Wind Power Basics. Dan Chiras

      I’d also like to thank my family. A world of thanks to my partner Linda who has listened patiently to my many discussions of wind turbines and wind site assessments. Thanks, too, to my sons, whose lives continue to grace mine.

      — Dan Chiras, Evergreen, Colorado

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       CHAPTER 1

       INTRODUCTION TO SMALL-SCALE WIND ENERGY

      Humans have harvested energy from the wind for centuries. Harnessed by the Europeans as early as 900 years ago, wind was used to grind grain and manufacture goods. Wind powered ships that helped open up new territories, spurring international trade. In North America, wind energy has been used since the late 1800s. Over the years, tens of thousands of farms in the Great Plains relied on wind pump water for livestock and domestic uses — some still do.

Windmills began to emerge in the 1860s in rural America. By 1890, there were over 100 manufacturers of water-pumping windmills (Figure 1.1). All told over 8 million were installed in this country. Many of these water-pumping windmills have been restored and are still operating today with minimal maintenance.

       Windmill vs. Wind Turbine

      A windmill is a machine that converts the energy of the wind into other, more useful forms like mechanical energy. Early windmills were designed to grind grain and pump water. Later on, windmills were designed to generate electricity. Electricity-generating windmills are commonly referred to as wind turbines or wind generators. Water-pumping windmills are generally referred to as such or simply as windmills.

      Wind energy was also extremely important to railroads in the West. Windmills were often used to fill water tanks along tracks to supply the steam engines of locomotives.

      In the 1920s through the early 1950s, many Plains farmers also installed wind turbines to generate electricity. The turbines powered lights and all their appliances, many of which were ordered from the Sears catalog — including electric toasters, washing machines and radios. Radios were particularly important, as they allowed farmers and their families to keep in touch with the world.

      Unfortunately, the use of water-pumping and small wind-powered electric generators began to decline in the United States in the late 1930s. Their demise was due in large part to America’s ambitious Rural Electrification Program. This program, which began in 1937, was designed to provide electricity to rural America. As electric service became available, wind-electric generators were mothballed.

Fig. 1.1: The Old and the New. Water-pumping windmills like the one in the foreground were once common in the West and Midwest. The technology hasn’t changed in 100 years. In the distance is a modern commercial wind turbine that generates electricity to power cities and towns.

      In fact, local power companies required farmers to dismantle their wind generators as a condition for providing service via the ever-growing electrical grid. The electrical grid, or simply the grid, is the extensive network of high-voltage electrical transmission lines that crisscross nations, delivering electricity generated at centralized power plants to cities, towns and rural customers. A key advantage of the grid was its ability to provide virtually unlimited amounts of electricity to customers.

      Unfortunately, rural electrification drove virtually all of the manufacturers of windmills and wind-electric generators out of business by the early 1950s. However, in the mid-1970s, wind energy made a resurgence as a result of intense interest in energy self-sufficiency in the United States, stimulated principally by back-to-back oil crises in the 1970s that resulted in skyrocketing oil prices and a period of crippling inflation. Generous federal incentives for small wind turbines, incentives from state governments, and changes in US law that required utilities to buy excess electricity from small renewable energy generators helped stimulate the comeback.

      Soon thereafter, however, wind energy took a nosedive. Conservation and energy efficiency measures in the United States and new, more reliable sources of oil drove the price of oil and gasoline down. Federal and state renewable energy tax incentives disappeared as a result of a precipitous decline in America’s concern for energy independence. As a result, all but a handful of the small wind turbine manufacturers went out of business.

      In the 1990s, commercial and residential wind energy staged another comeback as a result of many factors, among them rising oil prices, global awareness of the decline in world oil production, an increase in the cost of natural gas, and growing concern for global climate change and its impacts.

Because of these factors, many believe that this time around, wind energy is here to stay. Much to the delight of renewable energy advocates, large commercial wind farms have begun to appear in numerous countries, most notably the United States, Germany, Spain and Denmark. These facilities produce huge amounts of electricity and are changing the way the world meets its energy needs. Today, wind-generated electricity is the fastest growing source of energy in the world (Figure 1.2).

Fig. 1.2: Global Wind Energy Capacity. This graph shows the installed global capacity (in megawatts) of commercial wind turbines.

Although commercial wind farms are responsible for most of the growth in the wind industry, smaller residential-scale wind machines are also emerging in rural areas, supplying electricity to homes, small businesses, farms, ranches and schools (Figure 1.3). Most of the small-scale wind turbines “feed” the excess electricity they produce back onto the electrical grid.

World Wind Energy Resources

      Wind energy is clearly on the rise and could become a major source of electricity in years to come because wind is widely available and often abundant in many parts of the world. Significant resources are found on every continent. Tapping into the world’s windiest locations could theoretically provide 13 times more electricity than is currently produced worldwide, according to the Worldwatch Institute, a Washington, DC-based nonprofit organization.

Fig. 1.3: Small Wind Turbine on Tower. This ARE442 wind turbine installed at Mick’s house is mounted on a guyed lattice tower. Maintenance is performed by climbing the tower.

       Rated Power in Watts or Kilowatts

      Wind turbines are commonly described in terms of rated power, also known as rated output or rated capacity. Rated power is the instantaneous output of the turbine (measured in watts)