Wind Farm:

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Wind Farm
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Generators that produce AC are generally equipped
with features to produce the correct voltage (120
or 240 V) and constant frequency (60 cycles) of
electricity, even when the wind speed is
fluctuating.
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Controller The controller starts up the machine
at wind speeds of about 8 to 16 miles per hour
(mph) and shuts off the machine at about 55 mph.
Turbines do not operate at wind speeds above
about 55 mph because they might be damaged by the
high winds.
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Gear box Gears connect the low-speed shaft to
the high-speed shaft and increase the rotational
speeds from about 30 to 60 rotations per minute
(rpm) to about 1000 to 1800 rpm, the rotational
speed required by most generators to produce
electricity.
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Yaw drive Upwind turbines face into the
wind the yaw drive is used to keep the rotor
facing into the wind as the wind direction
changes. Downwind turbines don't require a yaw
drive, the wind blows the rotor downwind.
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Wind Classes Areas being developed today using
large wind turbines are ranked as class 5 and
above. Class 3 and 4 areas may be developed in
the near future as wind turbines are adapted to
run more efficiently at lower wind speeds. Class
l and 2 areas are not deemed suitable for large
wind machines, although smaller wind turbines may
be economical in areas (such as remote or
off-grid communities).
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Classes of wind power density at 10 m and 50
m(a).
http//rredc.nrel.gov
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Mass of air that supplies the energy to the wind
turbine is related to the area covered by the
sweep of the blades.
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Power available to turbine in a particular unit
of time is a function of kinetic energy and the
distance the wind travels in that unit of time as
determined by the wind velocity.
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Simplifying
Most important factors wind speed (v) and
diameter of turbine (D).
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Not all power is captured by turbine. The power
coefficient is used to determine efficiency of
energy capture. The power coefficient is power
produced by the turbine compared the power of the
undisturbed wind passing through an area equal
to that swept by the rotor.
Typical power coefficient for modern turbines is
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If AC power is used directly from the wind
turbine there must be frequency control and
electronic filtering to maintain a smooth 60
cycle AC current.
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Electrical Storage(for periods when demand does
not equal production) Batteries are the most
common form of electrical storage. Batteries can
store and deliver only DC power. Unless an
inverter is used to convert DC to AC, only DC
appliances can be operated from the stored power.
The least costly batteries for wind applications
are deep cycle, heavy-duty, industrial type
lead-acid batteries which can be fully charged
and discharged, while standard lead-acid
batteries (e.g., automobile type) cannot.
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Battery conversion efficiency is approximately
60 to 80. A battery's capacity is rated in
amp-hours, a measure of its ability to deliver a
certain amperage for a certain number of hours.
For example, for a rating of 60 amp-hours, 3 amps
can be delivered for 20 hours.
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Wind turbine land requirement 10 m2/kw
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Wind turbine should be located 30 ft above any
obstacles within 300 ft in order to avoid wind
turbulence and to maintain a steady air flow
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Current storage is required for low wind or when
wind power is in excess of electrical demand.
If batteries are used they should be of the
deep cycle type.
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Electrical energy demand for Appledore is shown
in the following graphic.
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The following graphic gives an estimate of the
turbine blade size required for various power
outputs.
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Source/ActivityIndicative noise level aB
(A) Threshold of hearing 0 Rural night-time
background 20-40 Quiet bedroom 35 Wind farm
at 350m 35-45 Car at 40mph at 100m 55 Busy
general office 60 Truck at 30mph at 100m
65 Pneumatic drill at 7m 95 Jet aircraft at
250m 105 Threshold of pain 140
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Why the turbine should not be located too near
the ground
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Possible hydrogen storage sites include the tower
structure for a wind turbine electricity source
(followed by electrolysis).
H2 storage
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• Assumptions
• Tower height 100 ft.
• Tower Diameter 8 ft.
• Tower hollow with wall thickness 1 in.
• Store H2 at 10 atm (150 psi) pressure

Volume of tower is approximately 5000 ft3 At 1
atm of pressure 11.1 m3 ( 392 ft3) of H2 1 kg
of H2 (ideal gas law pV nRT) At 10 atm 39.2
ft3 1kg of H2
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Capacity of tower 5000 ft3/39.3ft3/kg 128 kg
of H2
Energy content of H2 is approximately 30
kWh/kg Total energy of stored H2 is 3,840 kWh.
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Tower must be lined to prevent hydrogen
embrittlement. Hydrogen embrittlement is a
decrease in fracture strength of metal due
incorporation of hydrogen into the metal lattice.
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• Wind turbine being installed on Appledore
• Bergey 10kW (7.5 kW battery charging)
• 7 m (23) rotor diameter
• Cut-in wind speed 5.6 mph
• Mast height 18 37 m (59 121 ft)
• Tilting mast

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Possible hydrogen storage sites include the tower
structure for a wind turbine electricity source
(followed by electrolysis).
H2 storage
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Capacity of tower 5000 ft3/39.3ft3/kg 128 kg
of H2
Energy content of H2 is approximately 30
kWh/kg Total energy of stored H2 is 3,840 kWh.
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Tower must be lined to prevent hydrogen
embrittlement. Hydrogen embrittlement is a
decrease in fracture strength of metal due
incorporation of hydrogen into the metal lattice.
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Design Essentials for Wind Turbine
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Simplifying
Most important factors wind speed (v) and
diameter of turbine (D).
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Units for power equation
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D density of air. This varies with temperature
and elevation
Temp (oF)
Density (kg/m3)
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Density (kg/m3)
Elevation (ft)
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P must be multiplied by efficiency factor of
approximately 0.35. Only a fraction of wind
momentum in the direction of the turbine axis is
converted to momentum perpendicular to turbine
axis.
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For Appledore Island average wind speed at 150 ft
elevation is approximately 8
m/sec