Chapter 1
Overview
The terms wind energy and wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (e.g., grinding grain or pumping water), or a generator can convert this mechanical power into electricity to power homes, businesses, schools, and the like. Recently, generation of electricity using wind power has received much attention all over the world. This chapter provides an overview of wind energy systems.
1.1 Introduction
Wind energy is a free, renewable resource, so no matter how much is used today there will still be the same supply in the future. Wind energy is also a source of clean, nonpolluting electricity. Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases. Currently, extensive research on wind energy is going on in various countries of the world, including the United States, Germany, Spain, Denmark, Japan, South Korea, Canada, Australia, and India. There are several organizations for wind energy research in the world, like the Global Wind Energy Council (GWEC), National Renewable Energy Laboratory (NREL), and American Wind Energy Association (AWEA). According to a GWEC report [1], about 12% of the world’s total electricity demand can be supplied by the wind energy by 2020. This figure indicates the importance of wind energy research these days.
1.2 Why Renewable Energy
Coal, oil, and gas, which are being used as fuels for conventional power plants, are being depleted gradually, so exploration of alternative fuel sources—that is, renewable energy sources for producing electricity—is needed. There are various types of renewable energy sources, like solar energy, wind energy, geothermal, and biomass. Renewable energy is the use of nonconventional energy sources to generate electrical power and fuel vehicles for today’s residential, commercial, institutional, and industrial energy applications. This includes emergency power systems, transportation systems, on-site electricity generation, uninterrupted power supply, combined heat and power systems, off-grid power systems, electrical peak-shaving systems, and many more innovative applications.
Wind power has a great advantage over conventional fuels. Its operation does not produce harmful emissions or any hazardous waste. It does not deplete natural resources in the way that fossil fuels do, nor does it cause environmental damage through resource extraction, transport, and waste management.
The generation of electricity by wind turbines is dependent on the strength of the wind at any given moment. Wind farm sites are chosen after careful analysis to determine the pattern of the wind—its relative strength and direction at different times of the day and year. So wind power is variable but not unpredictable.
1.3 Wind Energy
Wind power or wind energy is the process by which the wind is used to generate mechanical power or electrical power and is one of the fastest-growing forms of electrical power generation in the world. The power of the wind has been used for at least 3,000 years. Until the twentieth century, wind power was used to provide mechanical power to pump water or to grind grain. At the beginning of modern industrialization, the use of the fluctuating wind energy resource was substituted by fossil-fuel-fired engines or the electrical grid, which provided a more consistent power source. So the use of wind energy is divided into two parts: (1) mechanical power generation; and (2) electrical power generation.
Wind is simple air in motion. It is caused by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of very different types of land and water, it absorbs the sun’s heat at different rates. During the day, the air above the land heats up more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air rushes in to take its place, creating winds. At night, the winds are reversed because the air cools more rapidly over land than over water. In the same way, the large atmospheric winds that circle the earth are created because the land near the earth’s equator is heated more by the sun than the land near the North and South Poles.
Today, wind energy is mainly used to generate electricity. Wind is called a renewable energy source because the wind will blow as long as the sun shines.
1.4 Advantages and Disadvantages of Wind-Generated Electricity
1.4.1 A Renewable Nonpolluting Resource
Wind energy is a clean, reliable cost effective source of electricity. Electricity generated from the wind does not contribute to global warming and acid rain. Compared to energy from nuclear power plants, there is no risk of radioactive exposure from wind power.
1.4.2 Cost Issues
Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators. Roughly 80% of the cost is the machinery, with the balance being site preparation and installation. If wind-generating systems are compared with fossil-fueled systems on a “life-cycle” cost basis (counting fuel and operating expenses for the life of the generator), however, wind costs are much more competitive with other generating technologies because there is no fuel to purchase and minimal operating expenses.
1.4.3 Environmental Concerns
Although wind power plants have relatively little impact on the environment compared with fossil fuel power plants, there is some concern over the noise produced by the rotor blades, aesthetic (visual) impact, and the death of birds and bats caused from flying into the rotors. Most of these problems have been resolved or greatly reduced through technological development or by properly siting wind plants.
