Showing papers on "Stand-alone power system published in 1995"

Generator power system and method

Abstract: An integrated power system includes an engine/generator power supply integrated with storage batteries to provide household-like AC power. For a small load demand, the storage batteries are used to provide electricity. For a large load demand, the engine/generator starts to supply electricity. The engine/generator also recharges the storage batteries if the load demand is smaller than the engine/generator maximum load capacity. For a larger load demand, both the engine/generator and the storage batteries supply electricity in parallel. The engine speed is variable for various loads. The bigger the load, the higher the engine speed is required to produce the necessary power and keep a constant high DC voltage.

Photovoltaic systems for small-scale remote power supplies

Abstract: This article considers the technical aspects of using photovoltaic systems for small power supplies where a connection from a main electricity distribution network is not appropriate. The technology of the various components of a photovoltaic power system is discussed and the overall system design considered. Typical applications of photovoltaic systems are described.

Harnessing the wind

Abstract: Wind power is now recognized as the one renewable-energy source on the verge of being economically viable. For developing countries, in fact, the technology is already practical for bringing pollution-free electricity to areas off the power grid. The author discusses the economic benefits of wind power and then discusses the basic principle involved in generating electricity from wind. The use of wind power by developing countries is outlined with particular reference to projects in Mexico and Indonesia. >

Marginal Capacity Costs of Electricity Distribution and Demand for Distributed Generation

Abstract: Marginal costs of electricity vary by time and location. Past researchers attributed these variations to factors related to electricity generation, transmission and distribution. Past authors, however, did not fully analyze the large variations in marginal distribution capacity costs (MDCC) by area and time. Thus, the objectives of this paper are as follows: (1) to show that large MDCC variations exist within a utility`s service territory; (2) to demonstrate inter-utility variations in MDCC; and (3) to demonstrate the usefulness of these costs in determining demand for distributed generation (DG). 27 refs., 3 figs., 2 tabs.

Time shift control of wastewater pumping system

Abstract: Reservoir flow or surge control systems frequently have large installed lifting or pumping capacity to deal with variations in either inflow or outflow, or both, and may form a part of a larger system of many such reservoirs. Taken together these reservoirs may have significant storage capacity. In operation such systems are large consumers of electricity. Electricity is often priced differently at different times of day. This invention employs this storage capacity to permit energy consumption to be shifted, at least in part, from periods of high electricity prices to periods of low electricity prices. This is done by permitting a greater amount of material to collect during periods of expensive electricity, and then removing the material to a lower level during periods of less expensive electricity, or the reverse, depending on the nature of the system and the material in question. Either an `On-Off` or flow rate control method of pump control may be used. The invention is illustrated by application to a wastewater pumping system. In this case a control unit works in conjunction with a pulse-echo acoustic level sensor to control the operation of a battery of wastewater pumps at wastewater pumping stations in an urban sewage system.

Battery power monitoring apparatus for vehicle

Abstract: A battery power monitoring apparatus for use in an electric automobile is provided. The battery power monitoring apparatus determines the amount of available reserve electric power remaining in a storage battery based on electric power discharged from the storage battery to an electric motor and a battery characteristic stored in a memory, representing a relation between a voltage level at which a given level of current flows from the storage battery and the then discharged electric power. The battery characteristic is updated based on the latest detected voltage of the storage battery and current flowing from the storage battery. The battery power monitoring apparatus determines that charge polarization has occurred when a voltage level of the storage battery from which the given level of current flows is increased, and prohibits the updating of the battery characteristic. With this operation, the amount of available electric power is calculated correctly even under the influence of charge polarization.

Superconducting power delivery systems for transmission and distribution applications

Abstract: Transmission and distribution power systems are presently experiencing tremendous changes in both load requirements and system operation. End-users demand increased reliability and power quality. System operations change to optimize the distribution and number of generation sources to take advantage of load diversity and fuel availability. Superconducting Magnetic Energy Storage (SMES) and modern power electronics systems emerge as technologies enabling power utility systems to adapt to these changes. These systems deliver services unique and previously unavailable and the authors suggest the term Superconducting Power Systems to describe them. Babcock and Wilcox (B and W) is working with Anchorage Municipal Light and Power (ML and P) to design, manufacture and install a 50 MW, 1,800 MJ system in Anchorage, Alaska. The system will be commissioned in early 1998.

