Increase In Cell Temperature Research Articles

Analysis of thermal response and electrical characterisation of triple-junction solar cells based on variable solar spectral irradiance and air mass

This paper presents the effects of Air Mass (AM) on solar cell performance. This atmospheric parameter has a strong influence on the behaviour of high concentrating photovoltaic solar cells. As air mass increases, the Direct Normal Irradiance (DNI) decreases and resulting cell temperature (Tc) decrease. The objective of this work is to assess the effects of air mass (AM = 1–10D) on triple-Junction solar cells. A thermal model using a convergent iterative technique has been developed; the predicted convergent cell temperature is ≤80 °C for the range of parameters tested. The rate of heat loss by convective heat transfer from the cell is also considered for air mass values AM = 1.5, 4 and 8D. A Finite Element Method (FEM) model is developed in COMSOL Multiphysics in order to predict the temperature distribution on PV cells and the thermal behaviour of the receiver assembly. The proportion of the absorbed radiation not converted to electricity is converted to heat; also, heat from potential current mismatch resulting in an increase in cell temperature is taken into account. As the air mass increases, results show that the spectral attenuation has a significant effect on the thermal and electrical conversion efficiency of triple-junction solar cells. In addition, spectral change is one of the causes of the current mismatch in triple-junction cells. Thus, cell parameters such as short current density (Jsc), efficiency and output power are affected.

Towards improving the performance of solar photovoltaic energy system: A review

Performance of solar PV energy system is affected by many factors like solar radiation intensity, solar radiation geometry, temperature, wind speed and direction, relative humidity, dust, etc. Many researchers have been working on the effect of temperature on solar PV cell efficiency and have reported that increased cell temperature tends to reduce the efficiency of solar PV cell. Solar PV cell temperature also considerably deteriorates the mechanical properties of backsheet of solar PV panel. This paper reviews the various attempts to improve the performance of crystalline silicon solar photovoltaic (PV) system. Performance of a solar PV panel when exposed to hot and dry climate is different from performance of similar solar PV panel in cold climate. From solar beam radiation, light is a desired component whereas heat is not. Therefore many researchers have reported cooling techniques for Solar PV system. However, backsheet material of solar PV panel is one of the factors affecting the solar PV panel efficiency which is pulling the attention of many researchers for performance enhancement of Solar PV system. Solar PV cells using Perovskite material have emerged as one of next generation of photovoltaic technologies having capability of significant enhancement in solar cell efficiency.

Design and Development of 21700 Type Cells for Electric Vehicle Applications

The world’s transition to sustainable energy has been largely accelerated from the transportation field. Thanks to the increasingly wide deployment of charging station and government incentives, electric vehicles are seeing a fast growth in sales over years. Most of them are completely or partially powered by Li-ion batteries, which store and distribute the energy whenever is the needed for the operation of the vehicle. The battery pack consists of tens, hundreds, or thousands of individual cells, depending on the size (kWh) of the pack and cell as well as the form factor of the cell. As an EV start up, SF Motors is trying to produce the intelligent EV for everyone. One prominent feature of EV is their fast acceleration. A high power is delivered during fast acceleration, which requires the cell to be discharged at extreme high rates. Simultaneously, extensive heat is generated during fast acceleration, causing cell temperature increase and stimulating safety concerns. Here, we’re developing 21700-type cylindrical cells which can deliver extreme high power safely in a short time without compromising its high energy density. Each factor affecting cell rate capabilities like electrode materials, areal loadings, electrode architecture and electrolytes are individually investigated by various electrochemical techniques such as symmetric cells and three-electrode cells. By integrating state-of-art electrode materials, advanced cell design and processing, we’re able to build cells with high energy density, high power, and long cycling life while keeping a high standard for safety. The successful implementation of this extreme high power cell will enable advanced electric vehicles with long drive range (> 300 miles) and top performance driving experiences.

A novel heat exchanger design procedure for photovoltaic panel cooling application: An analytical and experimental evaluation

The performance of photovoltaic modules is adversely affected by an increase in photovoltaic cell temperature. Cooling of panels may lead to temperature non-uniformity in the photovoltaic panel, thus limiting the maximum efficiency of the cooled photovoltaic panel. In the current work, the design of a novel heat exchanger that can be used for uniform cooling of photovoltaic modules is presented. For this purpose, a computational fluid dynamics model has been set up. Using the model, the effects of various heat exchanger design parameters (like channel numbers, manifold width, the location of inlet/exit ports, and tapered channels) on its performance are sequentially analyzed resulting in fourteen designs. The performance is quantified by three parameters: top surface average temperature, temperature non-uniformity for photovoltaic module cooling quality, and the heat transfer per unit pumping power. The resulting optimized design is found to be a novel V-shaped heat exchanger design for the photovoltaic module cooling. It has a lower average temperature and temperature non-uniformity, smaller hotspots, and lower pumping power. The optimal design is further examined using experimental particle image velocimetry measurements.

