Showing papers on "Stand-alone power system published in 1991"

Method and system for electricity storage and discharge

Abstract: The present invention features a method and system for storing electrical energy, and then using the stored energy to recharge automobiles. The system of the invention features a number of storage and recharging facilities that are connected to a main power generating station. Power is generally demanded from the power station in the evening or during off-peak power demand periods, in order to obtain lower rates from the power utility. Also, off-peak power loading does not put a strain on the power system. The energy obtained from the power utility company is then stored at each recharging facility in a bank of capacitors. A high voltage transformer and rectifier arranged ahead of the capacitor banks converts the incoming AC high voltage power from the utility to the required DC voltage for capacitor storage. The controller distributes power to a number of charging bays that are connected to the capacitor bank. A vehicle needing charging pulls into an individual bay in the recharging facility, and is connected to a metering device having feedback control. A sensing unit interrogates the power remaining in the batteries of the vehicle, and passes this information onto a controller. In this manner, the exact amount of required energy is transferred to the vehicle.

Power supply system for continuously energizing a D.C. load

Abstract: This power supply system for a D.C. electrical load, such as an illuminated sign, is normally energized by batteries. A central processing unit monitors the battery voltage and when it falls below a predetermined magnitude, the central processing unit then activates a starter motor which cranks an engine coupled to it. The central processing unit also actuates a valve and fuel pump to pass fuel to the engine. The engine drives an alternator which produces A.C. voltage which is then rectified by aa rectifier to recharge the batteries. When the batteries are fully charged the central processing unit stops the engine. The central processing unit employs a microprocessor chip to control operations of the system.

Methods for identifying potential power quality problems

Abstract: An increasing number of end-users in industrial, commercial, and residential areas are becoming aware of the power quality problems they experience in their power systems. The electric utilities are receiving an increased number of customer complaints due to this. This work outlines potential power quality problems that could exist in the power system along with methods to identify them. The authors present the power quality related issues from the end-user's and utility's standpoint. >

Power supply system in highly-airtight heat-insulated residence

Abstract: PURPOSE:To cut down the cost of power facility and attain comfortable residence space by supplying power by a solar battery system wherein the primary components are a storage battery which charges the power from a solar battery or midnight power and a controller which controls the power charge method for the storage battery CONSTITUTION:For the charge method for the storage battery 24 of a solar battery system 21, the power is charged from a solar battery array board 22 or midnight power 23 to a storage battery 24 by the operation of the time switch 30 being set to specified time unit For example, in the daytime, the time switch 30 on the side of a solar battery board 22 is turned on, and the power generated in the solar battery board 22 is charged in the storage battery 24 through the second charge circuit S4 Moreover, late at, the time switch 30 on the side of the solar battery 22 is turned off, and the time switch 30 on the side of an AC main power source 23 is turned on, whereby the midnight power is charged in the storage battery 24 through the first charge circuit S3

Developments in battery storage for wind/diesel systems

Abstract: This paper presents a review of the latest developments in battery storage system for hybrid wind/ diesel systems. A summary of the state-of-the-art of such systems is given, along with a review of recent developments in prototype experimental systems. Work at the University of Massachusetts involving application and modeling of lead/acid battery storage in a wind/diesel system is described. The application of a rainflow cycle counting method for estimating battery life is presented.

The parallel operation of generating plant within a regional electricity company's distribution network

Abstract: The Energy Act (1983) established a right for persons or companies to use the public electricity supply systems to transmit energy from one location to another or to third parties. The publishing in October 1988 of the revised Electricity Supply Regulations set out the statutory requirements for those wishing to operate private generating plant. This has led to a considerable increase in generation embedded in distribution networks ranging in size from about 15 kW to 10 MW or more. Connections can be at a voltage level ranging from 1 V through to 33 kV or even 132 kV and typical energy sources used are water, waste heat from chemical processes, combined heat and power units and gas from refuse disposal plant or tips. The author addresses the effect of the growing numbers and sizes of relatively small embedded generators on the operation and performance of distribution networks. The author concentrates on technical issues and not on the regulatory or operational procedures. The issues discussed include voltage regulation, fault currents, islanding, system stability, earthing and protection of the interface between the network and embedded generator.

Hydrogen Energy Storage for Photovoltaic Power Systems

Abstract: This paper describes the status of a three year photovoltaic hydrogen energy system development project launched at Helsinki University of Technology in 1990. The project is a part of the Finnish national research program on advanced energy systems (NEMO) financed by the Ministry of Trade and Industry. The scope of the project is to demonstrate the technical feasibility of a 100% self sufficient photovoltaic hydrogen energy system consisting of a PV array, an electrolyzer, hydrogen storage and a fuel cell. When succesfully demonstrated the system concept could be used in remote power applications and advanced low energy houses. Component tests for an experimental system of 1 kWh daily load are being carried out and mathematical models have been developed for approximate system sizing and detailed system analysis. Finally, the economic potential of the concept is discussed.

