Number Of Cells In Series Research Articles

Adaptive design for the connection of multicell HHO generator with solar photovoltaic panels

Hydrogen is considered a new source of energy and one of the sources of clean energy. One of the most widely used methods of hydrogen production is water electrolysis. Water electrolysis causes water molecules to break down into hydrogen and oxygen by passing an electric current through water molecules and using an intercellular membrane. If the intercellular membrane is removed, hydrogen gas and oxygen are mixed to produce hydroxy gas. This gas, which contains hydrogen and oxygen molecules, has been considered an auxiliary fuel and combustion enhancer. In this research, the design and construction of a multi-cell electrolyzer producing hydroxy gas without a membrane was carried out using 316 stainless steel sheets. Potassium hydroxide (KOH) solution was used as an electrolyte to increase water conductivity, and solar panels were used to supply the energy required for the electrolyzer. Adjusting the number of electrolyzer plates with the voltage of the solar panels is one of the most critical points in the optimal design of this combined system. The effect of parameters on the amount of hydroxy gas production, energy intensity, and production per electrolyzer surface has been evaluated. The experimental results show that due to the internal resistance of each electrolyzer cell, the voltage of each cell varies between 2 and 3 V in different currents. The number of series cells in the electrolyzer determines its total voltage, which should be matched to the solar system to stay at the optimum point of operation. In the studied electrolyzer, optimized design of electrolizer have 18, 17 and, 15 plates, when one, two, and three 325W solar panels is used, respectively. In the next step, the daily test is performed for optimized electrolyzers. Daily production per surface of the solar panel for the three states was 530, 600 and 533L/m2, respectively. This indicates that daily production increases with increasing the number of panels but specific production per solar panel area may not increase and will have an optimal value. So, in the combination of an HHO generator with a solar system, the number of electrolyzer plates and also the surface area of solar panels should be optimally selected to achieve the optimum operation. This issue can be completed with accurate modeling in future studies.

An execution time optimized state of charge estimation method for lithium-ion battery

State of charge (SOC) estimation is one of the most important outputs of the battery management system (BMS). There are several algorithms for SOC estimation. Each method has advantages like self-correction ability and disadvantages like computational complexity for an embedded system. In the first part of this article, different estimation techniques are reviewed and compared. Particular emphasis was placed on two methods: Coulomb Counting (CC) and Sigma Point Kalman Filter (SPKF). These two methods are analyzed in terms of several aspects such as tolerance to noisy signal, recovery ability from an intentional SOC distortion as well as estimation accuracy comparison. Also, an embedded development kit is used to analyze execution time of each method. The results show that using SPKF alone is a computationally expensive method especially for a battery pack with a high number of cells in series. On the other hand, using CC alone could be vulnerable to SOC distortion and noisy measurement signals and this may lead to inaccurate predictions. Based on these facts, a hybrid approach has been proposed to take advantage of each method’s superiority. The emphasis in this paper is on execution step time analyses under different conditions and drive cycles. On top of this article, further studies may pave the way for more cost effective solutions like downsizing of the processor.

Research on the Influence of Battery Cell Static Parameters on the Capacity of Different Topology Battery Packs

The parameter inconsistency of the battery cells and the series-parallel connection mode are closely related to the battery pack capacity. Studying the degree of influence of battery pack capacity by battery cell parameters is of great significance to the series-parallel design of battery packs. This paper establishes battery cell models and battery pack models with different topologies. In the MATLAB/Simulink environment, simulation studies were conducted to study the influence of the battery pack capacity by the monomer parameters as the number of cells in series and parallel in the topology changes. Then, from a statistical point of view, the simulation results were analyzed in principle. Finally, a small-scale battery pack experimental platform was built in the laboratory environment to verify the correctness of the simulation conclusions and theoretical analysis.

Implementation of Three Phase High Voltage Gain Boost Converter for Fuel Cell

Generally, the power generating from the Fuel cell is an electrochemical reaction between H2 and oxygen and it generates electric energy, and the by-product is water vapour. However, the output from the fuel cell systemsis very low, then it becomes necessary to connect more number of cells in series to improve the output. The proposed method electrically divides the fuel cell stack into different sections, and each stack is powered by a direct boost inverter. This paper proposes a concept of high voltage dc-dc boost converter topology for a three phase systemto a typical output voltage from the fuel cell as a stand-alone supply. The main advantage of the proposed boost inverter method include ability to deliver the operations of both boosting and inversion of the power in only one stage, compactness, and economical. The output voltage from the fuel cell is a voltage controlled method and output from the battery is a current controlled method. Analysis, and Simulation are taken from a 1kW prototype.