Effects of Direct Window Film Installation on Photovoltaic Solar Panel

Indonesia is very suitable country to use solar energy because Indonesia has a tropical climate and produces daily average energy radiation per unit area and time equivalent to about 4.8 kilo watt/m2, however there are several factors that influence the performance of solar energy, namely PV panel temperature and shadow. Both of these factors are parameters with big influences on PV system behavior due to it greatly affects the system efficiency and output energy. The main effect of increased cell temperature is that on open circuit voltage decreases linearly while cell temperature is increasing. Cell voltage decreases about 2.2 mV per 1°C increase in operating temperature and thus efficiency decreases by about 0.5% for crystalline PV cells. One of the solutions to reduce the effects of excessive heat which results in high temperature in solar PV panels is by installing window film with a distance of 2.5 cm which can produce solar panel output power product with the increase of 23.53% to 24.39% compared to output power product without coating. From the results above, researcher tried to install the window film directly onto the PV solar panel with observation and research methods as well as to analyze the results of the study. The outcome of the study was the temperature was stable at the same conditions while the energy produced was reduced due to direct installation of window film making it as a shadow for PV solar panel

Numerical and outdoor real time experimental investigation of performance of PCM based PVT system

Photovoltaic power generation is a suitable option to counter depleting and environmentally hazardous fossil fuels. However, increased cell temperature of the photovoltaic module reduces the electrical performance. Therefore, for enhancing the electrical performance as well as to obtain the useful thermal, a combined photovoltaic thermal system is suitable technology. Furthermore, the addition of phase change materials into photovoltaic thermal systems adds more dual benefits in terms of cooling of PV cell as well as heat storage. Hence, there are still issues to transfer heat from the system efficiently, which cause lower performance of PVT and PVT-PCM systems. In this paper, the aluminium material of thermal collector is used by introducing a novel design to enhance heat transfer performance, which is assembled in PVT and PVT-PCM systems. Experimental validation is carried out for the 3D FEM-based numerical analysis with COMSOL Multiphysics® at 200 W/m2 to 1000 W/m2 varying irradiation levels while keeping mass flow rate fixed at 0.5LPM and inlet water temperature at 32 °C. The experiment is carried out at outdoor free weather conditions with passive cooling of the module by an overhead water tank scheme. A good agreement in numerical and experimental results is achieved through experimental validation. Cell temperature reduction of 12.6 °C and 10.3 °C is achieved from the PV module in case of the PVT-PCM system. The highest value of the electrical efficiency achieved is 13.72 13.56% for PV and 13.85 and 13.74% for PVT numerically and experimentally respectively. Similarly, for PVT-PCM, electrical efficiency is achieved as 13.98 and 13.87% numerically and experimentally respectively. In the case of the PVT system, electrical performance is improved as 6.2 and 4.8% and for PVT-PCM, it is improved as 7.2 and 7.6% for numerically and experimentally respectively.

NUMERICAL INVESTIGATION OF EFFECTS OF WORKING CONDITIONS ON PERFORMANCE OF PEM FUEL CELL

In this study, the effects of the working pressure and temperature on the performance of the PEM fuel cell were investigated numerically. Non-isothermal, steady - state and single-phase model was used to examine the behaviour of the proton exchange membrane (PEM) fuel cells in the three-dimensional condition. The three-dimensional single-cell model has been developed within FLUENT 6.3 software by utilizing the PEMFC module. The results of polarization (voltage) variation curves and current density distribution were given and compared with each other. According to the results obtained, by keeping humidification and cell temperatures in equilibrium, the performance of the cell improves with the increasing cell temperature. In addition, the current density of the cell increases with the increasing operating pressure.

