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Showing papers on "Photovoltaic system published in 1997"


Journal ArticleDOI
TL;DR: A low-power low-cost highly efficient maximum power point tracker (MPPT) to be integrated into a photovoltaic (PV) panel is proposed, which can result in a 25% energy enhancement compared to a standard photovolar panel, while performing functions like battery voltage regulation and matching of the PV array with the load.
Abstract: A low-power low-cost highly efficient maximum power point tracker (MPPT) to be integrated into a photovoltaic (PV) panel is proposed. This can result in a 25% energy enhancement compared to a standard photovoltaic panel, while performing functions like battery voltage regulation and matching of the PV array with the load. Instead of using an externally connected MPPT, it is proposed to use an integrated MPPT converter as part of the PV panel. It is proposed that this integrated MPPT uses a simple controller in order to be cost effective. Furthermore, the power converter has to be very efficient, in order to transfer more energy to the load than a directly-coupled system. This is achieved by using a simple soft-switched topology. A much higher conversion efficiency at lower cost will then result, making the MPPT an affordable solution for small PV energy systems.

632 citations


Journal ArticleDOI
TL;DR: In this article, an artificial neural network (ANN) was used for the estimation of the maximum power generation from a PV module under the conditions of irradiation, temperature and wind velocity.
Abstract: This paper presents an application of an artificial neural network for the estimation of maximum power generation from PV module. The output power from a PV module depends on environmental factors such as irradiation and cell temperature. For the operation planning of power systems, the prediction of the power generation is inevitable for PV systems. For this purpose, irradiation, temperature and wind velocity are utilized as the input information to the proposed neural network. The output is the predicted maximum power generation under the condition given by those environmental factors. The efficiency of the proposed estimation scheme is evaluated by using actual data on daily, monthly and yearly bases. The proposed method gives highly accurate predictions compared with predictions using the conventional multiple regression model.

340 citations


Journal ArticleDOI
Lena Neij1
TL;DR: In this paper, experience curves are used to analyse the prospects for diffusion and adoption of renewable energy technologies, with special emphasis on wind turbines and photovoltaic (PV) modules.

313 citations


31 Dec 1997
TL;DR: In this article, the authors present a performance model for photovoltaic arrays based on annual energy production, which is used for designing and sizing arrays for different types of solar cells.
Abstract: As photovoltaic systems become larger and more numerous, improved methods are needed for testing and modeling their performance. Test methods that successfully separate the interacting, time-of-day dependent influences of solar irradiance, operating temperature, solar spectrum, and solar angle-of-incidence have now been developed. These test methods have resulted in a new array performance model that is reasonably simple, yet accurately predicts performance for all operating conditions. This paper describes the new model, outdoor tests required to implement it, results of field tests for five arrays of different technologies, and the evolution of the model into a numerical tool for designing and sizing photovoltaic arrays based on annual energy production.

209 citations


Proceedings ArticleDOI
01 Nov 1997
TL;DR: In this article, the authors describe straightforward methods for directly measuring the effects of time-of-day dependent factors on photovoltaic module and array performance, such as changes in the solar spectrum over the day and optical effects in the module that vary with the solar angle of incidence.
Abstract: Historically, two time-of-day dependent factors have complicated the characterization of photovoltaic module and array performance; namely, changes in the solar spectrum over the day and optical effects in the module that vary with the solar angle-of-incidence. This paper describes straightforward methods for directly measuring the effects of these two factors. Measured results for commercial modules, as well as for typical solar irradiance sensors (pyranometers) are provided. The empirical relationships obtained from the measurements can be used to improve the methods used for system design, verification of performance after installation, and diagnostic monitoring of performance during operation.

206 citations


Journal ArticleDOI
TL;DR: In this paper, it is shown that reduction in temperature of up to 20 K can be obtained by heat transfer to an air flow induced by buoyancy in a duct behind the PV component, with a significant increase in the electrical output and reduction of heat gain into the building.

205 citations


Journal ArticleDOI
TL;DR: In this article, the authors designed and constructed a photovoltaic-thermal hybrid collector on campus, which consisted of a liquid heating flat-plate solar collector with mono-Si PV cells on substrate of nonselective aluminum absorber plate, the collector area was 1.3 × 0.5 m.

