Showing papers on "Photovoltaic system published in 1996"

Methodology for optimally sizing the combination of a battery bank and PV array in a wind/PV hybrid system

Abstract: In this paper, a methodology for calculation of the optimum size of a battery bank and the PV array for a standalone 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 average power generated by a wind turbine and a PV module for every hour of a typical day in a month. A load of a typical house in Massachusetts, USA, was used as a load demand of the hybrid system. For a given load and a desired loss of power supply probability, an optimum number of batteries and PV modules was calculated based on the minimum cost of the power system.

Dynamic maximum power point tracker for photovoltaic applications

Abstract: A dynamic process for reaching the maximum power point of a variable power source such as a solar cell is introduced. The process tracks maximum power nearly cycle-by-cycle during transients. Information from the natural switching ripple instead of external perturbation is used to support the maximizing process. The method is globally stable for DC-DC power converters, provided that a switching action is present. A prototype boost power converter that uses this method for control can follow power transients on time scales of a few milliseconds. This performance can be achieved with a simple analog control structure, which supports power processing with minimum loss.

Photovoltaic module and array performance characterization methods for all system operating conditions

Abstract: This paper provides new test methods and analytical procedures for characterizing the electrical performance of photovoltaic modules and arrays. The methods use outdoor measurements to provide performance parameters both at standard reporting conditions and for all operating conditions encountered by typical photovoltaic systems. Improvements over previously used test methods are identified, and examples of the successful application of the methodology are provided for crystalline- and amorphous-silicon modules and arrays. This work provides an improved understanding of module and array performance characteristics, and perhaps most importantly, a straight- forward yet rigorous model for predicting array performance at all operating conditions. For the first time, the influences of solar irradiance, operating temperature, solar spectrum, solar angle-of- incidence, and temperature coefficients are all addressed in a practical way that will benefit both designers and users of photovoltaics.

Apparatus and method for maximizing power delivered by a photovoltaic array

Abstract: A method and apparatus for maximizing the electric power output of a photovoltaic array connected to a battery where the voltage across the photovoltaic array is adjusted through a range of voltages to find the voltage across the photovoltaic array that maximizes the electric power generated by the photovoltaic array and then is held constant for a period of time. After the period of time has elapsed, the electric voltage across the photovoltaic array is again adjusted through a range of voltages and the process is repeated. The electric energy and the electric power generated by the photovoltaic array is delivered to the battery which stores the electric energy and the electric power for later delivery to a load.

Influence of photovoltaic power generation on required capacity for load frequency control

Abstract: We developed a mathematical model to evaluate the impact of small (rooftop) photovoltaic (PV) power-generating stations on economic and performance factors for a larger scale power system, and applied this model to the Tokyo metropolitan area. We used solar radiation data from five local meteorological stations to estimate both the individual and aggregate contributions of the projected PV stations to the local power grid. We found that an electrical power system containing a 10% contribution from PV stations would require a 2.5% increase in load frequency control (LFC) capacity over a conventional system. The break-even cost for PV power generation was found to be relatively high for contribution levels of less than 10%. Higher proportions of PV power generation gave lower break-even costs, but economic and LFC considerations imposed an upper limit of about 10% on PV contributions to the overall power systems.

A new panel-integratable inverter concept for grid-connected photovoltaic systems

Abstract: This paper describes the problems of conventional inverter concepts for photovoltaic power systems and presents a new, panel-integratable inverter concept as a solution. This concept is advantageous regarding safety (no DC-lines), flexibility (modular concept), converted energy per year (no mismatch losses due to individual MPP tracking of each panel) and costs (no reinforced isolation due to AC distribution). Furthermore a 250 W DC to AC inverter is developed, which consists of a series resonant DC-DC power converter and a line inverter. The inverter has a high efficiency and consumes little power itself. Meeting international standards, sinusoidal line current with low distortion is achieved. The inverter has a built-in controller to operate the panel in the maximum power point. Above this, the concept allows the flexible use with many different combinations of solar panels. To realize an inexpensive system, the controller is built up using standard low-cost components.

Temperature dependence of photovoltaic cells, modules and systems

Abstract: Photovoltaic (PV) cells and modules are often rated in terms of a set of standard reporting conditions defined by a temperature, spectral irradiance and total irradiance Because PV devices operate over a wide range of temperatures and irradiances, the temperature and irradiance-related behavior must be known This paper surveys the temperature dependence of crystalline and thin-film, state-of-the-art, research-size cells, modules and systems measured by a variety of methods The various error sources and measurement methods that contribute to cause differences in the temperature coefficient for a given cell or module measured with various methods are discussed

A study of lead-acid battery efficiency near top-of-charge and the impact on PV system design

Abstract: Knowledge of the charge efficiency of Pb-acid batteries near top-of-charge is important to the design of small PV power systems. In order to know how much energy is required from the photovoltaic array in order to accomplish the task of meeting load, including periodic full battery charge, a detailed knowledge of the battery charging efficiency as a function of state of charge is required, particularly in the high state-of-charge regime, as PV power systems are typically designed to operate in the upper 20 to 30% of battery state-of-charge. This paper presents the results of a process for determining battery charging efficiency near top-of-charge and discusses the impact of these findings on the design of small PV power systems.

