar energy into electricity is projected to play a significant role in renewable development in Malaysia. However, its electrical efficiency decreases with the increase in cell temperature. Therefore, a photovoltaic thermal (PV/T) system uses water to boost electrical efficiency by cooling PV cells. The PV/T system, on the other hand, is the combination of solar PV and solar thermal collector (STC) to simultaneously produce electricity and heated flowing fluid. This research study fabricated monocrystalline and polycrystalline PV panels with tempered glass and epoxy lamination to compare with front flow cooling PV/T systems using similar panels. The experiment with real-time data recording on power output and surface temperature was performed at Wisma R&D, the University of Malaya, during clear sunny weather in Kuala Lumpur, Malaysia. The highest daily electrical efficiency for Monocrystalline PV/T is 16.05%, while Polycrystalline PV/T produces 15% efficiency at a flow rate of 1.3 LPM. In comparison, monocrystalline and polycrystalline PVs have an average electrical efficiency of 14.54% and 13.80%, respectively. The highest thermal efficiency for Monocrystalline and Polycrystalline PV/T was 41.26% and 47.71% at a flow rate of 0.8 LPM. Monocrystalline PV/T has the best electrical efficiency, whereas Polycrystalline PV/T is the best for thermal efficiency.

Passive Cooling Module to Improve the Solar Photovoltaic (PV) Performance

Solar energy is a renewable clean energy. Photovoltaic (PV) cells or solar panels use the sun light as the main source to produce electricity. However, the operating temperature has a significant impact on the PV conversion process and its performance. PV cell technology performance is sensitive to the operating temperature. Increasing cell temperature causes a significant reduction in the output voltage which in turn leads to reducing electrical efficiency. In other words, when the temperature rises, the output current rises exponentially which leads to output voltage to fall. Therefore, PV efficiency decreases. This paper aims to develop a new PV panel passive cooling system that enhances the efficiency of the panel and improves its performance. The design is based on air channels and air chimneys. Overall, cooled solar panels are efficient and cost-effective as their performance is better and their efficiency is higher than the non-cooled solar panels. Our project is designed to serve UAE’s 2021 vision (increased dependence on clean energy and green development), reduce pollution in the environment, and save energy for the next generations. The goal of this research is to lower the temperature of the PV panel., therefore, enhancing the efficiency as well as improving the performance by cooling the PV panel. So, It has the potential to alleviate the problem of overheating solar panels.

WiSE: When Learning Assists Resolving STT-MRAM Efficiency Challenges

Spin Transfer Torque Magnetic RAM (STT-MRAM) is one of the most promising on-chip technologies, which delivers high density, non-volatility, and near-zero leakage power. However, Spin Transfer Torque Magnetic RAM (STT-MRAM) suffers from three reliability issues, namely, read disturbance, write failure, and retention failure, that present significant challenges to its use as a reliable on-chip memory. All of these three reliability challenges become even more threatening with any increase in STT-MRAM cell temperature. Write operations are regarded as the main source of heat generation and temperature increase in STT-MRAM on-chip memories. This article first presents experiments to show how the heat generated by consecutive writes affects the reliability of an STT-MRAM on-chip cache. Then, it proposes the WiSE framework, an approach to reduce the STT-MRAM-based cache memory temperature and improve its reliability. WiSE utilizes the Reinforcement Learning (Reinforcement Learning (RL)) technique to detect high-density write operation patterns in STT-MRAM cache. To manage the write operations across the STT-MRAM caches, WiSE introduces a new temperature-aware replacement policy. The simulation results show that while WiSE imposes only about 1% performance overhead, it improves retention failure rate, read disturbance rate and write failure rate by 64%, 57%, and 47%, respectively, compared to Least Recently Used (Least Recently Used (LRU)) replacement policy.

Oxidant starvation under various operating conditions on local and transient performance of proton exchange membrane fuel cells

Oxidant starvation in proton exchange membrane fuel cells could cause severe fluctuation on dynamic performance and the significant reduction in durability. In this work, dynamic transfer and distribution characteristics of reactants and water under oxidant starvation are studied by measuring local current densities, temperatures, and the cell voltage in situ. Besides, high frequency resistance and pressure drop along the flow channel at the cathode are obtained to determine the membrane hydration state, and mass transfer and distribution. The effects of cathode humidity, cell temperature and operating modes on the local and overall transient behavior of the cell under oxidant starvation are analyzed. The experimental results show that with the air stoichiometry of 0.8, the current fluctuation distribution is much non-uniform and hydrogen pumping occurs in the downstream. When oxidant starvation occurs under potentiostatic mode, current densities in the upstream gradually increase to the steady-state; while under galvanostatic mode, local current densities in the upstream show overshoots and current variations coefficient along the flow channel are about two times of potentiostatic mode. As cell temperature increases, severe oxygen starvation occurs in the downstream and local temperature differences tend to be larger. When the unhumidified air is supplied into the cell, the combined effect of local membrane hydration state and local oxygen concentration plays a dominant role, leading to greater magnitudes of current fluctuation and higher change rate of current variation coefficient in the downstream.

Experimental study on the power losses of a single photovoltaic cell and two series and parallel connected cells with partial shadows

This study explores the adverse impact on photovoltaic (PV) cells (monocrystalline silicon) caused by obstacles covering different amounts of cell surface area. Experiments for a single cell, as well as modules with two PV cells in series or parallel connections, have been conducted. Under partially shaded conditions, the single cell and parallel modules exhibit a decrease in output current and the decrease ratio is equal to the shading ratio. The series PV module exhibits more deleterious effects including an increase in cell temperature and large decline in output current under different shading conditions. Shading 7.4%, 18.5%, or 29.6% of the area of one of the cells in the series module decreased the current by 15.6%, 37.4%, and 57.6%, respectively, with excess decrease ratios of 8.2%, 18.9%, and 28.0%. This study allows us to conclude that the variations in the reduction of the output of PV cells is highly dependent on the shading conditions of series modules in PV arrays.

Thermal characterization of a photovoltaic panel under controlled conditions

To avoid large variability in environmental factors, the thermal and electrical behavior of a 310 W PV panel exposed to a 6 kW halogen light source was studied in a 48 m3 climatic room. The physical quantities measured were panel temperature (front and back), radiation illuminating the panel, ambient temperature, air speed, panel current and panel voltage. Under these conditions, it was possible to estimate the thermal constant of the panel at 9 minutes. The effect of forced convection on the panel temperature was quantified using a fan. The results obtained confirm that the panel temperature decreases exponentially with air speed. The part of the incident radiation that is converted into electricity and therefore does not contribute to the heating of the panel was quantified. The results show that the front panel temperature decreases by about 3°C and the rear panel temperature by about 3.7°C when the system produces electricity. The Maximum Power Point from I–V and P–V characteristics was studied for different PV temperatures to confirm the linear decay of the electrical efficiency with increasing cell temperature.