Showing papers on "Electricity generation published in 1987"

High average power harmonic generation

Abstract: High average power frequency conversion using solid-state nonlinear materials is discussed. Recent laboratory experience and new developments in design concepts show that current technology, a few tens of watts, may be extended by several orders of magnitude. For example, using KD*P, efficient doubling (> 70 percent) of Nd:YAG at average powers approaching 100 KW is possible; for doubling to the blue or UV regions the average power may approach 1 MW. Configurations using segmented apertures permit essentially unlimited scaling of average power. High average power is achieved by configuring the nonlinear material as a set of thin plates with a large ratio of surface area to volume, and cooling the exposed surfaces with a flowing gas. The design and material fabrication of such a harmonic generator is well within current technology.

The Effects of Moving Clouds on Electric Utilities with Dispersed Photovoltaic Generation

Abstract: As the incident solar radiation on a utility service area changes, the power generated by utility-interactive solar photovoltaic (PV) generators dispersed throughout that area also changes. The utility must follow these changes with its own generation, just as it now follows normal fluctuations in customer load. This paper presents the results of a simulation designed to assess the maximum possible changes in PV generation that a utility can expect over certain time intervals for different service area sizes. The simulation can be used with a power flow program to study the actual effects of dispersed residential PV generation on a utility.

The Quality of Load Matching in a Direct-Coupling Photovoltaic System

Abstract: The quality of load matching in a photovoltaic system determines the quality of system performance and the degree of the solar cells utilization. In a matched system, the operation of the load-line is close to the maximum power-line of the solar cell (SC) generator. Some load-lines inherently exhibit a relatively good matching when they are directly connected to the SC generator; for others, the matching is rather poor, and therefore, requires the inclusion of a maximum-power-point-tracker (MPPT) in the system. This present study deals with the performance analysis of six common types of loads that are directly connected to the SC generator, and defines a factor that describes the quality of matching of the load to the solar cells. The results of the study indicate the compatibility of the different loads when powered by solar cells, and will assist the designer of the photovoltaic system in considering whether to include an MPPT. The quality of load matching is defined here as the ratio of the load input power to the SC generator maximum power as a function of the solar insolation, or as a function of the solar time. The six loads are: an ohmic load, a storage battery, an ohmic load and storage battery, a water electrolyzer, a power conditioner--constant power load, and a dc motor driving volumetric and centrifugal pumps.

Low Frequency Oscillations in Longitudinal Power Systems: Experience with Dynamic Stability of Taiwan Power System

Abstract: Sustained low frequency oscillations have been observed in Taiwan power system which is of longitudinal structure. It is the purpose of this paper to examine the various factors affecting the damping characteristics of these oscillations which caused dynamic instability problem in the operation of Taiwan power system. It is observed that the amount of power flow on the EHV transmission line and the characteristics of load have a significant effect on the damping of the system while the speed-governing system and the gain of automatic voltage regulator have only a minor one. Detailed investigation using both the frequency domain and time domain approaches also reveals that power system stabilizers can be employed as an effective means for improving dynamic stability of Taiwan power system.

Compressed gas system and method

Abstract: A system and method of selectively deployed and utilized compressed air energy storage satellite facilities within an electrical power grid network. The satellite facilities are independent of geological formations and provide means for increasing the load carrying capacity of an electrical power system without increasing the size of the baseload electrical power generation facility or of the power transmission lines. A portion of the compressed gas is circulated back through a compressor located in a gas flow circuit, causing turbulent flow in a series of tanks, thus slowing heat energy loss to the environment. A heat exchanger located in the circuit of gas flow cools the gas while it is being stored, thus reducing the work needed to compress a given mass of gas into the tanks. The system and method utilizes low cost electrical energy produced by a baseload facility during non-peak periods and converts such electricity into potential energy in the form of compressed air. The compressed air is deployed in outlying areas, away from the baseload facility, to provide ready electrical energy during peak demand periods from a location closer to the peak electrical demand consumer. The system and method may also be utilized to boost dropped and/or lagging voltage and/or current to reduce line loss during electrical power transmission.

Optimal Reactive Power Allocation

Abstract: A systematic procedure is developed to locate reactive power devices in a power system based on a set of indices, that are based on overall system conditions. After identifying the desired locations, the cost of installation and number of reactive power devices, subject to any required practical and real economic constraints, are minimized. Existing controllers are fully utilized before adding any new devices. Linearized sensitivity relationships of power systems are used to obtain an objective function for minimizing the cost of installation. The constraints include the limits on dependent variables (reactive powers of the generators, load bus voltages) and control variables (generator voltages, tap positions, switchable reactive power sources). A parametric linear programming technique based on active set analysis is proposed to solve the reactive power allocation problem.

