Showing papers on "Photovoltaic system published in 1991"

A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films

Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

Control of parallel connected inverters in stand-alone AC supply systems

Abstract: A scheme for controlling parallel-connected inverters in a standalone AC supply system is presented. This scheme is suitable for control of inverters in distributed source environments such as in isolated AC systems, large and distributed uninterruptible power supply (UPS) systems, photovoltaic systems connected to AC grids, and low-voltage DC power transmission meshes. A key feature of the control scheme is that it uses feedback of only those variables that can be measured locally at the inverter and does not need communication of control signals between the inverters. This is essential for the operation of large AC systems, where distances between inverters make communication impractical. It is also important in high-reliability UPS systems where system operation can be maintained in the face of a communication breakdown. Real and reactive power sharing between inverters can be achieved by controlling two independent quantities: the power angle and the fundamental inverter voltage magnitude. Simulation results are presented. >

CuInSe2 for photovoltaic applications

Abstract: The properties and most successful methods for producing CuInSe2 films for solar‐cell applications are reviewed and the production, analysis, and performance of photovoltaic devices based on CuInSe2 are discussed. The most successful methods for depositing thin CuInSe2 films for high‐efficiency solar cells are three‐source elemental evaporation and selenization of Cu/In layers in H2Se atmospheres. Devices based on CuInSe2 have achieved the highest conversion efficiencies for any nonepitaxial thin‐film solar cell, 14.1% for a small cell and 10.4% (aperture efficiency) for a 3916‐cm2 (4 sq. ft) device. Furthermore, high‐efficiency devices have been produced by several groups and have shown no evidence of degradation of performance with time. The internal quantum efficiency is remarkably close to 100%, although various losses prevent making use of all of the generated carriers. The high performance results, in part, from the very‐high‐absorption coefficient of CuInSe2, which is of the order of 105 cm−1 for photons with energies slightly above 1 eV. Models of the operation of CuInSe2/CdS heterojunctions have begun to explain the processes limiting the device performance. The success of the models is based, in part, on the large amount of data which has accumulated on CuInSe2 in spite of the relatively short time it has been extensively studied.

Photovoltaic panel support assembly

Abstract: A solar energy power source is provided comprising at least two flat photovoltaic panels disposed in co-planar side-by-side relation and an improved support structure for supporting the panels for pivotal movement on a pivot axis that extends transversely of the panels, the improved structure including a single selectively operable drive means for pivoting all of the panels simultaneously and by the same amount of angular displacement.

Loss of power supply probability of stand-alone photovoltaic systems: a closed form solution approach

Abstract: A closed-form solution approach to the evaluation of the loss of power supply probability of stand-alone photovoltaic system with energy storage is presented. Nontracking and single-axis tracking systems are considered. In both cases, the tilt is assumed to be fixed. A numerical example is included to illustrate the usefulness of the expressions developed. Relationships between the amount of energy storage and the loss of power supply probability under various operating conditions can be investigated using the results. These relationships can be used in the design of stand-alone photovoltaic systems. >

Tandem photovoltaic solar cell with iii-v diffused junction booster cell

Abstract: A photovoltaic cell array involving rows and columns of tandem or stacked solar cell units composed of GaSa/GaSb associated with a radiation collector have produced measured energy conversion efficiencies of 31% AMO. The booster GaSb cell is manufactured by a process which produces a p-type diffusion region within an n-type substrate, has improved energy conversion efficiencies and can be mounted as part of a four terminal stacked solar cell unit.

The Artificial Leaf, Molecular Photovoltaics Achieve Efficient Generation of Electricity from Sunlight

Abstract: A new molecular photovoltaic system for solar light harvesting and conversion to electricity has been developed. It is based on the spectral sensitization of a thin ceramic membrane by suitable transition metal complexes. The film consists of nanometer-sized colloidal titanium dioxide particles sintered together to allow for charge carrier transport. When derivatized with a suitable chromophore these membranes give extraordinary efficiencies for the conversion of incident photons into electric current, exceeding 90% for certain transition metal complexes within the wavelength range of their absorption band. The present paper discusses the underlying physical principles of these astonishing findings. Exploiting this discovery, we have developed a new type of photovoltaic device whose overall light to electric energy conversion yield is 11% in diffuse daylight and 6% under direct (AM1) solar irradiation.