1.4.4 Supply and Transport Issues
The major challenge to using wind as a source of power is that it is intermittent and does not always blow when electricity is needed. Wind cannot be stored (although wind-generated electricity can be stored if batteries are used), and not all winds can be harnessed to meet the timing of electricity demands. Further, good wind sites are often located in remote locations far from areas of electric power demand (such as cities). Finally, wind resource development may compete with other uses for the land, and those alternative uses may be more highly valued than electricity generation. However, wind turbines can be located on land that is also used for grazing or even farming.
1.5 Worldwide Status of Wind Energy
The following provides an overview of the worldwide status of wind energy based on the GWEC report [1].
1.5.1 Europe
Wind is the fastest growing power technology in Europe. Although Europe was home to only one-third of the world’s new installed capacity in 2008, the European market continues its steady growth, and wind power is now the fastest growing power generation technology in the European Union. Indeed, 43% of all new energy installations in 2008 was wind power, well ahead of gas (35%) and oil (13%).
Overall, almost 8.9 GW of new wind turbines brought European wind power generation capacity up to nearly 66 GW. There is now clear diversification of the European market, relying less and less on the traditional wind markets of Germany, Spain, and Denmark. The year 2008 saw a much more balanced expansion, with a “second wave” led by Italy, France, and the United Kingdom. Of the EU’s 27 member states, 10 now have more than 1 GW of wind power capacity.
In 2008 the European wind turbine market was worth €11 billion. The entire wind fleet will produce 142 TWh of electricity, or about 4.2% of EU demand, in an average wind year. This will save about 100 m tons of CO2 each year.
1.5.2 Germany
Though at the global level Germany has been surpassed by the United States, it continues to be Europe’s leading market, in terms of both new and total installed capacity. Over 1.6 GW of new capacity was installed in 2008, bringing the total up to nearly 24 GW. Wind energy is continuing to play an important role in Germany’s energy mix. In 2008, 40.4 TWh of wind power was generated, representing 7.5% of the country’s net electricity consumption. In economic terms, too, wind power has become a serious player in Germany, and the sector now employs close to 100,000 people.
1.5.3 Spain
Spain is Europe’s second largest market and has seen growth in line with previous years (with the exception of 2007, when regulatory change brought about a higher than usual amount of new wind capacity). In 2008, 1.6 GW of new generating equipment was added to the Spanish wind fleet, bringing the total up to 16.7 GW. This development confirms Spain as a steadily growing market, which at this rate is likely to reach the government’s 2010 target of 20 GW of installed wind capacity.
In 2008, wind energy generated more than 31,000 GWh, covering more than 11% of the country’s electricity demand.
1.5.4 Italy
One noteworthy newcomer among the growing European markets in 2008 was Italy, which experienced a significant leap in wind power capacity. Over 1,000 MW of new wind turbines came online in 2008, bringing the total installed capacity up to 3.7 GW.
1.5.5 France
France is also continuing to see strong growth, after progressing steadily in recent years. In 2000, France had only 30 MW of wind-generating capacity, mostly small wind turbines in the French overseas territories. At the end of 2008, the total installed capacity stood at 3.4 GW, representing an annual growth rate of 38%.
Wind power is now France’s fastest growing energy source; in 2008, around 60% of all new power generation capacity in France was wind energy. The biggest potential in the coming years is estimated to be in the north and the northeast of the country. Out of 4,000 MW of approved wind power projects, more than 700 MW are in the region Champagne-Ardennes and 500 MW in Picardy.
1.5.6 United Kingdom
Despite being host to some of the best wind resources in Europe, the United Kingdom’s wind energy market has taken a long time to start realizing this potential. For the first time, in 2009 the UK wind energy sector delivered more than 1,000 MW of new wind power capacity in 1 year, spread over 39 wind farms. From January to December 2009 a total of 1,077 MW of capacity was installed on and offshore, taking the United Kingdom’s installed total to 4,051 MW.
1.5.7 European Union
The European Union continues to be the world’s leader in total installed wind energy capacity and one of the strongest regions for new development, with over 10 GW of new installed capacity in 2009. Industry statistics compiled by the European Wind Energy Association (EWEA) show that cumulative EU wind capacity increased by 15% to reach a level of 74,767 MW, up from 64,719 MW at the end of 2008.
