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DOE OSTI2026

Electrochemical Modeling of PID Leakage Current of PV Modules: Steady-State Current, Transient Current, and RC-Equivalent Circuit

Potential-induced degradation (PID) remains a significant reliability concern for photovoltaic (PV) modules, arising when a voltage difference between the module frame and the solar cells drives unintended leakage current through the glass-encapsulant stack. Although PID ultimately manifests as PID-s, PID-p, or PID-c, the underlying behavior of the leakage current-its magnitude and time dependence-requires clearer electrochemical interpretation. Traditional explanations attribute the initial transient current to bulk capacitive elements of the glass, encapsulant, and antireflection coatings, and the steady-state current according to their effective ohmic resistance. More recent studies, however, indicate that electrochemical charge-transfer processes at the encapsulant-metallization interface can play a dominant role in defining the leakage-current path. This paper develops a unified electrochemical framework for modeling PID leakage current. First, an RC-equivalent circuit is formulated by combining conventional RC elements with a Randles-type interface to capture transient leakage current through double-layer capacitance and faradaic processes at ionic-electronic boundaries. Second, the steady-state current-voltage behavior is explained using a linearized Butler-Volmer relationship, showing that the measured ohmic response corresponds to the low-overpotential limit of charge-transfer kinetics. Analytical results demonstrate that, for typical module materials-3.2-mm soda-lime glass and 0.45-mm encapsulant-the dominant modulators to PID leakage current are the glass surface resistance (under dry-surface conditions), the glass bulk capacitance, and the encapsulant resistance (under wet-surface conditions), with soda lime glass surface and EVA/POE encapsulant resistances primarily governing steady-state current. The proposed electrochemical model is validated against measured leakage-current data, showing good agreement in both the magnitude and the time-dependent evolution of PID leakage current.

14 SOLAR ENERGY↗

NASA NTRS2010

ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and its Implication to the Cross-Polar Cap Pedersen Currents

In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar windmagnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approximately 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

Le, Guan↗

NASA NTRS2011

ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and Its Implication to the Cross-Polar Cap Pedersen Currents

In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of ~ 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

Le, Guan↗

DOE OSTI2025

High tensile alloy of copper to mitigate current collector deformation in silicon electrodes for lithium-ion batteries

The volumetric changes of silicon electrodes, along with the strong adhesive properties of certain binders, can lead to plastic deformation of the current collector and create damage in the electrode coating. Here, in this study, we report a detailed study of silicon coatings on a high-tensile alloy (HTA) foil of copper with strength over twice that of conventional copper foils. The HTA current collectors with high mechanical strength can mitigate plastic deformation upon continuous cycling. At moderate areal capacities (2.5–3 mAh cm −2 ), conventional copper foils show significant wrinkling after only a few electrochemical cycles, whereas the HTA foils remain intact. We demonstrate viability of the HTA foils in large format xx6395 pouch cells, in which the HTA current collectors remain intact even at an areal capacity of 4.5 mAh cm −2 ; in contrast, wrinkles form in conventional copper current collectors increasing the likelihood of lithium plating. Computational studies show that stresses generated during cycling of silicon electrodes are very high in the current collector and at the current collector-coating interface, explaining the wrinkling of conventional Cu foils. Our studies highlight importance of current collector to solve the electrochemical and chemo-mechanical performance challenges associated with high-loading silicon electrodes.

Chemo-mechanical degradation↗

DOE OSTI2025

Kinetics Measurements in Resistive Electrolytes Using Ring-Disk Electrode: Ring as Current “Shield” Enables Uniform Disk Current Distribution

Rotating disk electrodes are commonly used for electrochemical kinetics measurements. A major disadvantage of these types of electrodes is their nonuniform secondary current distribution, especially when performing electroanalytical measurements in resistive electrolytes. Such nonuniform current distribution can render the values of kinetics constants extracted from the disk electrode to be highly inaccurate. Furthermore, one emerging class of electrolytes that suffer from low ionic conductivities is deep eutectic solvents (DES). DES are a promising class of electrolytes for various emerging applications; however, due to their resistive nature, the secondary current distribution when using them is typically highly nonuniform. For example, the Wagner number when measuring Cu²⁺/Cu⁺ kinetics in choline chloride–ethylene glycol DES (1:4 molar ratio of ChCl:EG) is very low (<0.1), indicating highly nonuniform current distribution over the disk electrode. We show here that the Cu²⁺/Cu⁺ exchange current density measured using disk electrodes is very inaccurate due to the aforementioned nonuniform current distribution. To obtain uniform disk current distribution, we employ here a coplanar concentric rotating ring-disk electrode (RRDE), where the ring serves the function of a current “shield.” Specifically, we show using modeling that the ring minimizes the current distribution nonuniformity at the disk by effectively shielding the disk against current spikes near the disk edge. This enables improved precision in electrode kinetics measurements for the Cu²⁺/Cu⁺ couple in resistive DES. To enable broad applicability of this technique, an analytical expression based on the Wagner number is integrated into an iterative algorithm to help users identify ring conditions to achieve uniform current distribution and thus improved electroanalytics at the disk.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2002

