Showing papers on "Electricity generation published in 1988"

High Power Electronics and flexible AC Transmission System

Abstract: During the last decade, higher energy costs, the difficulty in building new power plants and improved converter technology provided an increased Market for HVDC transmission. However, HVDC, due to the high cost of converters, will play a limited role in the overall ac power system. The author discusses the potential of thyristors in ac power systems. The concept of a thyristor-assisted ac power system, called Flexible AC Transmission System is introduced and discussed.

Power electronics in electric utilities: role of power electronics in future power systems

Abstract: The role of power electronics in future power systems is considered The improvement of power semiconductors is held up as a major factor to the increased importance of this role Power electronics applications for HVDC transmission are discussed >

Short term generation scheduling in a small autonomous system with unconventional energy sources

Abstract: The authors present a method for problem solving the short-term generation-scheduling problem in a small autonomous system with both conventional and unconventional energy sources and a storage battery. The system generation consists of diesel generators, wind turbine generators, and photovoltaic panels. This is the generation mix of the power system of the Greek island of Kythons, and may be applied to other Greek islands. A dynamic programming algorithm together with a standard unit commitment, is used to determine the optimal short-term scheduling, which minimizes the fuel consumption for a certain scheduling horizon, e.g., for the next 24 h. >

Underground nuclear power station using self-regulating heat-pipe controlled reactors

Abstract: A nuclear reactor for generating electricity is disposed underground at the bottom of a vertical hole that can be drilled using conventional drilling technology. The primary coolant of the reactor core is the working fluid in a plurality of thermodynamically coupled heat pipes emplaced in the hole between the heat source at the bottom of the hole and heat exchange means near the surface of the earth. Additionally, the primary coolant (consisting of the working flud in the heat pipes in the reactor core) moderates neutrons and regulates their reactivity, thus keeping the power of the reactor substantially constant. At the end of its useful life, the reactor core may be abandoned in place. Isolation from the atmosphere in case of accident or for abandonment is provided by the operation of explosive closures and mechanical valves emplaced along the hole. This invention combines technology developed and tested for small, highly efficient, space-based nuclear electric power plants with the technology of fast-acting closure mechanisms developed and used for underground testing of nuclear weapons. This invention provides a nuclear power installation which is safe from the worst conceivable reactor accident, namely, the explosion of a nuclear weapon near the ground surface of a nuclear power reactor.

Optimal short term operation of a purely hydroelectric system

Abstract: The short-term production scheduling problem for a purely hydroelectric system can be simplified so that the power production and water can be managed separately. This approximation is possible when plants have large daily reservoirs with fixed or controllable heads. The model described by the authors optimizes the hourly power production of a system of hydroplants by minimizing losses in turbines and waterways, while maintaining production to meet load. The problem is inherently of the mixed integer nonlinear type, but an algorithm has been developed to solve it in two stages by linear programming (LP). The model has been tested with data from an existing purely hydroelectric system, the Icelandic power system being the model system. Results indicate considerable savings in water usage from large seasonal reservoirs. These results also indicate the feasibility of installing the model in a control center computer when conditions are similar to the model system. >

Wave action electricity generation system and method

Abstract: This invention discloses a wave action electricity generation system that includes a floating platform that supports the system components on the surface of a body of water, an anchor means for controlling movement of the platform to a desired water surface area of the body of water, a kinetic energy converter that converts wave motion energy into mechanical energy and an electricity generator that converts the mechanical power transfer strokes into electrical energy. The kinetic energy converter includes a cylinder containing a fluid, such as a lubricant, in opposed cylinder chamber portions, a first heavily weighted piston that is slidably and freely disposed within the body of the cylinder. The heavily weighted piston is slidably responsive to the wave motion energy of the body of water and is used to compress the fluid to produce respective compression power strokes in each of the cylinder chamber portions. The energy in the compression stroke is received by a second and third pistons located in the cylinder chamber portions that further produce power transfer strokes through the ends of the cylinder. The power transfer strokes associated with the first and second pistons are further converted by a geared transmission to rotary motion that turns a flywheel coupled to an electricity generator. The electrical energy produced is then distributed to a remote power station via a power transmission line.

Economies of Scale in Nuclear Power Generation

Abstract: Current prospects for the expansion of nuclear electric generating capacity appear dim; there has not been a domestic order placed for a nuclear power plant since 1978, and over 80 plants have been cancelled since the early 1970s. While a host of economic, political and environmental factors are responsible for the current state of the nuclear power industry, concern has increasingly focused on the cost effectiveness of nuclear power, with critics arguing that nuclear power is not an economically feasible alternative.' Economies of scale are a crucial consideration in addressing nuclear power costs. At the plant level, scale economies could be associated with the size of generating units or with multiunit siting. If the former is important, the strong trend toward larger reactors would imply that, all else equal, electricity produced by new plants should cost less than previous experience would indicate. Siting several reactors at a plant, which is common practice in France, for example, would lead to lower costs if the latter factor is important. Despite the importance of these issues, virtually no empirical evidence on economies of scale in nuclear power operations is available.2 Existing studies of nuclear power production costs [20; 7; 26; 23; 22] typically specify some plant size and type, often the proverbial 1,000 MWe plant, and sum up the costs of the inputs required to run it, including a capital cost. By contrast, cost analyses for fossil-fueled electricity generation are more sophisticated.3 Perhaps the first application of econometric modeling in this area was by Nerlove [19]. However, a more up-to-date example is the study of Christensen and Greene [4], who estimated a translog cost function using cross sections of privately owned utilities in 1955 and 1970. Straightforward application of Christensen and Greene's techniques to nuclear power is prob-