182 citations


Journal ArticleDOI
01 May 1997
TL;DR: In this paper, the authors focused on crystalline silicon solar cells and proposed several high-efficiency features to improve the efficiency and decrease the price of the commercial PV modules, and showed that increasing the PV market size toward 500 MWp/y and accounting for realistic industrial improvements can lead to a drastic PV module price reduction to $1/Wp.
Abstract: Approximately 2 billion people, mainly in Third World countries, are not connected to an electric grid. The standard, centralized grid development is too expensive and time consuming to solve the energy demand problem. Therefore, there is a need for decentralized renewable energy sources. The main attractiveness of solar cells is that they generate electricity directly from sunlight and can be mounted in modular, stand-alone photovoltaic (PV) systems. Particular attention is paid in this paper to crystalline silicon solar cells, since bulk silicon solar-cell (mono and multi) modules comprise approximately 85% of all worldwide PV module shipments. Energy conversion efficiency as high as 24% has been achieved on laboratory, small-area monocrystalline silicon cells, whereas the typical efficiency of industrial crystalline silicon solar cells is in the range of 13-16%. The market price of PV modules remains for the last few years in the range of $3.5-4.5/watt peak (Wp). For the photovoltaic industry, the biggest concern is to improve the efficiency and decrease the price of the commercial PV modules. Efficiency-enhancement techniques of commercial cells are described in detail. Adaptation of many high-efficiency features to industrially fabricated solar cells. The latest study shows that increasing the PV market size toward 500 MWp/y and accounting for realistic industrial improvements can lead to a drastic PV module price reduction down to $1/Wp.

167 citations


Journal ArticleDOI
TL;DR: In this article, a general methodology is presented for the sizing and optimization of renewable power supply systems, including hybrids such as those with solar photovoltaic and wind power components, by reference to periods over which the average resource (e.g. wind/solar) is least or the average load demand is greatest.
Abstract: A general methodology is presented for the sizing and optimization of renewable power supply systems, including hybrids such as those with solar photovoltaic and wind power components. The technical and economic optimum configurations are found by reference to periods over which the average resource (e.g. wind/solar) is least or the average load demand is greatest. For stand-alone systems, the annual autonomy is an important further design factor. This is the fraction of time for which the specified load can be met. The optimization seeks the least expensive system configuration which achieves the required autonomy level. It is the autonomy level which largely determines the size of battery storage capacity required. A system performance simulation procedure, with an hourly time-step, is used to obtain the autonomy levels of potentially optimum arrangements as the battery size is varied. Illustrative examples of the use of the method employ annual and monthly averaging periods, although any other period may be used. Data refer to the particular location and load pattern for an existing hybrid system, but the method is quite generally applicable. © 1997 by John Wiley & Sons, Ltd.

163 citations


Journal ArticleDOI
TL;DR: In this article, the performance analysis of a conventional hybrid photovoltaic/thermal air heating collector is studied. But, the authors focus on the performance of a single-glass and double-glass configuration.

161 citations


Patent
20 Aug 1997
TL;DR: In this paper, a power control apparatus of a solar power generation system for converting power generated by a solar panel and supplying the converted power to a load, the output voltage and output current of the solar panel are sensed, and, under ordinary conditions, MPPT control is performed so that the solar cells will operate at a maximum output point.
Abstract: In a power control apparatus of a solar power generation system for converting power generated by a solar panel and supplying the converted power to a load, the output voltage and output current of the solar panel are sensed, and, under ordinary conditions, MPPT control is performed so that the solar cells will operate at a maximum output point. If the output power of the solar panel exceeds a predetermined power, a power conversion unit is controlled so as to raise the output voltage of the solar panel, thereby limiting the output power of the solar panel. As a result, excessive power is prevented from being output by the power control apparatus.

Journal ArticleDOI
TL;DR: In this paper, the performance, safety, and maintenance issues of a photovoltaic (PV) power plant which uses hydrogen energy storage and fuel cell regenerative technology are reported.

