Showing papers on "Electricity generation published in 1998"

Self-powered signal processing using vibration-based power generation

Abstract: Low power design trends raise the possibility of using ambient energy to power future digital systems. A chip has been designed and tested to demonstrate the feasibility of operating a digital system from power generated by vibrations in its environment. A moving coil electromagnetic transducer was used as a power generator. Calculations show that power on the order of 400 /spl mu/W can be generated. The test chip integrates an ultra-low power controller to regulate the generator voltage using delay feedback techniques, and a low power subband filter DSP load circuit. Tests verify 500 kHz self-powered operation of the subband filter, a level of performance suitable for sensor applications. The entire system, including the DSP load, consumes 18 /spl mu/W of power. The chip is implemented in a standard 0.8 /spl mu/m CMOS process. A single generator excitation produced 23 ms of valid DSP operation at a 500 kHz clock frequency, corresponding to 11,700 cycles.

Generation unit sizing and cost analysis for stand-alone wind, photovoltaic, and hybrid wind/PV systems

Abstract: This paper presents the results of investigations on the application of wind, photovoltaic (PV), and hybrid wind/PV power generating systems for utilization as stand-alone systems. A simple numerical algorithm has been developed for generation unit sizing. It has been used to determine the optimum generation capacity and storage needed for a stand-alone, wind, PV, and hybrid wind/PV system for an experimental site in a remote area in Montana with a typical residential load. Generation and storage units for each system are properly sized in order to meet the annual load and minimize the total annual cost to the customer. In addition, an economic analysis has been performed for the above three scenarios and is used to justify the use of renewable energy versus constructing a line extension from the nearest existing power line to supply the load with conventional power. Annual average hourly values for load, wind speed, and insolation have been used.

Decentralized biomass combustion: state of the art and future development

Abstract: The present amount of biomass used for heat, and to a smaller extent electricity production, is already considerable in several European countries but the potential unused in Europe is even higher. Combustion is the most mature conversion technology utilized for biomass. The systems addressed in this paper are plants with a nominal boiler capacity greater 0.5 MWth. The main combustion technologies used for these systems are underfeed stoker furnaces, moving grate firings (over-bed stoker fired units), bubbling and circulating fluidized beds. The most important biomass fuels are sawdust, wood chips, bark, straw, cereals and grass. The essential differences between them are their different combustion behaviour as well as the different concentrations of combustion relevant elements (such as N, S, Cl, K) they contain, influencing the necessary combustion, process control and flue gas cleaning technology. Important points that are now under development focus on possibilities of NOx reduction by primary measures, as well as on higher plant efficiencies by efficient biomass drying by well adjusting the excess oxygen level in the flue gas to the requirements for a complete combustion and by recovering energy from the flue gas. Furthermore, possibilities of influencing the material fluxes of ash forming elements by primary measures aiming at a sustainable ash utilization and an efficient dust precipitation are in progress. Problems still unsolved that need comprehensive R&D in the near future are reactions taking place in the hot flue gas, causing depositions and corrosion in furnaces and boilers (especially when K-, S- and Cl-rich biomass fuels such as straw, cereals and grass are used). Research on possibilities to prevent or control them (by material selection or appropriate technologies) are of great importance. Furthermore, the ash melting behaviour and its influencing variables have to be treated as urgent. Staged combustion systems, hot fly ash precipitation as well as specially designed boilers could represent solutions for these ash and aerosol related problems. Combined heat and power (CHP) production, already realized in plants with a nominal boiler capacity greater 10 MWth based on steam turbines, is also of growing importance for small-scale applications. Moreover, the lower limit for CHP plants is a nominal boiler capacity of about 5 MWth at the moment, due to the lower electric efficiencies achievable and to the economy of scale. Interesting technologies which are right now under development are sterling engines, a newly developed steam engine (screw-type motor) and organic rankine cycles (ORC) with hydrocarbons as working fluids operating at low temperature and pressure levels (in comparison with conventional steam processes). The basic requirements for the selection of an appropriate CHP process are a high electric efficiency to investment costs ratio and a well tested technology to ensure a continuous and undisturbed operation of the plant.