Slip power recovery induction generators for large vertical axis wind turbines

Abstract: Simulation results are presented for the performance of a slip power recovery induction generator coupled to a vertical-axis wind turbine. The suitability of this type of generator for wind-driven applications is discussed. A qualitative comparison with two other alternatives is made, highlighting the basic features of the generator configuration studied. Quantitative simulation analysis showed that it is possible to reduce the ripple in the electrical power substantially with stable operation through various changes in wind speed. Regenerative braking is possible, especially in the upper range of speed, which reduces the wear on the mechanical brakes. The design described ensures smooth motor start-up for the induction machine in the motor-mode. >

Fast generation shedding equipment based on the observation of swings of generators

Abstract: A novel method and recently developed stabilizing equipment to prevent the loss of synchronism of generators in pumped-storage plants due to spreading are presented. The method includes functions to estimate the swing of each generator by using online generator output sampled 600 times per second after an occurrence of a disturbance (such as a fault, faulty equipment, etc). Generator swing 200-300 milliseconds ahead and loss of synchronism between generators in pumped-storage plants and those in thermal and nuclear plants can be predicted 200-300 ms ahead, and the number of generators that must be shed to maintain stability can be decided. >

Windtrap energy system

Abstract: A windmill of two designs, both aesthetically acceptable and operational without noise pollution, having a rotatable vertical shaft with either three or four windtraps consisting of a pair of concave vanes. These vanes are attached by welding to both the base and top disk plate making up a windtrap unit. Each windtrap vane is positioned to the others at 60 degree displacement for the first design and 45 degrees on the second design. The horizontal exposure area to the wind fluctuates from 50% to 100% as the shaft makes a complete turn. Torque is applied to the shaft by the impact of the wind from any direction against the curved vanes. The kenetic energy of the wind is transmitted through the shaft, flywheel, and belts which turn multiple generators that are used to produce electricity. The electricity is further processed by a micro controller to make it usable for home, farm, and business use. It further utilizes battery packs for storing electricity. The system can be lowered to a horizontal position in the event of a severe storm. The invention also contemplates using superconductivity for maximum generation of electricity and magnetic shielding.

Automatic generation control for hydro systems

Abstract: The authors present the decision of an automatic generation control (AGC) system implemented with digital computers that periodically sample tie-line real power flows, line frequency, and generator power outputs. These analog signals are measured at 2-5 intervals and combined with desired interchange to obtain the area control error (ACE). The ACE digital quantity is allocated to regulating hydro turbines and transmitted via telemetry to the remote terminal units (RTU). The RTUs convert the raise/lower megawatts (MW) into timed relay contact closures to the governor which result in wicket gate open/close movement to change the generator output power. The output power of each generator is monitored by the digital AGC, which closes a feedback loop around the governor-turbine-generator to assure that the desired power level is attained. The feedback loop design, which is essentially a sampled-data control, is described. Additional feedback loops due to the ACE and load regulation are also analyzed. A method for allocating water usage between reservoirs on a generator command-time basis is presented. The theoretical designs are verified by online measurements. >

Aeroderivative Turbines for Stationary Power

Abstract: According to the authors, a revolution is under way in electricity generating technology. It may soon radically transform the power industry in both industrial and developing countries. This revolution involves the upgrading of the familiar but little-used gas turbine. In the electric utility industry the gas turbine has until recently been restricted largely to little-used peaking plants; in cogeneration (simultaneous production of electricity and process heat in the same unit), the gas turbine has been used mainly in applications characterized by steady steam loads. This paper describes how innovations are making it possible for gas turbines to compete in cogeneration markets characterized by variable heat loads, and to compete in central-station applications with conventional baseload and load-following technologies, using low-quality as well as high-quality fuels.

The history of utility-interactive photovoltaic generation

Abstract: A history is presented of utility photovoltaic generation. Material from readily available publications is discussed and referenced chronologically to show the reader how utility-interactive photovoltaic generation reached its present status. >

Power electronic circuit topology

Abstract: A generalized concept of 'sources' that embraces both power generators and power consumers is presented. This approach simplifies the basic topological aspects of power electronic converter circuits, which are reduced to an array of switches for selectively interconnecting two source systems. Capacitive and inductive filters can modify the nature of the systems, because they act as short-time sources and determine whether the converter sees a voltage source or a current source at its terminals. These differing source qualities require different types of switching devices and have ramifications in the mode of operation of the equipment. Some basic configurations are presented, and their significant properties are described, with emphasis on the most widely used circuits in high-power equipment, particularly AC/DC converters. >

