Showing papers on "Photovoltaic system published in 2000"

Comparative study of maximum power point tracking algorithms using an experimental, programmable, maximum power point tracking test bed

Abstract: Maximum power point tracking (MPPT) is important in solar power systems because it reduces the solar array cost by decreasing the number of solar panels needed to obtain the desired output power. Several different MPPT methods have been proposed, but there has been no comprehensive experimental comparison between all the different algorithms and their overall maximum power point (MPP) tracking efficiencies under varying conditions (i.e. Illumination, temperature, and load). This paper such a comparison. Results are using a microprocessor controlled MPPT powered by a 250 W photovoltaic (PV) array and also a PV array simulator.

Energy pay-back time and CO2 emissions of PV systems

Abstract: The energy requirements for the production of PV modules and BOS components are analyzed in order to evaluate the energy pay-back time and the CO2 emissions of grid-connected PV systems. Both c-Si and thin film module technologies are investigated. Assuming an irradiation of 1700 kWh/m2/yr the energy pay-back time was found to be 2·5–3 years for present-day roof-top installations and 3–4 years for multi-megawatt, ground-mounted systems. The specific CO2 emission of the rooftop systems was calculated as 50–60 g/kWh now and possibly 20–30 g/kWh in the future. This leads to the conclusion that in the longer term grid-connected PV systems can contribute significantly to the mitigation of CO2 emissions. Copyright © 2000 John Wiley & Sons, Ltd.

A fuzzy-logic-controlled single-stage converter for PV-powered lighting system applications

Abstract: This paper presents a fuzzy-logic-controlled single-stage power converter (SSC) for photovoltaic (PV)-powered lighting system applications. The SSC is the integration of a bidirectional buck-boost charger/discharger and a class-D series resonant parallel loaded inverter. The designed fuzzy logic controller (FLC) can control both the charging and discharging current, and can improve its dynamic and steady-state performance. Furthermore, a maximum power point tracker (MPPT) based on a perturb-and-observe method is also realized to effectively draw power from PV arrays. Both the FLC and the MPPT are implemented on a single-chip microprocessor. Simulated and experimental results obtained from the proposed circuit with an FLC have verified the adaptivity, robustness and feasibility.

CIGS‐based solar cells for the next millennium

Abstract: Thin-film photovoltaic (PV) solar cells based on Cu(In,Ga)Se2 (CIGS) have two key distinctive features: highest performance of any true thin-film solar cell (18·8% efficient) and leading performance on the module level. There is no evidence of limits to further improvement of the efficiency. Device stability is not curtailed by intrinsic material properties. The obstacles to large-scale production and commercialization of Cu(In,Ga)Se2-based modules are the complexity of the material and the manufacturing processes. Published in 2000 by John Wiley & Sons, Ltd.

Application of radial basis function networks for solar-array modelling and maximum power-point prediction

Abstract: A neural network-based approach for solar array modelling is presented. The logic hidden unit of the proposed network consists of a set of nonlinear radial basis functions (RBFs) which are connected directly to the input vector. The links between hidden and output units are linear. The model can be trained using a random set of data collected from a real photovoltaic (PV) plant. The training procedures are fast and the accuracy of the trained models is comparable with that of the conventional model. The principle and training procedures of the RBF-network modelling when applied to emulate the I-V characteristics of PV arrays are discussed. Simulation results of the trained RBF networks for modelling a PV array and predicting the maximum power points of a real PV panel are presented.

Efficient organic photovoltaic diodes based on doped pentacene

Abstract: Recent work on solar cells based on interpenetrating polymer networks1,2,3 and solid-state dye-sensitized devices4 shows that efficient solar-energy conversion is possible using organic materials. Further, it has been demonstrated that the performance of photovoltaic devices based on small molecules can be effectively enhanced by doping the organic material with electron-accepting molecules5. But as inorganic solar cells show much higher efficiencies, well above 15 per cent, the practical utility of organic-based cells will require their fabrication by lower-cost techniques, ideally on flexible substrates. Here we demonstrate efficiency enhancement by molecular doping in Schottky-type photovoltaic diodes based on pentacene—an organic semiconductor that has received much attention as a promising material for organic thin-film transistors6,7,8, but relatively little attention for use in photovoltaic devices9,10. The incorporation of the dopant improves the internal quantum efficiency by more than five orders of magnitude and yields an external energy conversion efficiency as high as 2.4 per cent for a standard solar spectrum. Thin-film devices based on doped pentacene therefore appear promising for the production of efficient ‘plastic’ solar cells.

