Showing papers on "Photovoltaic system published in 1992"

Photorefractive systems and methods

Abstract: A new type of holographic recording in photorefractive crystals is disclosed, termed orthogonal data storage, in which counterpropagating, reflection mode holograms are wavelength multiplexed to form gratings lying along a common axis. It is shown that this configuration provides substantial improvements in data storage capacity in comparison to prior art systems and that higher coupling coefficients are achieved. In consequence, not only storage of data but a wide range of other devices including wavelength selective filters, lenses and optical correlation systems are disclosed. Further, methods of writing and processing metastable images are disclosed which substantially improve the strength of the gratings that are permanently developed in the medium. These methods include advantageous use of electrical potentials and photovoltaic properties, together with different interrelationships during processing.

Self-tuning control of a solar power plant with a distributed collector field

Abstract: A self-tuning proportional-integral controller for a solar distributed collector field that is based on a pole-assignment approach employing serial compensation to cope with measurable external disturbances is presented. The scheme is compared with the more commonly adopted parallel feedforward approach by both simulation and implementation on the plant itself. >

Photovoltaic solar water heating system

Abstract: A system for heating water using solar energy comprises a photovoltaic array, a water heater comprising a variable resistive load, and a controller for varying either the load characteristics of the resistive load or the power generating characteristics of the photovoltaic array, or both, to ensure maximum power transfer efficiency.

A rule-based fuzzy logic controller for a PWM inverter in photo-voltaic energy conversion scheme

Abstract: A rule-based controller based on fuzzy set theory for controlling the output power of a pulse width modulation (PWM) inverter in a photovoltaic (PV) energy conversion interface scheme is presented. The objective is to track and extract the maximum available solar power from the PV array under varying solar insolation levels. To achieve this the power error and the rate of change of this error are used as input signals to the fuzzy rule-based controller and its output signal is used to control the PWM inverter. The input error signals are fuzzified and expressed as linguistic labels characterized by their membership grades. Using a fuzzy relation matrix, a set of 49 rules find fuzzy logic operations, the controller output is obtained. The fuzzy controller output expressed in linguistic labels is defuzzified to obtain the actual analog signal to control the PWM inverter. The proposed fuzzy rule-based controller is simulated and experimentally verified, and is found to give good power tracking performance. >

45% efficient silicon photovoltaic cell under monochromatic light

Abstract: Improvements in the performance of silicon photovoltaic cells for solar applications are adapted for nonsolar photovoltaic applications. Improved monochromatic light efficiencies above 45% are reported including efficiencies close to 40% for relatively long-wavelength (1.064 mu m) light as produced by neodymium-doped yttrium-aluminum garnet (Nd:YAG) lasers. >

Low temperature solar-to-electric power conversion system

Abstract: The apparatus is a low-temperature solar to electric power conversion system. A solar collector directs solar insolation to a cavity receiver which heats primary thermal transport fluid to approximately 700° F. An auxiliary fossil or biomass heater may be used to replace or supplement the solar-powered cavity receiver. The primary thermal transport fluid is provided to a Stirling engine which provides electric power and hot water heated to approximately 160° F.

Control circuit for a solar-powered rechargeable power source and load

Abstract: An inexpensive circuit for controlling the recharging of a rechargeable power source by a photovoltaic panel is used for powering a load such as the lamp of a walk light Using a minimum number of components, the circuit can charge a rechargeable battery anytime sunlight is sufficient to place a potential across the battery that is greater than the present potential of the battery, can sense a decrease in voltage across the photovoltaic panel with diminishing ambient light and energize the load, can prevent the load from being energized when the ambient light level is sufficient to re-charge the battery, can provide positive feedback at turn-on of the load, thereby hastening turn-on and providing hysteresis, can provide for adjusting the hysteresis bands, can shift the turn-on and turn-off thresholds, and can provide an adequate current to guarantee turn-on when using low leakage solar panels A further embodiment can additionally exhibit hysteresis at load turn-off so that the load does not cycle on and off and can further raise the load turn-off threshold above the level where the battery is substantially discharged, thereby hastening recharging of the battery A still further embodiment provides temperature compensation for improved performance