Design and analysis of a multigeneration system with concentrating photovoltaic thermal (CPV/T) and hydrogen storage

Concentrated photovoltaics (CPV) is an auspicious technology to overcome the high cost problem of highly efficient multi-junction solar cells. However, due to huge concentration of light energy, high heat flux dissipation from a confined space is a challenge. The proposed system here is first of its type to apply and thermodynamically analyze the Nucleate Pool Boiling Heat Transfer (NBHT) for thermal management of CPV. In order to increase overall efficiency of CPV system, a multigeneration system using concentrated photovoltaic thermal (CPV/T) and hydrogen storage is designed and thermodynamically analyzed to fulfill electricity, hot and cold water, heating ventilation and cooling (HVAC) requirement of a residential community with continuous operation. A part of the generated electricity from CPV is used to power the electrolyzer to produce hydrogen and oxygen. The produced gases are stored, and reused by proton exchange membrane fuel cell (PEMFC) to fulfill the system's electrical energy requirement during night time and unfavourable energy conditions in day time. The resultant thermal energy from CPV/T is used for the heating, hot water and cooling requirement of the buildings by employing lithium bromide absorption chiller (AbC). A humidity harvesting system is connected, at the outlet of the absorption chiller, to convert humid air into water and ventilation air requirement of the building. The designed system performs at 67.52% overall energy efficiency, 34.89% of overall exergy efficiency and up to 1862 times concentration ratio at designed steady-state conditions. The results show that with an increase in boiling temperature of NBHT from 353 K to 373 K, the maximum concentration ratio ability increases significantly from 1392 to 2400 times due to increase in critical heat flux, while the electrical efficiency of the CPV system decreases from 28.65% to 27.09% because of increase in cell temperature. To verify the performance of the designed system for different locations, operating conditions and capacities, the effects of Direct Normal Irradiance (IDNI), ambient temperature, relative humidity ratio and the installed capacity are also analyzed by the parametric studies.

Modelling of the thermal behaviour of solar high concentrating photovoltaic receiver

The effect of the cell temperature increase associated with the optic concentration is a matter requiring consideration. A monolithic cascade stack of three layers consisting of GaInP/GaInAs/Ge results in high conversion efficiency. This research presents a performance analysis of a triple-junction solar cell based on modelling, in order to describe and understand its operating behaviour. A numerical model was created to predict the performance characteristic of the solar cell at CR = 1000x, which can then be used to optimise and enhance the cell design. The cell temperature was predicted by the iteration technique, and the convergent occurs at steady state. The initial cell temperature was set at 25 °C, and the new modified cell temperature Tc2 convergence after iteration at convection heat transfer coefficient >2 kW/m2K to keep the cell temperature below 100 °C. However, in order to maintain cell integrity, it is necessary to design the operating cell temperature below 80 °C. The Tc2 convergence after iterations at convection heat transfer coefficient >2.4 kW/m2K.

Morphology control of hybrid Cu–Cu2O nanostructures fabricated by electrochemical migration

The morphological control of hybrid Cu–Cu2O nanostructures during electrochemical migration (ECM) fabrication was systematically investigated by performing a series of current-stressing experiments. Here, in order to induce ECM, a direct voltage was applied to two separated Cu electrodes at a fixed distance, which were set in an acrylic cell filled with deionized water. By changing the cell temperature and voltage, porous spongy and bamboo-leaf-like hybrid Cu–Cu2O nanostructures were obtained. The branch diameter and length increased with an increase in cell temperature, while the increase in applied voltage resulted in fine nanostructures. These results indicate that the morphology of hybrid Cu–Cu2O nanostructures can be easily controlled by changing experimental parameters, which is advantageous over conventional fabrication methods in which special chemical agents are usually necessary.

NUMERICAL INVESTIGATION OF EFFECTS OF WORKING CONDITIONS ON PERFORMANCE OF PEM FUEL CELL

In this study, the effects of the working pressure and temperature on the performance of the PEM fuel cell were investigated numerically. Non-isothermal, steady-state and single-phase model was used to examine the behaviour of the proton exchange membrane (PEM) fuel cells in the three-dimensional condition. The three-dimensional single-cell model has been developed within FLUENT 6.3 software by utilizing the PEMFC module. The results of polarization (voltage) variation curves and current density distribution were given and compared with each other. According to the results obtained, by keeping humidification and cell temperatures in equilibrium, the performance of the cell improves with the increasing cell temperature. In addition, the current density of the cell increases with the increasing operating pressure.