Past, present and future of grid connected photovoltaic- and hybrid-power-systems

Abstract: As a short introduction on the general development and forecast of world market in photovoltaics (PV) are presented. The general classification introduces grid connected, stand alone, large scale and roof-top PV-systems. The core of presentation concentrates on the development and trends of converters for grid connected PV-systems. The novel multi-string converter is introduced representing one of the major trends in PV system technology towards modular PV-system design based on string converter technology with low specific costs and optimal energy yield. A brief excursion into the area of hybrid power systems deals with the development of hybrid power system technology using some representative examples installed by SMA around the world. As one of the future trends in that area a new bi-directional battery-converter for a modularly-structured hybrid power system technology is introduced.

Simple maximum power point tracker for photovoltaic arrays

Abstract: A new technique is presented for tracking the maximum power point (MPP) of solar arrays. Although the control circuit is extremely simple and robust, its dynamics are complex. The MPP becomes inherently the global attractor of the system, thus ensuring optimum operation under transient and steady-state conditions. Experimental results confirm excellent tracking effectiveness and rapid dynamic response.

Experience Curves of Photovoltaic Technology

Abstract: This paper examines the technological evolution, application, and cost trend of photovoltaic (PV) technology over the last three decades. It presents the longest experience curve for PV systems assembled to date; stretching back to the pre-commercialization period in the late 1960s. Cooperative investments by manufacturers and individual governments have resulted in the accumulation of experience within the solar industry and the subsequent cost reduction of PV systems. Significant cost reductions have occurred in both PV modules, that house the solar cells, and the ancillary components, known as balance-of-system (BOS). Between 1968 and 1998, the worldwide cumulative installed capacity of PV modules doubled more than thirteen times, from 95 kW to 950MW, while costs ($/Wp) were reduced by an average of 20.2% for each doubling. Cost reductions for PV modules are attributed to technology innovation, manufacturing improvements, and economies of scale. Though BOS are difficult to compare to one another - due to the customization of PV applications - targeted studies have shown that BOS costs have fallen over the past two decades and in some instances, more than module costs. BOS cost reductions are attributed to greater system integration and the experience of system designers and installers. Future cost improvements will be attained through greater standardization and pre-assembly of BOS components in the factory.

Technology development in the solar absorption air-conditioning systems

Abstract: An environmental control system utilizing solar energy would generally be more cost-effective if it were used to provide both heating and cooling requirements in the building it serves. Various solar powered heating systems have been tested extensively, but solar powered air-conditioners have received little more than short-term demonstration attention. This paper reviews past efforts in the field of solar powered air-conditioning systems with the absorption pair of lithium bromide and water. A number of attempts have been made by researchers to improve the performance of the solar applied air-conditioning (chiller) subsystems. It is seen that the generator inlet temperature of the chiller is the most important parameter in the design and fabrication of a solar powered air-conditioning system. While collector choice, system design and arrangement are other impacting factors for the system operation.

A grid-interactive photovoltaic uninterruptible power supply system using battery storage and a back up diesel generator

Abstract: This paper presents a practical implementation of a grid interactive photovoltaic uninterruptible power supply (UPS) system using battery storage and a back up diesel generator. The system incorporates 2.5 kWp of photovoltaic arrays, a 10 kVA power conditioning unit capable of operating in both inverting and charging modes, and a 300-Ah battery bank. Two such systems were installed in two Indian cities. The project was implemented using soft loans available in India through a World Bank Loan for photovoltaic market development. The system has been working satisfactorily since May 1997 and has demonstrated the capability of the system to provide uninterrupted power, demand side management function and load voltage stabilization in a grid which experiences frequent blackouts and under/over voltage problems. Some results from the field installation are also included in this paper.