Development of a model for photovoltaic arrays suitable for use in simulation studies of solar energy conversion systems

Abstract: The work described in this paper was carried out as part of the development of an advanced solar photovoltaic (PV) conversion system. During the design of the system, simulation of both the power chain and the control algorithms was found to be useful, but to simulate a system as a whole requires a non-application specific circuit-based simulation model of a PV array for a simulator such as Saber, or the well known SPICE. There were found to be no such models readily available and thus the development of one became necessary. This work successfully sought to develop a cheap, but effective system to characterize existing cells and generate the device-dependent data that provides the link between the environmental variables irradiance and temperature, and the electrical characteristics of the device.

A novel on-line MPP search algorithm for PV arrays

Abstract: A novel maximum power point (MPP) search algorithm for photovoltaic (PV) array power systems is introduced. The proposed algorithm determines the maximum power point of a PV array for any temperature and solar irradiation level using an online procedure. The method needs only the online values of the PV array output voltage and current, which can be obtained easily by using just current and voltage transducers. The algorithm requires neither the measurement of temperature and solar irradiation level nor a PV array model that is mostly used in look-up table based algorithms. Satisfactory results were obtained with the proposed algorithm in a laboratory prototype implementation scheme consisting of a PV array computer emulation model, a chopper controlled permanent magnet DC motor, and a DT2827 data acquisition board with the ATLAB software drivers for interfacing.

Novel grid-connected photovoltaic inverter

Abstract: Detailed analysis and simulation results of a novel solar photovoltaic inverter configuration interconnected to the grid are presented. From the simulation results it is confirmed that the harmonic distortion of the output current waveform of the inverter fed to the grid is within the stipulated limits laid down by the utility companies. Typical hardware aspects are also discussed in detail and the applicability of the design is verified.

DSP-based controller application in battery storage of photovoltaic system

Abstract: Photovoltaic power systems normally use maximum power point tracking (MPPT) to continuously deliver the highest possible power to the load when changes in insolation and temperature occur. This overcomes the problem of mismatch between the solar cells and the given load. The solar array is normally treated as a voltage source, but it is treated as a current source in this paper. A simple method of tracking the maximum power point (MPP) and forcing the PV power system to operate near this point is also presented. The effect of the negative impedance of power converters on the MPPT process is also considered. As to the system equivalent circuit model, the principle of energy conservation is used to develop large- and small-signal models and the transfer function. By using this model, the drawbacks of the state-space-averaging method can be overcome. A TI320C25 digital signal processor (DSP) was used to implement the proposed MPPT controller; simulations and experimental results show its excellent performance.

Method of checking solar panel characteristics in an operating solar electrical system

Abstract: In a solar electric supply system in which an electrical load is supplied with current produced by a solar array formed of multiple solar panels, each solar panel is individually selected and tested to ensure proper performance by varying the duty cycle of an associated variable transconductance device connected between such solar panel and the electrical load. The method determines the respective solar panel's open circuit voltage, its full-load current and obtains various output voltage and current values responsive to different duty cycles, whereby the maximum power point for the solar panel may be determined.

Photovoltaic solar roof

Abstract: This invention concerns a solar roof consisting of unmodified mass-produced roofing elements (1), for example of fiber cement, upon which solar cells (2) which have also been mass produced have been made fast using adhesive or clamps. Each solar cell (2) has a border element (3) on its upper edge upon which a connecting terminal (4) is placed. This connecting terminal (4) has at least one receptacle (5) into which can be inserted an asymmetrically formed plug (6) at the end of a cable (7). All of the named elements (1 to 7) rest on the roofing elements (1) so that no ducts of any kind need to be provided through the roofing elements (1), for example, a longer cable (17) leads from the final roofing element (1) of a row under the next higher overlaying roofing element and under the roof to a converter or direct consumer. The switch type (series or parallel) of the individual solar cells (2) is established by the wiring in the connecting terminal (4). The roof can be laid by a roofer with no electrotechnical expertise.