Design Considerations of Ultracapacitor Stack for Optimal Sizing of Energy Storage Systems in Contingency Applications

Ultracapacitors (UCs) today are playing an increasing role in the energy storage systems (ESSs) of several power conversion applications. In this article, a design method for optimal sizing of a UC stack is proposed, which minimizes the overall cost of the ESS. The problem is cast with normalized cost parameters of the ESS subsystem, using which the discharge ratio of the stack is optimized for the given ESS specifications. An iterative design algorithm is proposed which systematically engineers the stack parameters of unit cell capacitance, the number of series cells and parallel strings along with the initial and final stack voltage levels that meet the specified ESS requirements while also supplying the equivalent series resistance (ESR) loss. The iterative sizing process also factors in the maximum power transfer constraint imposed by the ESR to guarantee stable operation of the cost-optimal design even as the stack voltage varies during discharge. The design considerations, optimization framework, ESR effects, and the proposed sizing algorithm are synthesized in a generalized formulation in order to capture the variations in cost and subsystem parameter values that typically vary based on scaling requirements as well as the UC and power converter technology. Experimental results on a 4 kWmin UC stack validate the proposed cost-optimal design algorithm and the ESR induced voltage collapse.

Active cell balancing for electric vehicle battery management system

The shrink in accessibility of petroleum products and increment in asset request are eventual outcomes for Electrical Vehicles (EVs). The battery has an impact on the performance of electrical vehicles, the driving range. Lithium ion (Li-ion) chemistry is extremely sensitive to overcharge and deep discharge, which can harm the battery, shortening its period of time, and even inflicting risky things. The Battery Management System (BMS) comprises of the consequent parts: management, equalization and protection. Of the three components, equalization is that the most crucial with respect to the durability of the battery framework. The ability of the full pack diminishes rapidly amid the procedure which leads to degradation of the full battery framework. This condition is extreme once the battery incorporates a more number of cells in series and frequent charging is conveyed through the battery string. The cell imbalance during charging, discharging is a major issue in battery systems used in EVs. To circumvent the cell imbalance, cell balancing is used. Cell balancing enhances battery safety and extends battery life. This paper discusses about different active balancing method to increase the life span of the battery module. Based on the comparison, the inductor based balancing method for 60V battery system is implemented in the MATLAB/Simscape environment and the results are discussed.

The Effects of Thermal Gradients in Automotive Battery Packs Balancing Strategy

In order to reduce current and enable fast charging, future packs will operate between 800 V and 1000 V; these high voltage ratings will be achieved by connecting a large number of cells in series [1]. Unbalance in series strings occurs even if all cells are supplied with the same amount of current, it is induced by the differences in cell State of Health (SOH) and exacerbated by temperature gradients across the pack. The focus of this study is demonstrating that temperature gradients are a major source of voltage imbalance [2]. It is suggested that, if not temperature-informed, dissipative balancing could induce further discrepancies in the amount of charge (Ah) stored in each cell and overcharge cells incorrectly, triggering degradation. The work compares the performance of different balancing strategies applied to a string of 3 cells. During operation an automotive pack is subject to non-uniform temperatures; to experimentally reproduce this scenario isothermal boundary conditions are imposed on the cells, with cells artificially held at different temperatures. The study compares no balancing against simple top-up balancing based upon voltage limits, and more intelligent strategies based upon state-of-charge estimation with and without temperature correction. Each of the balancing techniques are assessed in terms of the energy (Wh) and power (W) available for operation and also by the amount of dissipated energy due to balancing. It is proposed that simple top-up balancing can exacerbate charge imbalance; whilst more advanced strategies can increase useable pack energy and cycle life. The work also explores how many cycles the string can undergo before charge dissipation is necessary. [1] S. Ahmed et al., “Enabling fast charging – A battery technology gap assessment,” J. Power Sources, vol. 367, pp. 250–262, Nov. 2017. [2] Y. Troxler et al., “The effect of thermal gradients on the performance of lithium-ion batteries,” J. Power Sources, vol. 247, pp. 1018–1025, Feb. 2014.

