The earliest use of wind power was the sail boat. Ancient sailors came to understand the power of wind. Around 500 AD windmills were created to convert wind power into mechanical energy. The windmills liberated people from some manual labor and allowed them to pump and store water, as well as mill grain from their crops by turning stones.
Today's wind power is generated by modern wind turbines, a somewhat updated version of a windmill. Wind power is considered very clean and a major renewable energy source. Wind power does not generate carbon emissions, pollutants, or consume water.
The wind turbines convert the wind into electricity; the turbine blades are connected to an electro-magnetic generator that produces electricity when the blades spin. A typical small wind turbine may have several blades that are assembled atop a steel tube-shaped tower. Larger wind turbines may be over 300 feet and service a large development or campus. Multiple wind turbines in a location is called a wind farm.
There are some shortcomings for wind power. The largest issue is that wind speeds can vary throughout the day and year. However wind power may be used in conjunction with other electric power sources to provide a
Figure 16.1 reliable supply; this could include a connection to a utility grid, the use of other renewable sources such as solar, and power storage.
Can wind power be used in buildings? Yes, but there are many questions and serious concerns. Tall buildings are the best candidates because wind speed increases with height, but the wind flow is very turbulent on a tall building; wind turbines work better with smooth or regular wind flow.
If a turbine is installed on a building it's likely to be modest turbine, resulting in marginal energy production. In addition, noise produced by the rotor blades, along with the stresses and vibration of the turbines which can be transmitted to the building structure are all serious concerns. There are other issues with land use, aesthetic impacts, birds and bats having been killed (avian/bat mortality) by flying into the rotors, and obtaining insurance for the turbines.
Some manufacturers are using wind velocities from the building parapet or walls but the wind flow is very narrow thus minimizing energy production. One could install a wind turbine on a rooftop, although experts suggest that a wind turbine be elevated at least 30 feet within anything within 500 feet. In addition, rooftops with turbines would have to be quite sizable in order to be cost effective. Overall, the idea of a significant wind turbine on a building would have a very long return on investment, and provide numerous risks and challenges.
Large commercial wind projects require about 60 to 70 acres of land per megawatt (MW), primarily to facilitate and protect wind flow. A small amount of the land is for equipment, access roads and infrastructure such as conduit, cable, connectivity, and substations. Most of the land is a buffer zone to preserve wind flow.
Some farmers lease their farmland to a wind farm to provide another source of income. They can continue to farm the land although wind agreements can create complex legal and financial issues related to the land use. Wind-power leases often last 25-50 years. A frequent fear of landowners is that the developer or contractor of the wind farm will default and the landowner will be left with large inoperable equipment on the property.
Wind speed is the critical feature of wind resources, because the energy in wind is proportional to wind speed. In order for a wind turbine to work efficiently, wind speeds usually must be above 12 to 14 miles per hour to generate electricity. Wind energy is very plentiful in many parts of the United States. Good wind resources have an average annual wind speed of at least 13 miles per hour.
Wind turbines are available in a variety of sizes. The largest turbines can produce enough electricity to power 1,400 homes. A small home-sized wind turbine can supply the power needs of an all-electric home. Single small turbines are used for homes, telecommunications equipment, or pumping water.
One economic issue for wind is that the cost of solar panels has decreased as the solar panels become more efficient. Solar power can now produce 60% more power for the same money as wind turbines; obviously effecting the value of wind turbines and the overall wind power market. One result of this market change is that the U.S. Department of Energy has ended their Residential Small 'Wind Turbines program. The cost of wind power has also been higher than conventional electricity generation, with a much slower return on investment. Although once the wind turbines are constructed, the cost for ongoing operations and maintenance is fairly low.
USA wind power topped 4 percent of the U.S. power grid in 2014 for the first time. In two states, Iowa and South Dakota, wind power now exceeds 25 percent of total electricity production. The United States is recognized as a world leader for wind energy production, primarily due to massive capital infusion via federal and state subsides, tax incentives and grants, that distort the real cost of wind power, with many foreign companies being eligible for the subsides. The tax credit for wind is $0.023/kWh.
The worldwide market for wind energy is growing. The growth year-on year is estimated to be 44%. 45% of new wind power installations in 2014 were in China, which had 110,000,000 homes powered by wind energy by the end of 2014 (total capacity 114,609 MW) (source: The Economist, 1 August 2015). In 2014, the United States represented 17.8% of the world's installed wind power. Twenty four countries have more than 1,000 MW of wind power installed across the world; 11 countries have installed more than 5,000 MW.