DC Current Generation Research Articles

PHOTOVOLTAIC SOLAR CELL LIKE RECEIVER FOR ELECTROMAGNETIC WAVES IN VHF-UHF BANDS

This paper describes the photovoltaic solar cell like receiver for electromagnetic waves in VHF-UHF bands and the application of photovoltaic solar cell in planar antenna structures. The radiating patch element of a planar antenna is replaced by a solar cell. Furthermore radiating slots are built due to the cell spacing in a solar cell array. The original feature of a solar cell (DC current generation) remains, but additionally the solar cell is now able to receive and transmit electromagnetic waves, because the electromagnetic radiation is an important source of interference on the useful signals in the electric and electromagnetic devices.

Quantum Advantage in a Molecular Spintronic Engine that Harvests Thermal Fluctuation Energy.

Recent theory and experiments have showcased how to harness quantum mechanics to assemble heat/information engines with efficiencies that surpass the classical Carnot limit. So far, this has required atomic engines that are driven by cumbersome external electromagnetic sources. Here, using molecular spintronics, an implementation that is both electronic and autonomous is proposed. The spintronic quantum engine heuristically deploys several known quantum assets by having a chain of spin qubits formed by the paramagnetic Co center of phthalocyanine (Pc) molecules electronically interact with electron-spin-selecting Fe/C60 interfaces. Density functional calculations reveal that transport fluctuations across the interface can stabilize spin coherence on the Co paramagnetic centers, which host spin flip processes. Across vertical molecular nanodevices, enduring dc current generation, output power above room temperature, two quantum thermodynamical signatures of the engine's processes, and a record 89% spin polarization of current across the Fe/C60 interface are measured. It is crucially this electron spin selection that forces, through demonic feedback and control, charge current to flow against the built-in potential barrier. Further research into spintronic quantum engines, insight into the quantum information processes within spintronic technologies, and retooling the spintronic-based information technology chain, can help accelerate the transition to clean energy.

DC current generation and power feature in strongly driven Floquet-Bloch systems

We study the DC current generation in a periodically driven Bloch system connected to a heat bath. Under a relaxation time approximation, the density matrix for such a system is obtained, which is related to two equilibria: a Floquet quasiequilibrium where the density matrix is diagonal under the Floquet-Bloch eigenbasis and an instantaneous Bloch thermal equilibrium. Then, the current responses and their power features, i.e., the power input behavior, are discussed in a unified manner, which reveals that there exist an intrinsic current and an extrinsic correction. Remarkably, the intrinsic part consumes no energy and corresponds to the Floquet quasiequilibrium, while the extrinsic part needs a sustained energy input and originates from a shift between two equilibrium ensembles. We further investigate the role of the external driving field strength finding that large DC currents can be generated under a relatively strong but not too strong driving field.

Control and Validation of a Reinforced Power Conversion System for Upcoming Bioelectrochemical Power to Gas Stations

This paper presents a proposal for potential bioelectrochemical power to gas stations. It consists of a two-level voltage source converter interfacing the electrical grid on the AC side and an electromethanogenesis based bioelectrochemical system (EMG-BES) working as a stacked module on the DC side. The proposed system converts CO2 and electrical energy into methane, using wastewater as the additional chemical energy input. This energy storage system can contribute to dampening the variability of renewables in the electrical network, provide even flexibility and grid services by controlling the active and reactive power exchanged and is an interesting alternative technology in the market of energy storage for big energy applications. The big challenge for controlling this system lays in the fact that the DC bus voltage of the converter has to be changed in order to regulate the exchanged active power with the grid. This paper presents a cascade approach to control such a system by means of combining external control loops with fast inner loops. The outer power loop, with a proportional-integral (PI) controller with special limitation values and anti-windup capability, is used to generate DC bus voltage reference. An intermediate loop is used for DC bus voltage regulation and current reference generation. A new proportional resonant controller is used to track the current reference. The proposed scheme has been validated through real-time simulation in OPAL OP4510.

