Physics Project t6k20

Index: 1. 2. 3. 4. 5.

Introduction Theory Diagram and Pictures Application Bibliography

Introduction: Wind energy is the kinetic energy associated with the movement of atmospheric air. It has been used for hundreds of years for sailing, grinding grain, and for irrigation. Wind energy systems convert this kinetic energy to more useful forms of power. Wind energy systems for irrigation and milling have been in use since ancient th times and since the beginning of the 20 century it is being used to generate electric power. Windmills for water pumping have been installed in many countries particularly in the rural areas. Wind turbines transform the energy in the wind into mechanical power, which can then be used directly for grinding etc. or further converting to electric power to generate electricity. Wind turbines can be used singly or in clusters called ‘wind farms’. Small wind turbines called aero-generators can be used to charge large batteries. Five nations – , USA, Denmark, Spain and India – for 80% of the world’s installed wind energy capacity. Wind energy continues to be the fastest growing renewable energy source with worldwide wind power installed capacity reaching 14,000 MW.

Theory: Differences in atmospheric pressure due to differences in temperature are the main cause of wind. Because warm air rises, when air fronts of different temperatures come in , the warmer air rises over the colder air, causing the wind to blow. Wind generators take advantage of the power of wind. Long blades, or "rotors", catch the wind and spin. Like in hydroelectric systems, the spinning movement is transformed into electrical energy by a generator. The placement or "siting" of wind systems is extremely important. In order for a wind-powered system to be effective, a relatively consistent wind-flow is required. Obstructions such as trees or hills can interfere with the rotors. Because of this, the rotors are usually placed atop towers to take advantage of the stronger winds available higher up. Furthermore, wind speed varies with temperature, season, and time of day. All these factors must be considered when choosing a site for a wind-powered generator. Another important part of wind systems is the battery. Since wind does not always blow consistently, it is important that there be a backup system to provide energy. When the wind is especially strong, the generator can store extra energy in a battery. There are certain minimal speeds at which the wind needs to blow. For small turbines it is 8 miles an hour. Large plants require speeds of 13 miles an hour.

Diagram and Pictures: ( Will be Done )

Application:

1) Energy-generating wind turbines: Wind turbines are installed to capture the power of the wind and be able to convert it to energy. This can be on a broad scale, such as the wind turbines found on wind farms or can be on a smaller scale, such as individual wind turbines people use to generate power for their home. Companies even want to take advantage of the wind. For example, Sam’s Club was the first retailer reported to install a “significant” number of on-site micro wind turbines. 2) Wind-powered vehicles: You’ve probably heard about this one recently. A car, powered primarily by wind (using kites), just completed a 3,100 mile journey across Australia. While it wasn’t 100% powered by the wind, it was a good example of how cars can also be powered using alternative energies. It used a combination of wind, kite and batteries. In total, it reportedly used about $10-$15 of energy for the entire 3,100 mile journey. Not too shabby! 3) Wind/Kite-Powered Cargo Ships: Another great example of tapping into the power of the wind can be found with Cargill. Cargill has stepped up and gone with the innovative idea of installing a large kite on one of its cargo ships in order to tap into the power of the wind and thus reduce fuel consumption and CO2 emissions. Now, of course wind has been used for hundreds and thousands of years to “power” sailing and smaller vessels, but now it is being used to help power larger cargo ships as well. 4) Wind-Powered Sports: For many, many years the wind has been used to power our love of sports, both literally and figuratively. Everything from simple kite-flying to sailing, wind-surfing, kite-surfing, hang-gliding, Para-sailing, wind-skiing and more. 5) Wind-Powered Water Pumps: Using the wind to help pump water out of the ground is not something new. It is however a very helpful and sometimes much needed tool when it comes to some communities and countries. Tapping into the power of the wind makes sense, esp. when it comes to the work needed to pump water.

Bibliography: 1) 2) 3) 4)

http://library.thinkquest.org/20331/types/wind/theory.html http://edugreen.teri.res.in/explore/renew/wind.htm http://biofriendly.com/blog/renewable-energy/5-smart-uses-for-wind-powered-energy/ http://web.mit.edu/10.391J/www/proceedings/Wind-India_Mallet2001.pdf

Another Theory: The power carried by a flowing mass of air that is called wind is the product of the cross-sectional area of the mass and the wind, the density of the wind, ρ, and the wind speed, v. Wind Power, P = ½ * A * v 3 (Watts) ρ = Air density (kg/m3) v = wind speed ( m/s) The air density is proportional to the air temperature and the air pressure, both of which vary with height above sea level. The power in the wind cannot be completely converted to mechanical energy of a wind turbine. Otherwise the air mass would be stopped completely in the intercepting rotor area and would cause a “congestion” of the cross-sectional area for the following air masses. The theoretical maximum of energy extraction from wind was discovered by Betz in 1926, and is written as PBetz = ½ * ρ * A * v3 * Betz = ½ * ρ * A * v3 * 0.59

Though this is not a hard and fast limit such as the Carnot efficiency it happens to be a Useful rule-of-thumb estimate. According to Betz, even if no losses occurred a wind turbine could utilize only 59% of the wind power. In addition when unavoidable swirl losses are included, this figure reduces to about 0.42. This happens to be observed as the current limit of well-designed turbines today