Wind Poster

Highlights

• How do Wind turbines work? Very similarly as airplane wings. When the wind passes over the blade it creates a localized low pressure area behind the blade. The blade is then pulled into this area, causing the rotor to turn. This is called lift. The push of the wind on the blade is drag. The force of lift is significantly stronger than the drag. The combination of lift and drag cause the rotor to turn and spins the generator creating electricity. In turbines, the blades are connected to a drive shaft that turns a generator that creates electricity.
• HAWT vs. VAWT
  • Hawt - Horizontal Axis Wind Turbine – make up 95% of all wind machines in the world. The blades look like airplane propellers. There can be 1, 2, or 3 blades on a tower. Most commonplace are 2 or 3 blades because the blades correct torque
  • VAWT – Vertical Axis Wind Turbines. Have a much higher strain on rotors because of the guy wires needed to keep it erect. Also can't be placed on higher towers. There are different styles of VAWT, but all experience the same problems.
    • VAWT picture -- http://www.memagazine.org/backissues/jun04/features/apptowind/30topc.jpg HAWT picure -- http://www.bergey.com/images/Excel.CEC.jpg
• Wind Prospecting
  • Before a wind farm is set up, prospecting must be done. Anemometers are set up to determine the average wind speed. For a wind turbine to be practice the general consensus is the average windspeed is greater than 12 mph. (1)

Power

• Power available works as a CUBE of the amount of wind present. In general a site needs to have average wind speeds of over 5m/s (11mph) for cost effective generation. Stronger less turbulant wind is 30 m above the ground and higher. A single 750-kilowatt (kW) wind turbine, typical of those now being installed in power plants around the world, produces roughly 2 million kilowatt-hours (kWh) of electricity annually

Environmental Impact

• Polution
  • Based on the U.S. average fuel mix, approximately 1.5 pounds of CO2 is emitted for every kWh generated. A 750 W Wind turbine can prevent the production of CO2 that 500 acres of forest can absorb. On average, 300 American homes can be powered by a 1kW turbine.
• Noise
  • At a distance of 700-1000 ft, an operating wind farm is no louder than the hum of a refridgerator or a moderately quiet room.

Rural night-time background	20-40 dB
Wind farm at 350m	35-45 dB
Car at 40 mph at 100m	55 dB
Busy general office	60 dB
Jet aircraft at 250m	105 dB

• • Small turbines generally create more noise than the larger ones, because:
    • they have a higher rotational speed of the tip
    • more research money has been devoted to decreasing the noise in larger turbines.
• Bird and Bats
  • The national Audubon Society has recently isssued a statement that wind turbines are not more harmful to bird populations than cars, planes, and other man-made contributions. The National Audubon Society has supported the development of Wind Energy. According to research in the U.S. And Denmark, the leading country in wind energy production, powerlines poses a higher threat to birds than wind turbines.
  • The deaths that are caused by Wind towers and turbines are on the individual level, not the population.
    • Places with high mortality rates are being investigated.
  • Newer technology has lowered the mortality rate to bats and birds. The single tower instead of a latice support or guy wires makes collisions with the pole itself less of an issue. Blades are not required to spin as fast as they were 20 years ago and towers spaced farther apart to lower the risk to the avian population.

Comparison of Power Plants

	Wind Energy	Natural Gas	Pulverized Coal
Project Life (years)	30	30	30
Construction Period (years)	0.5	1	2
Plant Size (MW)	100	500	500
Average Operation & Maitenance ($/Mwh)	15	24	20
O&M percent of original cost annually	1.5-2%
per kWh	$.01-.02
Variable O&M ($/Mwh)	0	2.4	1.8

• Background
  • History of Windmills: Earliest known is from Persia (area now known as Iraq). These were of the vertical axis design. Centuries later, Holland (Denmark) perfected the art of harvesting winds with propeller blades on a rotating axis to face the wind.
  • Windmills are primarily used to gather water or grind grain. Turbines (or modern windmills) are used to harvest electricity. Early grain grinders were straight forward, with the grinding stone attached to the vertical shaft of the windmill.

• More information
  • www.awea.org – American Wind Energy Association
  • http://www.eere.energy.gov/RE/wind.html
  • http://lsa.colorado.edu/essence/texts/wind.htm
  • http://www.ece.umr.edu/links/power/wind1.htm – pictures
  • http://telosnet.com/wind/ - history
  • http://windeis.anl.gov/
  • http://www.awea.org/faq/vawt.html – general information about VAWTs
  • http://www.eere.energy.gov/RE/wind_technologies.html – links to other sites
  • http://www.masstech.org/cleanenergy/wind.htm
  • (1) http://www.newtonhouse.info/wind.htm