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Lithium-ion (Li-ion) batteries have increasingly been used in diverse applications. Accurate estimation of the state of health (SOH) of the Li-ion batteries is vital for all stakeholders and critical in various applications such as electric vehicles (EVs). The electrical equivalent circuit (EEC) 2-RC model is often used to model the battery operation but has not been used to capture the degradation of battery cells over time. This paper uses the 2-RC model to capture the degradation of the Li-ion battery. The proposed model is not only time-dependent but also captures the effect of temperature on battery degradation. The proposed approach estimates the SOH accurately and is also considerably flexible for diverse cells of different chemistry. We further generalize an N-RC model approach to evaluate the SOH of the battery. We compare the proposed model (2-RC) with the 1-RC model, and through numerical results, we show that the 2-RC model outperforms 1-RC and reduces the computational cost significantly. Similarly, the 2-RC model outperforms 3-RC and higher-order circuits. We also show that the proposed approach can capture the battery dynamics better for specific smaller orders of the polynomial (associated with Arrhenius equation) when compared with the 1-RC approach with considerably reduced (up to 60%) root mean square error (RMSE). Lastly, the average testing RMSE for 2-RC is 52.4%.

Battery Open Circuit Voltage (OCV) is of fundamental characteristic for enabling battery modeling and states estimation. However, the traditional OCV measurement method takes a very long time to make the battery reaches its equilibrium, which is rather inconvenient and cannot be performed online for battery energy storage application. Motived by this, this paper proposes an effective method for fast OCV estimation in the relaxation process. In this work, a novel relaxation model is designed for capturing the voltage response of a battery during relaxation time and the Genetic Algorithm (GA) is further applied for optimizing the model parameters and acquiring accurate OCV estimation results. Experimental results confirm the validity of the proposed method under different State of Charges (SOCs), current rates, ambient temperatures, and aging conditions. The results suggest that the proposed method can accurately and quickly estimate battery OCV, which only takes 10 minutes of measurement data (more than 2 hours for the traditional method) and the maximum estimation error is limited to merely 1.8 mV.

Lithium-ion battery is generally used as energy storage device in spacecraft and other applications. Spacecraftbattery modeling and energy balance estimation is critical. The proposed genetic algorithm driven generic estimation - energy balance (GAGE-EB) model uses cell open circuit voltage characteristics, internal resistance (rint) characteristics, and coulomb counting. The cell characteristics are obtained by offline tests. For series-parallel or parallel-series configured battery, the model estimates deliverable capacity and internal resistance by accurately matching the terminal voltage. Estimated parameters are used to check the energy balance for new load and generation profiles. The GAGE-EB model is validated for electrical performance with various cell types and battery configurations with respect to experimental data and is within 1% and 2% accuracy for voltage and capacity estimation, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a novel fast open circuit voltage prediction approach for Lithium-ion battery, which is potential to facilitate a convenient battery modeling and states estimation in the energy storage system. Open circuit voltage measurement suffers from a long relaxation time (several hours, even days) to reach the thermodynamic equilibrium of the battery. On the basis of the feedback control theory, the proposed multiple correction approach utilizes the constrained nonlinear optimization of the power function in each curve fitting step. The voltage measurement in a short period is divided into several segments to correct the voltage prediction multiple times with the feedback errors after each curve fitting. The similarity between the shape of the power function and the variation of the terminal voltage during the relaxation time is utilized. The proposed method can speed up the time-consuming open circuit voltage measurement and predict the open circuit voltage with high accuracy. Experimental tests on a LiFePO4 battery prove the validation and effectiveness of the proposed method in accurately predicting the open circuit voltage within a very short relaxation time (less than 15 min). [ABSTRACT FROM AUTHOR]

Interest in single-junction III–V-based semiconductor photovoltaic (PV) devices under monochromatic illumination has been renewed in recent years due to their potential to produce high conversion efficiencies. We have designed a PV converter for monochromatic power conversion at $\sim 1070$ nm, which would be ideal for Nd-/Yb-doped solid-state laser sources emitting from 1030 to 1070 nm. A single-junction PV converter is developed on InP platform using quaternary InAlGaAs Q1.1 eV as absorption material. The front grid is designed for the Gaussian nature of the incident laser beam to achieve the optimum power conversion. Preliminary tests are performed on devices under a 1070-nm laser. An open circuit voltage of 0.79 V, the current density up to 5.7 A/cm2, and the fill factor of 0.79 have been achieved. Efficiency up to 40.7% has been achieved at an incident intensity of $\sim 0.16$ W/cm2. Efficiency of these devices can be further improved by design optimization and suppressing series resistance. [ABSTRACT FROM PUBLISHER]

