Showing papers on "Power station published in 2006"

Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey

Abstract: The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power-electronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented

Wind turbines emulating inertia and supporting primary frequency control

Abstract: The increasing penetration of variable-speed wind turbines in the electricity grid will result in a reduction of the number of connected conventional power plants. This will require changes in the way the grid frequency is controlled. In this letter, a method is proposed to let variable-speed wind turbines emulate inertia and support primary frequency control. The required power is obtained from the kinetic energy stored in the rotating mass of the turbine blades.

Low-Calcium fly ash-based geopolymer concrete: Long-term properties

Abstract: From 2001, we have conducted some important research on the development, manufacture, behaviour, and applications of Low-Calcium Fly Ash-Based Geopolymer Concrete. This concrete uses no Portland cement; instead, we use the low-calcium fly ash from a local coal burning power station as a source material to make the binder necessary to manufacture concrete.

Dynamic modeling, design, and simulation of a combined PEM fuel cell and ultracapacitor system for stand-alone residential applications

Abstract: The available power generated from a fuel cell (FC) power plant may not be sufficient to meet sustained load demands, especially during peak demand or transient events encountered in stationary power plant applications. An ultracapacitor (UC) bank can supply a large burst of power, but it cannot store a significant amount of energy. The combined use of FC and UC has the potential for better energy efficiency, reducing the cost of FC technology, and improved fuel usage. In this paper, we present an FC that operates in parallel with a UC bank. A new dynamic model and design methodology for an FCand UC-based energy source for stand-alone residential applications has been developed. Simulation results are presented using MATLAB, Simulink, and SimPowerSystems environments based on the mathematical and dynamic electrical models developed for the proposed system

Power Electronics for Modern Wind Turbines

Abstract: Wind energy is now the world's fastest growing energy source. In the past 10 years, the global wind energy capacity has increased rapidly. The installed global wind power capacity has grown to 47.317 GW from about 3.5 GW in 1994. The global wind power industry installed 7976 MW in 2004, an increase in total installed generating capacity of 20%. The phenomenal growth in the wind energy industry can be attributed to the concerns to the environmental issues, and research and development of innovative cost-reducing technologies. Denmark is a leading producer of wind turbines in the world, with an almost 40% share of the total worldwide production. The wind energy industry is a giant contributor to the Danish economy. In Denmark, the 3117 MW (in 2004) wind power is supplied by approximately 5500 wind turbines. Individuals and cooperatives own around 80% of the capacity. Denmark will increase the percentage of energy produced from wind to 25% by 2008, and aims for a 50% wind share of energy production by 2025. Wind technology has improved significantly over the past two decades, and almost all of the aspects related to the wind energy technology are still under active research and development. However, this monograph will introduce some basics of the electrical and power electronic aspects involved with modern wind generation systems, including modern power electronics and converters, electric generation and conversion systems for both fixed speed and variable speed systems, control techniques for wind turbines, configurations of wind farms, and the issues of integrating wind turbines into power systems.

Operation planning of hydrogen storage connected to wind power operating in a power market

Abstract: In this paper, a methodology for the operation of a hybrid plant with wind power and hydrogen storage is presented. Hydrogen produced from electrolysis is used for power generation in a stationary fuel cell and as fuel for vehicles. Forecasts of wind power are used for maximizing the expected profit from power exchange in a day-ahead market, also taking into account a penalty cost for unprovided hydrogen demand. During online operation, a receding horizon strategy is applied to determine the setpoints for the electrolyzer power and the fuel cell power. Results from three case studies of a combined wind-hydrogen plant are presented. In the first two cases, the plant is assumed to be operating in a power market dominated by thermal and hydropower, respectively. The third case demonstrates that the operating principles are also useful for isolated wind-hydrogen systems with backup generation

Use of mobile fast pyrolysis plants to densify biomass and reduce biomass handling costs—A preliminary assessment

Abstract: ROI BioOil plants can be made modular and transportable, allowing them to be located close to the source of biomass and the subsequent transportation of high energy density BioOil to a central plant. Conversely, one central BioOil plant could supply several energy users in distributed locations, or several plants could supply numerous end-users, just as in the petroleum industry. Renewable Oil International® LLC (ROI) is one of several developers of fast pyrolysis technology. The production of BioOil can convert raw biomass into a low-viscosity liquid that, depending on the moisture content of the feedstock, increases the energy density of biomass by a factor of 6 to 7 times over green wood chips. The increase in energy density increases the amount of energy that can be hauled by standard tanker trucks versus a chip trailer van by a factor of two. Capital costs, exclusive of land costs, are comparable for a 50 MWe biomass handling system at the power plant. Land area requirements for fuel storage and handling are reduced roughly half for BioOil systems versus solid fuel handling systems. No analysis was made of operating and maintenance costs.