Current-Produced Magnetic Field Effects on Current Collection

Current collection by an infinitely long, conducting cylinder in a magnetized plasma, taking into account the magnetic field of the collected current, is discussed. A region of closed magnetic surfaces disconnects the cylinder from infinity. Due to this, the collected current depends on the ratio between this region and the plasma sheath region and, under some conditions, current reduction arises. The current collection along a realistic "bare wire" space tether is considered. A number of factors are taken into account, including the resistance of the wire and shielding resulting from the current-induced magnetic field produced by current flow in the tether. The plasma density, tether length and radius, the geomagnetic field strength and angle to the orbital velocity vector were all used as parameters in the study. It is shown that magnetic shielding for certain tether system configurations, when combined with particular values of the governing parameters, significantly reduces the collected current. Specifically, it is shown that an electrodynamic tether in the "thruster" mode suffers greater reduction from magnetic shielding than a tether with the same characteristics deployed in the "generator" mode. We find that, for both modes, current-induced magnetic shielding becomes more significant as plasma density and wire radius increase. The same is true for the dependence on the angle of the geomagnetic field to the orbital velocity vector and the motion-induced electric field for the generator mode For the thruster mode, the effect is larger for smaller angles. In both operating modes, the shielding is more important for smaller angles between the tether and magnetic field. In addition to the above dependencies, the effect for the thruster mode essentially depends on the tether length. In general, any parametric change that increases tether current, relative to the strength of the electric field between the tether and the ambient plasma, will increase the shielding effect (thereby reducing overall tether current compared to the case without considering these effects). The effect of the induced magnetic shielding can be significant in some cases.

Khazanov, George V.↗

NASA NTRS2008

ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and its Implication to Ionospheric Closure Currents

A major unsolved question in the physics of ionosphere-magnetosphere coupling is how field-aligned currents (FACs) close. In order to maintain the divergence free condition, overall downward FACs (carried mainly by upward electrons) must eventually balance the overall upward FACs associated with the precipitating electrons through ionospheric Pedersen currents. Although much of the current closure may take place via local Pedersen currents flowing between Region 1 (R1) and Region 2 (R2) FACs, there is a generally an imbalance, i.e., more currents in R1 than in R2, in total currents between them. The net currents may be closed within R1 via cross-polar cap Pedersen currents. In this study, we use the magnetic field observations from Space Technology 5 mission to quantify the imbalance of R1 and R2 currents. We will determine the net R1-R2 currents under various solar wind conditions and discuss the implication of such imbalance to the ionospheric closure currents.

Le, G.↗

NASA NTRS2006

Lightning Return-Stroke Current Waveforms Aloft, from Measured Field Change, Current, and Channel Geometry

Three-dimensional reconstructions of six rocket-triggered lightning channels are derived from stereo photographs. These reconstructed channels are used to infer the behavior of the current in return strokes above the ground from current waveforms measured at the channel base and electric-field-change waveforms measured at a range of 5.2 kilometers for 24 return strokes in these channels. Streak photographs of 14 of the same strokes are analyzed to determine the rise times, propagation speeds, and amplitudes of relative light intensity for comparison with the electrical inferences. Results include the following: 1) The fine structure of the field-change waveforms that were radiated by these subsequent return strokes can be explained, in large part, by channel geometry. 2) The average 10 - 90% rise time of the stroke current increased by about a factor of seven in our sample, from an observed 0.31 plus or minus 0.17 microseconds at the surface to an inferred 2.2 plus or minus 0.5 microcseconds at 1 kilometer path length above the surface. 3) The three-dimensional propagation speed of the current front averaged 1.80 plus or minus 0.24 X 10(exp 8) meters per second over channel lengths typically greater than 1 kilometer. 4) Assuming that the measured current was entirely due to the return stroke forced an unreasonably large and abrupt reduction in inferred current amplitude over the first few tens of meters above the surface, especially in cases when the leader was bright relative to its stroke. Therefore, a significant fraction of the current at the surface was probably due to the leader, at least in such cases. 5) Peak return-stroke currents decreased by approximately 37 plus or minus 12% from 100 meters to 1 kilometer of path length above the surface. Because of uncertainty about how to partition the measured current between leader and return stroke, we are unable to infer the variation of current amplitude near the ground.