Generation of DC, AC, and Second-Harmonic Spin Currents by Electromagnetic Fields in an Inversion-Asymmetric Antiferromagnet

Manipulating spin currents in magnetic insulators is a key technology in spintronics. We theoretically study a simple inversion-asymmetric model of quantum antiferromagnets, where both the exchange interaction and the magnetic field are staggered. We calculate spin currents generated by external electric and magnetic fields by using a quantum master equation. We show that an ac electric field with amplitude E 0 leads, through exchange-interaction modulation, to the dc and second-order harmonic spin currents proportional to E 0 2 . We also show that dc and ac staggered magnetic fields B 0 generate the dc and ac spin currents proportional to B 0 , respectively. We elucidate the mechanism by an exactly solvable model, and thereby propose the ways of spin current manipulation by electromagnetic fields.

Modeling Solar Modules Performance Under Temperature and Solar Radiation of Western Iraq

<p>This paper demonstrates a mathematical representation of Photovoltaic (PV) solar cells and hence panels performance. One-diode solar cell model is implemented to simulate the cell and extract the performance indications. The tested PV modules are BP Solar (60 Watt) and Synthesis Power (50 Watts), which are operating in a PV generation system in the University of Anbar - Iraq, College of Applied Sciences. The math model demonstrates Power versus Voltage (P-V) characteristic curves to depict and study various parameters with affecting variations in the PV array performance. The parameters include ambient and cell temperature degrees and solar irradiance (G) level which are the main elements to dictate the productivity of a solar system. G is represented by sun unit (1 sun=1 kW/m<sup>2</sup>). The outcomes of the simulation model characteristics curves have been compared with curves provided by the tested modules data sheets. MATLAB software has been used to simulate the model and extract the results. This paper also investigated photovoltaic simulation with maximum power point tracking (MPPT) converter to evaluate hence predict the behaviors of the whole photovoltaic DC current generation using PSIM Power Electronics program. The model focuses on the basic components in PV systems; The panel and the DC-DC converter. The modeling outcome data will be used as a reference verifying the performance of the tested modules during the year seasons under the dominating dusty hot weather in western Iraq.</p>

Enhanced Equivalent Electrical Circuit Model of Lithium-Based Batteries Accounting for Charge Redistribution, State-of-Health, and Temperature Effects

Accurate models capable to predict the dynamic behavior, and the state of charge of battery energy storage systems (BESSs) is a key aspect for the definition of model-based controls in electric vehicles and in power grid applications of these energy storage systems. In this context, this paper presents an enhanced electrical BESS model capable to accurately represent the effects of charge redistribution in lithium-based cells. In fact, this phenomenon is the main source of nonlinearity in the behavior of such devices. The improvement of the proposed model is achieved by a virtual dc current generator accounting for the internal charge transfer. The behavior of this virtual generator is inferred from experimental results describing the effects of the charge redistribution during different subphases, namely, charge, discharge, and rest phases. The proposed model, along with its parameter assessment, has been experimentally validated for: 1) two types of Li-ion chemistry; 2) aged cells; 3) different cell operating temperatures ranging from −20 °C up to 55 °C; and 4) a complex battery cell pack of 25-kWh rated energy.

Pulse width modulation as energy-saving strategy of shape memory alloy based smart soft composite actuator

This paper presents electrical power consumption decreased in actuating a shape memory alloy (SMA) based smart soft composite (SSC) actuator using pulse width modulation (PWM). A DC current input generator and a PWM signal generator were designed to apply inputs to SSCs. Experiments were carried out on two types of SSC: one conventional, using a single SMA wire, and the other using multiple wires. The blocking force was measured to analyze the performance of the SSC. The experiments demonstrated that the PWM signal was able to reduce the actuation energy while showing the same performance as an analog current input. These results suggest that a PWM signal could be an alternative candidate for the input paradigm for SSCs to reduce energy consumption, expanding the uses of SSC actuators in robotic applications.