A solar thermophotovoltaic converter using PbS photovoltaic cells

Abstract: A solar thermophotovoltaic converter using PbS photovoltaic cells is proposed. The converter is in the form or a flat plate consisting or a heat mirror, a black absorber, a cell filter and PbS photovoltaic cells. Theoretical analysis shows that, ideally, the efficiency or such a system is about 30%

Solar powered light

Abstract: A solar powered light adapted to be mounted under the eaves of a building, a wall or the like for use in security applications. In a preferred embodiment of the present invention, the solar powered light comprises an adjustable configuration having a lamp with an infrared detector or sensor rotatably mounted thereto and a photovoltaic or solar cell array rotatably disposed at a remote end of an extension arm movably attached to the lamp. Such a flexible arrangement allows the photovoltaic array to be positioned to receive direct sunlight. The sensor activates the solar powered light upon sensing infrared to illuminate the surrounding areas when a presence is sensed and turn it off when a presence is no longer sensed. In accordance with a second embodiment, the solar powered light does not include an infrared detector and provides continuous illumination for a given period of time. In accordance with a third embodiment, the solar powered light does not include an infrared detector, but includes a battery having a higher capacity configured to provide illumination for extended periods of time. In accordance with a fourth embodiment, the solar powered light is configured to be used directly with a user's battery. The solar powered light utilizes a compact fluorescent bulb and circuitry for providing longer lamp life, instantaneous illumination and eliminating flickering during start up.

Simplified feed-forward control of the maximum power point in PV installations

Abstract: A novel simplified control strategy, based on the positive feedback of a maximum power point tracking (MPPT) converter output current, is introduced. Cost-effective MPPT reduces the energy cost from renewable energy generators by optimizing the utilization of the renewable energy source. MPPT for relative small photovoltaic (PV) systems, with battery back-up, is achieved by maximization of the output current to the battery by employing this simplified positive feedback control strategy. This strategy was tested by using a buck converter topology. Experimental verification of the operation of this controller is included. This controller can be utilized in small (one or two panel) as well as larger installations, so that the total MPPT converter cost may be a fraction of the solar panel cost. >

Arcing rates for High Voltage Solar Arrays - Theory, experiment, and predictions

Abstract: All solar arrays have biased surfaces which can be exposed to the space environment. It has been observed that when the array bias is less than a few hundred volts negative then the exposed conductive surfaces may undergo arcing in the space plasma. A theory for arcing is developed on these high voltage solar arrays which ascribes the arcing to electric field runaway at the interface of the plasma, conductor and solar cell dielectric. Experiments were conducted in the laboratory for the High Voltage Solar Array (HVSA) experiment which will fly on the Japanese Space Flyer Unit (SFU) in 1994. The theory was compared in detail to the experiment and shown to give a reasonable explanation for the data. The combined theory and ground experiments were then used to develop predictions for the SFU flight.

Solar energy system

Abstract: The present invention provides a photovoltaic module for converting solar energy into electrical energy The module comprises a substrate having a relatively large first surface and a relatively small second surface A first photovoltaic cell is mounted to the first surface, the first photovoltaic cell having a first response band The module is positioned such that the solar energy is incident onto the active area of the first photovoltaic cell A second photovoltaic cell substantially smaller than the first photovoltaic cell is mounted to the second surface of the substrate The substrate is formed such that a portion of the solar energy transmitted by the first photovoltaic cell into the substrate is directed onto the active area of the second photovoltaic cell Because of the smaller area of the second photovoltaic cell, the cost per unit cell area is lower than in conventional tandem cell designs