Dispersion type power supply

Abstract: PURPOSE: To provide a storage battery for controlling power supply having a small capacity which makes unnecessary the installation of an expensive UPS (Non-Break Power Supply) as the control power supply and can be used as the backup power supply for changeover of the control power supply. CONSTITUTION: When the power system is operated normally, a low voltage bus 4 supplies the control power source, in combination with the power system, solar battery 7 and inverter 10 (power generating apparatus) to a measuring apparatus 22g, a display apparatus 23 (monitoring apparatus), a protection relay 19 and a grounding over voltage relay 21 (protection device) via a relay 24 for changing over the control power supply. Moreover, when the power supply system fails, the control power source is supplied, by changing over the relay 24 for changing over the control power supply, through the self- operation of the solar battery 7, storage battery 9 for solar battery and inverter 10 (power generating apparatus).

Applications of transient phenomena during earth-faults in electricity distribution networks

Abstract: The treatment of the neutral of a medium voltage power system has a major influence on the system behaviour. Earth faults in isolated and compensated power systems are simulated. The results contribute to various developments for improved power system protection. Conditions in radially operated rural 20 kV overhead distribution networks are considered.

Solar-hydrogen electricity generation in the context of global CO2 emission reduction

Abstract: The relative costs and CO2 emission reduction benefits of advanced centralized fossil fuel electricity generation, hybrid photovoltaic-fossil fuel electricity generation, and total solar electricity generation with hydrogen storage are compared. Component costs appropriate to the year 2000–2010 time frame are assumed throughout. For low insolation conditions (160 W m−2 mean annual solar radiation), photovoltaic electricity could cost 5–13 cents/kWh by year 2000–2010, while for high insolation conditions (260 W m−2) the cost could be 4–9 cents/kWh. Advanced fossil fuel-based power generation should achieve efficiencies of 50% using coal and 55% using natural gas. Carbon dioxide emissions would be reduced by a factor of 2 to 3 compared to conventional coal-based electricity production in industrialized countries. In a solar-fossil fuel hybrid, some electricity would be supplied from solar energy whenever the sun is shining and remaining demand satisfied by fossil fuels. This increases total capital costs but saves on fuel costs. For low insolation conditions, the costs of electricity increases by 0–2 cents/kWh, while the cost of electricity decreases in many cases for high insolation conditions. Solar energy would provide 20% or 30% of electricity demand for the low and high insolation cases, respectively. In the solar-hydrogen energy system, some photovoltaic arrays would provide current electricity demand while others would be used to produce hydrogen electrolytically for storage and later use in fuel cells to generate electricity. Electricity costs from the solar-hydrogen system are 0.2–5.4 cents/kWh greater than from a natural gas power plant, and 1.0–4.5 cents/kWh greater than from coal plant for the cost and performance assumptions adopted here. The carbon tax required to make the solar-hydrogen system competitive with fossil fuels ranges from $70–660/tonne, depending on the cost and performance of system components and the future price of fossil fuels. Leakage of hydrogen from storage into the atmosphere, and the eventual transport of a portion of the leaked hydrogen to the stratosphere, would result in the formation of stratospheric water vapor. This could perturb stratospheric ozone amounts and contribute to global warming. Order-of-magnitude calculations indicate that, for a leakage rate of 0.5% yr−1 of total hydrogen production -which might be characteristic of underground hydrogen storage - the global warming effect of solarhydrogen electricity generation is comparable to that of a natural gas-solar energy hybrid system after one year of emission, but is on the order of 1% the impact of the hybrid system at a 100 year time scale. Impacts on stratospheric ozone are likely to be minuscule.