Equivalencing the collector system of a large wind power plant

Abstract: As the size and number of wind power plants (also called wind farms) increases, power system planners will need to study their impact on the power system in more detail. As the level of wind power penetration into the grid increases, the transmission system integration requirements becomes more critical. A very large wind power plant may contain hundreds of megawatt-size wind turbines. These turbines are interconnected by an intricate collector system. While the impact of individual turbines on the larger power system network is minimal, collectively, wind turbines can have a significant impact on the power systems during a severe disturbance such as a nearby fault. Since it is not practical to represent all individual wind turbines to conduct simulations, a simplified equivalent representation is required. This paper focuses on our effort to develop an equivalent representation of a wind power plant collector system for power system planning studies. The layout of the wind power plant, the size and type of conductors used, and the method of delivery (overhead or buried cables) all influence the performance of the collector system inside the wind power plant. Our effort to develop an equivalent representation of the collector system for wind power plants is an attempt to simplify power system modeling for future developments or planned expansions of wind power plants. Although we use a specific large wind power plant as a case study, the concept is applicable for any type of wind power plant.

Control of PEM fuel cell distributed generation systems

Abstract: This paper presents modeling, controller design, and simulation study of a proton exchange membrane fuel cell (PEMFC) distributed generation (DG) system The overall configuration of the PEMFC DG system is given, dynamic models for the PEMFC power plant and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units to control the power flow from the fuel cell power plant to the utility grid are presented A MATLAB/Simulink simulation model is developed for the PEMFC DG system by combining the individual component models and the controllers designed for the power conditioning units Simulation results are given to show the overall system performance including load-following and fault-handling capability of the system

Analytical and numerical investigation of the solar chimney power plant systems

Abstract: There is a surge in the use of the solar chimney power plant in the recent years which accomplishes the task of converting solar energy into kinetic energy. As the existing models are insufficient to accurately describe the mechanism, a more comprehensive model is advanced in this paper to evaluate the performance of a solar chimney power plant system, in which the effects of various parameters on the relative static pressure, driving force, power output and efficiency have been further investigated. Using the solar chimney prototype in Manzanares, Spain, as a practical example, the numerical studies are performed to explore the geometric modifications on the system performance, which show reasonable agreement with the analytical model. Copyright © 2005 John Wiley & Sons, Ltd.

Energy-exergy analysis and modernization suggestions for a combined-cycle power plant

Abstract: Energy and exergy analysis were carried out for a combined-cycle power plant by using the data taken from its units in operation to analyse a complex energy system more thoroughly and to identify the potential for improving efficiency of the system In this context, energy and exergy fluxes at the inlet and the exit of the devices in one of the power plant main units as well as the energy and exergy losses were determined The results show that combustion chambers, gas turbines and heat recovery steam generators (HRSG) are the main sources of irreversibilities representing more than 85% of the overall exergy losses Some constructive and thermal suggestions for these devices have been made to improve the efficiency of the system Copyright © 2005 John Wiley & Sons, Ltd

Solar Chimney Power Plant Performance

Abstract: This paper evaluates the performance of a large-scale solar chimney power plant. The study considers the performance of a particular reference plant under specified meteorological conditions at a reference location in South Africa. A computer simulation program is employed to solve the governing conservation and draught equations simultaneously. Newly developed convective heat transfer and momentum equations are included in the numerical model and multiple simulations are performed. Results indicate 24 hr plant power production, while illustrating considerable daily and seasonal power output variations. It is shown that plant power production is a function of the collector roof shape and inlet height.

