Showing papers on "Electric power published in 2002"

Adaptive piezoelectric energy harvesting circuit for wireless remote power supply

Abstract: This paper describes an approach to harvesting electrical energy from a mechanically excited piezoelectric element. A vibrating piezoelectric device differs from a typical electrical power source in that it has a capacitive rather than inductive source impedance, and may be driven by mechanical vibrations of varying amplitude. An analytical expression for the optimal power flow from a rectified piezoelectric device is derived, and an "energy harvesting" circuit is proposed which can achieve this optimal power flow. The harvesting circuit consists of an AC-DC rectifier with an output capacitor, an electrochemical battery, and a switch-mode DC-DC converter that controls the energy flow into the battery. An adaptive control technique for the DC-DC converter is used to continuously implement the optimal power transfer theory and maximize the power stored by the battery. Experimental results reveal that use of the adaptive DC-DC converter increases power transfer by over 400% as compared to when the DC-DC converter is not used.

The state of the art of electric and hybrid vehicles

Abstract: In a world where environment protection and energy conservation are growing concerns, the development of electric vehicles (EV) and hybrid electric vehicles (HEV) has taken on an accelerated pace. The dream of having commercially viable EVs and HEVs is becoming a reality. EVs and HEVs are gradually available in the market. This paper will provide an overview of the present status of electric and hybrid vehicles worldwide and their state of the art, with emphasis on the engineering philosophy and key technologies. The importance of the integration of technologies of automobile, electric motor drive, electronics, energy storage, and controls and also the importance of the integration of society strength from government, industry, research institutions, electric power utilities, and transportation authorities are addressed. The challenge of EV commercialization is discussed.

Geothermal energy technology and current status: an overview

Abstract: Geothermal energy is the energy contained as heat in the Earth’s interior. This overview describes the internal structure of the Earth together with the heat transfer mechanisms inside mantle and crust. It also shows the location of geothermal fields on specific areas of the Earth. The Earth’s heat flow and geothermal gradient are defined, as well as the types of geothermal fields, the geologic environment of geothermal energy, and the methods of exploration for geothermal resources including drilling and resource assessment. Geothermal energy, as natural steam and hot water, has been exploited for decades to generate electricity, and both in space heating and industrial processes. The geothermal electrical installed capacity in the world is 7974 MWe (year 2000), and the electrical energy generated is 49.3 billion kWh/year, representing 0.3 % of the world total electrical energy which was 15,342 billion kWh in 2000. In developing countries, where total installed electrical power is still low, geothermal energy can play a significant role: in the Philippines 21% of electricity comes from geothermal steam, 20% in El Salvador, 17% in Nicaragua, 10% in Costa Rica and 8% in Kenya. Electricity is produced with an efficiency of 10–17%. The geothermal kWh is generally cost-competitive with conventional sources of energy, in the range 2–10 UScents/kWh, and the geothermal electrical capacity installed in the world (1998) was 1/5 of that from biomass, but comparable with that from wind sources. The thermal capacity in non-electrical uses (greenhouses, aquaculture, district heating, industrial processes) is 15,14 MWt (year 2000). Financial investments in geothermal electrical and non-electrical uses world-wide in the period 1973–1992 were estimated at about US$22,000 million. Present technology makes it possible to control the environmental impact of geothermal exploitation, and an effective and easily implemented policy to encourage geothermal energy development, and the abatement of carbon dioxide emissions would take advantage from the imposition of a carbon tax. The future use of geothermal energy from advanced technologies such as the exploitation of hot dry rock/hot wet rock systems, magma bodies and geopressured reservoirs, is briefly discussed. While the viability of hot dry rock technology has been proven, research and development are still necessary for the other two sources. A brief discussion on training of specialists, geothermal literature, on-line information, and geothermal associations concludes the review.