Willett, J. C.↗

DOE OSTI2025

Uniform secondary current distribution at disk electrodes under Tafel kinetics enabled by concentric current-shielding rings

Non-uniform secondary current distribution at rotating disk electrodes (RDE) is a common problem when using resistive electrolyte media or large applied currents. In a recent publication, we have shown that auxiliary electrodes such as the ring of a rotating ring disk electrode (RRDE) can help suppress current non-uniformities at the disk enabling reliable electroanalytical measurements. However, this previous work considered linear kinetics where current distribution non-uniformities were moderate. In the present contribution, we consider current distribution non-uniformities encountered under Tafel kinetics. We show, for the case of 2,5-dihydroxy-1,4-benzoquinone (DHBQ) reduction, that optimally chosen ring conditions serve to provide effective shielding at the disk edge rendering the overall disk current distribution to be uniform. Numerical modeling and scaling analysis (using the Wagner number) are presented to aid a user in determining the optimal ring current density for achieving uniform disk current distribution under Tafel kinetics. This approach is especially useful when studying soluble-soluble redox transitions for which, unlike deposit distribution in electrodeposition, the current distribution non-uniformity is not visually apparent.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Current ramp-up studies for NSTX-U in support of the development of non-inductive current ramp-up scenarios in STs

The Spherical Tokamak (ST) is a low-aspect-ratio tokamak projected to enable simultaneous operation at high normalized toroidal beta and high bootstrap current fraction. However, a compact ST reactor cannot be built with a full-sized solenoid. The remaining current required for sustained operation must be ramped up non-inductively. Sustained 100% non-inductive current drive at the MA level has not yet been demonstrated on an ST. Non-inductive current ramp-up is therefore a more challenging objective that the NSTX-U research program aims to address. In support of this development, free-boundary TRANSP simulations have been used to develop a current ramp-up scenario in which a significant fraction of the current is driven non-inductively by a combination of neutral-beam and bootstrap current drive. The resulting discharge has properties favorable for non-inductive current drive, such as a low normalized internal plasma inductance of approximately 0.45, a minimum safety factor exceeding 2, and a slightly reversed-shear q-profile. In these discharges, the plasma current ramps to 900 kA within 250 ms in an L-mode configuration, with varying electron density and density profiles. These discharges should be suitable for next-step NSTX-U experiments aimed at generating a robust L-mode fiducial scenario with low central solenoid flux consumption, which could be progressively improved as new NSTX-U experimental discharges are developed.

Raman, Roger [Univ. of Washington, Seattle, WA (Un↗

NASA NTRS2005

Dynamic Harris current sheet thickness from Cluster current density and plasma measurements

We use the first accurate measurements of current densities in the plasma sheet to calculate the half-thickness and position of the current sheet as a function of time. Our technique assumes a Harris current sheet model, which is parameterized by lobe magnetic field B(o), current sheet half-thickness h, and current sheet position z(sub o). Cluster measurements of magnetic field, current density, and plasma pressure are used to infer the three parameters as a function of time. We find that most long timescale (6-12 hours) current sheet crossings observed by Cluster cannot be described by a static Harris current sheet with a single set of parameters B(sub o), h, and z(sub o). Noting the presence of high-frequency fluctuations that appear to be superimposed on lower frequency variations, we average over running 6-min intervals and use the smoothed data to infer the parameters h(t) and z(sub o)(t), constrained by the pressure balance lobe magnetic field B(sub o)(t). Whereas this approach has been used in previous studies, the spatial gnuhen& now provided by the Cluster magnetometers were unavailable or not well constrained in earlier studies. We place the calculated hdf&cknessa in a magnetospheric context by examining the change in thickness with substorm phase for three case study events and 21 events in a superposed epoch analysis. We find that the inferred half-thickness in many cases reflects the nominal changes experienced by the plasma sheet during substorms (i.e., thinning during growth phase, thickening following substorm onset). We conclude with an analysis of the relative contribution of (Delta)B(sub z)/(Delta)X to the cross-tail current density during substorms. We find that (Delta)B(sub z)/(Delta)X can contribute a significant portion of the cross-tail c m n t around substorm onset.

Thompson, S. M.↗

NASA NTRS2015

Effect of Interhemispheric Field-Aligned Currents on Region-1 Currents

An asymmetry in ionospheric conductivity between two hemispheres results in the formation of additional, interhemispheric field-aligned currents flowing between conjugate ionospheres within two auroral zones. These interhemispheric currents are especially significant during summer-winter conditions when there is a significant asymmetry in ionospheric conductivity in two hemispheres. In such conditions, these currents may be comparable in magnitude with the Region 1 field-aligned currents. In this case, the R1 current is the sum of two FACs: one is going from to the solar wind, and another is flowing between conjugate ionospheres. These interhemispheric currents can also cause the formation of auroras extended along the nightside polar cap boundary, which may be related to the so-called double auroral oval. In this study, we present the results of analytical and numerical solutions for the interhemispheric currents and their effect on the Region 1 currents.

interhemispherical currents↗

NASA NTRS1978

Currents and electric fields in the ionosphere due to field-aligned auroral currents

Birkeland (1908, 1913) did a detailed analysis of the upper atmospheric current system in the high-latitude region, and suggested that field-aligned currents flowing into and out of the auroral ionosphere were the driving mechanism for this current system. In the present paper, static electric field and current patterns due to the field-aligned Birkeland currents are examined, using a model in which currents approximating those reported by Iijima and Potemra (1976) are used as input to a global model of the ionospheric conductivities, in which interhemispheric coupling along field lines is included. The model reproduces the main features of the high-latitude current and voltage system and the penetration of these currents within the plasmasphere.