Wind Farm Configuration and Energy Efficiency Studies - Series DC versus AC Layouts

Abstract: In this thesis, the design and control of a wind farm utilizing series-connected wind turbines with a DC output has been evaluated. The advantage is that a suitable DC voltage level, appropriate for transmission of the generated power directly, without using a large centralized DC/DC converter, can be obtained. This is achieved by series-connecting a number of wind turbines. In addition, the energy production using various wind turbines and wind park layouts have been investigated. Furthermore, the energy production costs have been determined. Finally, the limiting factors for the installation of smaller wind parks have been evaluated. For instance, when dynamic power pulsations have to be considered, from a power quality point of view, when a wind energy installation is to be connected to the grid. The results found are that the uneven power production from the individual wind turbines creates design as well as control difficulties for the wind farm with series-connected wind turbines. A control scheme for the wind turbines is proposed and investigated in this thesis. It is found that the proposed control scheme manages to safely operate the wind farm, even when large deviations in the individual power production of the turbines exist. A down-scaled prototype has been built, representing one wind turbine unit, and the base current control ability was verified experimentally. Moreover, it is found that it is necessary to design the individual wind turbine converters for a voltage level of about 35 % higher than the nominal voltage. Otherwise there will be a substantial energy loss due to the uneven power production from the individual wind turbines that occurs in actual installation. In addition, it is found that the series dc wind park has a good economical potential, since it eliminates the need for an offshore platform in the wind park. Finally, the electrical limiting factors for the installation of wind farms are determined using field experimental data. For instance, it is shown that for a wind park of about 10 wind turbines, the power pulsations are "smoothened" sufficiently so that the flicker emission never will be the limiting factor, even for fixed-speed turbines, when a wind energy installation is connected to a network. Worth mentioning is that it was found that the summation formula for flicker given in IEC 61400-21 can give a flicker prediction that is too low.

Dynamic Simulation of a Pressurized 220kW Solid Oxide Fuel-Cell–Gas-Turbine Hybrid System: Modeled Performance Compared to Measured Results