Micropower generation using combustion: Issues and approaches

Abstract: The push toward the miniaturization of electro-mechanical devices and the resulting need for micro-power generation (milli-watts to watts) with low-weight, long-life devices has led to the recent development of the field of micro-scale combustion. The concept behind this new field is that since batteries have low specific energy, and liquid hydrocarbon fuels have a very high specific energy, a miniaturized power generating device, even with a relatively inefficient conversion of hydrocarbon fuels to power would result in increased lifetime and/or reduced weight of an electronic or mechanical system that currently requires batteries for power. In addition to the interest in miniaturization, the field is also driven by the potential fabrication of the devices using Micro Electro Mechanical Systems (MEMS) or rapid prototyping techniques, with their favorable characteristics for mass production and low cost. The micro-power generation field is very young, and still is in most cases in the feasibility stage. However, considering that it is a new frontier of technological development, and that only a few projects have been funded, it can be said that significant progress has been made to date. Currently there is consensus, at least among those working in the field, that combustion in the micro-scale is possible with proper thermal and chemical management. Several meso-scale and micro-scale combustors have been developed that appear to operate with good combustion efficiency. Some of these combustors have been applied to energize thermoelectric systems to produce electrical power, although with low overall efficiency. Several turbines/engines have also been, or are being, developed, some of them currently producing positive power, also with low efficiency to date. Micro-rockets using solid or liquid fuels have been built and shown to produce thrust. Hydrogen-based micro size fuel cells have been successfully developed, and there is a need to develop reliable reformers (or direct-conversion fuel cells) for liquid hydrocarbons so that the fuel cells become competitive with batteries. In this work, some of the technological issues related to meso and micro-scale combustion and the operation of thermochemical devices for power generation will be discussed. Some of the systems currently being developed will be presented and described.

Integration of distributed energy resources. The CERTS Microgrid Concept

Abstract: Evolutionary changes in the regulatory and operational climate of traditional electric utilities and the emergence of smaller generating systems such as microturbines have opened new opportunities for on-site power generation by electricity users. In this context, distributed energy resources (DER)--small power generators typically located at users' sites where the energy (both electric and thermal) they generate is used--have emerged as a promising option to meet growing customer needs for electric power with an emphasis on reliability and power quality. The portfolio of DER includes generators, energy storage, load control, and, for certain classes of systems, advanced power electronic interfaces between the generators and the bulk power provider. This white paper proposes that the significant potential of smaller DER to meet customers' and utilities' needs can be best captured by organizing these resources into MicroGrids.

Feasibility of a DC network for commercial facilities

Abstract: This paper analyzes the feasibility of direct current for the supply of offices and commercial facilities. This is done by analyzing a case study, i.e. the supply to the Department of Electric Power Engineering, Chalmers University of Technology, Gothenburg, Sweden. Voltage drop calculations have been carried out for different voltage levels. A backup system for reliable power supply is designed based on commercially available batteries. Finally, an economic evaluation of AC versus DC is performed and protection of the proposed system is briefly addressed.

One-Hour-Ahead Load Forecasting Using Neural Networks

Abstract: Load forecasting has always been the essential part of an efficient power system planning and operation. Several electric power companies are now forecasting load power based on conventional methods. However, since the relationship between load power and factors influencing load power is nonlinear, it is difficult to identify its nonlinearity by using conventional methods. Most of papers deal with 24-hour-ahead load forecasting or next day peak load forecasting. These methods forecast the demand power by using forecasted temperature as forecast information. But, when the temperature curves changes rapidly on the forecast day, load power changes greatly and forecast error would going to increase. In conventional methods neural networks uses all similar day's data to learn the trend of similarity. However, learning of all similar day's data is very complex, and it does not suit learning of neural network. Therefore, it is necessary to reduce the neural network structure and learning time. To overcome these problems, we propose a one-hour-ahead load forecasting method using the correction of similar day data. In the proposed prediction method, the forecasted load power is obtained by adding a correction to the selected similar day data.

Control system and method for electric vehicle

Abstract: An electric traction vehicle is described herein which may be used to provide power to off-board electric power-consuming systems or devices. The electric traction vehicle may provide 250 kilowatts or more of three phase AC power to an off-board electric power consuming system. The electric traction vehicle may also include an electrical power storage device which can be selectively discharged to allow the vehicle to be serviced.