Logistics management and costs of biomass fuel supply

Abstract: Discusses part of a project conducted by the authors into the logistics planning and management and costs of supplying biomass fuels to biomass‐fired power stations in the UK. Defines biomass fuels and the reasons for the growth in interest in their use for electricity generation. The activities and parties involved in the biomass fuel supply chain are discussed together with the management of the chain in order to achieve smooth and consistent flow of biomass fuel to power stations. Explains the approach used to modelling the delivered costs of biomass fuels for four types of biomass fuel included in the project: forest fuel, short rotation coppice, straw and miscanthus. Comments are given on the environmental impacts of the fuel supply chains. The results indicate that straw supply systems are capable of producing the lowest delivered costs of the four fuels studied. Short rotation coppice and miscanthus, two new energy crops, are likely to have the highest delivered costs at present. This is due to the cost of growing these fuels and the financial incentives required by farmers to persuade them to grow these crops. Logistics costs (i.e. transport, storage and handling) are shown to represent a significant proportion of total delivered cost in biomass supply. Careful supply chain planning and logistics management will be of central importance to the success of the biomass industry.

A study on optimal sizing of stand-alone photovoltaic stations

Abstract: One major application of photovoltaic (PV) power has been in remote areas as isolated small power generation for essential electric power. This paper discusses issues in optimizing the use of such stations and presents a procedure to evaluate different PV schemes considering the stochastic natures of the insolation and the load. The reliability measures in terms of loss of load hours (LOLH), the energy loss and the total cost have been used as the indices for evaluation of different schemes. The insolation and the load demand are modeled as stochastic variables using historical data and experimentation respectively. The operation of various stand-alone schemes are simulated for a specific load. Actual commercially available panel and battery sizes with actual costs have been used in the various configurations studied. The long run expected values of the performance indices for various configurations of the solar station have been measured. Comparative analysis of the results show that higher cost not necessarily translates into better performance. The panel size and the battery size have different impacts on the indices of performance, and a proper balance between the two is necessary to optimize the operation of a stand-alone PV scheme.