Thermal performance of a novel confined flow Li-ion battery module

Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) are clean energy vehicles in comparison with a traditional internal combustion engine. Li-ion batteries are a viable option for EVs and HEVs due to their advantages of high specific energy and energy density. At high discharge rate, there is a significant increase in battery temperature and non-uniform cell temperature. This work presents a numerical study of the transient behavior of a novel confined flow battery module dissipating the heat at very high discharge rate around 6.94 C and 11.11 C. The conventional open flow battery modules are modified considering the controlled/ guided flow stream around the cell for reducing the local heat spots and unevenness in the cell temperatures. The results provide insights and comparisons into a cell-to-cell heat interaction based on three-dimensional transient thermal response and thermal regimes developed in a conventional open flow module and confined flow module. During battery discharging condition, the proposed battery module exhibit lower surface temperature as well as near uniform cell temperature as compared to open flow module.

Recent developments in photovoltaic-thermoelectric combined system

The photovoltaic system converts solar radiation into electricity. The output of the solar photovoltaic systems is strongly depending on the operating cell temperature. The power output of photovoltaic system reduces as the operating cell temperature increases. Several techniques have been reported in the literature to maintain the low operating temperature of the solar cell by utilizing module heat for separate thermal application. Integration of photovoltaic thermoelectric (PV-TE) system is one of these techniques. In these PV-TE systems, the hot junctions of thermoelectric modules are coupled with the photovoltaic. The thermoelectric module uses heat from PV system and generates additional power. This PV-TE system not only generates more power but also improves the PV efficiency. The present article reports a comprehensive review of latest developments in the PV-TE systems. A detailed classification, key outcomes of published research and the future research scope are discussed in this article.

Numerical investigation on cooling performance of Li-ion battery thermal management system at high galvanostatic discharge

Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) are clean energy transportation options emerged over traditional internal combustion engine. Li-ion batteries are a viable option for EVs and HEVs due to their advantages of high energy density. At high battery discharging condition, there is a significant increase in battery temperature and non-uniform cell temperature. The cooling performance of battery module at constant current discharge rate about 6.94 C (25 A) have presented. The two side wall of the battery module kept fully open for inflow and outflow of cooling media and better heat dissipation. Larger inter-cell spacing was considered to provide sufficient circulation of cooling air and removal of gases generated by the batteries. The heat generation in the battery cell during discharge process has simulated with the help of user-defined function (UDF). The paper gives insight into a three-dimensional transient thermal response, flow field and thermal regimes developed in the battery module. Different air temperature profiles are confirmed in the flow direction and across the width and depth of the battery pack. At specific zones, the air temperature rises to 7 °C thus indicating the localized heat spots. In the considered BTMS, maximum cell-to-cell temperature non-uniformity is restricted to 0.11 °C and battery temperature is lesser than 28 °C despite the high discharge rate and lower cooling air flow condition.

Experimental investigation and thermal modelling of a series connected LiFePO4 battery pack

The present paper reports the results from modelling and experimentation with a lithium-ion battery pack operating at room temperature and under varying discharge rates. The variation in the internal resistance of the cell with change in the temperature is investigated experimentally. The prismatic Li-ion battery pack is discharged at 1C, 2C, 3C and 4C and significant parameters, such as pack voltage, temperature, and state of charge, are obtained. This is accomplished by connecting three LiFePO4 20 A h capacity prismatic batteries in series and applying 18 thermocouples at various locations on the surface of all three cells. The results show that there is a significant increase in battery surface temperature with an increase in discharge rate. The highest average surface temperature of the battery pack (56.5 °C) is observed experimentally at a 4C discharge rate, and the lowest (30.7 °C) at 1C based on modelling. Similarly, the maximum total heat generation (59.2 kJ) is observed at 4C experimentally and the minimum (37.5 °C) at 1C from modelling. A comparison of the modelling results with the experimentally determined temperature, voltage and heat generation shows good agreement. Also, the internal resistance of the cell is observed to increase as the state of charge decreases, and to decrease with increasing cell temperature.

Experimental Investigation of Enhancing the Energy Conversion Efficiency of Solar PV Cell by Water Cooling Mechanism

Solar photovoltaic cells produce electricity by receiving solar radiation. The output power of photovoltaic cells (PV) is mainly influenced by the significant increase in cell temperature during the absorption of radiation. The solar cooling system has been considered and investigated experimentally in this research paper. A passive cooling system was designed and fabricated for efficiently cool the PV module, with inlet/outlet manifold considered for uniform flow of water at the rear side of the PV module. The experimentation was performed with and without the cooling system. In this paper, a linear trend has been established between the electrical efficiency and the temperature of the photovoltaic cells. Without a cooling system, the average cell temperature reaches to 600C, and the solar panel efficiency reduced to 8 to 16%. However, when the panel was operated under the passive water system, the temperature of the PV cell was reduced to 47°C, resulting in a 10% -21% improve in the solar PV cell efficiency. Both systems, without cooling and with cooling systems are validated experimentally.

