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Über dieses Buch

The present book was written to address the needs of those readers interested in wind energy converters. The authors have tried to strike a balance between a short book chapter and a very detailed book for experts in the field. There were three prime reasons behind doing so: first, the field is highly interdisciplinary and requires a more accessible format for non-experts. The second reason for this more compact version is that both authors have encountered many students and technically oriented people who were searching for this type of book on wind energy. The third reason and motivation for writing this book was to provide some initial information to people who are embarking on a career in the wind industry. It is this group of people that the present book is targeted at.



Chapter 1. Wind Energy Today

This chapter introduces the reader to wind energy with a quick journey starting at the origin of wind energy systems, passing through landmark developments in the history of these systems, and describing the current state of the art of wind energy systems. The status of wind energy in different countries worldwide is described, especially covering North America, Europe and Asia, to present a worldwide picture of this field. For a quick comparison of wind energy systems with other systems including non-renewable energy systems, a section highlighting advantages and disadvantages of wind energy systems has been included in this chapter. In the last part, an overview of different types of wind energy converters is presented to prepare the reader of this book for venturing to the following chapters.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 2. Wind: Origin and Local Effects

It is important to understand the origin of wind and the factors affecting the wind availability on any site before it is possible to appreciate the construction and performance of wind energy systems. Available wind data is usually aggregated over time, and it has a strong variability within. Extreme care is to be taken in connection with natural or artificial obstructions in wind flow that reduce the wind velocity or produce turbulence. These concepts are useful for identifying appropriate sites for an installation, as well as for estimating the power output at a location. Principles of spacing between adjacent machines are to be followed when installing multiple wind turbines in a wind park.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 3. Physics of Wind Energy

Wind velocity increases with height, its rate depending on the type of terrain. The energy content of wind depends on the third power of its velocity, and the area through which it is passing. Conversion of wind power to rotation of turbine depends on the geometry of the blades with respect to the incoming wind velocity vector. The rotation of blades is governed by the basic principles of aerodynamics. The ratio of the circumferential velocity of blade tip to the velocity of wind is defined as the tip-speed ratio. This ratio has a strong influence on the coefficient of power or efficiency of conversion, which has an upper limit of 59.25 % as per the Betz’s theorem.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 4. Components of a Wind Energy Converter

Rotor blades, gear box, generator and tower are the main components of a wind energy converter. Glass fiber reinforced plastic blades are preferred in modern turbines due to less weight and more strength. Hydrodynamic gear boxes may offer efficiency related advantage over conventional design. Synchronous as well as asynchronous generators are both used in wind energy converters. Depending upon the height of converter, the type of tower is chosen out of a simple pole or lattice tower to a modern tubular steel tower are concrete tower. Other components, such as yaw mechanism and anemometer, also play an important role in the efficient operation of a wind turbine, whereas foundation, vibration measurement, and brakes are important for its safe operation.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 5. Design Considerations

Several options—e.g. one large or a greater number of smaller machines, the number of blades in a rotor, the type of generator, a gearless machine or one with gear box, upwind or downwind operation—are available when a decision on the specifications of a wind energy converter is taken. These different design options are compared in this chapter. A modern trend is to use large size horizontal axis upwind machines that usually have three blades and are with or without gear box. However, this decision is highly case specific depending upon the usage, wind profile, land availability, and other, similar factors.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 6. Operation and Control of Wind Energy Converters

Power output from wind energy converters depends upon the power curve of the machine and the controls exercised to operate it. Pitch controlled machines are used more often than yaw controlled and stall controlled machines. The capacity factor of wind turbines, which represents utilization of the installed capacity, usually does not exceed 40 %. Controlling the rotational speed of the blades is necessary in some designs for keeping the frequency constant; however, this forces the turbine to run in non-maximum power output regime for most of the time. Therefore, modern converters run with variable rotation and produce a constant frequency by specific asynchronous generators or by using electronic converters. Due to heavy fluctuations in wind speed, wind energy converters are not suitable for stand alone applications unless provided with storage or backed-up system.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 7. Economics and Policy Issues

The economics of power generation using wind energy systems depends upon the capacity utilization factor. Higher initial cost is offset by lower operating cost due to free availability of the source of energy. For locations that have relatively lower utilization factors, several promotional policy measures are adopted by different countries. A feed-in tariff system is adopted by countries like Germany, whereas a net-metering system is adopted by India for promoting the use of wind energy. Other schemes, such as time dependent rates and quota systems, are used by other countries. For encouraging the investment in the wind sector, various countries worldwide have adopted tools like the capacity credit scheme, Clean Development Mechanism, exemption of import duty, accelerated depreciation, and income tax rebate.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 8. Life Cycle Assessment of a Wind Farm

Life Cycle Assessments is an important tool for industry and policy makers, used to determine the actual emissions of a product or technology throughout its whole life cycle. In case of energy production systems or power plants, analysis of energy required to produce the materials and processes; emissions resulting from various processes for materials production and processes resulting into their Cumulated Energy Demand and Global Warming Potential become important parameters when making decisions on further research, development and deployment of any technology. The method of carrying out such analysis is explained in this chapter through a case study.
Hermann-Josef Wagner, Jyotirmay Mathur

Chapter 9. Outlook

More than 50 countries around the world have an organized set up in the field of wind power. Large progress in wind power has been witnessed in the countries of the European Union especially Germany, but the situation is changing quite rapidly. China, United States are experiencing a surge of activity. Other markets like South America are also catching up quite rapidly. In the past few years, a new frontier for wind power development has also been established in the sea. With offshore wind parks beginning to make a contribution, the possibilities of using wind energy systems worldwide are likely to increase many times in the future. Establishing wind energy projects in the sea has opened up new demands, including the need for stronger foundations, long underwater cables and larger individual turbines, but offshore wind parks are expected to contribute an increasing proportion of global capacity.
Hermann-Josef Wagner, Jyotirmay Mathur


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