Understanding Electric Utilities and De-Regulation

Abstract: THE ELECTRIC INDUSTRY AND ITS TRADITIONAL REGULATED STRUCTURE Introduction Electric Utility Functions and Systems Electric Utility Resources and Organization Vertical Integration and Monopoly Regulation Electric Utility Business Frameworks Government Regulatory Agencies and Commissions Electrical Equipment Suppliers and Developers A Complex Industry Undergoing Major Changes THE ELECTRIC INDUSTRY UNDER DE-REGULATION - AN OVERVIEW Introduction De-Regulation: Concepts and Evolution No Competition at the Retail Level Competition at the Wholesale Generation Level Independently Operated Regional Transmission Grids The Electricity Doesn't Care Although People and Money Do The Electric Utility Industry Under De-Regulation An Industry In Need of Fine Tuning A HISTORY OF THE ELECTRIC POWER INDUSTRY Three Intertwined Aspects Grew Simultaneously Growth of Electrical Usage The Growth of Electrical Systems Technology The Rise of the Electrical Utility Industry Looking to the Future For Further Reading ELECTRIC POWER Introduction Voltage, Current, and Power Characteristics of Electric Power and Systems Key Points For Further Reading USING ELECTRIC ENERGY Introduction A Flexible Form of Energy Four Basic Applications Electricity is Bought for End-Uses The Utility's Perspective on Customer Power Usage Conservation, Energy Efficiency, and Demand-Side Management Summary For Further Reading CREATING ELECTRICITY: POWER GENERATION Generating Electric Power Electric Generating Systems Types of Generating Plants Summary For Further Reading RENEWABLE POWER GENERATION Free Fuel and Low Environmental Impact Hydro Power Wind-Driven Power Generation Solar Power Other Renewable Generation Technologies Are Renewable Resources Practical? For Further Reading DISTRIBUTED GENERATION AND STORAGE Distributed Power Generation Types of Distributed Generators Distributed Power Storage Summary For Further Reading ELECTRIC UTILITY POWER SYSTEMS Introduction T&D System Equipment T&D System Layout Summary For Further Reading REGULATION AND DE-REGULATION Introduction Why Were Electric Utilities Regulated? Why De-Regulate? The Good and Bad of Utility Regulation Goals for and Effects of De-Regulation Comparing Four Approaches to Regulation and De-Regulation Increased Services From and Financial Pressures On LDCs For Further Reading DE-REGULATION AT THE WHOLESALE POWER LEVEL Introduction The Wholesale Power Marketplace Do Buyers Submit Bids? Buying Energy vs. Buying Capacity How is Wholesale Power Priced? Summary THE POWER GRID IN THE DE-REGULATED INDUSTRY Generation and Transmission in a De-Regulated Industry The Wholesale Transmission Level What is Being Sold at the Transmission Level? How Is Transmission Service Priced? The Eventual Winner: Locationally-Based Pricing? Summary of Key Points For Further Reading POWER DISTRIBUTION IN A DE-REGULATED INDUSTRY Introduction Open Access Distribution Changes in Distribution Operations Will Distribution Performance Improve Due to "Competition"? For Further Reading RETAIL SALES IN A FULLY DE-REGULATED INDUSTRY Introduction Load Aggregation and Services RESCO Identities and Industry Position How Does It All Work? For Further Reading SERVICE RELIABILITY AND AGING INFRASTRUCTURES Introduction Aging T&D Infrastructures Sustainable-Point Analysis of Aging Infrastructures Outages and Reliability For Further Reading SYSTEM BLACKOUTS AND OPERATIONAL COMPLEXITY Introduction Blackouts: An Overview Synchronized Operation of Power Systems Why Do Blackouts Occur? Summary and Concluding Comments For Further Reading GLOSSARY INDEX

Automatic generation control in a deregulated power system

Abstract: Load frequency control (LFC) has been used for many years as part of the automatic generation control (AGC) in power systems around the world. In the synchronous Nordic power system, however, this function (termed secondary control) has so far been handled with manual control actions. Increased operational strain due to new HVDC connections in the next decade will make it increasingly difficult to maintain the current manual control system. In this paper a model of the interconnected power systems of Norway and Sweden is used to show how introduction of AGC might aid the system operator in handling the increased strain. However, the classical LFC based on the area control error is difficult to implement in a deregulated environment. An alternative concept is thus introduced where selected units are automatically following load changes on the HVDC connections. This ramp following controller (RFC) supported by manual control seems to be a promising option.

HVDC Light: A New Technology for a Better Environment

Abstract: A new transmission and distribution technology, HVDC Light, makes it economically feasible to connect smallscale, renewable power generation plants to the main AC grid. Vice versa, using the very same technology, remote locations as islands, mining districts and drilling platforms can be supplied with power from the main grid, thereby eliminating the need for inefficient, polluting local generation such as diesel units. The voltage, frequency, active and reactive power can be controlled precisely and independently of each other. This technology also relies on a new type of underground cable which can replace overhead lines at no cost penalty.

System for generating electricity in a vehicle

Abstract: A wind-powered system for generating electricity in a vehicle or other power consumption unit generally having a multi-stage impeller system for driving an electric generator/alternator, an improved air channel, and an improved start-up/back-up air compressor. The multi-stage impeller system includes high-speed impellers and low-speed impellers for efficient energy conversion throughout the entire range of a vehicle's operating speeds or forward motion. The improved start-up/back-up air compressor discharges air directly to the multi-stage impellers, abolishing the need for heavy air accumulators. The improved air channel includes a specially formed air scoop/vortex, a wind tube/tunnel and a heating element to increase the velocity of the air passing therethrough.