An Examination of the Factors That Influence Primary Battery Longevity Performance Under Multiple-Cell Vs Single-Cell Testing Conditions

Primary alkaline batteries still account for the vast majority of battery sales in the US. According to the test standards the American National Standards Institute (ANSI), primary alkaline cell longevity performance is intended to be measured by discharging individual cells under specific load and duty cycle conditions to prescribed cutoff voltages. However, market research studies indicate that greater than 90% of battery-driven devices in the US require more than 1 cell, in electronic series configuration, to function. Thus, the analysis of primary alkaline battery performance in multiple-cell configuration will yield results that are far closer to the battery performance observed in actual devices and, therefore, is more consumer relevant. Focusing on AA size batteries, multiple cells discharged in series configuration demonstrated consistently lower cell performance (measured in service hours) vs single cells discharged under similar load and duty cycle conditions. The magnitude of decrease in performance for any battery design was highly related to the performance variability exhibited in single cell performance testing. Additional factors that influenced the lower performance observed in multiple-cell testing included the number of cells in series, discharge load magnitude, load type, endpoint voltage and battery design characteristics such as rate of increase of polarization during discharge. The relative importance of these factors to multiple-cell performance was quantified along with consideration of the deficiencies of reporting primary battery performance based on single-cell performance testing.

An Examination of the Factors That Influence Primary Battery Longevity Performance Under Multiple-Cell Vs Single-Cell Testing Conditions

Primary alkaline batteries still account for the vast majority of battery sales in the US. According to the test standards of the American National Standards Institute (ANSI), primary alkaline cell longevity performance is intended to be measured by discharging individual cells under specific load and duty cycle conditions to prescribed cutoff voltages. However, market research studies indicate that greater than 90% of battery-driven devices in the US require more than 1 cell, in electronic series configuration, to function. Thus, the analysis of primary alkaline battery performance in multiple-cell configuration will yield results that are far closer to the battery performance observed in actual devices and, therefore, is more consumer relevant. Focusing on AA size batteries, multiple cells discharged in series configuration demonstrated consistently lower cell performance (measured in service hours) vs single cells discharged under similar load and duty cycle conditions. The magnitude of decrease in performance for any battery design was highly related to the performance variability exhibited in single cell performance testing. Additional factors that influenced the lower performance observed in multiple-cell testing included the number of cells in series, discharge load magnitude, load type, endpoint voltage and battery design characteristics such as rate of increase of polarization during discharge. The relative importance of these factors to multiple-cell performance was quantified along with consideration of the deficiencies of reporting primary battery performance based on single-cell performance testing.

Thermally Sprayed Large Tubular Solid Oxide Fuel Cells and Its Stack: Geometry Optimization, Preparation, and Performance

In this study, we develop a large tubular solid oxide fuel cells design with several cells in series on a porous cermet support, which has many characteristics such as self-sealing, low Ohmic loss, high strength, and good thermal expansion coefficient matching. Here, we investigate aspects of the cell design, manufacture, performance, and application. Firstly, the cell length and number of cells in series are optimized by theoretical analysis. Then, thermal spraying is applied as a cost-effective method to prepare all the cell components. Finally, the performance of different types of cells and two types of stacks is characterized. The maximum output power of one tube, which had 20 cells in series, reaches 31 and 40.5 W at 800 and 900 °C, respectively. Moreover, the output power of a stack assembled with 56 tubes, each with ten cells in series, reaches 800 W at 830 °C. The excellent single tube and cell stack performance suggest that thermally sprayed tubular SOFCs have significant potential for commercialized application.

Active Balancing System for Electric Vehicles With Incorporated Low-Voltage Bus

Electric-drive vehicles, including hybrid, plug-in hybrid, and electric vehicles, require a high-voltage (HV) battery pack for propulsion and a low-voltage (LV) dc bus for auxiliary loads. This paper presents an architecture that uses modular dc-dc bypass converters to perform active battery cell balancing and to supply current to auxiliary loads, eliminating the need for a separate HV-to-LV high step-down dc-dc converter. The modular architecture, which achieves continuous balancing of all cells, can be used with an arbitrary number of cells in series, requires no control communication between converters, and naturally shares the auxiliary load current according to the relative state-of-charge (SOC) and capacities of the battery cells. Design and control details are provided for LV low-power dual active bridge (DAB) power converters serving as the bypass converter modules. Furthermore, current sharing is examined and worst-case SOC and current deviations are derived for mismatches in cell capacities, SOCs, and parasitic resistances. Experimental results are presented for a system consisting of 21 series 25 Ah Panasonic lithium-ion NMC battery cells and 21 DAB bypass converters, with combined outputs rated to supply a 650-W auxiliary load.

