Wind energy for electricity generation
Today, wind energy is mainly used to generate electricity, although water pumping windmills were once used throughout the World.
Wind energy use expanded in the wake of oil shortages and environmental concerns
The oil shortages of the 1970s changed the energy environment for the United States and the world. The oil shortages created an interest in developing ways to use alternative energy sources, such as wind energy, to generate electricity. The U.S. federal government supported research and development of large wind turbines. In the early 1980s, thousands of wind turbines were installed in California, largely because of federal and state policies that encouraged the use of renewable energy sources.
In the 1990s and 2000s, the U.S. federal government established incentives to use renewable energy sources in response to a renewed concern for the environment. The federal government also provided research and development funding to help reduce the cost of wind turbines and offered tax and investment incentives for wind power projects. In addition, state governments enacted new requirements for electricity generation from renewable sources, and electric power marketers and utilities began to offer green power to their customers. These policies and programs resulted in an increase in the number of wind turbines and in the amount of electricity generated from wind energy.
The share of U.S. electricity generation from wind in 1990 was less than 1%. In 2016, the share of U.S. electricity generation from wind was about 6%. Incentives in Europe have resulted in a large expansion of wind energy use there. China is investing heavily in wind energy and now has the world’s largest wind electricity generation capacity.
Energy from moving air
Wind is caused by uneven heating of the earth’s surface by the sun. Because the earth’s surface is made up of different types of land and water, it absorbs the sun’s heat at different rates. One example of this uneven heating is the daily wind cycle
The daily wind cycle
During the day, air above the land heats up faster than air over water. Warm air over land expands and rises, and heavier, cooler air rushes in to take its place, creating wind. At night, the winds are reversed because air cools more rapidly over land than it does over water.
In the same way, the atmospheric winds that circle the earth are created because the land near the earth’s equator is hotter than the land near the North Pole and the South Pole.