Question Video: Understanding the Electric Current Produced by Wind Turbines Physics

Video Transcript

What type of electric current do wind turbines produce?

A great way to start answering this question is to sketch out what a wind turbine looks like as it’s working. Let’s say that this is our wind turbine, and we have wind blowing past it. The pressure of the wind on the turbine blades will cause this whole turbine to start to rotate in a certain direction. As that happens, as the turbine rotates, it’s connected internally to a device called a generator. The generator is what takes the rotational energy of the turning turbine and converts it to electrical energy. And we want to know when that electricity is produced, what kind of current is output?

Going back to the internal workings of our turbine, as the shaft of our turbine rotates, that causes the rotation of a coil of wire inside magnets in the generator. Depending on the angle of this rotating wire more or less electrical current is induced in it. It’s this current, which is the output of the electrical generator. And it goes up and down, depending on the rotation of the turbine. For one position of the turbine and therefore the position of the wire inside the magnets, the current generated is at a maximum value. But then later on, as this wire rotates, the current is at a minimum. But then with rotation continuing, it goes back to a maximum value then back to a minimum then to a max, and so on and so forth.

If we drew a line connecting these points, that line would go up and down like a sine wave. Now, because of the way this generator works, some of this current flows in one direction, and some of it flows in the opposite direction. We could say the current above this horizontal line is positive; it flows one way. And the current below the line is negative; it flows the other direction. And this alternation between positive and negative current happens over and over again. In other words, we have electrical current, which goes from positive to negative and back again in a periodic or regular way. And in fact, that’s the definition of alternating current or AC. Because the electricity from a wind turbine is generated thanks to the rotation of the turbine, that electrical energy is output with an alternating current, a current that reverses direction periodically.