Showing papers on "Photovoltaic system published in 1994"
TL;DR: In this article, a methodology for calculation of the optimum size of a PV array for a stand-alone hybrid wind/PV power system is developed, where long term data of wind speed and irradiance recorded for every hour of the day for 30 years were used.
Abstract: A methodology for calculation of the optimum size of a PV array for a stand-alone hybrid wind/PV power system is developed. Long term data of wind speed and irradiance recorded for every hour of the day for 30 years were used. These data were used to calculate the probability density functions of the wind speed and the irradiance for each hour of a typical day in a month. The wind speed and irradiance probability density functions and manufacturer's specification on a wind turbine and a PV module were used to calculate the average power generated by the wind turbine and the PV module for each hour of a typical day in a month. The least square method is used to determine the best fit of the PV array and wind turbine to a given load. On the basis of the energy concept an algorithm was developed to find the optimum size of the PV array in the system. >
350 citations
TL;DR: In this article, a multijunction GaInP/GaAs photovoltaic cells with efficiencies of 29.5% at 1 −sun concentration and air mass (AM) 1.5 global and 25.7% 1−sun, AM 0.
Abstract: We report on multijunction GaInP/GaAs photovoltaic cells with efficiencies of 29.5% at 1‐sun concentration and air mass (AM) 1.5 global and 25.7% 1‐sun, AM0. These values represent the highest efficiencies achieved by any solar cell under these illumination conditions. Three key areas in this technology are identified and discussed; the grid design, front surface passivation of the top cell, and bottom surface passivation of both cells. Aspects of cell design related to its operation under concentration are also discussed.
301 citations
20 Jun 1994
TL;DR: In this article, a new maximum power point tracker (MPPT) using fuzzy set theory is proposed to improve the energy conversion efficiency of photovoltaic systems, where a fuzzy algorithm based on linguistic rules describing the operator's control strategy is applied to control the step-up converter for the MPPT.
Abstract: Studies on photovoltaic systems are increasing because of a large, secure, essentially exhaustible and broadly available resource as a future energy supply. However, the output power induced in the photovoltaic modules is influenced by an intensity of solar cell radiation, temperature of the solar cells and so on. Therefore, to maximize the efficiency of the renewable energy system, it is necessary to track the maximum power point of the input source. In this paper, a new maximum power point tracker (MPPT) using fuzzy set theory is proposed to improve energy conversion efficiency. A fuzzy algorithm based on linguistic rules describing the operator's control strategy is applied to control the step-up converter for the MPPT. Fuzzy logic control based on coarse and fine mode has been incorporated in order to reduce not only the time required to track the maximum power point but also the fluctuation of power. The MPPT algorithm is implemented by a 16 bit single chip 80C196KB microcontroller. Simulation and experimental results show that performance of the fuzzy controller in a maximum power tracking of a photovoltaic array is better than that of controller based upon the hill climbing method. >
229 citations
TL;DR: In this paper, a theoretical study of a hybrid photovoltaic cum thermal (PV/T) solar system is presented, where air/water is made to flow in a duct placed below the surface on which the solar cells are mounted to extract heat from the system, thereby cooling the cells and increasing their efficiency.
212 citations
TL;DR: In this article, a theoretical investigation of the impurity photovoltaic (IPV) effect for improving silicon solar-cell efficiency is presented, which is better than previous analyses because of the improved treatment of generation and recombination via impurities.
Abstract: A theoretical investigation of the impurity photovoltaic (IPV) effect for improving silicon solar‐cell efficiency is presented. The approach is better than previous analyses because of the improved treatment of generation and recombination via impurities, and because it includes the effects of optical competition and light trapping. The approach is applied to the nonmidgap, deep‐level impurity indium as the IPV effect impurity incorporated into an idealized silicon solar cell. The analysis is based on experimentally determined parameters for indium. Improvements of cell current, subgap spectral response, and energy conversion efficiency are quantified. The analysis reveals the importance of light trapping and proper selection of indium and dopant concentrations. The impurity photovoltaic effect is predicted to improve solar‐cell efficiency.
209 citations
Patent•
11 Oct 1994TL;DR: In this paper, a solar array maximum power point tracking system for regulating the power output of a solar arrays associated with a spacecraft is presented, where an on-board computer measures the bus voltage and current from the solar array and generates a power calculation of the solar arrays power output.
