Wind power probably brings to mind Dutch tower windmills rising up from a field of tulips. It’s not that this is incorrect, maybe just a little outdated. What you should be thinking of when you hear the phrase “wind power” is wind farms, complete with dozens and dozens of new, streamlined windmills with airfoil blades, jutting up out of fields and even bodies of water. So how does wind actually produce power? Let’s find out.

Image © Jeremy Woodhouse/Getty Wind Energy Farm, Mojave, California, USA

It's hard sometimes to imagine air as a fluid. It just seems so ... invisible. But air is a fluid like any other except that its particles are in gas form instead of liquid. And when air moves quickly, in the form of wind, those particles are moving quickly. Motion means kinetic energy, which can be captured. At its essence, generating electricity from the wind is all about transferring energy from one medium to another.

Wind power all starts with the sun. When the sun heats up a certain area of land, the air around that land mass absorbs some of that heat. At a certain temperature, that hotter air begins to rise very quickly because a given volume of hot air is lighter than an equal volume of cooler air. Faster-moving (hotter) air particles exert more pressure than slower-moving particles, so it takes fewer of them to maintain the normal air pressure at a given elevation. When that lighter hot air suddenly rises, cooler air flows quickly in to fill the gap the hot air leaves behind. That air rushing in to fill the gap is wind. If you place an object like a boat’s sail in the path of that wind, the wind will push on it, transferring some of its own energy of motion to the sail, causing the boat to move. The same thing happens with the blades on a windmill.

The simplest possible wind-energy turbine consists of three crucial parts. The rotor blades are basically the sails of the system. When the wind forces the blades to move, it has transferred some of its energy to the rotor. The wind-turbine shaft connects to the center of the rotor. When the rotor spins, the shaft spins too. The rotor has transferred its mechanical, rotational energy to the shaft, which enters an electrical generator on the other end. The 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. 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.

Why Wind?
The two biggest reasons for using wind to generate electricity are the most obvious ones: Wind power is clean, and it's renewable. It doesn't release harmful gases like CO2 and nitrogen oxides into the atmosphere the way coal does, and we are in no danger of running out of wind anytime soon. But there are downsides, too. Wind turbines can't always run at 100 percent power, since wind speeds fluctuate. Wind turbines can be noisy and they can be hazardous to birds. Also, since wind is a relatively unreliable source of energy, operators of wind-power plants have to back up the system with a small amount of reliable, non-renewable energy for times when wind speeds die down.

WORLD WINDS The American Wind Energy Association projects that by 2020, wind will provide 6 percent of all U.S. electricity. The United Kingdom has a stated goal of 10 percent wind power by 2010. Germany currently generates 8 percent of its power from wind, and Spain is at 6 percent. Denmark, the world leader in clean-energy consumption, gets more than 20 percent of its electricity from wind.