Wind energy as a significant source of electricity

Abstract: Wind energy is a commercially available renewable energy source, with state-of-the-art wind plants producing electricity at about $0.05 per kWh. However, even at that production cost, wind-generated electricity is not yet fully cost-competitive with coal- or natural-gas-produced electricity for the bulk electricity market. The wind is a proven energy source; it is not resource-limited in the US, and there are no insolvable technical constraints. This paper describes current and historical technology, characterizes existing trends, and describes the research and development required to reduce the cost of wind-generated electricity to full competitiveness with fossil-fuel-generated electricity for the bulk electricity market. Potential markets are described.

Government, industry, and utility development and evaluation of a modular utility battery energy storage system

Abstract: A prototype 250 kVA modular battery energy storage system was developed and tested for utility peak-shaving applications-in a cooperative Department of Energy, industry, and utility project. The system consists of battery- and converter-integrated modules with AC terminals. Data on the system's energy capacity, power quality, power factor, auxiliary power, thermal regulation, speed of response, and islanding and other protective measures are presented. A simple method of identifying the presence of a defective battery was revealed during the test period. >

The self-sufficient Solar House Freiburg

Abstract: The Frauhofer Institute for Solar Energy Systems has built a completely Self-Sufficient Solar House (SSSH) in Freiburg Germany. The entire energy demand for heating, domestic hot water, electricity and cooking is supplied by the sun. The combination of highly efficient solar systems with conventional means to save energy is the key to the successful operation of the house. Seasonal energy storage is accomplished by electrolysis of water and pressurized storage of hydrogen and oxygen. The energy for electricity and hydrogen generation is supplied by solar cells. Hydrogen can be reconverted to electricity with a fuel cell or used for cooking. It also serves as a back-up for low temperature heat. There are provisions for short-term storage of electricity and optimal routing of energy. The SSSH is occupied by a family. An intensive measurement program is being carried out. The data are used for the validation of the dynamic simulation calculations, which formed the basis for planning the SSSH.

Device for determining state of electricity generation of solar battery

Abstract: A device for determining a state of electricity generation of a solar battery and an apparatus, such as a camera, including such a device are disclosed. The device comprises a first circuit for connecting different loads to the solar battery, and a second circuit for determining a state of electricity generation of the solar battery in accordance with a state of a load current of the solar battery relative to the different loads.

Power controller for battery power supply

Abstract: PROBLEM TO BE SOLVED: To provide a power controller capable of stably taking out the maximum output from a solar battery. SOLUTION: This equipment comprises a battery power supply 1, power conversion means 2 for converting power from the battery power supply and supplying it to a load 3, voltage detection means 4 for detecting a voltage value of the battery power supply, current detection means 5 for detecting a current value of the battery power supply, output value setting means 6 for setting an output value of the battery power supply based on the detected values of the voltage detection means and the current detection means, and control means 7 controlling the power conversion means in such a manner that the output value of the battery power supply coincides with the set point of the output value setting means. And the output value setting means 6 fluctuates the operating point of the battery power supply 1 and samples the voltage value and current value at a plurality of operating points, calculates power value from voltage and current values at each operating point, and the setting method for a set point is selected depending on the curvature of an approximate curve of voltage-power or current-power characteristics curves by polarized functional equations based on the power value and the voltage value of current value. COPYRIGHT: (C)1997,JPO

Distribution load estimation-a function for the electric utility in the de-regulated electricity market

Abstract: In the de-regulated electricity market the distribution utility is no longer a monopoly supplier of electricity in its operating area. Only transmission of electricity remains as local monopoly and energy sales will be separated from distribution and transmission. In Finland, the de-regulation of electricity market is planned to begin in the middle of 1995. The first phase allows 500 kW and bigger customers a freedom to select their power supplier. Later on this limit will be removed. The energy balance of the energy selling companies will no longer be equal to measurements in primary substations. Energies of different suppliers must be separated from each other according to the customer measurements. The remaining load, that is measured with conventional energy meters, belongs then to the utility, which is obliged to sell electricity in the area. Some of the load data will be available after a delay, because it must first be calculated from the customers of different suppliers. The utility's online load must therefore be estimated from various data sources. The distribution load estimation (DLE) prototype is implemented in VTT Energy's Distribution Energy Management (DEM) project.