In the European Union, wind power is by far the most popular electricity-generating technology. For the second year running, wind energy had the largest market share: Of almost 26 GW installed in the European Union in 2009, wind power accounted for 39%. All renewable technologies combined accounted for 61% of new power-generating capacity. Since 2000, installed wind capacity has increased from 9.7 GW to 75 GW.
By the end of the year, a total of more than 190,000 people were employed in the wind energy sector, and investments in wind farms amounted to about €13 billion in the European Union during 2009. The wind power capacity installed by the end of 2009 will, in a normal wind year, produce 162.5 TWh of electricity, equal to 4.8% of the European Union’s electricity demand. Spain and Germany remain the two largest annual markets for wind power, competing each year for the top spot (2,459 MW and 1,917 MW, respectively, in 2009), followed by Italy (1,114 MW), France (1,088 MW), and the United Kingdom (1,077 MW). A total of 11 EU member states—over one-third of all EU countries—now each has more than 1,000 MW of installed wind energy capacity. Austria and Greece are just below the 1,000 MW mark.
Offshore wind is setting itself up to become a mainstream energy source in its own right. In 2009, 582 MW of offshore wind was installed in the European Union, up 56% from the previous year. Cumulative capacity increased to 2,063 MW. The main markets were the United Kingdom and Denmark. For 2011, it is expected that a further 1,000 MW of offshore wind will be installed in Europe. This would represent around 10% of the 2010 market.
1.5.8 North America
1.5.8.1 United States
In 2008 the United States was the number one market in terms of both new capacity and total wind generation capacity, and it broke all previous records with new installations of 8.5 GW, reaching a total installed capacity of over 25 GW. The massive growth in the U.S. wind market in 2008 doubled the country’s total wind-power-generating capacity. The new wind projects completed in 2008 accounted for about 42% of the entire new power producing capacity added in the United States in 2007 and created 35,000 new jobs, bringing the total employed in the sector up to 85,000.
1.5.8.2 Canada
Canada in 2008 surpassed the 2 GW mark for installed wind energy capacity, ending the year with 2.4 GW. Canada’s wind farms now produce enough power to meet almost 1% of Canada’s total electricity demand.
The year 2008 was Canada’s second best ever for new wind energy installations, with 10 new wind farms coming online, representing 526 MW of installed wind energy capacity. Included in this total were the first wind farms in the provinces of New Brunswick, Newfoundland, and Labrador. In British Columbia, the only Canadian province without a wind farm, construction began on the first wind farm, with completion expected in early 2009.
1.5.9 Asia
The growth in Asian markets has been breathtaking, and nearly a third of the 27 GW of new wind energy capacity added globally in 2008 was installed in Asia.
1.5.9.1 China
China continued its spectacular growth in 2008, once again doubling its installed capacity by adding about 6.3 GW, to reach a total of 12.2 GW. The prospects for future growth in the Chinese market are very good. In response to the financial crisis, the Chinese government has identified the development of wind energy as one of the key economic growth areas, and in 2009 new installed capacity is expected to nearly double again. At this rate, China is on its way to overtaking Germany and Spain to reach second place in terms of total wind power capacity in 2011. This means that China would have met its 2020 target of 30 GW 10 years ahead of time.
The growing wind power market in China has also encouraged domestic production of wind turbines and components, and the Chinese manufacturing industry is becoming increasingly mature, stretching over the whole supply chain. According to the Chinese Renewable Energy Industry Association (CREIA), the supply is starting to not only satisfy domestic demand but also meet international needs.
1.5.9.2 India
India is continuing its steady growth, with 1,800 MW of wind energy capacity added in 2008, bringing the total up to 9.6 GW. The leading wind producing state in India is Tamil Nadu, which hosts over 4 GW of installed capacity, followed by Maharashtra with 1.8 GW and Gujarat with 1.4 GW.
1.5.9.3 Japan
Japan’s wind energy industry has surged forward in recent years. Development has also been encouraged by the introduction of market incentives, both in terms of the price paid for the output from renewable plants and in the form of capital grants towards clean energy projects. Power purchase agreements for renewables also have a relatively long life span of 15 to 17 years, which helps to encourage investor confidence. The result has been an increase in Japan’s installed capacity from 136 MW at the end of 2000 to 1,880 MW at the end of 2008. In 2008, 346 MW of new wind capacity was added in Japan. Other Asian countries with new capacity additions in 2008 include Taiwan (81 MW for a total of 358 MW) and South Korea (43 MW for a total of 236 MW).