Modeling and simulation of graphene-gated graphene-GaAs Schottky junction field-effect solar cell is performed using in-house developed algorithm based on finite-difference method, where Poisson and drift-diffusion equations are solved in an appropriate way. Our algorithm is verified by comparing the simulated J – V curve of solar cell with the previous experimental one. The carrier generation rate is calculated with light multireflection in the solar cell excluded, due to large optical absorption coefficient of GaAs, and the radiative recombination in GaAs leads to \sim 5 % light generated carrier loss. The charge transfer effect in graphene is investigated, which can affect open circuit voltage, and in particular for the semiconductor substrate with very low hole mobility. It is further numerically demonstrated that: 1) both open circuit voltage and short circuit current J_{\textrm {SC}} of the solar cell are governed by doping concentration through affecting Schottky barrier height and depletion width; 2) the value of V_{\textrm {OC}}$ can be effectively adjusted by decreasing the thickness of gate oxide; however, it may result in oxide breakdown or reliability problem; and 3) there is tunability inertia for V_{\textrm {OC}} with multilayer junction graphene implemented, but it can provide low series resistance. [ABSTRACT FROM AUTHOR]

The performance improvements of adding InAs quantum dots (QDs) in the middle subcell of a lattice matched triple-junction InGaP/InGaAs/Ge photovoltaic device are studied using the simulated external quantum efficiency, photocurrent, open circuit voltage, fill factor, and efficiency under standard testing conditions. The QDs and wetting layer are modeled using an effective medium consisting of trap states for the former and low confinement potentials for the latter. Although the efficiency stabilizes for more than 100 layers of QDs for the structure studied, the efficiency achieves an absolute efficiency of 31.1% under one sun illumination for 140 layers of QDs. This corresponds to a relative increase of 1.3% compared with a control structure with no QD layers. The performance of the device depends intricately on the magnitude of the confinement potentials representing the wetting layer. [ABSTRACT FROM PUBLISHER]

Using higher temperature without any additives, poly(diketopyrrolopyrrole-terthiophene) was successfully dissolved with PC60BM in a commonly used high-boiling point solvent namely chlorobenzene (CB). Use of CB allowed us to heat the blend solution at a higher temperature, which leads to improved nanoscale phase separation between donor and acceptor, which is important for an efficient exciton dissociation. Devices were fabricated in both regular and inverted bulk heterojunction structure for comparison by spin coating an active layer. Inverted structure solar cells exhibited higher power conversion efficiency than regular structure with significant improvement in current density, possibly attributed to increased light absorption in the active layer due to less parasitic absorption in the PEDOT:PSS and the Ca layer, which were used in normal structures. Furthermore, ultraviolet (UV) ozone treatment of ZnO film improved the solar cell performance. A UV ozone treatment of 5 min was found to be the optimal time resulting in the highest device efficiency (4.45%) with short circuit current density of 9.3 mA/cm2, open circuit voltage of 0.69, and fill factor 69.5% without the need for any solvent additives. [ABSTRACT FROM AUTHOR]

We present a methodology for the direction of arrival (DOA) estimation using the induced voltages that are measured at the loads connected to electrically small tuned dipole antenna arrays illuminated by the signal of interest (SOI). The matrix pencil method is applied directly to the induced voltages to estimate the DOA of the various signals. Using electrically small tuned antennas can be advantageous as they can be placed in close proximity of each other saving the real estate and, thus, making it possible to deploy phased arrays on small footprints. When dealing with closely spaced tuned electrically small antennas, it is necessary to use a transformation matrix to compensate for the strong mutual coupling that may exist between the antenna elements. The transformation matrix converts the voltages that are induced at the loads corresponding to the feed point of the array operating in the presence of mutual coupling and other near field scatterers to an equivalent set of voltages that will be induced by the same incident wave in an uniform linear virtual array (ULVA) consisting of omnidirectional isotropic point radiators equally spaced and operating in free space. For any given incident field, the open circuit voltage developed across the feed-point of the small dipole will always be less than the open circuit voltage developed across the feed-point of the half-wavelength dipole. The difference is in the voltage developed across the loads connected to the dipole's feed-point. With the small dipole antenna, the voltage developed across the load impedance will be orders of magnitude greater than the voltage developed across the load connected to the half-wavelength dipole, even though the power captured by any conjugately matched antenna is approximately the same irrespective of their lengths. Three different scenarios are presented to illustrate the methodology. First, we consider resonant dipole elements spaced half wavelength apart, electrically small tuned an- - tenna elements spaced half wavelength apart and electrically small tuned antenna elements placed in close proximity of each other to reduce the footprint without affecting the performance of the phased array. In addition, we consider the possibility of DOA estimation using a combination of different type of electrically small antennas both uniformly and nonuniformly spaced. Numerical examples are presented to illustrate the principles of this methodology [ABSTRACT FROM PUBLISHER]