Method and device for supplying electric energy power to an appliance

Abstract: The invention concerns a portable device for electric power supply comprising: connection means ( 8 ) for connecting an appliance ( 1 ) to be powered; and a power supply circuit ( 6; 16 ) supplying in output a supply voltage for the appliance when the circuit is selectively connected to a mains supply or to a low-voltage electric power source. It may also comprise a battery ( 10 ). In that case, the circuit ( 6, 16 ) can charge the power storage means when the circuit is connected to an appropriate electric power source, the connection means ensuring power supply to the appliance ( 1 ) from the power storage means ( 10 ).

Electrical power metering system

Abstract: A wireless electrical power metering system is provided. A processor having a multichannel power line transceiver, a wireless transceiver, and a power meter attached thereto measures power consumption information on a power line inductively coupled with the power meter. The processor converts the power consumption information into IP-based data, and transmits same over the wireless transceiver. The information can be wirelessly received by a remote monitoring station or transmitted across the Internet for storage, analysis, and billing. The processor generates appliance control signals and generates same across the multichannel power line transceiver to remotely control appliances in response to power consumption trends. The processor provides firewall capabilities, and relays information between a wired or wireless network and a power line network, thereby expanding the size of existing household networks. Further, the processor allows multiple dwellings to be networked using power lines, and households to be connected to the Internet via a power line network.

Final Test and Evaluation Results from the Solar Two Project

Abstract: Solar Two was a collaborative, cost-shared project between 11 U. S. industry and utility partners and the U. S. Department of Energy to validate molten-salt power tower technology. The Solar Two plant, located east of Barstow, CA, comprised 1926 heliostats, a receiver, a thermal storage system, a steam generation system, and steam-turbine power block. Molten nitrate salt was used as the heat transfer fluid and storage media. The steam generator powered a 10-MWe (megawatt electric), conventional Rankine cycle turbine. Solar Two operated from June 1996 to April 1999. The major objective of the test and evaluation phase of the project was to validate the technical characteristics of a molten salt power tower. This report describes the significant results from the test and evaluation activities, the operating experience of each major system, and overall plant performance. Tests were conducted to measure the power output (MW) of the each major system, the efficiencies of the heliostat, receiver, thermal storage, and electric power generation systems and the daily energy collected, daily thermal-to-electric conversion, and daily parasitic energy consumption. Also included are detailed test and evaluation reports.

Electrically heated smoking system and methods for supplying electrical power from a lithium ion power source

Abstract: An electrically heating smoking system wherein tobacco smoke is generated by heating a portion of a cigarette with an electrical resistance heating element powered by lithium ion battery cells. The lithium ion battery cells supply current to the electrical resistance heating element with current up to 20 times greater than the recommended discharge rate. To prevent damage to the lithium ion battery cells under such high discharge conditions, the smoking system includes a controller which provides modulated pulses of electrical power from the battery cells to the resistance heating element during smoking of the cigarette.

A laser-micromachined multi-modal resonating power transducer for wireless sensing systems

Abstract: This paper presents the development of a vibration-induced power generator with total volume of ∼1 cm 3 which uses laser-micromachined springs to convert mechanical energy into useful electrical power by Faraday’s law of induction. The goal of this project is to create a minimally sized electric power generator capable of producing enough voltage to drive low-power ICs and/or microsensors for applications where ambient mechanical vibrations are present. Thus far, we have fabricated generators with total volume of 1 cm 3 that are capable of producing up to 4.4 V peak-to-peak, which have a maximum RMS power of ∼830 μW with loading resistance of 1000 Ω. The mechanical vibration required to generate this electrical energy has frequencies ranging from 60 to 110 Hz with ∼200 μm amplitude. The generator was shown to generate sufficient power at different resonating modes. We have demonstrated that this generator can drive an infrared (IR) transmitter to send 140 ms pulse trains every minute, and also a 914.8 MHz FM wireless temperature sensing system.