1.5.10 Pacific
1.5.10.1 Australia
After several years of stagnation in Australia’s wind market, the speed of development picked up again in 2008, with 482 MW of new installations, a 58% leap in terms of total installed capacity. Australia is now home to 50 wind farms, with a total capacity of 1.3 GW. Seven additional projects totaling 613 MW are currently under construction and expected to become operational in 2009.
1.5.10.2 New Zealand
New Zealand’s installed capacity grew by only 3.5 MW in 2008 to reach 325 MW. However, this does not adequately reflect the wind industry’s activity over the year, and a further 187 MW is currently under construction.
1.5.11 Latin America
The Latin American market, despite the tremendous wind resources in the region, saw only slow growth in 2008.
1.5.11.1 Brazil
The only country installing substantial new capacity is Brazil, which added 94 MW of wind energy across five wind farms, mostly located in Ceará in the northeast of the country. Brazil’s Programme of Incentives for Alternative Electricity Sources (PROINFA) was initially passed in 2002 to stimulate the addition of over 1,400 MW of wind energy capacity and other renewable sources. The first stage was supposed to finish in 2008, but it has now been extended.
Mexico offers significant wind energy potential with conditions that are considered among the best in Latin America, especially in the area of La Ventosa, Oaxaca (7,000 MW), with average capacity factors above 40%. In addition, other sites in several states also offer good wind power potential, in particular La Rumorosa in Baja California and sites in Tamaulipas, Yucatán, Veracruz, Zacatecas, Hidalgo, and Sinaloa, Mexico. The Ministry of Energy (SENER) has estimated that a total of 40,000 MW of wind energy potential could be developed in Mexico.
Despite this significant potential, wind development in Mexico has been slow, mainly due to inadequate financial incentives, issues with the existing regulatory framework, and a lack of policies to encourage use of wind energy. However, in 2009, new laws and regulations were introduced to boost renewable energy development, and more than 560 MW of wind projects are currently under construction.
1.5.11.2 Mexican Power Generation System
Mexico has around 50 GW of total installed electricity generation capacity, including 11,457 MW from independent power producers (IPP) and about 7,900 MW of self-generation and cogeneration capacity. During the last years, the generation mix in Mexico changed significantly, moving away from fuel-oil generation plants to natural-gas-based ones. Traditionally, large hydroelectric and geothermal energy have been Mexico’s most widely used renewable sources. Other renewable energy sources, such as wind power, photovoltaic (PV), small hydro, biomass, and biofuels have experienced only slow growth to date.
1.5.12 Africa and Middle East
1.5.12.1 130 MW Installed in Africa and Middle East
In North Africa, the expansion of wind power continues in Egypt, Morocco, and Tunisia, with 55 MW, 10 MW, and 34 MW of new capacity installed, respectively. In the Middle East, Iran installed 17 MW of new capacity. The total installed wind energy capacity in Africa and the Middle East now stands at 669 MW.
Figures 1.1, 1.2, 1.3, and 1.4 show the global cumulative installed wind capacity since 1996 to 2010, the total installed capacity in 2008, top 10 cumulative capacity in December 2010, and annual market forecast by region in 2010–2015, respectively [1].
1.6 Aim and Scope of the Book
This book aims to provide basic concepts of wind energy conversion system. Various means to enhance transient stability and to minimize power, frequency, and voltage fluctuations of wind generator systems are discussed. Comparison is made among the stabilization tools to help researchers and engineers understand their relative effectiveness and then to select the best one. Graduate as well as undergraduate students can use this book as a good reference for wind generator systems and can gain insight into grid integration and stability issues and various methods of stabilization of wind generator systems. They can then apply the knowledge they gain from this book in their own research. Thus, it is hoped that this book would be of high interest and very helpful for researchers, engineers, and students intending to perform research in wind energy systems.
Figure 1.1 (See color insert.) Cumulative installed capacity, 1996–2010.
Figure 1.2 (See color insert.) Total installed capacity 2008.
Figure 1.3 (See color insert.) Top 10 cumulative capacity, December 2010.
Figure 1.4 (See color insert.) Annual market forecast by region, 2010–2015.
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