Abstract: A solar array maximum power point tracking system for regulating the power output of a solar array associated with a spacecraft. An on-board computer measures the bus voltage and current from the solar array and generates a power calculation of the solar array power output. The on-board computer applies a first reference signal to a remote error amplifier representative of an incremental change in the solar array power. Additionally, the solar array bus voltage is applied to the remote error amplifier such that the remote error amplifier senses the solar array bus voltage and generates an output voltage indicative of the change of the solar array power. The output voltage of the error amplifier is applied to a power processor unit. The output voltage from the remote error amplifier and the bus voltage are applied to a power stage within the power processor unit. The power stage generates an output current that is applied to an arcjet thruster. The output current is also applied to a transconductive circuit that converts the output current to a voltage so as to condition the input voltage to the power stage.
144 citations
12 Apr 1994
TL;DR: A maximum power point tracker unit is developed for the optimum coupling of photovoltaic panels (PVP) to the batteries and load through a controlled DC-DC power converter (chopper) and regulates the panel output voltage at its optimum value in the control mode.
Abstract: A maximum power point tracker unit is developed for the optimum coupling of photovoltaic panels (PVP) to the batteries and load through a controlled DC-DC power converter (chopper). The system consists of three main units: (i) the photovoltaic panels that convert solar power to electricity; (ii) a chopper which couples the power of PVP to the load or batteries at a constant voltage; and (iii) maximum power point (MPP) computing unit that determines the set point of the chopper to keep the panel voltage at a maximum power transfer (MPT) condition. The tracking of the MPP for low power PVP (50 W-1 kW) is feasible only when the power consumption of the tracking unit is lower than the increase of the output power that they provide. The developed and tested circuit consumes only 40 mW, and therefore is suitable even for low power applications down to 50 W. The tracking unit performs MPP computation periodically through analog computing stages. The computation mode requires 20 mA from the /spl plusmn/5 V source for a 50 ms period. In the control and sleep mode, the consumption falls down to 4 mA. The developed unit regulates the panel output voltage at its optimum value in the control mode. The modes are switched by a timing circuit. The sleep mode is initiated when maximum PVP output power of the existent illumination level drops to a preset value, which cannot balance the losses of the chopper and the consumption of the MPP tracker unit. >
129 citations
30 Jun 1994
TL;DR: A new solar radiation data manual is nearing completion by the National Renewable Energy Laboratory's (NRELs) Analytic Studies Division under the Solar Radiation Resource Assessment Project and the Photovoltaic Solar Radiation Research Task as mentioned in this paper.
Abstract: A new solar radiation data manual is nearing completion by the National Renewable Energy Laboratory’s (NREL’s) Analytic Studies Division under the Solar Radiation Resource Assessment Project and the Photovoltaic Solar Radiation Research Task. These tasks are funded and monitored by the Photovoltaics Branch of the Department of Energy’s Office of Energy Efficiency and Renewable Energy. The new manual is entitled Solar Radiation Data Manual for Flat‐Plate and Concentrating Collectors. For designers and engineers of solar energy related systems, it gives the solar resource available for various types of collectors for 239 stations in the United States and its territories. The data in the manual are modeled using diffuse horizontal and direct beam solar radiation values from the National Solar Radiation Data Base (NSRDB). The NSRDB contains modeled (93%) and measured (7%) global horizontal, diffuse horizontal, and direct beam solar radiation for 1961–1990. This paper describes what is contained in the new data manual and how it was developed.
120 citations
Patent•
23 Sep 1994
TL;DR: In this paper, a controller monitors the solar array's output power and adjusts the battery charging by generating a current control signal that tracks a peak of the available output power, and sets a current limit such that the combined current draw of the plurality of dc-to-dc converters is substantially equal to the solar arrays's optimum current at which it provides its maximum available power.
Abstract: An electrical power conversion system that supplies the maximum available output power from a power source such as a solar array to a plurality of loads such as rechargeable batteries. The output power of the solar array peaks at an optimum current that is less than is maximum available output current. The system includes a controller and a plurality of dc-to-dc converters that charge the batteries. The controller monitors the solar array's output power and adjusts the battery charging by generating a current control signal that tracks a peak of the solar array's available output power and sets a current limit such that the combined current draw of the plurality of dc-to-dc converters is substantially equal to the solar array's optimum current at which it provides its maximum available power. The electrical power and control signals are transmitted from the power source and controller to the power converters on three bus bars, including a power bus, a control bus, and a common bus. The current control signal and the voltage control signal are multiplexed onto the single control bus. The controller and the dc-to-dc converters are mounted on planar printed circuit boards having clips arranged in a triangular pattern that allow the dc-to-dc converters to be easily attached to and removed from the buses.