A method and apparatus for reading and controlling electric power consumption

Abstract: An electro-optical, automatic reader (104) for enabling a consumer to view and manage power consumption through a browser (602). A sensor (210) attached to a bracket (202) is mounted to the outside cover (306) of a utility meter without modification of the meter (102) or removal of its housing. A data-collector (106) stores data obtained from the sensor (210) via a serial port which may also provide power for the sensor (210), thus avoiding use of a dedicated power supply. The data-collector (106) connects to a computer (110) which provides a centralized object through which to view and manage power consumption. The real-time and combined historic data can be used to forecast whether usage will fall above or below a predetermined usage level at the end of a given period of time. In response to a forecast exceeding the level, the computer (110) displays the appropriate graph in a red colored bar within a quantity vs. time chart. The computer (110) may control power consuming devices. A communication system (804) may be established to the system for remote management by the consumer or by the utility company (806) for its own billing and management purposes.

Roadway-powered electric vehicle system having automatic guidance and demand-based dispatch features

Abstract: A roadway-powered electric vehicle (RPEV) system includes: (1) an all-electric vehicle; and (2) a roadway network over which the vehicle travels. The all-electric vehicle has one or more onboard energy storage elements or devices that can be rapidly charged or energized with energy obtained from an electrical current, such as a network of electromechanical batteries. The electric vehicle further includes an on-board controller that extracts energy from the energy storage elements, as needed, and converts such extracted energy to electrical power used to propel the electric vehicle. The energy storage elements may be charged while the vehicle is in operation. The charging occurs through a network of power coupling elements, e.g., coils, embedded in the roadway. The RPEV system also includes: (1) an onboard power meter; (2) a wide bandwidth communications channel to allow information signals to be sent to, and received from, the RPEV while it is in use; (3) automated garaging that couples power to the RPEV for both replenishing the onboard energy source and to bring the interior climate of the vehicle to a comfortable level before the driver and/or passengers get in; (4) electronic coupling between “master” and “salve” RPEV's in order to increase passenger capacity and electronic actuators for quick-response control of the “slave” RPEV; (5) inductive heating coils at passenger loading/unloading zones in order to increase passenger safety; (6) an ergonomically designed passenger compartment; (7) a locating system for determining the precise location of the RPEV; and (8) a scheduling and dispatch computer for controlling the scheduling of RPEV's around a route and dispatch of RPEV's based on demand.

Coupling between power line and customer in power line communication system

Abstract: Apparatus for coupling communication signal modulated radio frequency signals between an electrical power distribution line and the electrical power wiring at a customer's premises which includes a first transceiver for transmitting and receiving electromagnetic energy is inductively coupled to the distribution line and a second transceiver for receiving electromagnetic energy from, and transmitting electromagnetic energy to, the first transceiver. The second transceiver is coupled to the customer's power wiring to receive communication signals from, and to supply communication signals to, the customer's power wiring. The electrical power for the first transceiver can be supplied by inductive coupling to the power line and/or a battery, the battery being a back-up source when both inductive coupling and a battery are present.

Method and system to increase the throughput of a communications system that uses an electrical power distribution system as a communications pathway

Abstract: A method and system to increase the throughput of a communications system that uses an electrical power distribution system as a communications pathway, determines the phase of the power distribution power cycle and compares this determined phase to predetermined regions of the power cycle. If the power cycle is within a predetermined region, a particular communication scheme is used for transmitting and receiving information. The power cycle can have two or more predetermined regions. Optionally, the throughput for any or all regions can be determined so as to provide for modification of the associated communication scheme if the throughput is determined to be outside some predetermined range.

Hybrid construction equipment

Abstract: A hybrid construction equipment capable of sufficiently exhibiting performance of a battery with strategic arrangement of the apparatuses being carried out is provided. For this purpose, the hybrid construction equipment includes, on an upper revolving superstructure ( 10 ) rotatably placed on a lower traveling unit, an engine ( 1 ), a generator ( 3 ) driven by the engine ( 1 ), a battery ( 5 ) charged with electric power generated by the generator ( 3 ), an electric motor ( 7 ) driven by electric power of the battery ( 5 ), an inverter ( 6 ) for controlling drive of the electric motor ( 7 ) and a driver's cab ( 12 ), and the battery ( 5 ) is placed to be isolated from the engine ( 1 ) and the generator ( 3 ).