Nisbet, J. S.↗

NASA NTRS1984

Current carriers for the field-aligned current system

The Dynamics Explorer satellites have returned a large body of data containing high resolution magnetometer measurements and distributions of charged particles of all but thermal electrons. From these data the relations of the field aligned currents to particle precipitation structures were investigated and the charge carriers were identified. Results include the following: (1) during very quiet periods, field aligned currents exist primarily as fine structure; (2) during onset of substorms, region 1 and region 2 become clearly evident but contain significant structure; (3) as magnetic activity subsides, current regions become less distinct, and structure becomes more dominant; (4) the distribution of the upward currents derived from magnetometer data and calculated from suprathermal electron data agree remarkably well in shape but not necessarily in magnitude; (5) at all local times, 5 eV electrons seldom carry most of the upward current; (6) except for the accelerated inverted-V electrons, the dominant upward current carriers which are measured are below 500 eV and are distributed in energy; (7) dusk upward currents (region 1) are associated with the boundary plasma sheet; and (8) suprathermal electron bursts are important current carrying structures.

Hoffman, R. A.↗

NASA NTRS1985

Current carriers for the field-aligned current system

The Dynamics Explorer satellites have returned a large body of data containing high resolution magnetometer measurements and distributions of charged particles of all but thermal electrons. From these data the relations of the field aligned currents to particle precipitation structures were investigated and the charge carriers were identified. Results include the following: (1) during very quiet periods, field aligned currents exist primarily as fine structure; (2) during onset of substorms, region 1 and region 2 become clearly evident but contain significant structure; (3) as magnetic activity subsides, current regions become less distinct, and structure becomes more dominant; (4) the distribution of the upward currents derived from magnetometer data and calculated from suprathermal electron data agree remarkably well in shape but not necessarily in magnitude; (5) at all local times, 5 eV electrons seldom carry most of the upward current; (6) except for the accelerated inverted-V electrons, the dominant upward current carriers which are masured are below 500 eV and are distributed in energy; (7) dusk upward currents (region 1) are associated with the boundary plasma sheet; and (8) suprathermal electron bursts are important current carrying structures.

Hoffman, R. A.↗

NASA NTRS1994

Cross-tail current, field-aligned current, and B(y)

Orbits of individual charged particles were traced in a one-dimensional magnetic field model that included a uniform cross-tail component B(sub yo). The effects of B(sub yo) on the cross-tail current distribution j(sub y)(z), the average cross-tail drift velocity(nu(sub y)z), and the average pitch angle change(delta alpha) experienced during current sheet encounters were calculated. The addition of a B(sub yo) that exceeded several tenths of one nanotesla completely eliminated all resonance effects for odd-N orbits. An odd-N resonance involves ions that enter and exit the current sheet on the same side. Pitch angles of nearly all such ions changed substantially during a typical current sheet interaction, and there was no region of large cross-tail drift velocity in the presence of a modest B(sub yo). the addition of a very large B(sub yo) guide field in the direction that enhances the natural drift produces a large j(y) and small (Delta alpha) for ions with all energies. The addition of a modest B(sub yo) had less effect near even-N resonances. In this case, ions in a small energy range were found to undergo so little change in pitch angle that particles which originated in the ionosphere would pass through the current sheet and return to the conjugate ionosphere. Finally, the cross-tail drift of ions from regions dominated by stochastic orbits to regions dominated by either resonant or guiding center orbits was considered. The ion drift speed changed substantially during such transitions. The accompanying electrons obey the guiding center equations, so electron drift is more uniform. Any difference between gradients in the fluxes associated with electron and ion drifts requires the presence of a Birkeland current in order to maintain charge neutrality. This plasma sheet region therefore serves as a current generator. The analysis predicts that the resulting Birkeland current connects to the lowest altitude equatorial regions in which ions drift to or from a point at which stochastic orbits predominate. The proposed mechanism appears only in analyses that include non-guiding-center effects.

Kaufmann, Richard L.↗

NASA NTRS2000

Current-Produced Magnetic Field Effects on Current Collection

Khazanov, G. V.↗

NASA NTRS2000

Current-Produced Magnetic Field Effects on Current Collection

Khazanov, G. V.↗