Abstract: R. A. Roberts J. Brouwer e-mail: jb@nfcrc.uci.edu National Fuel Cell Research Center, University California, Irvine, Irvine, CA 92697-3550 Dynamic Simulation of a Pressurized 220 kW Solid Oxide Fuel-Cell–Gas-Turbine Hybrid System: Modeled Performance Compared to Measured Results Hybrid fuel-cell–gas-turbine (FC/GT) systems are technologically advanced systems that are promising for electric power generation with ultralow emissions and high efficiency for a large range of power plant sizes. A good understanding of the steady-state and dynamic performance of a FC/GT system is needed in order to develop and advance this hybrid technology. In this work, a detailed dynamic model of a solid oxide fuel cell/gas turbine (SOFC/GT) system has been developed. The system that is simulated represents the 220 kW SOFC/GT hybrid system developed by Siemens Westinghouse. Results of the dynamic model and experimental data gathered during the operation and testing of the 220 kW SOFC/GT at the National Fuel Cell Research Center are compared and presented. 关DOI: 10.1115/1.2133802兴 Introduction and Background Fuel cell/gas turbine 共FC/GT兲 hybrids integrate high- temperature fuel cells with gas turbine engines in a manner that converts fuel cell thermal energy through turbo machinery to power compressors and/or electric generators. In both thermody- namic simulation and experiment, these hybrid systems have dem- onstrated lower environmental impact compared to conventional combustion-driven power plants. Lower carbon dioxide emissions can be achieved through higher fuel-to-electrical efficiencies, while NO x and other criteria pollutant emissions are greatly re- duced by primary electrochemical conversion of the fuel versus the combustion process of conventional plants 关1兴. In this work, a dynamic model of a hybrid system is developed and applied to analyze a specific hybrid cycle that is applicable to distributed generation. More complex cycles have been considered for larger scale power plants that may utilize a combined cycle to drive the efficiency up and the environmental impact down 关2兴. Today much work is being done to reduce the cost and increase the reliability of solid oxide fuel cell 共SOFC兲 systems. Several cell geometries are being advanced by fuel cell manufacturers includ- ing tubular and planer SOFC designs, and even cell geometries that combine planer and tubular features. Each geometry has its advantages and disadvantages with regard to thermal expansion compliance, power density, potential cost, manufacturability, and internal resistivity 关3兴. Many companies are advancing these dif- ferent types of SOFCs, but no commercial products exist today. Only demonstration and prototype systems have been built and tested to date. Mathematical models provide a cost-effective and efficient tool in aiding the development of SOFCs and SOFC/GT systems. Sev- eral entities around the world have developed steady-state simu- lation capabilities for FC/GT systems. These research groups in- clude efforts at the Georgia Institute of Technology, University of Genova, NFCRC, Nanyang Technical University, and others Manuscript received February 8, 2005; final manuscript received August 19, 2005. Review conducted by Subhash C. Singhal. 18 / Vol. 3, FEBRUARY 2006 关2–8兴. Dynamic FC/GT simulation capabilities are less common, but increasingly being developed as the demand for dynamic un- derstanding and controls development grows. Examples of previ- ous dynamic simulation efforts include work at the National En- ergy Technology Laboratory and FuelCell Energy among others 关9–13兴. Model validation is very important, and there remains a great need to produce experimental hybrid system data. To date there have been two hybrid systems built and success- fully demonstrated. The first uses an atmospheric fuel cell located after the turbine exhaust has been built and demonstrated by Fu- elCell Energy that integrated a molten carbonate fuel cell and a Capstone C30 gas turbine. This system successfully ran for 2900 h in grid-connected mode at 51.7% fuel-to-electrical effi- ciency. See Ghezel-Ayagh et al. 关14兴 for more information on this system. The second system uses a pressurized fuel cell located between the compressor and turbine, which is the system of direct interest to the current work. Experiment Description Siemens Westinghouse developed the very first pressurized SOFC/GT hybrid system using their tubular SOFC stack design. This system, presented in Fig. 1, was tested at the NFCRC with support from Southern California Edison, the U.S. Department of Energy, and others. The system was designed, constructed, and tested to demonstrate and prove the hybrid concept. The system operated for over 2900 h and produced up to 220 kW at fuel-to- electricity conversion efficiencies of up to 53%. In parallel, NFCRC developed dynamic simulation capabilities for each of the system components together with a simulation framework for modeling and developing control strategies for integrated SOFC/GT systems. A diagram of the integrated SOFC/GT system is presented in Fig. 2. This system is comprised of a tubular SOFC with inte- grated internal reformer and anode off-gas oxidizer as illustrated in Fig. 3. These components 共stack, reformer兲 are placed between the compressor and turbine so that they operate under pressurized conditions. The gas turbine is a dual shaft Ingersoll-Rand 75 kW Copyright © 2006 by ASME Transactions of the ASME Downloaded From: http://fuelcellscience.asmedigitalcollection.asme.org/ on 12/02/2015 Terms of Use: http://www.asme.org/about-asme/terms-of-use

Power plant with energy recovery from fuel storage

Abstract: Power plant systems and processes are described that enable recovery of at least a portion of the fuel storage energy associated with a storage system for supplying fuel to the power plant systems. A first embodiment of an energy-recovery power plant system includes at least one fuel storage container and at least one expander that can receive fuel from the fuel storage container at a first pressure and provide the fuel to the power plant at a second pressure that is lower than the first pressure. A second embodiment of an energy-recovery power plant system includes a first conduit fluidly coupling the fuel storage container and the power plant for delivering fuel from the fuel storage container to the power plant and at least one regenerative thermodynamic cycle engine thermally coupled to the first conduit such that heat may be exchanged between the fuel and a working fluid for the regenerative thermodynamic cycle engine.

Developing Wind Power Projects: Theory and Practice

Abstract: Wind power is developing rapidly, in terms of both the number of new installations and in interest from stakeholders including policy-makers, NGOs, research scientists, industry and the general public. Unlike the majority of other texts on wind power, which are written primarily for engineers or policy analysts, this book specifically targets those interested in, or planning to develop, wind power projects. Having outlined wind power basics and explained the underlying resource and technology, the author explores the interactions between wind power and society, and the main aspects of project development, including siting, economics and legislation. This book will be an essential reference for professionals developing new sites, government officials and consultants reviewing related applications, and both specialists and non-specialists studying wind power project development.