Adaptive Battery Equalization Algorithm for Capacitor-based Battery Management System

In recent years, as energy-saving and environmental protection were widely concerned around the world, the lithium iron phosphate (LFP) battery has been widely used in hybrid electric vehicle (HEV) and electric vehicle (EV). Generally the battery pack for HEV is composition of the number of cells in series. In this case, imbalance among cells due to the difference of degradation and temperature will be accelerated by the cycles of charge and discharge without an appropriate battery equalization management system. However, the balancing system only intended to reduce the difference of cell voltage or Stage of Charge (SoC) before. Adaptive Battery Equalization Algorithm for Capacitor-based Battery Management System this thesis proposed re-explains the meaning of battery equalization. Instead of long-term using battery equalizer on standby, this thesis equalizes the battery when charging to save much spending time. It could not only adjust the balancing mechanism automatically in order to keep the available charge but also raise the average SoC to prevent the effect of battery aging and improve the cycle number of battery. Experiment results indicate that the available charge increases 1.5% and the battery capacity efficiently improves 7.3%.

Modelling and Output Power Evaluation of Series-Parallel Photovoltaic Modules

Solar energy has received attention in the Middle East given the abundant and free irradiance and extended sunny weather. Although photovoltaic panels were introduced decades ago, they have recently become economical and gained traction. We present a mathematical model for series-parallel photovoltaic modules, evaluate the model, and present the I-V and P-V characteristic plots for various temperatures, irradiance, and diode ideality factors. The power performance results are then analyzed and recommendations are made. Unlike other related work, our evaluation uses standard spreadsheet software avoiding commercial simulation packages and application programming. Results indicate improved power performance with irradiance and parallel connections of cell series branches. Given the hot weather in our region, increasing the number of cells connected in series from 36 to 72 is not recommended. I. INTRODUCTION The push for renewable energy solutions is steady to reduce carbon emissions, protect the environment and population health, and effect climate and sea water level changes. Solar energy has received attention in the Middle East given the abundant and free irradiance and sunny weather. Although photovoltaic (PV) panels were introduced decades ago, they have recently become economical and gained traction. Saudi Arabia recently saw the successful installation of a 3.5 megawatt photovoltaic field, the largest solar power plant built in the country, and has plans to install 41 Gigawatts of solar power over the next 20 years. PV fields geographically distributed can be located near loads and cut down on fuel consumed by power generating plants. PV cells generate DC electricity during the day, which can be immediately consumed or stored in batteries for future consumption. An inverter is used to convert the generated power from DC to AC. The PV panel has a number of solar cells connected in series (typically 36 or 72) with the possibility to connect PV cell series branches in parallel. The solar cell is a p-n junction fabricated in a silicon (or other material) wafer or semiconductor layer. The photovoltaic effect causes the electromagnetic radiation of the solar energy hitting the PV cells to generate electricity. Photons with energy greater than the band gap energy of the wafer's semiconductor material are absorbed, creating electron-hole pairs, which in turn create a photocurrent in the presence of the p-n junction's internal electric field. The photocurrent's magnitude rises with the number of electron-hole pairs created, which is dependent on the irradiance level. Therefore the magnitude of the current generated by the PV module is proportional to the amount of incident solar radiation. PV module models have evolved to include detailed parameters and even multiple piecewise linear regions or better accuracy. However, most have focused on modeling a number of PV cells in series and stopped short of modeling multiple parallel branches of serially connected PV cells. In this paper, we present a mathematical model for series- parallel photovoltaic modules, evaluate the model, and present the I-V (module current vs. module voltage) and P-V (module power vs. voltage) characteristic plots for various temperatures, irradiance and diode ideality factors. The power performance results are then analyzed and recommendations are made. Unlike others' work, we model series-parallel PV cells with multiple parallel branches each consisting of a number of PV cells in series, and evaluate the model with a basic spreadsheet application, avoiding application programming and commercial simulators. This is facilitated by the mathematical technique (i.e. Newton-Raphson) used in the model evaluation which makes the model evaluation possible with a spreadsheet application. Thus, a key advantage of our approach is that our model can be reused by a larger population of researchers with no access to commercial simulator packages.