Industrial power demand response analysis for one-part real-time pricing

Abstract: Demand-side management (DSM) programs in the industrial sector appear to be economically feasible due to the large controllable loads and relatively low costs per control point. Innovative electricity tariffs provide one of the most important DSM alternatives. Because real-time pricing (RTP) is considered as an excellent management option which reflects the real cost of generating electricity to the end user, the electricity cost saving potential of RTP through demand management is presented in this paper. A unique analytical approach is followed to describe the potential electricity cost savings mathematically in terms of variables familiar to both the end user and utility. These variables include the installed power consumption capacity of the plant, the plant's spare energy consumption capacity, and terms that describe the structure of the RTP tariff.

Electron Crystals and Phonon Glasses: A New Path to Improved Thermoelectric Materials

Abstract: In materials that conduct both electricity and heat, the thermal and electrical currents are coupled. This thermoelectric coupling can be used to construct devices that act as temperature sensors, heat pumps, refrigerators, or power generators. A temperature difference ΔT across any electrical conductor will generate a corresponding voltage difference ΔV The ratio ΔV/ΔT is defined as the Seebeck coefficient S after Thomas See-beck who first discovered the effect in 1823. Probably the most familiar use of this effect is the thermocouple in which the union of two dissimilar metals generates a voltage in response to an imposed temperature difference. Interestingly an electrical current I passing through the junction of two dissimilar conductors results in the absorption or release of heat in the vicinity of the junction depending on the direction of the current. The ability to heat or cool in this manner was first discovered by Peltier and explained by Lord Kelvin. The latter showed that the amount of heat produced (or absorbed) near the junction is given by ΠI = STI where Π is called the Peltier coefficient and T is the temperature. It is primarily this effect that makes thermoelectric (Peltier) refrigeration possible. Thermoelectric refrigerators and power generators are attractive for many applications as they have no moving parts (except electrons and holes), use no liquid refrigerant, and last indefinitely.

Pulsed power corona discharges for air pollution control

Abstract: Successful introduction of pulsed corona for industrial purposes very much depends on the reliability of high-voltage and pulsed power technology and on the efficiency of energy transfer. In addition, it is of the utmost importance that adequate electromagnetic compatibility (EMC) is achieved between the high-voltage pulse source and the surrounding equipment. Pulsed corona is generated in a pilot unit that produces narrow 50 MW pulses at 1000 pps (net average corona power 1.5 kW). The pilot unit can run continuously for use in industrial applications such as cleaning of gases (100 m/sup 3//h) containing NO or volatile organic compounds (VOCs) or fluids (e.g., waste water). Simultaneous removal of NO and ethylene to obtain clean CO/sub 2/ from the exhaust of a combustion engine was tested at an industrial site. Various chemical processes, such as removal of toluene or styrene from an airflow are tested in the laboratory. We developed a model to analyze the conversion of these pollutants. To examine the discharges in the reactor we use current, voltage, and E-field sensors as well as a fast charge-coupled device (CCD) camera. Detailed energy input measurements are compared with CCD movies to investigate the efficiency of different streamer phases. EMC techniques incorporated in the pilot unit are based on the successful concept of constructing a low transfer impedance between common mode currents induced by pulsed power and differential mode voltages in signal lines and external main lines.