117 citations
TL;DR: In this paper, a shunt DC motor driving a centrifugal water pump is supplied from a photovoltaic generator via a step-up converter whose duty ratio is controlled using a current-locked feedback loop.
Abstract: A photovoltaic (PV) generator is a nonlinear device having insolation-dependent volt-ampere characteristics. Because of its relatively high cost, the system designer is interested in optimum matching of the motor and its mechanical load to the PV generator so that maximum power is obtained during the entire operating period. However, since the maximum-power point varies with solar insolation, it is difficult to achieve an optimum matching that is valid for all insolation levels. In this paper it is shown that for maximum power, the generator current must be directly proportional to insolation. This remarkable property is utilized to achieve insolation-independent optimum matching. A shunt DC motor driving a centrifugal water pump is supplied from a PV generator via a step-up converter whose duty ratio is controlled using a current-locked feedback loop. >
Patent•
02 May 1994TL;DR: In this article, a low concentration solar array for spacecraft and other uses which has a series of solar panels which can be deployed from a folded stowed configuration to a planar configuration is described.
Abstract: A low concentration solar array for spacecraft and other uses which has a series of solar panels which can be deployed from a folded stowed configuration to a planar configuration. When the solar panels are stowed, the padding of reflector panels cushions and protects the solar panels from the stresses and vibrations of launch and space flight. Once the solar panels are extended into a deployed planar configuration, the reflector panels are raised to concentrate sunlight upon the solar panels. These reflector panels are constructed from rigid honeycomb substrates and therefore are the active structural members of the solar array, providing the structural rigidity for the solar array.
Patent•
28 Nov 1994
TL;DR: In this paper, an electric power supply system consisting of an air conditioner serving as load, a solar photovoltaic cell for supplying power to the air conditioning system, and a system power control circuit was described.
Abstract: This electric power supply system includes an air conditioner serving as load, a solar photovoltaic cell for supplying power to the air conditioner, and a system power control circuit and further including a commercial power source for use in combination with the solar photovoltaic cell for supplying additional power when insufficient, power is supplied from the solar photovoltaic cell to the air conditioner In an operation state of the air conditioner, the system power control circuit operates to regulate an operating point of the solar photovoltaic cell and variably regulate the supplied power from the solar photovoltaic cell while comparing required power of the air conditioner with the supplied power from the solar photovoltaic cell
Patent•
12 Apr 1994TL;DR: In this article, a power plant consisting of an array of heliostats for concentrating sunlight on a central solar receiver is described. And a thermal shield is employed over the solar central receiver to insulate the solar receiver, provide leak and fire protection and shield the solar primary receiver from solar radiation.
Abstract: A design of a power plant which uses hydrocarbon fuels in conjunction with solar power to produce electricity. The power plant consists of an array of heliostats for concentrating sunlight on a central solar receiver. The heat energy thus gathered is used to create steam which runs a steam turbine. Steam to run the steam turbine can alternately or modularly be obtained from the exhaust gas of a turbo-burner and fuel added to a furnace. The solar energy gathered may be stored as hot fluid in a thermal storage tank or used immediately in the power plant. A thermal shield may be employed over the solar central receiver to insulate the solar central receiver, provide leak and fire protection and shield the solar central receiver from solar radiation.
Patent•
07 Dec 1994TL;DR: In this paper, a solar cell assembly is fabricated by adapting efficient microelectronics assembly techniques to the construction of an array of small scale solar cells, where each cell is mounted on an individual carrier (4), which is a conventional integrated circuit (IC) package such as a dual-in-line package.
Abstract: A solar cell assembly is fabricated by adapting efficient microelectronics assembly techniques to the construction of an array of small scale solar cells (2). Each cell (2) is mounted on an individual carrier (4), which is a conventional integrated circuit (IC) package such as a dual-in-line package. Electrical connections are made between the cell (2) and the carrier leads (6) by automated wire bonding, followed by the emplacement of an optional secondary solar concentrator element (10,14) if desired. The carriers (4) are then automatically mounted and electrically connected to a common substrate (16), such as a printed circuit board, that has its own electrical interconnection network to interconnect the various cells. Finally, a primary concentrator lens assembly (22) is placed over the array of cells. The resulting panel is thin and light weight, inexpensive to produce, allows for any desired interconnection to be made between the cells, and is capable of high conversion efficiencies.