Generation scheduling and control

Abstract: Within an Energy Management System, the Generation Scheduling and Control function controls the electrical power output of generators so as to supply the continuously changing customer power demand in an economical manner. This function is largely provided by an Automatic Generation Control (AGC) program operating within the control center computer. Power system dispatchers also play an important role, interacting with the program to incorporate current operating conditions. This paper summarizes the system characteristics associated with AGC, as well as current practices of program design and operation. Topics of current interest are also discussed. Current technology in this area is fairly mature, and existing performance is good over-all. Current issues such as fuel scheduling, dispersed generation technologies, and advanced load management schemes may change the nature of the AGC problem in the future.

Electricity production from alkalophilic organisms

Abstract: Selected strains of alkalophilicbacillus organisms showed a remarkable ability for reducing ‘redox’ mediator reagents, and were used as biocatalysts in the anode compartment of a redox-mediated microbial fuel cell. Substantial generation of electricity from oxidation of glucose as the fuel-substrate was demonstrated, particularly at the optimum growth pH.

Steam-Injected Gas Turbines

Abstract: Rising electricity prices, the near-term prospect of surplus natural gas supplies, and the provisions of the Public Utility Regulatory Policies Act (PURPA) and ensuing regulations that encourage cogeneration have stimulated a wave of innovation in gas turbine technology. Here the significance of one of these innovations, the steam-injected gas turbine, is assessed for both cogeneration and central station power generation.

Three-Phase Induction Generator for Single-Phase Line

Abstract: Hydroelectric generators of less than 20 kilowatts can be in remote areas served only by a single-phase line. For high efficiency and low cost, a three-phase induction generator should be used. This three-phase generator can operate with balanced voltages and currents when the ``phase-splitting'' circuit uses two capacitors connetted to two different single-phase voltage sources.

Output Power Controller for a Wind-Driven Induction Generator

Abstract: A constant stator power output controller for a wind-driven grid-connected induction generator is described. The load torque of the generator is controlled by varying the rotor resistance electronically. A dynamic model for the wind energy conversion system is proposed for both controlled and uncontrolled operation.The model is then used to predict the changes in shaft speed,turbine torque, and stator power output in response to change in wind speed. Data pertaining to a 60 kW commercial wind turbine generator is used in this investigation. Results based on analog computer simulation demonstrate the feasibility of the controller for scheduling a desired power output from the induction generator.Results of the tests on a laboratory induction generator driven by amicrocomputer-controlled dc motor drive simulating the characteristics of the wind turbine are included.

Power from the sea

Abstract: A review is presented of the technology for ocean thermal energy conversion, OTEC, for electricity generation. Warm seawater can generate electricity in two ways. In one warm water evaporates a working fluid with a low boiling point. In the second the seawater itself boils in a vacuum chamber. In each case the resulting vapor turns a turbine to generate power. Cold seawater from a depth of 600-1000 meters is used to condense the working fluid to complete the cycle. Both systems, research programs, and demonstration plants are described.

Control apparatus for variable-speed hydraulic power generating system

Abstract: Disclosed is a control apparatus for a variable-speed hydraulic power generating system comprising a variable-speed a.c. electric generator connected to an a.c. electric power system and a hydraulic machine system including a water turbine for driving the generator and a guide vane for controlling an amount of water supplied to the water turbine. The control apparatus comprises a frequency converter connected between the electric power system and the generator for controlling electric power supplied from the generator to the electric power system, control means operating in response to at least an externally applied power generation command signal for controlling, on one hand, the frequency converter thereby controlling the electric power supplied from the generator to the electric power system and generating, on the other hand, a guide-vane opening command signal for controlling the guide vane thereby controlling the amount of water supplied to the water turbine, and means for reducing resonance which may occur in the hydraulic machine system when the rotation speed of the water turbine changes in response to a change of the externally applied power generation output command signal.

Ocean wave energy extracting erosion reversal and power generation system

Abstract: An ocean wave energy extracting beach sand erosion reversal and electric power generation system. Moored seaward of the breaker zone it serves the function of beach sand accretion by extracting energy from the waves prior to their breaking thereby lessening turbulence responsible for tossing sand into suspension to then be swept away by currents. Two pontoons support a series of pyramidal frameworks from which is suspended a strong, flexible, weighted pendulum which is the drive shaft of a large electric generator. The pendulum is caused to swing by the undulations of the ocean waves. The pendulum is caused to rotate as it swings by means of loops of cable and ratcheted pulleys thereby becomming a drive shaft to turn a large generator. By applying the force of the rotating pendulum to turn an electric generator, electricity is produced as a by-product of erosion reversal.