Method for operating a wind park

Abstract: The invention relates to a method for operating a wind park; consisting of several wind power plants. The wind part is connected to an electric supply network into which the power produced by the wind park is fed and the wind park and/or at least one of the wind power plants of the wind park is provided with a control input which is used to adjust the electric power of the wind park or one or several individual wind plants within a range of 0-100 % of the respectively provided power, especially the nominal output thereof. A data processing device is connected to the control input and is used to adjust the control value within a range of 0-100 % according to the amount of power available from the entire wind part at the output where it is fed into the power network. The operator (EVU) of the electric power supply network to which the wind park is connected can adjust the power provided by the wind park via the control input.

Multiple-input DC-DC power converter for power-flow management in hybrid vehicles

Abstract: The search for a compact, lightweight, and efficient energy storage system (battery and/or combination of other emerging technologies, including ultracapacitors, flywheel energy storage system, advanced batteries, and fuel cells) that is both affordable and has acceptable cycle life remains the major roadblock to large-scale production of EVs and HEVs. In this paper a multiple input DC-DC power converter (MI-PEC) devoted to combine the power flowing from combined on-board energy sources is presented; the proposed arrangement for the propulsion system includes electric generator (EG), ultracapacitor tank (UC) and battery systems.

IEEE trial-use standard 1459-2000, definitions for the measurement of electric power quantities under sinusoidal, nonsinusoidal, balanced, or unbalanced conditions

Abstract: The definitions for active, reactive, and apparent powers that are currently used are based on the knowledge developed and agreed upon during the 1940s. Such definitions served the industry well, as long as the current and voltage waveforms remained nearly sinusoidal. Important changes have occurred in the last 50 years. New definitions in the Trial-Use Standard were developed to give guidance with respect to the quantities that should be measured or monitored for revenue purposes, engineering economic decisions, and determination of major harmonic polluters. The panel will discuss these issues.

System for controlling particulate filter temperature

Abstract: A system for controlling the temperature of a particulate filter coupled to an exhaust outlet of an internal combustion engine includes a controller responsive to volumetric flow and temperature of exhaust gas to determine a filter regeneration parameter. In a hybrid electric-engine vehicle application, various control strategies are implemented as a function of the regeneration parameter to control exhaust gas temperature suitably for proper regeneration of the particulate filter. Such strategies include shifting the duty cycle of the engine toward lower engine speed operation along lines of constant power output, modifying the ratio of electrical power and engine power and controlling recharging of the battery supplying electrical energy to the vehicle's electric drive motor under vehicle deceleration conditions. In vehicle applications including a transmission coupled directly to the engine, shift points of the transmission are modified as a function of the regeneration parameter to control exhaust gas temperature.

Communication system, communication terminal and communication method

Abstract: From an electric pole outside to a cordless handset inside a building/facility, a communication line is established via an electric power line. At this point, it is judged whether or not electric power line communication is possible, and if electric power line communication is possible, the communication line between the cordless handset and a base unit is switched to an electric power line communication system, and a communication line is formed via an optical fiber cable from the electric power line. By measuring the communication quality levels of all lines of the wireless and electric power lines, the communication line having the highest communication quality level may be selected.

Photovoltaic power generation system with storage batteries

Abstract: An object of the present invention is to provide a system capable of reducing optimally peak demand for power by using small capacity storage batteries. The present invention was made to provide a photovoltaic power generation system which links with a utility power system, feeds electric power generated by a solar cell device to an inverter in order to convert the electric power into alternating current, and supplies the alternating current to a power consumption section. The photovoltaic power generation system comprises storage batteries for storing electric power and a switch control device for switching to output electric power from the solar cell device to the storage batteries or the inverter. Also the photovoltaic power generation system controls discharge of the electric power stored in the storage batteries with reference to a specific period of high power demand represented by a fluctuation curve of power demand, and supplies the electric power from the storage batteries along with generation power from the solar cell device to the inverter.

Combined fuel cell and fuel combustion power generation systems

Abstract: A power generation system is provided which converts chemical energy in one or more fuels into electrical and/or mechanical power. The system includes both fuel cells to directly convert electrical energy in a fuel into electrical power and at lest one combustor and expander to generate mechanical power, optionally than converted to electrical power in a generator. Fuel cell products disclosed from the fuel cell are entered into the combustor to be heated along with products of combustion created in the combustor and expanded in the expander along with the products of combustion.