TL;DR: In this article, the results of experiments carried out on lead/acid batteries during charge and discharge processes at different currents and temperatures, selected to a cover a large range of operating conditions, including those encountered in photovoltaic (PV) system applications, are presented.
TL;DR: In this article, the authors present an experimental study of a thermosyphon water heater with solar cells, where the solar cells are pasted directly over the absorber plate and the solar insolation falling on the aperture area of the collector, using a simple parabolic reflector.
TL;DR: In this article, a parallel multijunction solar cell is described which allows fundamental radiative recombination limits upon photovoltaic cell energy conversion efficiency to be approached more closely in good quality material than possible in a single-junction device.
Abstract: A novel parallel multijunction solar cell is described which allows fundamental radiative recombination limits upon photovoltaic cell energy conversion efficiency to be approached more closely in good quality material than possible in a single‐junction device However, the real advantage arises for poor quality material with the structure shown to be particularly tolerant of both impurity and grain boundary effects A novel implementation approach is described for potentially high‐performance, low‐cost, thin‐film polycrystalline silicon solar cells
05 Dec 1994
TL;DR: In this article, a maximum power point tracking control of photovoltaic array using fuzzy control is proposed, where the controller only uses the output power of the solar cell to get the maximum power.
Abstract: The solar cell has an optimum operating point to be able to get the maximum power. To obtain the maximum power from a photovoltaic array, the photovoltaic power system usually requires a maximum power point tracking controller. This paper proposes a maximum power point tracking control of photovoltaic array using fuzzy control; the controller only uses the output power. Therefore, this control method is easy to implement to a real system. Moreover, this method can track maximum power point rapidly with fuzzy inference even if the optimum operating point changes. The usefulness of this control method is confirmed by experiments using step-down chopper with constant resistive rod. >
TL;DR: Tabulations of confirmed efficiencies for a range of photovoltaic cell and module technologies are updated to include recent results (since mid-1993).
Abstract: Tabulations of confirmed efficiencies for a range of photovoltaic cell and module technologies are updated to include recent results (since mid-1993). Also described are the results of two informal ‘round-robin’ comparisons of cell and module measurements from a representative sampling of the designated test centres participating in the compilation of these tables.
TL;DR: In this paper, a first principles computer model for simulating the performance of amorphous semiconductor solar cells has been developed, and the calculated results for the illuminated JV characteristics and solar cell quantum efficiencies are shown to agree well with experiments.
Abstract: A first principles computer model for simulating the performance of amorphous semiconductor solar cells has been developed. With a suitable choice of parameters, the calculated results for the illuminated J‐V characteristics and solar cell quantum efficiencies are shown to agree well with experiments. The model has been used in this paper to study the sensitivity of the light J‐V characteristics to various device and material parameters in p‐i‐n homojunction solar cells. The single most important factor controlling the open circuit voltage, short circuit current, fill factor, and cell efficiency is the transparent conducting oxide/p‐a‐Si:H contact barrier height φbo, when φbo is less than a certain critical value. Also shown is that practically no improvement in cell performance can be achieved by decreasing the dangling‐bond midgap state density, described by Gaussian distribution functions, to lower than 1016 cm−3, unless the valence‐band tail states are also reduced. Moreover, results indicate that lig...
TL;DR: In this article, the authors used a finite difference method to simulate the performance of a solar water heater with photovoltaic thermal (PV/T) cells and showed that the average cell efficiency is more or less independent of the cell area.
20 Jun 1994
TL;DR: A novel multi-step PWM inverter for a solar power generation system that has many features such as good output waveform, small size of filter, low switching losses, and low acoustic noise is presented.
Abstract: In this paper, the authors propose a novel multi-step PWM inverter for a solar power generation system. The circuit configuration is constructed by adding a bi-directional switch to the conventional bridge type inverter circuit using the isolated DC power supply for which the solar cell is very suitable. The new type of PWM inverter presented has many features such as good output waveform, small size of filter, low switching losses, and low acoustic noise. In this paper the authors describe the circuit configuration, control method and the characteristics of the system, and they also investigate the relation between the inverter and the solar cell characteristics. Finally, some simulation results and experimental results are shown. >
05 Dec 1994
TL;DR: Analyzes the energy performance of PV modules using six different energy calculation techniques and compares the results to the measured amount of energy produced and indicates which methods are the most effective for predicting energy output in Golden, Colorado, under prevailing meteorological conditions.