The energetic feasibility of CHP compared to the separate production of heat and power

Abstract: At present, promotion of combined production of heat and power (CHP) plays a significant role in most national energy strategies, aiming at primary energy savings and CO2-reduction. However, it is not correct to state that rational use of energy and reduction of CO2-emission are intrinsic to CHP. The amount of energy savings and CO2-reduction by using CHP strongly depend on the performances of the CHP plants (efficiencies, valorization of electricity and heat, number of running hours) and of the characteristics of the reference situation with separate production of heat and power. Especially nowadays, as performances of separate systems for the production of electricity and heat [electricity production by combined cycle plants (efficiency >50%) and heat production by high efficiency boilers (efficiency >90%)] are strongly improving, the required performances of CHP plants being preferable to separate systems for the production of heat and power, have to be tightened. In this paper, a calculation methodology for evaluating the primary energy consumption and CO2-emission for both options (CHP and separate production of heat and power) is presented. Based on calculations with this methodology and with practical figures of performances of CHP plants and separate systems for production of heat and power, the boundary conditions that have to be met by CHP systems for being less energy consuming and less CO2-producing are discussed.

A mathematical look at a physical power prediction model

Abstract: A mathematical look at a physical power prediction model This article takes a mathematical look at a physical model used to predict the power produced from wind farms. The reason is to see whether simple mathematical expressions can replace the original equations and to give guidelines as to where simplifications can be made and where they cannot. The article shows that there is a linear dependence between the geostrophic wind and the local wind at the surface, but also that great care must be taken in the selection of the simple mathematical models, since physical dependences play a very important role, e.g. through the dependence of the turning of the wind on the wind speed. Copyright

Inter-area oscillation damping with power system stabilizers and synchronized phasor measurements

Abstract: Low-frequency oscillations are detrimental to the goals of maximum power transfer and optimal power system security. A contemporary solution to this problem is the addition of power system stabilizers to the automatic voltage regulators on the generators in the power system. The damping provided by this additional stabilizer provides the means to reduce the inhibiting effects of the oscillations. A novel modification of this controller is the inclusion in the feedback loop of information from a remote source. In this manner, the controller acts on the changes from the local source and the remote source. As is demonstrated, this yields a controller capable of more rapidly diminishing the oscillations in a test power system.

A dual purpose battery charger for electric vehicles

Abstract: A dual purpose, high power, off-board battery charger for electric vehicles is presented. For higher viability and increased usage of the charger, grid conditioning capabilities are included in the concept. Conventional power electronic converter topologies are used in a new application, which combines fast EV battery charging with active filtering. Furthermore bi-directional power flow capabilities are provided to accommodate grid peak power requirements. Both simulation and experimental results are presented in this paper which demonstrate the capabilities of the new charger.

Management and dynamic performances of combined cycle power plants during parallel and islanding operation

Abstract: The subject of a cogeneration plant modeling has already been discussed in the past, but mostly from the thermal and energy point of view. There are several aspects to be considered for assuring that the plant will operate satisfactorily. Furthermore, the increasing number of energy producers poses more and more attention to these types of plants and to their regulation mode. Among these aspects, particular care is devoted in this paper to the modeling and setting-up of gas turbine regulators, also because it is not generally such a trivial work to adapt existing software for large power systems' dynamic analysis to the requirements of combined-cycle power plants. On the basis of the specialized literature, a detailed model for the regulator of a gas turbine unit is adopted, which includes speed, acceleration and temperature controls as well as inlet guide vanes' control. The proposed regulator is tested on a realistic industrial power plant with particular attention to parallel and isolated operation.

Environomic modeling and optimization of advanced combined cycle cogeneration power plants including CO2 separation options