Energy-generating plant, particularly propeller-type ship's propulsion plant, including a solar generator

Abstract: An energy-generating plant including a solar generator, having solar cells, for producing electrical energy. The electrical energy is supplied to a direct current converter, the output power of which may be used to charge an energy storage system, such as batteries. The input resistance of the direct current converter is adapted, such as by a microcomputer, to the maximum power point (MPP) of the solar generator, the MPP being dependent upon the solar insolation and the temperature of the solar cells. At start up of the plant, or when there is a change of power at the output of the direct current converter, a search process is carried out to attain the MPP of the solar generator. The energy storage system may be used to energize an electric motor for driving the propeller of a ship.

Planar photovoltaic solar concentrator module

Abstract: A planar photovoltaic concentrator module for producing an electrical signal from incident solar radiation includes an electrically insulating housing having a front wall, an opposing back wall and a hollow interior. A solar cell having electrical terminals is positioned within the interior of the housing. A planar conductor is connected with a terminal of the solar cell of the same polarity. A lens forming the front wall of the housing is operable to direct solar radiation incident to the lens into the interior of the housing. A refractive optical element in contact with the solar cell and facing the lens receives the solar radiation directed into the interior of the housing by the lens and directs the solar radiation to the solar cell to cause the solar cell to generate an electrical signal. An electrically conductive planar member is positioned in the housing to rest on the housing back wall in supporting relation with the solar cell terminal of opposite polarity. The planar member is operable to dissipate heat radiated by the solar cell as the solar cell generates an electrical signal and further forms a solar cell conductor connected with the solar cell terminal to permit the electrical signal generated by the solar cell to be measured between the planar member and the conductor.

A contribution to the simulation and design optimization of photovoltaic systems

Abstract: Guidelines for the proper selection of solar array and battery sizes for use in photovoltaic-powered dispersed systems located far from public power networks are presented. The choice of key design parameters of separately excited DC motors used for farm irrigation is addressed. The selection procedure is based on accurate system modeling and annual simulation using actual meteorological and typical load data. The procedure determines the useful, dumped, and commercial energy components forced by system-load interaction. Two systems are investigated. System one is an AC residential load of a given annual demand profile on hourly basis, while system two represents an irrigation set-up featuring a DC motor and a battery back-up. The results show that a properly sized battery interface would enhance the performance of the irrigation system by more than 12% compared to the directly coupled case. >

Method for producing solar cell devices of crystalline material

Abstract: A solar cell device is produced by forming at least one semiconductor layer of single crystalline material having an uneven surface on a substrate. A photovoltaic element utilizing the semiconductor layer is formed and bonded to another substrate. The produced solar cell device has a large area, high conversion efficiency and may be mass produced at low cost.

Solar Energy Thermal Technology

Abstract: The solar energy resource transmission of solar energy through transparent materials absorption of solar energy at surfaces flat plate collectors line-axis concentrating collectors solar ponds solar dryers solar refrigeration greenhouses passive and active solar design of buildings.

Depolyable retractable photovoltaic concentrator solar array assembly for space applications

Abstract: A deployable/retractable photovoltaic concentrator solar array assembly for space applications that includes a plurality of solar array panels that are carried by a pantograph arm arrangement that is deployable to position the panels in a predetermined canted arrangement for receipt of solar radiation. Each panel includes a plurality of spaced cylindrical off axis parabolic mirrors that concentrate the reflected light on a line that falls upon a series of photovoltaic cells arranged longitudinally along the back of each mirror. The cylindrical parabolic mirrors are aligned with the cylindrical axis perpendicular to the axis about which the panels are canted, so that such canting causes no loss of focus. The array panels may be hardened to resist perceived threats and the pantograph arm arrangement is operable to position the array panels in a preferred orientation according to the nature of the threat. A preferred method of making the parabolic concentrator mirrors and assembling them into array panels is disclosed.

Photovoltaic cells for converting light energy to electric energy and photoelectric battery

Abstract: A solar photovoltaic cell with a conductive current collecting contacts embedded in a block of optical transparent polymer material between the semiconductor wafer and protective cover in such a manner that at least the section thereof which are in contact with the surface of the semiconductor wafer protrude from the polymer block. This provides for a reliable ohmic contact between the current collecting contacts and the semiconductor wafer. The disclosed geometry of the solar cell reduces the shadowing area of the semiconductor wafer by up to 90%.

Method and apparatus for uniformly concentrating solar flux for photovoltaic applications

Abstract: A dish reflector and method for concentrating moderate solar flux uniformly on a target plane on a solar cell array, the dish having a stepped reflective surface that is characterized by a plurality of ring-like segments arranged about a common axis, and each segment having a concave spherical configuration.

Solar energy in agriculture.

