Cup and Propeller Anemometers

A widely used anemometer for wind resource measurements has a circular magnet (four poles) in the cup housing, and then one or two coils for pickup of the signal (Figure 4.10), which approximates

FIGURE 4.8 Meteorological station in Jujuy, Argentina.

a sine wave. The transducer counts zero crossings (sampling time is generally 1 Hz), so wind speed is related to number of counts. The advantage is that signals can be transmitted 150 m without loss of accuracy (none of the problems of attenuation and amplification needed with analog signals). An estimate of the accuracy of cup anemometers in wind tunnels is reported to be ±2% [27].

Another type of cup anemometer has a disk containing up to 120 slots and a photocell. The periodic passage of slots produces pulses in each revolution of the cup. This gives a better resolution, so the sampling rate can be increased to 5 Hz.

The propeller anemometers (Figure 4.11) have faster response and behave linearly in changing wind speeds. The wind speed is measured by measuring the voltage output of a DC generator. The propeller is kept facing the wind by a tail vane, which also works as a direction indicator. The accuracy normally is about 2% for wind speed and direction. The propeller is usually made of

- Speed

- Speed

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72 74 76 78 80 82 84 86 88 90 92 FIGURE 4.9 Wind speed data for Mexicali Airport, Mexico.

72 74 76 78 80 82 84 86 88 90 92 FIGURE 4.9 Wind speed data for Mexicali Airport, Mexico.

FIGURE 4.10 Maximum cup anemometer and wind vane. Anemometer is about 15 cm across.

FIGURE 4.10 Maximum cup anemometer and wind vane. Anemometer is about 15 cm across.

polystyrene foam or polypropylene. However, for turbulent winds, the values may be misleading in determining power curves for wind turbines. A propeller anemometer is better suited to measure the three components of wind velocity, because it responds primarily to wind parallel to its axis. An array of three units in mutually perpendicular directions measures the three components of wind.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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Responses

  • valdemar
    How to make a model of propeller anemometer?
    6 years ago

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