Journal ArticleDOI
R. Herberholz1, V. Nadenau1, U. Ruhle1, Ch. Köble1, H.W. Schock1, B. Dimmler 
TL;DR: In this article, a consistent picture of the problems encountered in the case of wide-gap absorbers is drawn on the basis of results from photoelectron spectroscopy in conjunction with electrical measurements on the devices.

Journal ArticleDOI
TL;DR: In this paper, an efficient approach to short-term resource scheduling for an integrated thermal and photovoltaic-battery generation was presented, which incorporates battery storage for peak load shaving.
Abstract: This paper presents an efficient approach to short term resource scheduling for an integrated thermal and photovoltaic-battery generation. The proposed model incorporates battery storage for peak load shaving. Several constraints including battery capacity, minimum up/down time and ramp rates for thermal units, as well as natural photovoltaic (PV) capacity are considered in the proposed model. A case study composed of 26 thermal units and a PV-battery plant is presented to test the efficiency of the method.

Patent
31 Mar 1997
TL;DR: In this article, a system for controlling power supplied by a solar array panel to one of either a load or a battery for optimal power consumption is presented, where a signal conditioner, processor and high gain amplifier cooperate to determine whether the solar array is capable of supplying the power demanded by at least one of the battery and the load.
Abstract: A system for controlling power supplied by a solar array panel to one of either a load or a battery for optimal power consumption is disclosed. The solar array power control system of the present invention includes a power stage for directing the solar array to discharge an appropriate amount of current, a signal conditioner for receiving and conditioning voltage and current signals from the solar array and determining the signs of the time derivatives of solar array voltage and power, a processor for evaluating the signs of the time derivatives of solar array power voltage and for directing operation of either a battery current control mode or a peak power tracking mode and a high gain amplifier for directing an appropriate voltage to the power stage according to the operating mode. The signal conditioner, processor and high gain amplifier cooperate to determine whether the solar array is capable of supplying the power demanded by at least one of the battery and the load. When it has been determined that the required power level to be supplied from the solar array is within the capability of the solar array, the system commands the solar array to discharge the exact power demanded. In times when the solar array is not capable of completely satisfying the required power level, the system commands the solar array to discharge the maximum power available under the present conditions.

Book
01 Oct 1997
TL;DR: The potential of solar power as a viable source of renewable energy has been expanded by the recent achievements in sunlight concentration techniques described in this paper, which provides a comprehensive treatment of the issues involved in this new efficient and cost-effective sustainable power resource.
Abstract: The potential of solar power as a viable source of renewable energy has been expanded by the recent achievements in sunlight concentration techniques described in this book, which provides a comprehensive treatment of the issues involved in this new efficient and cost-effective sustainable power resource. Fabrication problems for terrestrial and space photovoltaic installations and ohmic losses in solar cells are discussed, as are the semiconductor physics underlying photovoltaics. Concentrator solar cell structures and performance are noted. The book closes with a discussion on the optimization of solar photovoltaic power plants with concentrators. (UK)

Patent
19 Aug 1997
TL;DR: In this article, an electric power conversion unit for driving a pump run by electric power generated by a solar panel, a storage battery connected to the solar panel via the switch 6, and a controller 7 for controlling the EPC unit and switch 6 are provided.
Abstract: An electric power conversion unit 2 for driving a pump 3 run by electric power generated by a solar panel 1 , a storage battery 5 connected to the solar panel 1 via the switch 6 , and a controller 7 for controlling the electric power conversion unit 2 and the switch 6 are provided. The controller 7 closes the switch 6 during any period when the amount of insolation is large and performs the maximum power point tracking control of the solar panel 1 , and otherwise, controls the electric power conversion unit 2 to drive at one of plural fixed frequencies in dependence upon an output voltage from the solar panel 1 by closing the switch 6 . Accordingly, it is possible to utilize output from an unstable electric power supply efficiently, such as a solar cell, thereby providing a reliable electric motor driving apparatus having a simple configuration and a control method therefor.

Journal ArticleDOI
TL;DR: In this article, the authors compared present solar electricity technologies from the point of view of system analysis, taking into consideration their performance, costs and environmental impact, and presented a practical tool for decision-makers that facilitates a first estimate of the performance and costs of such plants under local conditions.