Abstract: Considering the economic importance of the electricity generation sector as well as its contribution to local, regional and global pollution, the development of new cost-effective and environmentally benign electricity generation and cogeneration systems is an essential task. In this context, combined cycle cogeneration power plants are among the most promising systems. The integration of gas turbines with a steam turbine cycle leads to complex systems and to an increasing number of technological options for their improvement. Faced with growing concerns about greenhouse gas emission, systems for CO2 separation become an additional option and compete with measures for efficiency improvement. The simultaneous consideration of economic and environmental concerns as well as the increasing system complexity and the growing number of options represent an important challenge to the engineer and require the development of new approaches and design tools. The present work contributes to the development of such an approach and its application to combined cycle cogeneration power plants and their advanced options. These options, such sequential combustion gas turbines, compressor intercooling of CO2 separation can improve performance with respect to efficiency and emissions, but require increased investment costs. These competing factors are united in a so-called environomic model which takes into account the costs of resources and capital investment, as well as the costs of pollution, and calculates a single criterion – the total cost of electricity production. The costs of pollution used in this work are based on economic studies from the literature. For internalization, a penalty factor allows the degree of pollution already present in the environment to be taken into account. Benefits due to the substitution of domestic furnaces through cogeneration are also considered. A so-called "superconfiguration" model allows the modeling of simultaneous changes in configuration and design. Uncertainties linked to thermodynamic performance and investment costs model are addressed through calibration by means of reference combined cycle power plants, as well as through a proposed method for directly taking them into account in the model. The influence of varying requirements such as the power plant size, operating time and emission limits can also be modeled, providing valuable information such as thermodynamic states, component performance and investment costs. The resulting optimization problem is of the non-linear, mixed integer type. The complex task of finding optimum solutions is accomplished by means of powerful optimization methods that allow searching of the entire solution space. In this work, a genetic algorithm was adapted to the requirements of the superconfiguration optimization, permitting the simultaneous optimization of configuration and design. Genetic algorithms work with populations instead of a single data point and rely on biological mechanisms such as mating, mutation and replacement, and provide multiple promising solutions. Reference cases with different electricity and heat demand as well as different annual operating time are optimized and analyzed in detail with respect to the solutions obtained. Based on these reference cases, sensitivity studies on the cost of pollution, as well as emission limits, show the influence of these factors on the combined cycle configuration and design, as well as on the cost structure of electricity, and demonstrate an application of the method.

A matrix converter excited doubly-fed induction machine as a wind power generator

Abstract: A grid-connected wind-power generation scheme using a doubly-fed induction generator (DFIG) in conjunction with a direct AC-AC matrix converter is proposed. The analysis employs a stator-flux vector-control algorithm and a space vector modulated matrix converter to control the generator rotor current. The system enables optimal speed tracking for maximum energy capture from the wind and high performance active and reactive power regulation. The paper discusses the operating principles of this power generation scheme. The matrix converter-based rotor current control method is described. Simulation studies of the proposed power generation system were carried out. Results obtained are presented illustrating good control performance of the system.

Energy and CO2 balances in different power generation routes using wood fuel from short rotation coppice

Abstract: By substituting fossil fuels and storing carbon in biomass and soil, the development of bioenergy can play a significant role in the reduction of CO2 emissions to the atmosphere. The objective of this study was to carry out an energy and carbon analysis of different power generation routes using wood fuel from short rotation coppice. Three scenarios of wood fuel production were considered, based on the level of intensification of cultivation practices, in terms of machinery and materials input. Local and regional transportation were distinguished, as well as natural convection or forced ventilation for drying. We also studied three conversion systems: local peak electricity generation, local cogeneration of heat and power (CHP), and centralised power generation by wood and coal pulverisation cofiring. The energy and carbon balances of different wood-energy routes were estimated by calculating direct and indirect energy and carbon costs of all their components (fuel, materials and machinery). Energy ratios of 22, 23 and 26 after storage and drying at the farm were obtained respectively for the different scenarios. An average of 1.7 kg of carbon (kgC) is released per GJ of wood energy produced. Crop maintenance, and chemical fertilisation, account for 40% of total energy costs and 25% of total carbon costs of wood fuel production. Final avoided carbon emissions by fossil fuel substitution reach 6.3 to 8.8 tC ha(-1) yr(-1) with CHP, 3.8 to 5.4 with peak power production and 3.3 to 4.6 with centralised cofiring. (C) 1998 Elsevier Science Ltd. All rights reserved.