Shadow effects on a series-parallel array of solar cells
Shadow effects on series-parallel array of solar cells
SHADOW↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Determination of flow areas for series-parallel compartment venting to satisfy pressure differential requirements.
A unique method for solving the design problem of determining the areas required to meet an imposed pressure differential limit is presented. The associated analytical technique for determining the transient pressure differentials in a multicompartment series-parallel connected system is also presented. In an effort to verify the results obtained by using the analytical methods presented, a test was conducted using a seven compartment system. It was found in the investigations that a computer program based on the analytical model described can determine the pressure, temperature, pressure differentials, and mass flow rates into and out of each compartment at subsonic or sonic velocities.
Kirby, C. E.↗
Series-parallel method of direct solar array regulation
A 40 watt experimental solar array was directly regulated by shorting out appropriate combinations of series and parallel segments of a solar array. Regulation switches were employed to control the array at various set-point voltages between 25 and 40 volts. Regulation to within + or - 0.5 volt was obtained over a range of solar array temperatures and illumination levels as an active load was varied from open circuit to maximum available power. A fourfold reduction in regulation switch power dissipation was achieved with series-parallel regulation as compared to the usual series-only switching for direct solar array regulation.
Gooder, S. T.↗
Theoretical gain in reliability by means of series-parallel and parallel-series standby redundancy
Reliability optimization of series, parallel, and combined redundancy systems
Leontev, L. P.↗
Impact of Different Thermal Gradients on the Dynamics of Cylindrical Lithium-ion Cells Subject to Accelerated Aging and on Module Performance
This study investigates the impacts of applying different thermal gradient patterns to cylindrical lithium-ion cells in a module on cell dynamics (temperatures, current flows, state of charge), module performance (evolution of resistance, capacity, and energy versus cycle number), and module lifetime. The thermal gradients were generated using cooling plates (CPs) with three different flow-field designs, namely, straight, perpendicular, and U-turn. The study uses computational fluid dynamics (CFD), the pseudo-two-dimensional (P2D) battery model, capacity loss and increased impedance due to the growth of a solid-electrolyte-interphase, and the electric current distribution from module terminals to cells that depends on the series-parallel electrical connections among the cells. The impact of the thermal gradient (resulting from the CP designs) on the variability in resistance, current, state of charge, and voltage among the cells was analyzed and linked to differences in the module's performance. Applying a thermal gradient to parallel-connected strings of series-connected cells led to variation in the current through each parallel string and an imbalance in the voltage of series-connected cells. Module performance is poorer when the thermal gradient causes a voltage imbalance than when it causes a current imbalance. Module performance becomes the worst when both current variation and voltage imbalance happen together. For instance, the module's lifetime (estimated as reaching 80% of its initial capacity) varied by 5% to 17.5%, depending on the magnitude and pattern of the imposed thermal gradient. As the relative orientation between thermal gradients and cells' electrical connectivity influences the module's performance, appropriate consideration should be given to the choice of the CP, especially if large thermal gradients are allowed.
Battery thermal management↗
Impact of Module Configuration on Lithium-Ion Battery Performance and Degradation: Part I. Energy Throughput, Voltage Spread, and Current Distribution
Batteries are commonly connected in series and parallel to create modules that fulfill the power and energy requirements of specific applications. However, conclusions about battery performance and degradation under different conditions, as well as predictive models, are often derived from single cell cycling results. In this study, we evaluate the performance of six different series-parallel configurations of commercial lithium nickel manganese cobalt cells over hundreds of cycles. Each cell within the modules was individually instrumented for voltage, current, and temperature monitoring. We quantified the impact of module configuration on overall energy throughput, the voltage spread among series-connected cells, and the current heterogeneity in parallel-connected cells. This module cycling study, one of the broadest reported to date, supports systematic evaluation of the performance trade-offs, pack penalty, and safety implications of different module configurations.
25 ENERGY STORAGE↗
The Schwaigerian driver transfer technique and the Thevenin's and the Norton's theorem Final report
Graphical technique for analyzing series-parallel networks by rectangular diagrams in solving power distribution problems
Ding, J. L.↗
Redundancy optimization for series k-out-of-n systems
Redundancy optimization for series-parallel systems and serially connected k-out-of-n type subsystems, with cost constraints and reliability considerations
Bien, D. D.↗
Redundancy optimization for series k-out-of-n systems
Redundancy optimization of series-parallel k-out-of-n systems for maximum reliability subject to multiple cost constraints
Bien, D. D.↗
The revised solar array synthesis computer program
The Revised Solar Array Synthesis Computer Program is described. It is a general-purpose program which computes solar array output characteristics while accounting for the effects of temperature, incidence angle, charged-particle irradiation, and other degradation effects on various solar array configurations in either circular or elliptical orbits. Array configurations may consist of up to 75 solar cell panels arranged in any series-parallel combination not exceeding three series-connected panels in a parallel string and no more than 25 parallel strings in an array. Up to 100 separate solar array current-voltage characteristics, corresponding to 100 equal-time increments during the sunlight illuminated portion of an orbit or any 100 user-specified combinations of incidence angle and temperature, can be computed and printed out during one complete computer execution. Individual panel incidence angles may be computed and printed out at the user's option.
