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The demand for energy supply, especially electricity, is an ever-increasing trend as the population grows and in order to meet the social and economic development of the world. This means we require more consumption of fossil fuels to produce electricity. Fossil fuels comprise mainly coal, oil and gas. These sources were formed millions of years ago from the decomposed bodies of dead plants and animals. These sources are likely to exhaust after few years as demand for fuel continues to grow at a fast rate. Apart from the possibility of depletion of these sources, pollution is a major disadvantage of fossil fuels. This is because they give off carbon dioxide when burned, thereby causing the greenhouse effect. This is also the main contributory factor to the global warming experienced by the Earth today. The current interest in the use of renewable is the need to reduce the high environmental impact of fossil-based fuels used in energy production. There are a number of renewable sources which are being investigated for harnessing energy on a large scale. Future energy sustainability depends heavily on how the renewable energy problem is addressed in the next few years and decades. The sources of renewable energy being considered for further development are solar, wind, biomass, geothermal, ocean, fuel cell and small hydro systems. The main problem with these resources is the cost and availability. Unlike conventional sources of electric power, the output of renewable sources is not controllable. Control is one of the key enabling technologies for the development of renewable energy systems. In this book, the generation of energy, mainly electrical, by using various renewable sources is addressed. Solar and wind power are the two major resources which are now in use in small- as well as large-scale power production. These sources also require effective use of advanced control techniques, which are discussed in this book. In addition, integration of renewable energy in the power grid and their working in the microgrid are also considered.
These contents are covered in 14 chapters. In Chapter 1, the types of renewable energy sources and the basic principles involving energy conversion are described. These include the theory of fluid mechanics which is required in hydro and ocean energy conversion and laws of thermodynamics required in understanding the thermal power conversion applied in biomass. The renewable energy systems extensively use power electronics for proper utilization of energy. Similarly, different types of generators are used in power generation which are more suitable for a particular type of energy source. Chapters 2 and 3, therefore, describe the theory of power electronics and various electric power generators. Since many renewable energy sources such as solar and wind are intermittent in nature, energy storage becomes essential for their utilization. Therefore grid-scale energy storage systems are described in Chapter 4.
Since solar energy has two main applications, one involving solar thermal and other photovoltaic, Chapter 5 deals with the solar thermal energy conversion technology and Chapter 6 covers the photovoltaic power generation. Wind energy conversion is presented in Chapter 7. Here, both horizontal and vertical wind turbines for power generation are described.
Biomass is another major source of renewable energy. Conversion of biomass into various forms of energy is described in Chapter 8. Chapter 9 deals with harnessing the geothermal energy for generation of electricity. Geothermal energy is heat from within the Earth. Geothermal power plants using hydrothermal resources are discussed in this chapter.
Technologies for generating electrical power from the ocean include tidal power, wave power, ocean thermal energy conversion, ocean currents, ocean winds and salinity gradients. All these methods are dealt with in Chapter 10.
A fuel cell converts stored chemical energy to electrical energy directly. Essentially, it takes the chemical energy that is stored within an energy source such as hydrogen, gasoline or methane, and then through two electrochemical reactions, it converts it directly to electricity. A number of fuel cell technologies are now available for various applications which are described in Chapter 11.
Hydropower is the most important and widely used renewable source of energy. Hydropower represents about 16% of total energy produced from renewable sources. In Chapter 12, only small hydropower is described as large power systems involving dams and reservoirs have already been in use for a long time and are generally described in many books on power systems.
With the availability of a large number of renewable energy sources distributed over a large area, the interconnection with distribution systems creates many new challenges. Wind energy and solar energy are not dispatchable sources, therefore, the power cannot be controlled. Solar and wind power plants exhibit changing dynamics, non-linearities and uncertainities. Effective control techniques are required to properly manage the distribution grid. Chapter 13 is devoted to the control and operation of grid-connected solar and wind energy systems.
As a large number of distributed sources of energy, mainly renewable, are available now, the secure and reliable power supply can be obtained with the help of the microgrid. Thus, Chapter 14 is devoted to integration of renewable sources in the microgrid and their operation and control. This type of material is not available in any renewable energy book and may be of interest to people working in the design of power supply with renewable sources.
This book can be used as a textbook for undergraduate and graduate courses. It can also be used by practicing engineers.