Optimal operation of large-scale power systems

Abstract: A method for optimal operation of large-scale power systems is presented that it is similar to the one utilized by the Houston Lighting and Power Company. The main objective is to minimize the system fuel costs while maintaining an acceptable system performance in terms of limits on generator real and reactive power outputs, transformer tap settings, and bus voltage levels. Minimizing the fuel costs of such large-scale systems enhances the performance of optimal real power generator allocation and of optimal power flow that results in an economic dispatch. To handle large-scale systems of this nature, the problem is decomposed into a real and a reactive power optimization problem. The control variables are generator real power outputs for the real power optimization problem and generator reactive power outputs, compensating capacitors, and transformer tap settings for the reactive power optimization. The gradient projection method (GPM) is utilized to solve the optimization problems. It is an iterative procedure for finding an extremum of a function of several constraint variables without using penalty functions or Lagrange multipliers. Mathematical models are developed to represent the sensitivity relationships between dependent and control variables for both real and reactive-power optimization procedures and thus eliminate the use of B-coefficients. >

Fuel cell air pressurization system and method

Abstract: Pressurization air systems in a multimodule fuel cell power plant are interconnected to provide improved power plant operating efficiency at part load. Each power generation module air pressurization subsystem has its own turbocompressor to provide a compressed air supply to its own power generation subsystem at rated power plant load. When load demand on the power plant is reduced, some of the turbocompressors in the interconnected power generation modules in the plant are shut off. The interconnecting valves are opened so that the remaining turbocompressors can supply all of the compressed air needed by all of the power generation subsystems in the interconnected power generation modules.

Light water reactor plant modeling for power system dynamics simulation

Abstract: Models have been developed for simulating the plant dynamics of light-water-reactor (PWR and BWR) plants under both small and large power system disturbances. The model permits precise and effective analysis of the dynamics of the nuclear plant response to power system faults by combining the plant model with the conventional power system dynamics simulation program. The modeling of the nuclear plant is described, and the application of the model to power system dynamics simulation is outlined. >

Method for preparation of coal derived fuel and electricity by a novel co-generation system

Abstract: A method for preparing a transportable fuel composition and for simultaneously producing electricity by utilizing a novel co-generation configuration. Coal or coal-derived fuels are used to generate electrical power. The waste heat from the power generation is used as the process heat for pyrolysis to produce a transportable, completely combustible slurry which contains particulate coal char and a liquid organic material.

Wind-hydrogen power station

Abstract: Against the background of the wasting of vital, valuable and non-renewable basic materials, such as coal, petroleum and natural gas, as fuels, and the increase in harmful gaseous combustion products and barely degradable residues, especially in the nuclear power sector, no burden is placed on the environment if my energy-production plant (wind-hydrogen power station) is implemented. There are no harmful residues. Due to the duality of energy production by means of wind power and/or hydrogen, electricity generation at all times is ensured.

Power generating system for solid electrolyte fuel cell

Abstract: PURPOSE:To improve the energy recovery percentage by burning the excess fuel in a combustion chamber provided separately from an SOFC module. CONSTITUTION:The fed air 1 compressed by a compressor 2 is heat-exchanged with the exhaust gas 4 from a gas turbine 11 by a heat exchanger 3 and heated. Part of it is fed to an SOFC module 5 as the reaction air 9 and utilized for the power generation reaction, and the remainder is fed to a combustion chamber 13 as the combustion air 14. The reaction fuel 6 is heat-exchanged with the exhaust gas 10 from the module 5 by a heat exchanger 15 and heated, the effective fuel 7 performs the power generation reaction with the air 9 in the module 5, the gas 10 is generated and exhausted to the outside of the system, the excess fuel 8 is reacted with the air 14 in the combustion chamber 13 to generate the combustion gas 16. The gas 16 drives a turbine 11 and becomes the gas 4 and is exhausted to the outside of the system, the compressor 2 and a generator 12 are driven, and the energy is recovered. Accordingly, the energy recovery percentage can be increased.

Reservoir operation policies for optimizing energy generation at the Shiroro Dam

Abstract: Reservoir water release policies are computed for the Shiroro Dam hydroelectric power scheme in Northern Nigeria, using a probabilistic dynamic programming model. The state variable is the reservoir storage volume, while the uncertain nature of the inflow process is accounted for in the model by considering different possible inflow volumes and their inflow probabilities. Simulation of the reservoir operations with the derived policies show that on the average the hydrosystem has acceptable reliability when two units are in use, at 45% design power plant factor. At 70% power plant factor, which is the desired optimum for the power system in Nigeria, system failures are frequent and, in most cases, severe. For normal operation of the Shiroro Dam hydroelectric power system, two or three generating units, running at 40–50% power plant factor is recommended.

Use of ejectors for high temperature power generation

Abstract: Heat engines having improved efficiencies are provided. In accordance with preferred embodiments, topping cycle engines are provided employing ejectors. Use of ejectors in accordance with the invention permits higher high side temperatures while permitting work extraction devices to be operated at standard temperatures. A preferred sodium-helium system is described in detail.