-grain was being grinded by vertical-axis windmills with woven reed sails in Persia and the Middle East.
History of Windmills: Dutch
1. Dutch Horizontal Axis Windmill 1400 AD
- sed it to drain lakes and marshes in the Rhine River Delta
History of Wind Energy: The earliest known use of wind power
1. Arab Sailboat (2000 BC)
History of Wind Energy: American
1. American steel-bladed watering pumping windmill (1860)
-Steel blades could be made lighter and worked into more efficient shapes. They worked so well, in fact, that their high speed required a reduction (slow-down) gear to turn the standard reciprocal pumps at the required speed.
History of Wind Energy: Polynesian
1. Polynesian Sailing Canoe 500 AD
-Double canoe made of two hulls connected by lashed crossbeams.
-Two hulls gave this craft stability and the capacity to carry heavy loads of migrating families and all their supplies and equipment
-Central platform laid over the crossbeams provided the needed working, living, and storage space.
The density of dry air
1.2 km m^-3 at sea level and decreases with altitude
What is atmospheric circulation primarily driven by?
- By latitudinal temperature gradients caused by enhanced solar heating at the equator relative to the poles
Speed: East-west winds vs. North-south winds
East-west winds are ~ 10x faster than north-south winds
How much is absorbed solar radiation converted into wind energy?
-Closed circulation loop
1. Begins at the equator with warm, moist air lifted aloft in equatorial low pressure areas
2. to the tropopause and carried poleward. At about 30°N/S latitude, it descends in a high pressure area.
3.Some of the descending air travels equatorially along the surface, closing the loop of the Hadley cell and creating the Trade Winds.
Wind patterns are stongly influence by?
Warm air _______at the equator, rains out ______, then descends _______ latitude.
Warm air rises at the equator, rains outmoisture, then descends at ~30° latitude.
East-West generally _______with altitude
Speed: Jet stream winds
Jet stream winds are most intense during....
Atmospheric Circulation Steps
1. Sun's radiation
2. Air rising and expands when it is warmed
3. when it cools, it descends and contracts, causing vertical motion
The power density of the wind: equation
Total global wind power
2 Peta Watts
-100 times human energy consumption
A wind turbine extracts energy in proportion to its_____and its________
A wind turbine extracts energy in proportion to its area, and its coefficient of performance
Wind turbines generally consist of.....
Wind turbines generally consist of a tower,rotors and generator
Why do larger turbines have lower cost per watt?
1. Wind speeds increase with altitude (greater efficiency)
2. Parts count per watt (towers, blades, generators)
3. Energy Payback Period (EPP) is roughly independentof size, so why not go bigger!
The largest wind turbine
The estimated Energy Payback Period for large wind turbines...