Photovoltaic cell and array with inherent bypass diode

Abstract: A photovoltaic cell (20) with a single pn-junction (46) is disclosed that is capable of functioning as both a current source and a bypass diode. The photovoltaic cell is made of material that has a low bandgap energy, 1.0 eV, or less. One version of the photovoltaic cell is formed of a GaSb wafer doped with Te to form an n-region (22); the Te concentration is between 3 and 15×1017 atoms/cm3. Multiple photovoltaic cells of this invention can be connected in series and placed in parallel across a like number of photovoltaic cells (76) that do not function as tunnel diodes in order to form a power-generating array (70). The photovoltaic cells are arranged in tandem pairs so that the photovoltaic cells (76), which are transparent to the light absorbed by the photovoltaic cells (20), overlie the photovoltaic cells (20). In the event one of the photovoltaic cell pairs (20, 76) is rendered inactive, current will flow through the inactive photovoltaic cell (20) to minimize the drop in output current from the array.

Interconnected silicon film solar cell array

Abstract: A plurality of thin polycrystalline silicon solar cells formed on a ceramic substrate and which are electrically series connected to form a monolithically interconnected submodule. Adjacent solar cells are electrically separated by a vertical trench and electrically connected by interconnects located below the light receiving surface of each solar cell. The submodules are provided with external electrical contacts for electrically connecting into a photovoltaic module assembly.

PROCESSING HIGH EFFICIENCY CdTe SOLAR CELLS

Abstract: High efficiency solar cells can be fabricated on CdTe films prepared by a wide variety of deposition techniques. Most of these methods yield CdTe layers that need to be subjected to post-deposition treatments before they can be utilized in high efficiency device fabrication. In some cases these treatments can be made an integral part of the film growth process so that a post-deposition step is not needed. This paper discusses the procedures that are commonly used in high efficiency CdTe solar cell fabrication and reports on a newly emerging technique that holds the promise of becoming a high-throughput industrial process for thin film photovoltaic module production.

43rd Congress of the International Astronautical Federation

Abstract: Missions to Mars will require electric power. A leading candidate for providing power is solar power produced by photovoltaic arrays. To design such a power system, detailed information on solar-radiation availability on the Martian surface is necessary. The variation of the solar radiation on the Martian surface is governed by three factors: (1) variation in Mars-Sun distance; (2) variation in solar zenith angle due to Martian season and time of day; and (3) dust in the Martian atmosphere. A major concern is the dust storms, which occur on both local and global scales. However, there is still appreciable diffuse sunlight available even at high opacity, so that solar array operation is still possible. Typical results for tracking solar collectors are also shown and compared to the fixed collectors. During the Northern Hemisphere spring and summer the isolation is relatively high, 2-5 kW-hr/sq m-day, due to the low optical depth of the Martian atmosphere. These seasons, totalling a full terrestrial year, are the likely ones during which manned mission will be carried out.

Battery charge controller characteristics in photovoltaic systems

Abstract: Typical strategies for battery charge regulation and load control in stand-alone photovoltaic (PV) systems are presented. Several charge algorithms (methods of controlling current to the battery) are presented, along with terminology used by the PV industry for battery charge controllers. Information gained from an extensive evaluation of commercially available charge controllers and data collected from tests on PV systems in the field are discussed. An overview of battery performance characteristics needed for the successful design and long-term operation of PV systems is presented with the intent of soliciting feedback on the information presented from the battery industry. >

Generating electric power from solar radiation

Abstract: An extensive photovoltaic array (10) for generating electric power from solar radiation as in a power plant includes an extensive unitary structural grid having substantial extent in both x and y directions and supported on a pedestal (16). The unitary structural grid is defined by a multiplicity of structural members (76, 90) connected to one another at angles and defining spaces therebetween. The structural grid has a depth sufficient to provide structural rigidity to the photovoltaic array (10). A large multiplicity of the lens assemblies (14), each including at least one lens, is directly supported by and in spaces defined between structural members (76, 90) of the unitary structural grid. The lens assemblies (14) close the upper side of the unitary structural grid. All other sides of the unitary structural grid are also closed. A plurality of solar cells (38) are located within spaces defined between structural members (76, 90) of the structural grid and positioned to receive solar radiation that passes through respective lenses of the lens assemblies (14). The lens assemblies (14) and the structural members (76, 90) of the structural grid have an integrated relationship.