Optimal Set-Point Scheduling in a Boiler-Turbine System

Abstract: A 32nd order boiler-turbine model is developed to solve the optimal set-point scheduling problem for main and hot reheat steam conditions in a 235 MW gas fired electric generating plant. The model has 7 states in the process and 25 in the control system. The optimization strategy uses control vector parameterization in which the boiler controller set-point function generators are modified to produce suboptimum signals. The performance index consists of the total energy input to the system from the fuel and boiler feedpump. Constraints in the process variables are monitored by critical alarm limits, and hoop stresses in the heat exchanger tubes are estimated as well. The optimization problem is solved for steady state and dynamic conditions in the 75 to 235 MW load range. Savings in fuel between 0.7 to 4.0% are predicted by computer simulations in the normal operating load range of the unit. Preliminary plant tests indicate these estimated savings may be realistic. The boiler-turbine model and optimization strategy illustrate the potential use of mathematical models for power plants.

Integrated mechanical vapor recompression apparatus and process for the cogeneration of electric and water-based power having a recirculation control system for part-load capacity

Abstract: Disclosed are a method and apparatus for selectively generating different amounts of electric power and high pressure steam power according to the user's needs, using a fluid-cooled engine and a dual-function screw machine that may be operated as either a compressor or an expander. Fluid from a cooling jacket fluid is separated into vapor and liquid portions and, to increase the amount of high pressure steam delivered by the apparatus, low pressure steam from a separator is compressed by the screw machine and liquid from the separator is heated to a high temperature and high pressure. When additional electric power is desired, the low pressure steam from the separator is diverted from the screw machine. High pressure steam, manufactured by compressing and heating the liquid of the separator, is expanded in the screw machine, which adds its power to the main drive shaft, thereby adding to the available electric power. Various combinations of amounts of electric power and steam power are possible by controlling the amounts of material presented to the screw machine as either a compressor or an expander. The apparatus also includes a recirculation system used when the screw machine is employed as a compressor during periods of off-design point engine load and which facilitates driving the screw machine without drawing down the pressure of the apparatus.

On the Control and Stability of Grid Connected Photovoltaic Sources

Abstract: A methodology is proposed for the effective integration of photovoltaic (PV) devices into the electric utility distribution network operations. The dispersed PV generator is viewed as an active device used to improve system stability by appropriately modulating the power conditioning unit's output power. Disturbances on the utility system can be damped out by injecting this power into the grid in such a way so that the net effect is a cancellation of undesirable oscillations. The approach is implemented by monitoring the oscillating power and generating control signals which shape accordingly the interface unit's output power. Successful implementation of the scheme relies heavily on the speed and flexibility with which the electronic inverter moves power from the primary source/storage facility to the utility lines. Simulation studies, using the proposed control approach, indicate that application of these policies may result in reduced load following requirements for conventional power generating units, increase the value and acceptability of new energy technologies, and improve power quality and stability of the interconnected system.

Simultaneous Production of Desalinated Water and Power Using a Hybrid-Cycle OTEC Plant

Abstract: A systems study for simultaneous production of desalinated water and electric power using the hybrid-cycle OTEC system was carried out. The hybrid cycle is a combination of open and closed-cycle OTEC systems. A 10 MWe shore-based hybrid-cycle OTEC plant is discussed and corresponding operating parameters are presented. Design and plant operating criteria for adjusting the ratio of water production to power generation are described and their effects on the total system were evaluated. The systems study showed technical advantages of the hybrid-cycle power system as compared to other leading OTEC systems for simultaneous production of desalinated water and electric power generation.

A 30-GHz 1-W power HEMT

Abstract: Millimeter-wave power high electron mobility transistors (HEMT's) employing a multiple-channel structure have been fabricated and evaluated in the R-band frequency range. An output power of 1.0 W (a saturated output power of 1.2 W) with 3.1-dB gain and 15.6-percent efficiency was achieved at 30 GHz with a 0.5-µm gate-length and 2.4-mm gate-periphery device. At 35 GHz, a 2.4-mm device delivered 0.8 W with 2.0-dB gain and 10.7-percent efficiency. These are the highest output power figures reported to date for single-chip power FET's in the 30-GHz frequency range.

