Harvesting Electricity From The Wind
Read all of Wind Energy 101: Part One: Harvesting Electricity from the Wind, Part Two: Wind Energy & Our Economy, Part Three: Wind Energy & The Environment, Part Four: Answering Wind Energy Critics, & Part Five: Wind Energy Myths & Facts.
Wind energy is nothing new: people have harnessed the wind for millennia, since the first sailboat! On land, wind mills convert wind energy into mechanical energy by connecting the turning blades to water pumps, flour mills and other machinery.
Wind turbines are a more modern invention. Instead of powering machinery directly, they convert the kinetic energy of wind into electricity. Some turbines are standalone ("distributed" generation capacity), for instance providing power to a college campus or military base. Utility-scale wind farms, which we'll mainly discuss here, feed electricity into the power grid, where it can then be sent hundreds of miles to where it's needed at that moment.
How Do Wind Turbines Work?
Wind turbines have three main parts: the tower, the blades, and a generator. Towers are often around 80 meters tall, just a little shorter than a football field is long. Towers are mainly made of steel, and they're build on a base of concrete. Modern towers are much taller than the ones installed just a couple of decades ago, helping them catch the steadier winds a few hundred feet above the ground.
The part of a wind turbine that usually catches our attention are the blades. They're usually made primarily of fiberglass or composite materials, which makes them both strong and relatively light. They're very carefully shaped to capture as much energy from moving air as they can.
A wind turbine is a like a fan in reverse! A fan uses an electric motor to spin blades that are shaped to move air. A wind turbine has blades that are turned by moving air, spinning an electric generator and creating electricity.
As the wind blows, it pushes on turbine blades. The blades are carefully shaped to move the air to one side, creating a difference in air pressure between the sides of the blades. This makes the blades rotate, and as they do, they spin a shaft that's connected through a gearbox to a generator. The generator then produces electricity to power our homes and businesses.
The stronger the wind, the more power a turbine can generate, up to a point. Turbines usually start producing electricity when the wind is blowing at around 6-9 miles per hour. For safety, they usually don't operate when the wind is above about 45 miles per hour. The average turbine generates electricity 90% of the time! That's one reason they're so tall: the winds are stronger and more regular a few hundred feet off the ground.
The Power Grid
Wind farms deliver electricity to the power grid. We call it a "grid" because electricity reaches us through an interconnected network of generators, transformers and power lines. Think about this the next time you plug your phone in to charge it: you may be connecting it via the power grid with a wind farm several states away!
This fact is important when you think about the question of "what happens when the wind isn't blowing." With many turbines connected to the power grid, local variations in wind speed tend to even out. In fact, many regional power companies find that wind energy helps with overall reliability of the system, in part since the generating capacity is spread over so many different individual turbines.
Wind turbines are almost always in rural areas, which means that utility companies may need to move the electricity they generate great distances to reach the towns and cities where it's needed. This is done through long-distance power transmission lines. Many parts of the long-distance power network are currently in the process of upgrade and expansion, in part to help move wind-generated electricity from rural areas to cities and industrial areas where it's most needed.
Why Does the Cost of Wind Keep Dropping?
The average cost of wind energy has dropped by two-thirds since 2009! And, it's expected to keep dropping for years to come. How does that happen?
Part of the answer is better technology. As companies build more turbines, they work to optimize each part, gaining efficiencies along the way. They come up with better blades and taller towers to catch steadier winds, for example. And, they gain more experience siting wind farms to catch the wind most effectively.
Another answer is scale. As we build more wind turbines -- and build more in the United States -- the cost of each individual turbine naturally comes down. These "economies of scale," married to ever-improving technology, mean that wind can now compete with fossil fuels in terms of cost. In many places, particularly in the Midwest, new wind power projects – even without tax incentives - are already the cheapest option.