Wind Farm:

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.

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.

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.

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.

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).

Wind Power Density (W/m2) Classes of wind power density at 10 m and 50 m(a). Wind Power Class* 10 m (33 ft) 50 m (164 ft) Wind Power Density (W/m2) Speed(b) m/s (mph)   1 100 4.4 (9.8) 200 5.6 (12.5)   2 150 5.1 (11.5) 300 6.4 (14.3)   3 400 7.0 (15.7)   4 250 6.0 (13.4) 500 7.5 (16.8)   5 600 8.0 (17.9)   6 800 8.8 (19.7)   7 1000 9.4 (21.1) 2000 11.9 (26.6) http://rredc.nrel.gov

Mass of air that supplies the energy to the wind turbine is related to the area covered by the sweep of the blades.

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.

Simplifying: Most important factors: wind speed (v) and diameter of turbine (D).

Not all power is captured by turbine 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: 35%

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.

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.

Battery conversion efficiency is approximately 60% to 80% 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.

Wind turbine land requirement: 10 m2/kw

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

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.

Electrical energy demand for Appledore is shown in the following graphic.

The following graphic gives an estimate of the turbine blade size required for various power outputs.

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

Why the turbine should not be located too near the ground:

Possible hydrogen storage sites include the tower structure for a wind turbine electricity source (followed by electrolysis). H2 storage

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

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.

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.

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

Possible hydrogen storage sites include the tower structure for a wind turbine electricity source (followed by electrolysis). H2 storage

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.

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.

Design Essentials for Wind Turbine

Simplifying: Most important factors: wind speed (v) and diameter of turbine (D).

Units for power equation:

D = density of air. This varies with temperature and elevation Temp (oF) Density (kg/m3) 50o 1.240 60o 1.216 70o 1.193 80o 1.171

Density (kg/m3) Elevation (ft) 1.1923 1000 1.152 5000 0.993

P must be multiplied by efficiency factor of approximately 0. 35 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.

For Appledore Island average wind speed at 150 ft elevation is approximately: 8 m/sec