A Comparison of the Predicted and Measured Thermodynamic Performance of a Gas Turbine Cogeneration System

Abstract: The thermodynamic performance of a gas turbine cogeneration system is predicted using a computer model The predicted performance is compared to the actual performance, determined by measurements, in terms of various thermodynamic performance parameters which are defined and discussed in this paper These parameters include the electric power output, fuel flow rate, steam production, electrical efficiency, steam efficiency, and total plant efficiency Other derived parameters are the net heat rate, the power-to-heat ratio, and the fuel savings rate This paper describes the cogeneration plant, the computer model, and the measurement techniques used to determine each of the necessary measurands The predicted and the measured electric power compare well The predicted fuel flow and steam production are less than measured The results demonstrate that this type of comparison is needed if computer models are to be used successfully in the design and selection of cogeneration systems

Future Developments and Applications of KrF Laser-Fusion Systems

Abstract: Two different types of KrF lasers currently being analyzed as potential laser-fusion drivers: large electron-beam (e-beam)- pumped amplifiers using pure optical multiplexing for pulse compression and small e-beam sustained discharge lasers using a hybrid pulse compression technique. Both types of KrF lasers appear able to satisfy all of the requirements for commercial-applications ICF drivers, including cost, efficiency, pulse shaping, energy scaling, repetition rate, reliability, and target coupling. The KrF driver can effectively operate at efficiencies > 10% and can contribute < 10 mill/kWh to the cost of electric power production, with the total estimated cost of electricity from either KrF laser system being comparable (25 to 50 mill/kWh, 1985 dollars) with the cost from other methods of electric power production. The Aurora facility is described.

Power generation cassette type power plant for marine electric propulsion and a controller thereof

Abstract: A power generation cassette type power plant for marine electric propulsion includes a multiplicity of power generation units each being formed as a power generation cassette including a power generator, a prime mover, for example an internal combustion engine for driving the power generator and a support structure for supporting the power generator and the engine internally. The support structure is formed in the same shape as that of a container for transporting cargo. When the power generators of the multiplicity of power generation units are operated in parallel to each other to supply electric power to a load, controllers serve to share the load to the generators properly.

Efficient electrical power generation system

Abstract: Batteries comprising an anode and liquid electrolyte produce an electrolyte effluent which may contain a solid particulate discharge. This discharge product inhibits the efficient generation of electrical power by the battery. It has been discovered that this solid particulate discharge may be effectively and economically separated from the electrolyte on a continuous basis by a solids separation means comprising a container having an axis and an impeller. This system provides for the efficient generation of electrical power.

Electrohydraulic/air screw engine

Abstract: A vehicle drive system in which batteries provide power for driving an electric motor connected to a pump for either compressing air or pressurizing hydraulic fluid for loading a fluid cylinder that is operatively connected for reciprocatably driving a series of drive gears operably connected to and for providing rotation to a series of worm screw gears having an output shaft connected for driving the wheels of a vehicle. A kinetic energy recovery system in which a series of gravitational alternators are operably connected between the axle and chassis/frame of a vehicle for providing electricity during vehicular movement. Additional kinetic energy is recovered as steam is generated by deriving heat from the operative fluid cylinder to the screw engine and transmitting the heated fluid to a low pressure steam boiler for providing steam in operating a screw engine generator for generating electricity.

Analysis of closed cycle megawatt class space power systems with nuclear reactor heat sources

Abstract: The analysis and integration studies of multimegawatt nuclear power conversion systems for potential SDI applications is presented. A study is summarized which considered 3 separate types of power conversion systems for steady state power generation with a duty requirement of 1 yr at full power. The systems considered are based on the following conversion cycles: direct and indirect Brayton gas turbine, direct and indirect liquid metal Rankine, and in core thermionic. A complete mass analysis was performed for each system at power levels ranging from 1 to 25 MWe for both heat pipe and liquid droplet radiator options. In the modeling of common subsystems, reactor and shield calculations were based on multiparameter correlation and an in-house analysis for the heat rejection and other subsystems.

Basic Characteristics of Cycloconverter for Linking Commercial and High-Frequency Distribution Lines

Abstract: A new method to improve the power factor and current waveform on the commercial ac system is proposed. The frequency of a local distribution line in a factory or a chemical plant is made high, up to about 500 Hz. The local distribution line is linked directly to the commercial line by using a cycloconverter operating in circulating current mode. Quasi-sinusoidal current with unity displacement factor is realized on the commercial line side regardless of the consumed power by loads. The system configuration and the basic principle of operation of the cycloconverter for linking both lines are described. The influence of system parameters on the operation limit is investigated based on the power equilibrium constraints. Experimental results obtained in the 5.2KVA laboratory system show the validity of the proposed system.

Method and module for the generation off solar power

Abstract: Photoelectric power generation becomes less effective as the temperature rises. If high temperatures are available, the thermoelectric method is suitable for power generation. In sunny regions, high temperatures can be achieved by means of sun collectors. If water is available, a temperature difference which is necessary for thermoelectric power generation can be reached and maintained.