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Battery Energy Storage
Published in Iqbal Husain, Electric and Hybrid Vehicles, 2021
The battery in its simplest form can be represented by an internal voltage Ev and a series resistance Ri as shown in Figure 5.5a. More representative but complex battery models are discussed later in the chapter. The battery internal voltage appears at the battery terminals as open-circuit voltage when there is no load connected to it. The internal voltage or the open-circuit voltage (OCV) depends on the state of charge of the battery, temperature and past discharge/charge history (memory effects) among other factors. The open-circuit voltage characteristics are shown in Figure 5.5b. As the battery is gradually discharged, the internal voltage decreases, while the internal resistance increases. The open-circuit voltage characteristics have a fairly extended plateau of linear characteristics with a slope close to zero. The open-circuit voltage is not a good indicator of the state of charge; state of charge of a battery pack needs to be calculated considering discharge current characteristics, battery chemistry, temperature effects and number of charge/discharge cycles. Once the battery is completely discharged, the open-circuit voltage decreases sharply with more discharge.
Advanced SOC Estimation of Lead-Acid Battery for HEM Application
Published in P. C. Thomas, Vishal John Mathai, Geevarghese Titus, Emerging Technologies for Sustainability, 2020
Saira Philip, Liss Abraham Maret, Heinz Varghese Maymana, Herma Mariam Jacob, Shameer Asharaf, Rani Chacko
SOC estimation methods are mainly classified as direct measurement, book-keeping estimation, adaptive systems and hybrid methods [2]. The direct measurement is done by directly measuring the physical properties of a battery such as voltage, impedance, etc. This method includes an open circuit voltage test, terminal voltage test, impedance method, and impedance spectroscopy. Open Circuit Voltage (OCV) is an important characteristic parameter of the battery, which is used to analyze the changes of electronic energy in electrode materials, and to estimate battery SOC to manage the battery pack [3]. There is a linear relationship between battery OCV and SOC. In Terminal voltage test, the battery terminal voltage is estimated and SOC is approximated with it. The terminal voltage drop, Electro-Motive Force (EMF) and SOC are related in this test [4]. In the impedance method, battery impedance is taken and is used for finding out the SOC of battery. But it varies for different battery specifications [5]. Impedance spectroscopy is an estimation method in which impedance of the battery is taken at different charging and discharging currents. Impedance models will be set up and SOC is found using the pre-determined impedance values [6]. Even though these methods are easy to implement but it has some disadvantages such as it is offline in nature and will not considering the losses during estimation.
Electrical Discharge Machining (EDM)
Published in Basil Kuriachen, Jose Mathew, Uday Shanker Dixit, Electric Discharge Hybrid-Machining Processes, 2022
Voltage: In EDM operation, generally, there are two types of voltages specified: open-circuit voltage and discharge voltage (or working voltage). Open circuit voltage is the voltage from the power supply to the electrodes or the voltage measured across the electrodes before actual machining or sparking starts. In contrast, the discharge voltage is the level of the voltage in the IEG during sparking. It is lesser than that of the open-circuit voltage by 35–38 %. The discharge voltage (or machining voltage) is controlled by the servo voltage set in the servo control unit that is available in most commercial EDM machines. During the actual machining, the tool is operated along with the feed motion, and it moves downwards and stops at a point very close to the workpiece. The downward movement of the tool increases the voltage between the tool and the workpiece. Once the voltage between the electrodes reaches a preset servo voltage, the downward movement of the tool stops, and a series of sparks take place. These sparks remove the material, thereby increasing the IEG and voltage between the tool and workpiece. The servo control feeds the tool downwards to maintain the preset servo voltage and the sparks continue. During sparking, ionization or plasma channel formation in the IEG takes place. As a result, current starts to flow, thereby the voltage drops and stabilizes the IEG [12]. On this basis, the servo voltage has a direct liner relationship to the inter-electrode gap. This is that the larger the servo voltage, the higher the IEG [13].
Recursive ARMAX-Based Global Battery SOC Estimation Model Design using Kalman Filter with Optimized Parameters by Radial Movement Optimization Method
Published in Electric Power Components and Systems, 2023
Alirıza Kaleli, Halil İ. Akolaş
In this figure, is open circuit voltage and is output terminal voltage. Equation (2) describes equivalent circuit model in continuous time form. where is obtained by using battery SOC value and battery surface temperature. Since and The discrete time model is obtained as follows. The state space equations are calculated as follows. where and system input is
Experimental investigation of a monitoring model for dust deposition on solar photovoltaic modules
Published in International Journal of Green Energy, 2023
Zhaohui Zhang, Ruilin Gao, Zhaohua Li, Junqiang Wu, Wenguang Yang, Xiaobao Liu, Kai Ma
Figure 13 shows the variation of the open-circuit voltage with the dust density at 12 irradiation intensities. It can be found that dust deposition has no significant effect on the open-circuit voltage of the solar cell. When the dust density is 0–10 g/m2, the open-circuit voltage value almost does not change under different irradiation intensity conditions. When the dust density exceeds 10 g/m2, the open-circuit voltage decreases slightly, indicating that irradiation intensity influences the open-circuit voltage. At the same irradiance, the open-circuit voltage of the solar cell with dust deposition is a little lower than that of a clean solar cell. Considering that there is no interference from other factors, it can be explained that the dust deposition causes the temperature improvement of the backplate of the solar cell, leading to the decrease in the open-circuit voltage. Besides, the decreasing trend is not distinct due to the slight temperature difference between the solar cell with dust and the clean solar cell, which is caused by heat dissipation of the solar simulator.
Study of Solar PV Panel Under Partial Vacuum Conditions: A Step Towards Performance Improvement
Published in IETE Journal of Research, 2022
Ankur Kumar Gupta, Yogesh K. Chauhan, Tanmoy Maity, Ria Nanda
dVoc /dT can be found as per the following equation as [11]: It is evident from the above equation that the open-circuit voltage of the solar cell influences the temperature sensitivity of a solar cell. The value of EGo is 1.2 for silicon. The resultant temperature-dependent Equation (6) comes out to be where VGO is the equivalent voltage of the prohibited band (eV) and it is 1.21 V for silicon. With the temperature elevation, the short-circuit current, Isc, improves slightly due to the decrement of band gap energy EG, and resulting into more electron-hole pairs to combine and give high photon energy. The temperature-dependent short-circuit current from a silicon solar cell is given by the equation as follows: The maximum power output, PM with the effect of temperature is given as [11] At the room temperature of 27°C (300 K), many of the characteristics of semiconductors are determined. In case of solar cells the measurement is done at 25°C (298 K).