Rating batteries for initial capacity, charging parameters and cycle life in the photovoltaic application

Abstract: Stand-alone photovoltaic (PV) systems typically depend on battery storage to supply power to the load when there is cloudy weather or no sun. Reliable operation of the load is often dependent on battery performance. This paper presents test procedures for lead-acid batteries which identify initial battery preparation, battery capacity after preparation, charge regulation set-points, and cycle life based on the operational characteristics of PV systems.

Silicon's usefulness in photovoltaics

Abstract: Today, more than ever, photovoltaic energy seems to be on its way to becoming a leading source of electrical power. Prices are dropping and photovoltaic power systems are improving in quality, reliability, and capacity to convert sunlight directly into electricity. One large purchaser of photovoltaics are electric utilities. Here, the author examines the prospects of PV power generation and outlines the economic, as well as environmental, benefits of using this technology. >

Control batteries: power system life savers

Abstract: If protective devices and relays represent the /spl Gt/OPEN "nerves" of a medium- or high-voltage electric power system, the DC control battery distribution system represents the system's "bloodstream." The battery distribution system delivers energy the battery provides to the control circuits of AC circuit breakers and other electrically operated interrupting equipment (the "muscle" of the electric power system), allowing operation. The battery is the DC power distribution system's "heart." Reliable control battery systems assure proper functioning of well designed, installed, and maintained power systems. Battery system failure jeopardizes a power system by eliminating the DC control power source for AC system circuit breakers and protective devices. Failure to protect DC system components also could result in disastrous consequences for the battery system itself. The author discusses battery faults, battery protection, and battery maintenance. Battery charger faults and protection are also briefly mentioned, as are load protection, and DC system protection. >

Reliable cost effective photovoltaic (PV) systems system approach with one-source responsibility

Abstract: In order to provide a reliable, cost-effective electrical power source for telecommunication systems, a system approach with a one source responsibility is imperative to compose a well matched PV system. State of the art application technology and product compatibility are requisites to assure users of PV systems of one of its major advantages: low life cycle costs. The battery having the shortest lifetime of the parts of a PV system, has a big impact on the life cycle costs. Next to the description of the recommended approach to compose a well matched PV system, the paper calls special attention to the performance and ageing of batteries in a PV system.

Open access and network services -- A global approach

Abstract: Utilities functioning in a competitive electricity market are required to provide unbundled services. This paper describes how to make unbundled transmission services available in a competitive electricity market. Methods are presented for developing the long-run marginal cost of transmission and for pricing stand-by and top-up electricity supply. The methods are illustrated with case studies based on current data.

Economic implications to electric power utilities of wind energy produced by nonutility generation

Abstract: A technique is presented in this paper to evaluate the appropriate price that results from a short term contract between a utility and a nonutility generation (NUG). In the technique, the price for purchase of energy from the NUG is considered to be based on the energy cost that a utility avoids. The energy cost that a utility avoids is termed as avoided operating cost (AOC). The evaluation of the AOC is based on the optimum loading configuration of the committed units both before and after the inclusion of NUG energy. The technique can be utilized by a utility as a basic framework upon which relevant system operating criteria, system constraints and cost parameters can be added.

Utility Interactive System by Induction Machines for Supplying the Desired Mechanical Power from Solar Batteries

Abstract: Solar energy is very attractive as a future power source because of an clean and inexhaustible supply. However electric power of solar batteries is variable according to weather conditions. Therefore it is stabilized by storage batteries or supplied to the utility line through an inverter for utility interconnection. These systems, however, have some problems of cost and maintenance.This paper proposes a new utility interactive system which is composed of an induction machine A related to a solar battery through a general purpose inverter and another induction machine B interconnected with the utility line. The frequency of the inverter to drive the machine A is given so that the solar power can be utilized maximumly. This system can stably supply a mechanical load with the desired power by parallel operation of two induction machines even in rainy weather, and moreover regenerate extra power of the solar battery to the utility line in fine weather. This proposed system is economic and useful as a small decentralized power supply because a power filter for rejecting high frequency noises and a detector for a power failure are not necessary.