Customized storage, high voltage, photovoltaic power station

Abstract: The present invention relates to a customized storage, high voltage, photovoltaic power station, having at least one photovoltaic solar module and a customized storage device.

Solar Cells: An Introduction to Crystalline Photovoltaic Technology

Abstract: List of Symbols. List of Figures. Preface. 1. An Overview of Solar Cell Technology. 2. Solar Cells as Semiconductor Diodes. 3. Solar Cell Mechanism and Performance. 4. Cell and Module Development. 5. Non-Ingot and Novel Technologies. Index.

Best Practices for Photovoltaic Household Electrification Programs: Lessons from Experiences in Selected Countries

Abstract: This report identifies an important economic niche for photovoltaic (PV) systems within rural electrification programs. Chapter 1 sketches the evolution of household photovoltaic systems. Chapter 2 describes solar home systems, their costs, consumer perceptions and the potential niche for household PV in rural electrification. Chapter 3 analyzes the economics of solar home systems vis-�vis grid and off-grid options. Chapter 4 outlines financial constraints to solar home system diffusion. Chapter 5 examines vehicles for program implementation. Chapter 6 sets out financing and cost recovery requirements. Chapter 7 focuses on technical standards. Chapter 8 lists the main conclusions and recommendations. Annex 1 summerizes the four case studies of household experiences in Indonesia, Sri Lanka, the Philippines, and the Dominican Republic. Annex 2 details the economic analysis and assumptions used to define the economic niche for solar home systems in rural electrification. It also examines the impact of productive loads and load growth on solar homes system competitiveness. The main conclusion of the report is that PV systems are a viable complement to grid-based energy service delivery and that within the rural electrification framework such systems can find a cost -effective niche and sustainable market.

Light pipe with solar bulb energy conversion system

Abstract: A light pipe with Solar Bulb energy conservation system that includes: one or more solar and/or artificial light sources; one or more opaque and/or transparent hollow tubular conduits; a reflective material means covering the inside surfaces of the hollow tubular conduits; a mirror at either end of the conduits and between any vertical and horizontal connecting joint sections; a plurality of photovoltaic cell arrays mounted on substrates, positioned inside the hollow tabular conduits, whereby part of the light energy source illuminates, and part of the light energy source is converted into electric energy. The light pipe system optionally includes: an exterior transparent protective dome and reflector; a light concentrator means; a battery charge controller; a rechargeable battery or plurality of batteries; a DC to AC inverter; an AC/DC light ballast, with a battery charge switch; and single or multiple light fixtures, that include conventional bulbs, and/or Power Saver Bulbs, and/or Solar Bulbs. The Solar Bulb converts sunlight or artificial light to electric energy, by photovoltaic means. The Power Saver Bulb illuminates and converts artificial light to electric energy, by photovoltaic means.

Vehicle top solar power generator

Abstract: A vehicle-top solar-power generator has a Photovoltaic frame (2) with mounting brackets (3) that are positioned on a top (4) of a vehicle (5) with a cooling space between the top of the vehicle and the photovoltaic frame. At least one and preferably a plurality of Photovoltaic panels (1) are positioned in the Photovoltaic frame and covered with a light-transmittable material (28) such as plexiglass or a screen of suitable material. Direct current generated from the Photovoltaic panels is transmitted to a primary battery (6), to a secondary battery (7), to AC electrical items (13) and to DC electrical items (14). Power generated in excess of needs for the vehicle is inverted to alternating current for electrical items in such structures (15) as a home, workplace, recreational vehicle, boat or other structure near the vehicle. A cooling fan (12) powered by current from the Photovoltaic panels is used to cool the Photovoltaic panels. Control regulators control flow of current from the Photovoltaic panels to one or more batteries for charging, for inverting to AC current and for distribution of AC current and DC current for nearby use.

Cell shunt resistance and photovoltaic module performance

Abstract: The shunt resistance of solar cells in photovoltaic modules can affect module power output and could indicate flawed manufacturing processes and reliability problems. The authors describe a two-terminal diagnostic method to directly measure the shunt resistance of individual cells in a series-connected module nonintrusively, without de-encapsulation. Peak power efficiency vs. light intensity was measured on a 12-cell, series-connected, single crystalline PV module having relatively high cell shunt resistances. The module was remeasured with 0.5-, 1-, and 2-ohm resistors attached across each cell to simulate shunt resistances of several emerging technologies. Peak power efficiencies decreased dramatically at lower light levels. Using the PSpice circuit simulator, the authors verified that cell shunt and series resistances can indeed be responsible for the observed peak power efficiency vs. intensity behavior. They discuss the effect of basic cell diode parameters, i.e., shunt resistance, series resistance, and recombination losses, on PV module performance as a function of light intensity.