| HAWT advantages |
| • |
Variable blade pitch, which gives the
turbine blades the optimum angle of
attack. Allowing the angle of attack to be
remotely adjusted gives greater control,
so the turbine collects the maximum
amount of wind energy for the time of
day and season. |
| • |
Tall tower allows access to stronger
wind in sites with wind shear. In some
wind shear sites, every ten meters up,
the wind speed can increase by 20%
and the power output by 34%.
|
| HAWT disadvantages |
| • |
HAWTs have difficulty operating in near
ground, turbulent winds.
|
| • |
The tall towers and long blades up to 90
meters long are difficult to transport on
the sea and on land. Transportation can
now cost 20% of equipment costs.
|
| • |
Tall HAWTs are difficult to install,
needing very tall and expensive cranes
and skilled operators.
|
| • |
Need massive tower construction to
support the heavy blades, gearbox, and
generator.
|
| • |
The FAA has raised concerns about tall
HAWTs effects on radar near Air Force
bases.
|
| • |
Their height can create local opposition
based on impacts to view sheds.
|
| • |
Downwind variants suffer from fatigue
and structural failure caused by
turbulence.
|
| • |
Need additional yaw control
mechanism to turn the blades toward
the wind..
|
|
| VAWT advantages |
| • |
Lower construction cost as compared to
HAWTs because there is no need to build a
massive tower structure to support the heavy
HAWT blades and turbine assembly.
|
| • |
As the rotor blades are vertical, a yaw drive
device is not needed, reducing cost.
|
| • |
Can be easier to maintain if the moving parts
are located near the ground.
|
| • |
VAWT's have a higher airfoil pitch angle,
giving improved aerodynamics while
decreasing drag at low and high pressures.
|
| • |
VAWT systems generate 50% more energy
than its HAWT counterpart. Newer systems
are made with rare-earth-alloy magnets
which are 25 times stronger than ferrite
magnets also eliminates any need for
grease or oil since no parts actually touch
each other.
|
| • |
Straight bladed VAWT designs with a square
or rectangular cross section have a larger
swept area for a given diameter than the
circular swept area of HAWTs.
|
| • |
Lower wind startup speeds than HAWTs.
Typically, they start creating electricity at 8 m.
p.h.
|
| • |
Usually have a lower Tip speed ratio/Tip-
Speed ratio so less likely to break in high
winds.
|
| • |
Low height useful at location where laws do
not permit structures to be placed high.
|
| • |
Mesas, hilltops, ridge lines and passes can
have faster winds near the ground because
the wind is forced up a slope or funneled
into a pass and into the path of VAWTs
situated close to the ground.
|
| • |
Does not need to turn to face the wind if the
wind direction changes making them ideal in
turbulent wind conditions.
|
| • |
VAWT blades are easily seen by birds so
pose little threat to wild life.
|
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