Separating the Heat from the Gap

Increasing the conversion efficiency of incident solar energy to electricity is a key goal in the solar R&D community. In this issue of Joule , a conceptual hybrid photovoltaic/thermal (PV/T) receiver design is reported by the research groups of Evelyn Wang and Gang Chen. High exergetic efficiency is achieved by absorbing below-bandgap and excessively high-energy photons as thermal energy, while allowing photons at the PV's bandgap to pass through to the underlying cell.

Dynamic bacterial community changes in the autothermal thermophilic aerobic digestion process with cell lysis activities, shaking and temperature increase

Autothermal thermophilic aerobic digestion (ATAD) is conducted for stabilization of sludge waste and is driven by the action of various microorganisms under aerobic conditions. However, the mechanism controlling bacterial community changes during ATAD via three (initial, middle and final) phases is currently unclear. To investigate this mechanism, activity analysis and a microcosm assay with shaking were performed on a bacterial community during the initial, middle, and final phases of incubation. Cell lysis activities toward gram-negative bacteria, but not gram-positive bacteria, were detected in the ATAD samples in the middle and final phases. During shaking incubation in initial-phase samples at 30°C, major operational taxonomic units (OTUs) related to Acinetobacter indicus and Arcobacter cibarius dramatically increased along with decreases in several major OTUs. In middle-phase samples at 45°C, we observed a major alteration of OTUs related to Caldicellulosiruptor bescii and Aciditerrimonas ferrireducens, together with distinct decreases in several other OTUs. Final-phase samples maintained a stable bacterial community with major OTUs showing limited similarities to Heliorestis baculata, Caldicellulosiruptor bescii, and Ornatilinea apprima. In conclusion, the changes in the bacterial community observed during ATAD could be partially attributed to the cell lysis activity toward gram-negative bacteria in the middle and final phases. The microcosm assay suggested that certain physical factors, such as a high oxygen supply and shearing forces, also might contribute to bacterial community changes in the initial and middle phases, and to the stable bacterial community in the final phase of ATAD.

Combining an Electrothermal and Impedance Aging Model to Investigate Thermal Degradation Caused by Fast Charging

Fast charging is an exciting topic in the field of electric and hybrid electric vehicles (EVs/HEVs). In order to achieve faster charging times, fast-charging applications involve high-current profiles which can lead to high cell temperature increase, and in some cases thermal runaways. There has been some research on the impact caused by fast-charging profiles. This research is mostly focused on the electrical, thermal and aging aspects of the cell individually, but these factors are never treated together. In this paper, the thermal progression of the lithium-ion battery under specific fast-charging profiles is investigated and modeled. The cell is a Lithium Nickel Manganese Cobalt Oxide/graphite-based cell (NMC) rated at 20 Ah, and thermal images during fast-charging have been taken at four degradation states: 100%, 90%, 85%, and 80% State-of-Health (SoH). A semi-empirical resistance aging model is developed using gathered data from extensive cycling and calendar aging tests, which is coupled to an electrothermal model. This novel combined model achieves good agreement with the measurements, with simulation results always within 2 °C of the measured values. This study presents a modeling methodology that is usable to predict the potential temperature distribution for lithium-ion batteries (LiBs) during fast-charging profiles at different aging states, which would be of benefit for Battery Management Systems (BMS) in future thermal strategies.

Continuously adjustable period optical grating based on flexoelectric effect of a bent-core nematic liquid crystal in planar cells

The structures of flexodomains, which are similar to optical gratings and can be controlled by the amplitude of applied voltage and temperature, were verified through polarizing microscopy and light diffraction techniques. The properties of the optical grating induced by a bent-core nematic liquid crystal in planar cells with varied cell gaps and pretilt angles were studied. The period of optical grating decreases with the increase in the amplitude of the applied voltage and pretilt angle. In addition, the period increases with the increase in cell gap and temperature. The period of optical grating has a linear relationship with temperature. The continuously adjustable period has the potential to become an important and extended application of optical grating.