MAGNETIC FIELD GENERATION IN CORE-SHEATH JETS VIA THE KINETIC KELVIN-HELMHOLTZ INSTABILITY

We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas we find generation of strong large-scale DC currents and magnetic fields which extend over the entire shear-surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates transverse structure similar to that produced by the Weibel instability.

Generation of Reference DC Currents at 1 nA Level With the Capacitance-Charging Method

The capacitance-charging method is a well-established and handy technique for the generation of dc current in the 100 pA range or lower. This method involves a capacitance standard and a sampling voltmeter, highly stable devices easy to calibrate, and it is robust and insensitive to the voltage burden of the instrument being calibrated. In this paper, we propose a range extender amplifier, which can be employed as a plug-in component in existing calibration setups, and allows the generation of currents in the 1 nA range. The extender has been employed in the Istituto Nazionale di Ricerca Metrologica setup and validated with two comparisons at 100 pA and 1 nA current levels. The calibration accuracy achieved on a top-class instrument is 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> at 1 nA.

Dirac fermion time-Floquet crystal: Manipulating Dirac points

We demonstrate how to control the spectra and current flow of Dirac electrons in both a graphene sheet and a topological insulator by applying either two linearly polarized laser fields with frequencies $\omega$ and $2\omega$ or a monochromatic (one-frequency) laser field together with a spatially periodic static potential(graphene/TI superlattice). Using the Floquet theory and the resonance approximation, we show that a Dirac point in the electron spectrum can be split into several Dirac points whose relative location in momentum space can be efficiently manipulated by changing the characteristics of the laser fields. In addition, the laser-field controlled Dirac fermion band structure -- Dirac fermion time-Floquet crystal -- allows the manipulation of the electron currents in graphene and topological insulators. Furthermore, the generation of dc currents of desirable intensity in a chosen direction occurs when applying the bi-harmonic laser field which can provide a straightforward experimental test of the predicted phenomena.

Low-voltage, wide-range, current-controlled DC current generator

Operating from a 1 V rail supply, a proposed CMOS current-controlled DC current generator can function as a repeater, attenuator or amplifier over the input current range, 1 µA to 1 mA, with a current-transfer ratio accuracy better than 1% using IBM technology, characterised by a process with a 0.13 µm minimum feature size. In repeater mode, the incremental output resistance exceeds 30 MΩ for an output current of 500 µA at an output voltage of 0.20 V, and exceeds 1 MΩ for an output current of 1 mA at an output voltage of 0.22 V. For zero input current, the circuit dissipation is 117 µW.

Design of Antenna with a Solar Cell as a Parasitic Element in the UHF RFID Tag

This paper presents a novel RFID antenna which makes solar cell and tag antenna combine as an integrated unit. The solar cell is used as a parasitic element in a tag antenna. The original feature of a solar cell (DC current generation) remains, and the solar cell which can supply the energy to activate the IC is now used as a parasitic patch at the same time. Besides a general description of solar cell antenna, the size and the simulated results of the antenna are also shown.

Generation of DC currents by ICRF near fields in the Scrape-off Layer

DC currents flowing along magnetic field lines connected to powered ICRF antennas have been observed experimentally. Negative current is collected on the powered ICRF antenna structure, while positive current is collected by magnetically connected Langmuir probes. Models based upon a double probe configuration are tested with the 2D electrostatic PIC code OOPIC and the 2D fluid code SEM. These models can be excited in a symmetrical (two electrode in antiphase) or an asymmetrical way (one electrode). Transverse RF currents can be exchanged with surrounding flux tubes. Simulations show that only “asymmetric” drive can draw net DC currents. As in experiments, they are negative on the “driven” electrode and positive on the grounded one. An electrostatic and low frequency analytical model explains how DC current is produced. The perpendicular width of current structures L⊥ depends on the parallel length L//.