Journal ArticleDOI
TL;DR: In this article, a set of model equations for evaluating the life-cycle energy performance of PV systems and other electricity-generating systems are presented, including material production, manufacturing and assembly, use and end-of-life management.
Abstract: This paper highlights results from a collaborative life-cycle design project between the University of Michigan, the US Environment Protection Agency and United Solar Systems Corporation. Energy analysis is a critical planning and design tool for photovoltaic (PV) modules. A set of model equations for evaluating the life-cycle energy performance of PV systems and other electricity-generating systems are presented. The total PV life-cycle, encompassing material production, manufacturing and assembly, use and end-of-life management, was investigated. Three metrics—energy payback time, electricity production eAciency and lifecycle conversion eAciency—were defined for PV modules with and without balanceof-system (BOS) components. These metrics were evaluated for a United Solar UPM-880 amorphous silicon PV module based on average insolation in Detroit, Boulder and Phoenix. Based on these metrics, a minimum condition for assessing the sustainability of electricity-generating systems was proposed and discussed. The life-cycle energy analysis indicated that the aluminum frame is responsible for a significant fraction of the energy invested in the UPM-880 module. #1997 John Wiley & Sons, Ltd.

Patent
19 Dec 1997
TL;DR: In this article, backcontact crystalline silicon solar cells are positioned atop electrically conductive circuit elements affixed to a planar support so that a circuit capable of generating electric power is created.
Abstract: Photovoltaic modules which comprise back-contact solar cells, such as back-contact crystalline silicon solar cells, positioned atop electrically conductive circuit elements affixed to a planar support so that a circuit capable of generating electric power is created. The modules are encapsulated using encapsulant materials such as EVA which are commonly used in photovoltaic module manufacture. The module designs allow multiple cells to be electrically connected in a single encapsulation step rather than by sequential soldering which characterizes the currently used commercial practices.

Proceedings ArticleDOI
22 Jun 1997
TL;DR: In this paper, a novel control method for DC-DC power converters with bi-directional power flow and galvanic isolation is presented, where a high efficiency is achieved by using a minimal number of power electronic devices working in the soft switching mode.
Abstract: This paper presents a novel control method for DC-DC power converters with bi-directional power flow and galvanic isolation. A high efficiency is achieved by using a minimal number of power electronic devices working in the soft switching mode. No reverse blocking switches are required. Different circuit variants can be derived from the proposed basic principle. Suitable industrial applications for the new principle of DC-DC conversion are UPS, photovoltaic applications, battery chargers, back-fire applications and auxiliary power supplies.

Proceedings ArticleDOI
09 Nov 1997
TL;DR: In this paper, a simple method which combines discrete time control and a PI compensator is used to track the maximum power points (MPPs) of the solar array, and the system is kept to operate close to the MPPs, thus the maximum possible power transfer from the PV power system is achieved.
Abstract: Solar power converters were used to convert the electrical energy from solar arrays to a stable and reliable power source. The object of this paper is to analyze and design DC/DC power converters of different types in a PV power system to investigate the performance of such converters. A simple method which combines discrete time control and a PI compensator is used to track the maximum power points (MPPs) of the solar array. The system is kept to operate close to the MPPs, thus the maximum possible power transfer from the solar array is achieved. The implementation of the proposed power converter system was based on a digital signal processor. Experimental tests were carried out for buck, boost and buck-boost power converters using a simple maximum power point tracking algorithm. The efficiencies for the system with different power converters are compared and presented.

Journal ArticleDOI
TL;DR: In this paper, the authors used a transient system simulation program to find possible system configurations for different climates and loads of a solar-hydrogen system, which can supply low-energy dwellings with energy.

Proceedings ArticleDOI
19 May 1997
TL;DR: The principles and specificities of the measurement systems and specially of the automatic data measuring device and its sensors and also some aspects of the database and expert system developed for this application are presented.
Abstract: In order to analyze the performance of photovoltaic (PV) systems, we have developed a real-time expert system based on a central microcomputer used as a microserver and can be easily consulted from different automatic stations. The developed system is able to ensure the monitoring, supervision, and control of PV systems installed over a wide area, on one hand, and to create a general PV systems database, on the other. This paper presents a design of a universal data acquisition system with available components and which is easily accessible through a server. The hardware and software configuration of the expert system are described. Performance of this system are also presented when applied on PV systems.

