Wind energy, or wind power, is any mechanical energy or electricity generated from wind or naturally occurring airflow in the earth’s atmosphere. Wind energy is an indirect form of solar energy: wind blows because the sun unevenly heats different areas of our atmosphere due to the earth’s rotation and differences in surface areas.
Wind power is one of the fastest-growing sources of electricity in the country; according to the American Wind Energy Association, U.S. wind power has more than tripled in the last ten years.
Wind power is generated using wind turbines. These turbines have large blades that rotate as the wind blows by them. When wind turbine blades spin, they turn a rotor connected to a generator inside the turbine, generating electricity.
The amount of electricity a turbine can generate depends on wind speeds, the length and size of the blades on the turbine, and the type of wind turbine. There are two major types of wind turbines used today: horizontal axis and vertical axis.
Horizontal axis turbines
Horizontal axis turbines are the most commonly used today; these turbines typically have three blades high above the ground that spin on a horizontal axis. To operate at maximum efficiency, horizontal axis turbines, and their rotors need to be pointed in an optimal position to capture the wind head-on, but some horizontal axis turbines have sensors that can shift the rotor in different directions to maximize production. Commercial wind energy projects almost exclusively use horizontal axis turbines.
Vertical axis turbines
Vertical axis turbines have blades that rotate around a vertical axis. Unlike horizontal axis turbines, vertical axis turbines do not need to be pointed directly at the wind to operate efficiently; they can capture wind that is coming at them from all different directions. These turbines are often installed closer to the ground and where wind speeds are more variable. In most situations, vertical axis turbines cannot produce as much electricity as horizontal axis turbines.
Wind power is generated similarly in different types of projects, but there are distinctions when it comes to the size and power capacity of the wind turbines:
Small wind refers to the smallest wind projects, typically powering individual households or businesses. Small wind projects are typically under 100 kilowatts (kW) in capacity.
Utility-scale wind projects provide electricity for utility companies to sell. These projects can range from 100 kW to multiple megawatts (MW) in capacity. Utility-scale wind projects are typically connected directly to the electrical grid and generate power that is distributed to a group of utility customers.
Offshore wind projects are built near large bodies of water. These turbines are typically located out in the ocean and are much larger than land-based utility wind projects. Offshore wind turbines generate more electricity than small wind or utility-scale wind projects not only due to the large size of the turbines themselves but also because of the higher and more consistent wind speeds on the water.
According to the Energy Information Administration (EIA), wind energy accounted for about seven percent of overall U.S. electricity generation in 2018. It was also the second-largest source of renewable energy generation, followed by hydropower.