System-linked power supply system

Abstract: PURPOSE: To effectively utilize energy by a method wherein a system power supply is connected to the AC side of an AC-DC bidirectional converter, a solar battery, a first storage battery and a second storage battery are connected to the DC side and a direct current is supplied to a load without being returned to an alternating current. CONSTITUTION: A system power supply 1 is connected to the AC side of an AC-DC bidirectional converter 5 via a switch 3. In addition, a solar battery 7, via a diode 9, and a first storage battery 13 and a second battery 21, via switches 11, 15, are connected in series with the DC side of the converter 5. When the output of the solar battery 7 is sufficient in the daytime, the first and second storage batteries 13, 21 are charged according to the output, and an alternating current is supplied to an uninterruptible load 23 additionally. The system power supply 1 is received during a night power time zone, an alternating current is supplied to a service-interruption load 25 and the uninterruptible load 23, and the first storage battery 13 is charged. In a power failure, the switch 3 is opened, the first storage battery 13 is used as a power supply, the power supply is DC/AC-converted 5, and it is supplied to the uninterruptible load 23. Thereby, solar energy can be utilized efficiently and without waste. COPYRIGHT: (C)1994,JPO&Japio

30th Aerospace Sciences Meeting and Exhibit

Abstract: The photovoltaic (PV) power system for Space Station Freedom (SSF) uses solar array blankets which provide structural support for the solar cells and house the electrical interconnections. In the low Earth orbital (LEO) environment where SSF will be located, surfaces will be exposed to potentially damaging environmental conditions including solar ultraviolet (UV) radiation, thermal cycling, and atomic oxygen. It is necessary to use ground based tests to determine how these environmental conditions would affect the mass loss and optical properties of candidate SSF blanket materials. Silicone containing, silicone coated, and SiO(x) coated polyimide film materials were exposed to simulated LEO environmental conditions to determine there durability and whether the environmental conditions of UV, thermal cycling and oxygen atoms act synergistically on these materials. A candidate PV blanket material called AOR Kapton, a polysiloxane polyimide cast from a solution mixture, shows an improvement in durability to oxygen atoms erosion after exposure to UV radiation or thermal cycling combined with UV radiation. This may indicate that the environmental conditions react synergistically with this material, and the damage predicted by exposure to atomic oxygen alone is more severe than that which would occur in LEO where atomic oxygen, thermal cycling and UV radiationmore » are present together.« less

Autonomous system expansion planning considering renewable energy sources-a computer package

Abstract: The authors describe the interactive package ASP (Autonomous System Planning), which determines the optimal expansion plan of an autonomous generation system including diesel units, wind generators, and photovoltaic generators. Utilizing meteorological data, load demand data and estimated economical parameters, the package finds the optimal system expansion policy for a period of N years. The solution algorithms implemented in the package recognize planning and operational constraints and take into consideration the stochastic nature of the meteorological conditions, loads, and the availability of the diesel units. >

Spacecraft bus regulation using solar panel position

Abstract: A spacecraft power bus regulation method and apparatus for a spacecraft. The spacecraft has solar arrays (10) and a battery (30) coupled to the spacecraft power bus (32) to drive electrical loads (34). A bus voltage limiter (38) controls the flow of current from the solar arrays while a bidirectional battery controller (36) controls power flow into and out of the battery. A processor (46) monitors current flow and battery condition using sensors (40, 42, 44, 48) and controls the bus voltage limiter accordingly. Auxiliary control is provided by the solar array drive (24) which controls the orientation of the solar arrays with respect to the sun.

Moonbase night power by laser illumination

Abstract: Moonbase solar-power concepts must somehow address the energy storage problem posed by the 354-hour lunar night. Attention is presently given to the feasibility of laser-array illumination of a lunar base, using technology that is projected to be available in the near term. Beam-spreading due to atmospheric distortions could be reduced through the use of adaptive optics to compensate for atmospheric turbulence.