An approach to evaluate the general performance of stand-alone wind/photovoltaic generating systems

Abstract: This paper reports the development of a computer approach for evaluating the general performance of stand-alone wind/photovoltaic generating systems. Simple models for different system components are developed, integrated, and used to predict the behavior of generating systems based on available wind/solar and load data. The model is useful for evaluating the performance of stand-alone generating systems and gaining a better insight in the component sizes needed before they are built. Simulation results are presented for performance evaluation of a stand-alone generating system that has been previously designed to supply the average power demand of a typical residential house. An electric water heater model is used as a dump load, and the excess available wind/solar-generated power is used to heat the water. The heated water is used as the inlet water to the main house water heater, which is assumed to be nonelectric. It is shown that this strategy can be effective in reducing the amount of fuel used by the main residential water heater.

Maximum power point tracking control of photovoltaic generation system under non-uniform insolation by means of monitoring cells

Abstract: A photovoltaic power generation system (PV system) is operated under various insolation conditions. Sometimes the PV system is operated under nonuniform insolation, which may generate several maximum output power points on the V-I curve of the PV array and raises serious problem on maximum power point tracking (MPPT) control of the system. In order to solve this problem, the authors propose a novel practical MPPT method, which uses monitoring cells to get a proper starting point of operation as well as the incremental resistance method (dV/dI method).

Maximum Collectable Solar Energy by Different Solar Tracking Systems

Abstract: The output energy from any solar energy system depends on the solar energy input to that system. Using different ways to track the solar energy system to follow the sun can increase solar energy input according to the type of the tracker. A practical study was carried out on different solar tracking systems. The layout of these systems are a fixed system facing south and tilted 40 degrees, a vertical-axis tracker, a 6 degrees tilted-axis tracker, and a two-axis tracker. All the trackers are microprocessor controlled systems, and all systems have photovoltaic arrays for electric energy production. The evaluation of the different systems is based on a complete year of measurements for solar radiation input to the systems and the electric power output from them. The study also includes the effect of some operating parameters on the tracker operation. These studies showed that the collected solar energy as well as the electrical output energy of the tracking solar system are more than that of the stationary s...

Surface-plasmon enhanced photovoltaic device

Abstract: A surface-plasmon enhanced photovoltaic device including: a first metallic electrode having an array of apertures, an illuminated surface and an unilluminated surface, at least one of the surfaces having an enhancement characteristic resulting in a resonant interaction of incident light with surface plasmons; a second electrode spaced from the first metallic electrode; and a plurality of spheres corresponding to the array of apertures and disposed between the first metallic and second electrodes, each sphere having a first portion of either p or n-doped material and a second portion having the other of the p or n-doped material such that a p-n junction is formed at a junction between the first and second portions.

Interconnection of a photovoltaic panels array to a single-phase utility line from a static conversion system

Abstract: This paper presents the analysis of a static conversion system for treatment of the solar energy from photovoltaic panels. This system is interconnected with the mains power supply, contributing to the generation of the electrical energy. The power structure is composed of a current-fed push-pull converter, a buck converter, and a current inverter. The main features of the system are: simple control strategy, robustness, lower harmonic distortion of the current and natural isolation. The principle of operation, design procedure and experimental results are presented.

Short-current pulse based adaptive maximum-power-point tracking for photovoltaic power generation system

Abstract: This paper proposes a novel maximum-power-point tracking (MPPT) method with a simple algorithm for photovoltaic (PV) power generation systems The method is based on the use of a short-current pulse of the PV array to determine an optimum operating current for the maximum output power and completely differs from conventional hill-climbing based methods In the proposed system, the optimum operating current is instantaneously determined by taking a product of the short-current pulse amplitude and a parameter k because the optimum operating current is exactly proportional to the short current under various conditions of illuminance and temperature Also, the system offers an identification function of k by means of fast power-vs-current curve scanning, which makes the short-current pulse based MPPT adaptive to disturbances such as shades partially covering the PV panels The above adaptive MPPT algorithm has been adopted to a current-controlled boost chopper and a multiple power converter system composed by PV-chopper modules Various operating characteristics have been examined, and excellent MPPT performance has been confirmed through the experimental tests

Real-time maximum power point tracking for grid-connected photovoltaic systems

Abstract: The paper presents a model-based method for photovoltaic array maximum power point prediction. The method was tested successfully on a small grid-connected PV system. A three-phase IGBT-voltage-source inverter is used as the power conditioner and a DSP-controller is employed to perform real-time control and prediction functions. The system and experimental results obtained are presented in the paper.