Abstract: The rating of photovoltaic (PV) modules has always been a controversial topic in the PV community. There is no industry standard methodology to evaluate PV modules for energy production. This issue must be discussed and resolved for the benefit of system planners, utilities, and other consumers. Several methodologies are available to rate a module's peak power, but do any accurately predict energy output for flat-plate modules? This paper analyzes the energy performance of PV modules using six different energy calculation techniques and compares the results to the measured amount of energy produced. The results indicate which methods are the most effective for predicting energy output in Golden, Colorado, under prevailing meteorological conditions.
TL;DR: In this paper, a deterministic approach to optimal unit sizing for hybrid power generation systems utilizing photovoltaic and wind energy is presented for minimizing the annual total cost and energy consumption from the viewpoints of economy and energy saving or reduction in NO[sub x] and CO[sub 2] emission.
Abstract: A deterministic approach to optimal unit sizing is presented for hybrid power generation systems utilizing photovoltaic and wind energy. Device capacities and electric contract demand are determined so as to minimize the annual total cost and annual energy consumption from the viewpoints of economy and energy saving or reduction in NO[sub x] and CO[sub 2] emission, respectively. This optimization problem is considered as a multiobjective one, and a discrete set of Pareto optimal solutions is derived numerically by using the weighting method. Two systems interconnected with the electric power grid are investigated: one has the option of reverse electricity flow into the grid, and the other has no option. By carrying out some case studies, the tradeoff relationships between the two objectives as well as the optimal values of device capacities are clarified. The influence of electricity deficit on unit sizing is also investigated.
TL;DR: In this paper, the authors investigated two technologies which have different applications but have many similar characteristics: nanocell photoelectrochemical solar cells and electrochromic window. And they compared the two technologies in terms of their performance.
TL;DR: The Fraunhofer Institute for Solar Energy Systems has built a completely self-sufficient solar house (SSSH) in Freiburg, Germany as discussed by the authors, where the entire energy demand for heating, domestic hot water, electricity, and cooking is supplied by the sun.
TL;DR: In this paper, the frequency of the inverter's PWM control signal is adjusted according to the insolation and temperature conditions to improve the overall efficiency of an induction motor drive system, powered by a PV array.
Abstract: The overall efficiency of an induction motor drive system, powered by a PV array, drops significantly when the insolation condition varies away from its nominal level. This problem can be overcame using a control method in which the frequency of the inverter's PWM control signal is adjusted according to the insolation and temperature conditions. The motor speed, and therefore, the power delivered to the load, are adjusted by controlling the inverter's frequency. This eliminates the mismatch between the maximum power that is available from the source and the power that is required by the load. Simulation results presented in this paper show that using the proposed control system allows the induction motor drive system to maintain its optimum efficiency and deliver consistently more power to the load when insolation and temperature vary from the nominal level. This method also offers an improvement in the system stability. >
TL;DR: In this paper, the authors proposed a method of not decreasing cell conversion efficiency with collecting solar thermal energy was proposed based on this evaluation, and evaluated the electric and thermal energy obtained from a PV/T panel is evaluated in terms of energy.
05 Dec 1994
TL;DR: In this article, the authors report the measurement results of temperature sensitivity for Voc of AMONIX's high-concentration photovoltaic (HCPV) cells at various temperatures (25/spl deg/C-65/spl dc) and various concentration levels (one-Sun up to 500 Suns under AM 1.5) and compares against typical one-Sun flat-plate manufacturer's data.
Abstract: Thermal management has been an important issue for both one-Sun flat-plate, and concentration PV power system applications. It is well known that system output power, or efficiency, decreases with the increasing temperature of the solar cell incorporated within the system mainly due to a decrease in open-circuit voltage (Voc) as a function of increasing temperature. This paper reports the measurement results of temperature sensitivity for Voc of AMONIX's high-concentration photovoltaic (HCPV) cells at various temperatures (25/spl deg/C-65/spl deg/C), and various concentration levels (one-Sun up to 500 Suns under AM 1.5) and compares against typical one-Sun flat-plate manufacturer's data. Even after taking into account the negative temperature dependence of the fill factor, the study shows that output power in concentration systems is less affected by temperature variations compared to one-Sun flat-plate designs. The overall effect of this reduced temperature sensitivity for Voc of the HCPV cell on the power output at operating temperature is analyzed and compared against typical single and poly-crystalline silicon, front-junction, one-Sun, flat-plate manufacturer's data. Experimental and analytical results show that typical flat-plate PV power systems have a -0.4%//spl deg/C (4000 PPM) decrease in power versus -0.25%//spl deg/C (2500 PPM) for high-concentration systems.