New Capability for Generating and Measuring Small DC Currents at NPL

This paper describes two systems recently developed at the National Physical Laboratory (NPL), Teddington, U.K., for the generation and measurement of dc currents in the range 100 fA to 1 nA. Both systems are based on the capacitor charging technique. One system generates known currents, and constitutes a new reference at NPL. The other was designed to meet the traceability requirements of the Ionizing Radiation sections of NPL and combines commercially available instrumentation and standards to produce a reliable stand-alone system for measuring small currents

Photocurrent, rectification, and magnetic field symmetry of induced current through quantum dots.

We report mesoscopic dc current generation in an open chaotic quantum dot with ac excitation applied to one of the shape-defining gates. For excitation frequencies large compared to the inverse dwell time of electrons in the dot (i.e., GHz), we find mesoscopic fluctuations of induced current that are fully asymmetric in the applied perpendicular magnetic field, as predicted by recent theory. Conductance, measured simultaneously, is found to be symmetric in field. In the adiabatic (i.e., MHz) regime, in contrast, the induced current is always symmetric in field, suggesting its origin is mesoscopic rectification.

Dynamical mechanisms of dc current generation in driven Hamiltonian systems.

Recent symmetry considerations [Flach et al., Phys. Rev. Lett. 84, 2358 (2000)] have shown that dc currents may be generated in the stochastic layer of a system describing the motion of a particle in a one-dimensional potential in the presence of an ac time-periodic drive. In this paper we explain the dynamical origin of this current. We show that the dc current is induced by the presence and desymmetrization of ballistic channels inside the stochastic layer. The existence of these channels is due to resonance islands with nonzero winding numbers. The characterization of the flight dynamics inside ballistic channels is described by distribution functions. We obtain these distribution functions numerically and find very good agreement with simulation data.

Order parameter phase sensitive experiments and SDJ dc SQUIDs

Spontaneous generation of persistent dc currents is one of the most striking aspects of the physics of superconducting samples in a frustrated geometry. Trapped vortices, however, are also sources of induced persistent circulating dc currents. In practice, usually, it is very difficult to establish which of the two is the real source of the observed persistent circulating dc currents and their only presence without additional and, very often, complicated approaches cannot serve as an unambiguous demonstration of frustration in a specific geometry. Recently, spontaneous generation of circulating ac currents in a frustrated geometry has been predicted. Experimentally observed in spatially distributed junctions dc SQUIDs, the effect cannot be reproduced by trapped vortices in the SQUID. Consequently, detection of spontaneous circulating ac currents is a straightforward demonstration of frustration in a given superconducting configuration. For that reason this effect can serve as an excellent tool to be used in order parameter phase sensitive experiments to determine the pairing symmetry of high transition temperature superconductors.

Spontaneous dc Current Generation in a Resistively Shunted Semiconductor Superlattice Driven by a Terahertz Field

We study a resistively shunted semiconductor superlattice subject to a high-frequency electric field. Using a balance equation approach that incorporates the influence of the electric circuit, we determine numerically a range of amplitude and frequency of the ac field for which a dc bias and current are generated spontaneously and show that this region is likely accessible to current experiments. Our simulations reveal that the Bloch frequency corresponding to the spontaneous dc bias is approximately an integer multiple of the ac field frequency.

Tracking real characteristics by multiple-point autocalibration and the tangent method applied to ideal characteristics

The measurement system transfer characteristic is an unsteady, nonlinear function that depends upon time and ambient conditions. The article presents a method of tracking the real characteristic by using periodic autocalibration of the real characteristic and by applying a tangent method to the ideal characteristic. The efficiency of the algorithm has been verified for dc current generation. Periodic autocalibration fixes the current state of the measurement system characteristic by measuring internal references. The correction of a quantity at the input of the current generator is calculated from measurement of its output quantity and by using a tangent method applied to the ideal current generator characteristic.