Optimum Design of a Grid-Connected Photovoltaic Power System

Abstract: As a part of various electric power sources, the photovoltaic power system are expected to be one of the important power systems in a near future The authors have developed the computer program of optimizing grid-connected photovoltaic power system from points of view of daily electric load and electrical energy cost In a grid-connected photovoltaic power system (PV system), electric power generated is supplied to distribution line and loadIn this paper, the optimum design of typical private residence with PV system in Tokyo is calculated by using the various system performance models, the cost models, the daily electric load pattern, environmental data and so onIt was found that the capacity of PV system is 26kW when the selling price of surplus power and buying price of shortage one are equivalent And then, the electrical energy cost of the optimum PV system at 2, 000 A D is estimated to be about 35yen/kWh

Dynamic switching technique for load control in a PV system

Abstract: The voltage load control of a stand-alone photovoltaic power (SAPV) system can be an indication for the optimum utilization of the system A low-cost online control by a simple electronic circuit using a switching technique for both the PV array and the storage batteries is presented This circuit makes it possible to control the load voltage, and the charging and discharging currents of the storage batteries The circuit can also rearrange the PV array cells with load variations The series and parallel cells are determined at each operating point The coordinates of the photovoltaic array N/sub p/ and N/sub s/ are obtained such that the total power is generated at the extreme condition In addition, the break-even point of the overall system is deduced as an index between the two boundaries of power generated >

A progress report on an isolated Darrieus wind electrical system

Abstract: An isolated electrical generation system powered by a Darrieus wind turbine is nearing completion. This is providing the University of Regina with a unique facility for the study of the economics and operation of isolated wind power systems, and for investigating the control and dynamics of such systems and alternatives for blade materials and coverings. It is suggested that the Darrieus wind system may provide significantly reduced costs in providing power to isolated locations. A demonstration system has been designed and installed. The motorizing circuit has been tested. >

Intelligent Power Station Control Systems for Remote Area Power Supply - Practical Experience in the Northern Territory with Medium Size Diesel/Battery Power Stations

Abstract: Multiple unit diesel driven power stations form the backbone of power generation in remote areas of inland Australia. These stations are chiefly operated by the Power and Water Authority (PAWA) where the load is domestic or community based. Similar stations are operated by specialist consumers such as mines, large cattle stations, and large tourist complexes, however, discussion in this paper is restricted to PAWA community based sites. The technology has two main aspects; system control, fault analysis, data logging and communications; and on-line battery storage to offer fuel savings. System control is based on a dedicated CPU 186 with I/0 and a specialist Pascal operating program. The control system selects which diesel set configuration is most efficient in supplying the load. It compensates for variable conditions, records all system events, logs all data channels and can auto-call a remote service center in the event of a critical failure.

Nuclear-driven technologies that could reduce the cost of electricity by several fold

Abstract: Dramatic reduction in the cost of electricity may potentially be achieved utilizing unconventional nuclear-driven technologies. The cost of electricity has three major contributors; fuel cycle cost, containment cost, and electrical generator (balance of plant) cost. A general discussion is given on the characteristics that nuclear energy sources must have in order to minimize fuel cycle costs. Two unconventional methods are covered for generating electricity with dramatic reduction in cost. One, is a water pump and contains low- technology components. The other is a plasma MHD generator and contains high-technology components that require further development, but may produce electricity at only 1/10 the present cost. A systems economic analysis is outlined that can be used to guide and evaluate the performance of various nuclear-driven electrical generating technologies to be pursued in future work. 11 refs.

Comparing battery back up units

Abstract: Current technology for uninterruptable power systems (UPSs) is discussed, and some guidelines for determining the cost-effectiveness of integrating battery backup with the power supply are presented. As the percentage of systems with backup increases, it becomes cost-effective to integrate the battery backup with the power supply. A custom design may be required for maximum cost benefit. The choice of an integrated magnetic approach would appear to be the most cost-effective, but the distributed power approach may offer some benefits because of its flexibility. Custom-designed battery-supported switching power supplies have been limited to high-power kilowatt and above power applications. The author attempts to show that a properly designed battery supported supply can be cost-effective to use at much lower power levels. >

Solid state regulator/charger for low power PV systems

Abstract: The different types of electronic regulator battery chargers employed in low-rating solar-powered lighting systems are discussed. A low-power photovoltaic (PV) lighting unit was built and tested which includes a basic constant-current series regulator interfacing with the PV module and the storage battery. The system is especially designed for use in remote areas to serve small farming communities. The system has proved to be practical, low in cost, and reliable. >

Multiprocessor structure for managing multi-nature energy sources

Abstract: A multiprocessor structure is proposed to manage the operation of an integrated power generating system, which includes a photovoltaic generator, a diesel generator set, and storage batteries. Economic and ecological considerations are the main factors which determine the choice of the mode of operation of the available unit. The multiprocessor maintains the operation of the whole system as an uninterruptible power supply with minimum total running cost. The proposed multiprocessor structure is not restricted to specific numbers or types of energy sources, but can be applied to any number of energy sources that differ in nature and operation policy. The system considered is suitable for generating power far from a power network. >

Importance Of Generation Scheduling Of Thermal Units For Economic Operation Of Power Systems

Abstract: The demand for electrical power is growing rapidly due to industrialisation and the utilities are not in a position to plan their generation capacity additions suitably to meet this growing demand for power. This has resulted in a large gap between generation and demand. In this context, economical operation of the system, so as to utilise the capacities optimally become very important. This can be achieved by suitably scheduling the thermal generating units and committing them appropriately, for a projected load demand on the system, arrived at, using short term load forecasting techniques.