This lesson requires a newer browser. Please see this page for more information.

When the wind pushes against the blades of a wind turbine, the blades spin part of a generator that generates electricity. There are many factors that influence how much power is generated by a turbine, let's take a look at what a few of them mean in a general sense.

When the wind is moving faster, or has a higher wind speed, it has more energy that it can give to the turbine. Careful though! If the wind blows too fast, the turbine can be damaged or even torn apart. Real turbines have complicated systems that limit how fast they can spin to prevent this. Air density is a measurement of how much mass a volume of air has. If it has more mass, it takes more energy to get it moving. And that means the turbine can get more energy from the same volume of air. Blade length is simply how long the blades are. If the turbine has longer blades, they cover a larger area. That larger area will have more air, and more energy, moving through it. Watch out though, eventually the blades can get too heavy, or bend too much, and that will make it harder for the turbine to generate energy.

The last one is a little strange: Efficiency is a measurement of how good the turbine is at taking energy from the wind. It turns out there's a trap here too! It's that if we took all the energy from the wind, it wouldn't be moving anymore. And if the wind stopped, we couldn't get any more energy! So it seems like there should be a maximum efficiency that will let us take the most energy from the wind without slowing it down so much that we can't get any more. There is! It's called the Betz limit, and it's about 59%.

In order to know how efficient a wind turbine is, we need a way to calculate how much power the turbine could get from the wind if everything was perfect. Then we can see how much power we're actually generating and compare the numbers.

We can calculate the available power in the wind if we know he density of the air, the length of the turbine blades, and how fast the wind is moving. You can use the sliders below to calculate the total power in the wind. Use them to answer the questions.