Journal ArticleDOI
TL;DR: In this article, the authors describe the methodology for quantification of solar irradiance fluctuation in order to analyze the areally totalized PV systems, which consist of a large number of PV systems connected to each other in the optimum size of a certain community area.

Proceedings ArticleDOI
01 Oct 1997
TL;DR: In this paper, the authors extend the use of dark I-V measurements to photovoltaic modules, illustrates their use in diagnosing module performance losses and proposes their use for process monitoring during manufacturing.
Abstract: Dark current-voltage (dark I-V) measurements are commonly used to analyze the electrical characteristics of solar cells, providing an effective way to determine fundamental performance parameters without the need for a solar simulator. The dark I-V measurement procedure does not provide information regarding short-circuit current, but is more sensitive than light I-V measurements in determining the other parameters (series resistance, shunt resistance, diode factor and diode saturation currents) that dictate the electrical performance of a photovoltaic device. The work documented here extends the use of dark I-V measurements to photovoltaic modules, illustrates their use in diagnosing module performance losses and proposes their use for process monitoring during manufacturing.

Patent
29 May 1997
TL;DR: In this paper, a novel solar inverter circuit is used to connect a solar photovoltaic (PV) array with an alternating current (AC) voltage source to convert direct current (DC) power from the PV array to AC power.
Abstract: A novel solar inverter circuit is used to connect a solar photovoltaic (PV) array with an alternating current (AC) voltage source to convert direct current (DC) power from the PV array to AC power. The solar inverter circuit employs the current-voltage (I-V) characteristic of the PV or solar cell, and an H-Bridge circuit with gate controller. The gate controller synchronizes the H-bridge with the AC voltage source. The PV array and the solar inverter circuit can plug directly into a residential AC plug and provides electrical power as a supplementary AC supply. Electrical energy required by the home appliances is supplied by the municipal AC line and solar energy concurrently. Advantages of the solar inverter circuit of the present invention include the flexibility of using the solar inverter circuit with any number of solar cell panels through the implementation of an impedance transformer, and the implementation of an additional, optional output for DC battery charging.

Journal ArticleDOI
TL;DR: In this article, rare-earth complexes were used as photovoltaic precursors, and the conversion efficiency of solar cells were improved by applying rare earth complexes as photoprocessors.

Proceedings ArticleDOI
03 Aug 1997
TL;DR: In this paper, a new scheme of maximum power tracking control is proposed and applied to a utility-interactive photovoltaic power conditioning system, where the boost chopper is responsible for maximum tracking control and the inverter responsible for unity power factor control and constant DC input voltage control.
Abstract: It is shown that the derivative (dp/sub s//de/sub s/) of output power (p/sub s/) with respect to output voltage (e/sub s/) of a photovoltaic array is equal to zero at the maximum power point. This kind of relationship is independent of insolation and temperature. This property may be utilized to perform maximum power tracking control, that is, at all insolation and temperature levels, the maximum power point can be obtained by regulating dp/sub s//de/sub s/ toward zero. Based on this concept, a new scheme of maximum power tracking control is proposed and applied to a utility-interactive photovoltaic power conditioning system, where the boost chopper is responsible for maximum power tracking control and the inverter responsible for unity power factor control and constant DC input voltage control. The related design method is described. The usefulness and validity of the proposed method are verified by simulation. Compared to conventional methods, this method show a considerably high tracking performance.

Proceedings ArticleDOI
01 Nov 1997
TL;DR: In this paper, the authors identify the time-of-day dependent factors responsible for solar irradiance errors and describe new procedures that effectively compensate for the systematic influences, which should improve calibration methods and the accuracy of field measurements.
Abstract: Small, low-cost, silicon-photodiode pyranometers are now widely used for solar irradiance measurements associated with solar thermal and photovoltaic power systems, as well as for agricultural applications. Without correction, the irradiance values indicated by these pyranometers may differ from the "true" broadband solar irradiance by over 10%. This paper identifies the time-of-day dependent factors responsible for these systematic errors and describes new procedures that effectively compensate for the systematic influences. Application of the procedures should improve calibration methods and the accuracy of field measurements.