Abstract: General Preface (B.A. Stout). Preface to Volume 4 (B.F. Parker). 1. Techniques of Estimating Incident Solar Radiation (D.G. Colliver). 2. Photovoltaic System Design (L. Rosenblum). 3. Agricultural Applications of Photovoltaic Systems (A. Ratajczak and W.J. Kaszeta). 4. Solar-Thermal Design (B.F. Parker). 5. Solar Water Heating (D. Faiman). 6. Production Solar Greenhouses (L.D. Albright). 7. Animal Housing: Solar Application (J.A. DeShazer and G.R. Bodman). 8. Water Desalination (A.I. Kudish). 9. Solar Grain Drying (H.M. Keener). 10. Design of Solar-Heated Forage Dryers (B.F. Parker). 11. Solar Fruit Drying (E.J. Carnegie). 12. Solar-Heated Lumber Kilns (R.A. Plumptre). 13. Solar Curing of Specialty Crops (J.M. Bunn). 14. Free Convection Dryers (R. Corvalan and W. Zambrano). 15. Solar Thermal Water Pumping (R. Burton). List of Contributors. List of SI Units and Conversion Factors to SI, compiled by V.H.A.M. Oosterbaan. Subject Index

Energy Pay-Back Time of Photovoltaic Modules

Abstract: The energy invested in photovoltaic modules has been investigated on the basis of currently operating commercial production lines in France. The analysis was made for two types of solar cells, polycrystalline silicon and amorphous silicon. The energy which was calculated in this way was compared with the energy produced by these modules under operating conditions in various European climates. An average energy pay-back time of 1.2 years for amorphous silicon modules and 2.1 years for crystalline silicon modules was found. It can be anticipated that these energy pay-back times will decrease in the future.

Solar array output regulator using variable light transmission

Abstract: A solar cell voltage regulating arrangement which is particularly advantageous for use in spacecraft includes a light valve such as a liquid crystal cell disposed before the solar cell, to thereby controllably vary the light transmission to the solar cell. A control arrangement varies the transmission of the liquid crystal to control the output voltage.

Microprocessor based automatic Sun tracker

Abstract: A microprocessor-based automatic position control scheme has been designed for controlling the azimuth angle of an optimally tilted photovoltaic flat type solar panel or a cylindrical parabolic reflector to get the illuminating surface appropriately positioned for the collection of maximum solar irradiance. The scheme presented results in considerable saving in power and is independent of the geographical location of the site of erection or temporal variations in environmental parameters.

Generic solar cell array using a printed circuit substrate

Abstract: There is disclosed a generic solar array panel which utilizes a printed circuit substrate. A series of electrically conductive paths for interconnecting the solar cells and other electronic components to form a solar electric power supply network is formed on or encapsulated into the substrate. An integral bus line conducts the collected power to a load. Stress relief loops routed in the substrate compensate for differences in characteristics of thermal expansion between the solar cell and the substrate while maintaining the integrity of the network's electrical connections.

Optimal design parameters for a PV array coupled to a DC motor via a DC-DC transformer

Abstract: A study is presented of the optimal operating parameters of a system comprising a photovoltaic solar array and a DC electromechanical energy converter (motor) driving a mechanical load. The analysis and design procedure includes the addition of a variable DC-DC matching transformer placed between the array and the motor. It is responsible for adjusting the load curve seen by the array to coincide with its maximum power point. The model takes into consideration the effect of different temperature as well as isolation profiles along the year. The analysis procedure guides the design of DC motors as well as variable DC transformers especially suited to be operated in conjunction with PV arrays. The procedure determines optimal motor constants which lead to an improved overall design in terms of maximizing the total annual gross mechanical energy delivered to a load of a given torque-speed characteristic. >

Platform for the utilization of solar power

Abstract: The invention relates to a platform of the utilization of solar power which makes use of linear concentrators to beam the solar radiation for use in thermal, chemical or photovoltaic solar power converters, in which the azimuthal movement of the sun is followed by rotation about the main axis. The aim of the invention is to ensure an approximately uniform conversion rate of the solar radiation largely independently of the height of the sun while avoiding the use of a twin-axis follower system. The area available for utilizing the solar power is to be used as fully as possible as the aperture area to capture the radiation. According to the invention, a floating pipe (2, 2', 112) forming a torus is fitted as a frame for a horizontally extending planar bearer (3-4) held, by substantially evenly distributed buoyant bodies (13, 36, 46, 64a, 64b, 80b) borne by a liquid, at a vertical distance from solar power converting devices (33, 53, 73, 73', 93, 94b).