Source record↗
Optimum allocation of redundancy among subsystems connected in series
This analysis considers the optimum allocation of redundancy in a system of serially connected subsystems in which each subsystem is of the k-out-of-n type. Redundancy is optimally allocated when: (1) reliability is maximized for given costs; or (2) costs are minimized for given reliability. Several techniques are presented for achieving optimum allocation and their relative merits are discussed. Approximate solutions in closed form were attainable only for the special case of series-parallel systems and the efficacy of these approximations is discussed.
Bien, D. D.↗
A programmable power processor for a 25 kW power module
The paper presents the concept and major design problems of a programmable power processor for the 25 kW electrical power system for the Shuttle Orbiter. The load will be handled by three parallel power stages operated in phase sequence with each power transistor having its own commutating diode and filter inductor. The power stages will be run at a fixed frequency of 10 kHz with the 'on'-time variable up to 100%. The input filter bank in the breadboard programmable power processor is planned to be a series-parallel combination of tantalum cased tantalum wet-slug capacitors.
Kapustka, R. E.↗
The Solarex Block IV module
Several innovative concepts were introduced for the Block IV contract. Semicrystalline silicon manufactured by SEMIX Inc. is the basic cell material. A front metallization pattern combined with a wraparound-style interconnect and in-plane stress relief combine to provide a new method to reliably accomplish series-paralleling. Laminated modules using Ethylene Vinyl Acetate (EVA) as the encapsulant were manufactured for the first time.
Hoelscher, J. F.↗
Study of multi-kilowatt solar arrays for Earth orbit applications
A miniaturized Cassegrainian concentrator (MCC) solar array concept is being developed with the objective of significantly reducing the recurring cost of multikilowatt solar arrays. The desired cost reduction is obtained as a result of using very small high efficiency solar cells in conjuction with low cost optics. The MCC single element concept incident slar radiation is reflected rom a primary parabolic reflector to a secondary hyperbolic reflector and finally to a 4 millimeter diameter solar cell. A light catcher cone is used to improve off axis performance. The solar cell is mounted to a heat fin. An element is approximately 13 millimeters thick which permits efficient launch stowage of the concentrator system panels without complex optical component deployments or retractions. The MCC elements are packed in bays within graphite epoxy frames and are electrically connected into appropriate series-parallel circuits. A MCC sngle element with a 21 sq cm entrance aperture and a 20 efficient, 0.25 sq cm gallium arsenide solar cell has the same power output as 30 sq cm of 11-percent efficiency (at 68 C) silicon solar cells.
Patterson, R. E.↗
Source-circuit design overview
The source circuit is the fundamental electrical building block of a large central-station array; it consists of a series-parallel network of solar cells that develops full system voltage. The array field is generally made up of a large number of parallel source circuits. Source-circuit electrical configuration is driven by a number of design considerations, which must be considered simultaneously. Array fault tolerance and hot spot heating endurance are examined in detail.
Ross, R. G., Jr.↗
Fracture behavior in silicon
The fracture mechanics of crystalline Si are reviewed, together with known techniques for minimizing the occurences of fracture and/or their effects. The fracture toughness (Kic) of Si varies only 10 percent from cell-to-cell and standard values have been established for different types of crystalline Si cells. A critical flaw size of 10-100 microns has been identified, and also pertains to polycrystalline materials. Chemical polishing is known to double the value of Kic, while edge rounding has no effect. Internal stresses, particularly those caused during ribbon growth, do not exceed 10 percent of Kic. External stresses are imposed by the module hardware and the ambient environment. Multiple contacts reduce the effects of cell fracture and series-parallel wiring in modules in arrays ameliorates the effects of single-cell failures. During manufacturing, maintenance of quality control and removal of sheets displaying aberrations can, depending on the costs and the implementation of the array reliability features, result in arrays delivering any desired level of reliability.
Leipold, M. H.↗
Design, performance investigation and delivery of a miniaturized Cassegrainian concentrator solar array
A miniaturized Cassegrainian concentrator (MCC) solar array concept is being developed with the objective of significantly reducing the recurring cost of multikilowatt solar arrays. The desired cost reduction is obtained as a result of using very small high efficiency solar cells in conjunction with low-cost optics. In the MCC single element concept and panel concept, incident solar radiation is reflected from a primary parabolic reflector to a secondary hyperbolic reflector and finally to a 4-millimetr diameter solar cell. A light catcher cone is used to improve off-axis performance. An element is approximately 13-millimeters thick which permits efficient launch stowage of the concentrator system panels without complex optical component deployments or retractions. The MCC elements are packed in bays within graphite epoxy frames and are electrically connected into appropriate series-parallel circuits. A MCC single element with a 21 sq cm entrance aperture and a 20 percent efficient, 0.25 sq cm gallium arsenide solar cell has the same power output as 30-sq cm of 11-percent efficiency (at 68 C) silicon solar cells. The MCC concept provides the potential for a significant reduction in array cost due to a 99 percent reduction in required cell area and a 30 percent reduction in array area relative to planar array of equivalent power.
Patterson, R. E.↗
Circuit analysis method for thin-film solar cell modules
The design of a thin-film solar cell module is dependent on the probability of occurrence of pinhole shunt defects. Using known or assumed defect density data, dichotomous population statistics can be used to calculate the number of defects expected in a module. Probability theory is then used to assign the defective cells to individual strings in a selected series-parallel circuit design. Iterative numerical calculation is used to calcuate I-V curves using cell test values or assumed defective cell values as inputs. Good and shunted cell I-V curves are added to determine the module output power and I-V curve. Different levels of shunt resistance can be selected to model different defect levels.
Burger, D. R.↗