Parts of a Wind Turbine
History of Wind Energy
As early as 3000 B.C., people used wind energy for the first time in the form of sail boats in Egypt. Sails captured the energy in wind to pull a boat across the water. The earliest windmills, used to grind grain, came about either in 2000 B.C. in ancient Babylon or 200 B.C. in ancient Persia, depending on who you ask. These early devices consisted of one or more vertically-mounted wooden beams, on the bottom of which was a grindstone, attached to a rotating shaft that turned with the wind. The concept of using wind energy for grinding grain spread rapidly through the Middle East and was in wide use long before the first windmill appeared in Europe. Starting in the 11th century A.D., European Crusaders brought the concept home with them, and the Dutch-type windmill most of us are familiar with was born.
Modern development of wind-energy technology and applications was well underway by the 1930s, when an estimated 600,000 windmills supplied rural areas with electricity and water-pumping services. Once broad-scale electricity distribution spread to farms and country towns, use of wind energy in the United States started to subside, but it picked up again after the U.S. oil shortage in the early 1970s. Over the past 30 years, research and development has fluctuated with federal government interest and tax incentives. In the mid-'80s, wind turbines had a typical maximum power rating of 150 kW. In 2006, commercial, utility-scale turbines are commonly rated at over 1 MW and are available in up to 4 MW capacity.
The simplest possible wind-energy turbine consists of three crucial parts:
- Rotor blades - The blades are basically the sails of the system; in their simplest form, they act as barriers to the wind (more modern blade designs go beyond the barrier method). When the wind forces the blades to move, it has transferred some of its energy to the rotor.
- Shaft - The wind-turbine shaft is connected to the center of the rotor. When the rotor spins, the shaft spins as well. In this way, the rotor transfers its mechanical, rotational energy to the shaft, which enters an electrical generator on the other end.
- Generator - At its most basic, a generator is a pretty simple device. It uses the properties of electromagnetic induction to produce electrical voltage - a difference in electrical charge. Voltage is essentially electrical pressure - it is the force that moves electricity, or electrical current, from one point to another. So generating voltage is in effect generating current. A simple generator consists of magnets and a conductor. The conductor is typically a coiled wire. Inside the generator, the shaft connects to an assembly of permanent magnets that surrounds the coil of wire. In electromagnetic induction, if you have a conductor surrounded by magnets, and one of those parts is rotating relative to the other, it induces voltage in the conductor. When the rotor spins the shaft, the shaft spins the assembly of magnets, generating voltage in the coil of wire. That voltage drives electrical current (typically alternating current, or AC power) out through power lines for distribution. (See How Electromagnets Work to learn more about electromagnetic induction, and see How Hydropower Plants Work to learn more about turbine-driven generators.)
Now that we've looked at a simplified system, we'll move on to the modern technology you see in wind farms and rural backyards today. It's a bit more complex, but the underlying principles are the same.