LSM Protective Coatings on Stainless Steel as Interconnects for Solid Oxide Fuel Cells

ABSTRACTOne of the major barriers to the adoption of solid oxide fuel cells (SOFCs) is the short lifetime of the fuel cell stacks. A stack consists of a number of cells in series separated by an interconnect. Due to the high temperatures necessary for SOFCs, typical commercial interconnects are ceramic. Great attention has been paid to decreasing the operating temperature of SOFCs in order to extend the life and decrease the cost of the stack. As operating temperatures decrease below 1000°C, alternative interconnect materials become viable. Stainless steel interconnects are more cost effective than ceramic interconnects but the high temperatures and the oxidizing environment of the cathode leads to the formation of a chromium oxide scale that increases the stack resistance. Chromium from the stainless steel can also enter the vapor phase and redeposit on the cathode thereby blocking the electrochemically active sites. One method to neutralize these effects is to coat the metallic interconnect in a ceramic such as La.8Sr.2MnO3 (LSM). The coating acts as a diffusion barrier both against chromium diffusing into the cathode and oxygen diffusing into the interconnect. In this study LSM has been deposited using plasma spray and tested in a dual atmosphere setup using impedance spectroscopy to analyze the performance of the coatings at various temperatures. The area specific resistance and chemical composition of the scale was examined in order to determine the affect of the LSM coating.

Fuzzy logic-based MPPT controllers for three-phase grid-connected inverters

In photovoltaic (PV) applications, a maximum power point tracking (MPPT) module is necessary to extract the whole energy that the PV module can generate depending on the instantaneous conditions of the PV system. A PV module is obtained by connecting a number of solar cells in series and parallel, which causes voltage and current to increase at module terminations. The present work is based on a three-phase grid-connected inverter designed for a 100 kW PV power plant that uses an MPPT scheme based on fuzzy logic controllers. The whole system presented is simulated in MATLAB. The fuzzy logic-based MPPT controllers show accurate and fast responses and are integrated into the inverter, so that the there is no requirement for a dc–dc converter. The inverter allows full control of reactive power.

Advances in the development of a hydrogen/oxygen PEM fuel cell stack

Recent advances in the design and construction of a hydrogen/oxygen PEM fuel cell stack are presented. A test bench including measurement and control devices to monitor the fuel cell operating parameters was mounted. The influence of the characteristics of the membrane electrode assembly, bipolar plates, etc., on the performance of the fuel cell stack was studied. The behavior of the fuel cell stack with a different number of cells in series was evaluated. In order to identify and minimize the energy losses a critical analysis of the results was done.

Short-cut method for flotation rates modelling of industrial flotation banks

The knowledge of the distributed performance of a flotation bank, consisting of a number of cells in series, is a key factor for different purposes such as process design, scale-up, diagnosis, operation, control and optimization. A common practice in plant operation is to develop mass balances around the whole flotation bank in order to characterize the overall recovery, typically in rougher flotation. However, testing to fit flotation rate models are seldom developed on industrial flotation banks because they are high consumers of human labor during sampling, mineral samples preparation and chemical analysis development. In this paper a short-cut method is proposed which allows obtaining the relevant information for flotation rate modeling in a flotation bank with minimum effort and cost, and within a reasonable accuracy (less than 1–2% error in estimating cell recovery along the bank). The procedure considers two mass balances, one around the first cell of the bank and the second is the overall mass balance around the whole flotation bank, with a total of only 5 sampling streams. Examples developed in four rougher flotation banks located in three industrial concentrators illustrate the merit of this procedure.

CELLS-IN-SERIES METHOD FOR SIMULATION OF HEAT REGENERATORS IN PERIODIC OPERATION

A new method has been developed for simulation of heat regenerators in periodic operation. The procedure is based on describing the system by a number of backmixed cells in series, in contrast to the differential equation formulation used in earlier studies. The method is highly efficient computationally and the calculation of thermal efficiency and temperature profiles in the system is reduced to the solution of a simple set of linear algebraic equations. The validity of the method is established by comparing it with other solution procedures. Finally, some illustrative results are presented to show the effect of switching time, normalized variance of the system, and mode of operation.