21-05-2012, 05:20 PM
WIND POWER
WINDPOWER.ppt (Size: 364 KB / Downloads: 543)
WIND POWER - What is it?
All renewable energy (except tidal and geothermal power), ultimately comes from the sun
The earth receives 1.74 x 1017 watts of power (per hour) from the sun
About one or 2 percent of this energy is converted to wind energy (which is about 50-100 times more than the energy converted to biomass by all plants on earth
Differential heating of the earth’s surface
and atmosphere induces vertical and horizontal
air currents that are affected by the earth’s
rotation and contours of the land WIND.
~ e.g.: Land Sea Breeze Cycle
WINDMILL DESIGN
A Windmill captures wind energy and then uses a generator to convert it to electrical energy.
The design of a windmill is an integral part of how efficient it will be.
When designing a windmill, one must decide on the size of the turbine, and the size of the generator.
LARGE TURBINES:
Able to deliver electricity at lower cost than smaller turbines, because foundation costs, planning costs, etc. are independent of size.
Well-suited for offshore wind plants.
In areas where it is difficult to find sites, one large turbine on a tall tower uses the wind extremely efficiently.
SMALL TURBINES:
Local electrical grids may not be able to handle the large electrical output from a large turbine, so smaller turbines may be more suitable.
High costs for foundations for large turbines may not be economical in some areas.
Landscape considerations
Wind Turbines: Number of Blades
Most common design is the three-bladed turbine. The most important reason is the stability of the turbine. A rotor with an odd number of rotor blades (and at least three blades) can be considered to be similar to a disc when calculating the dynamic properties of the machine.
A rotor with an even number of blades will give stability problems for a machine with a stiff structure. The reason is that at the very moment when the uppermost blade bends backwards, because it gets the maximum power from the wind, the lowermost blade passes into the wind shade in front of the tower.