How to measure wind speed

How to measure wind speed

Though the basic mechanics of the old-fashioned windmill are still present in the engineering of a personal wind turbine, time and technology have created a more efficient and effective machine. In our “How does it work?” series, we will discuss the ins and outs of how wind turns into watts.

Do you know the speed of the anemos in your backyard? What is an anemos you ask? No, it is not a small neighborhood creature, or the wild child running around your neighborhood. Anemos is the Greek word for wind. From this word the anemometer, a tool for measuring wind speed and pressure, originated. The first known description of the anemometer occurred in the 1400s, and since then the tool has evolved to include various designs and components that capture the wind.

Some of the most common styles include:

Cup - Four hemispherical cups, each mounted on one end of four horizontal arms, are mounted at equal angles to each other on a vertical shaft. The airflow past the cups in any horizontal direction turns the cups in a manner that is proportional to the wind speed. Counting the turns of the cups over a set time period produces the average wind speed for a wide range of speeds.

Windmill - An aerovane combines a propeller and a tail on the same horizontal axis to obtain accurate and precise wind speed and direction measurements from the same instrument.

Hot-wire – A very fine wire is electrically heated up to some temperature above the ambient. Air flowing past the wire has a cooling effect on the wire. As the electrical resistance of most metals is dependent upon the temperature of the metal, a relationship can be obtained between the resistance of the wire and the flow speed.

Laser Doppler - A beam of light from a laser that is divided into two beams, with one propagated out of the anemometer. Particles reflect, or backscatter, the light back into a detector, where it is measured relative to the original laser beam. The tool measures the speed of the particles, and therefore the air around the anemometer.

Sonic - Ultrasonic sound waves measure wind velocity. They measure wind speed based on the time of flight of sonic pulses between pairs of sensors.

Ping-pong ball – The most primitive form of the tool is constructed from a ping-pong ball attached to a string. The angle between the string-ball apparatus and the line normal to the ground is measured as the wind blows and gives an estimate of the wind speed.

To find out if harnessing the power of the wind for energy is right for your home or business, visit our Sitelook tool for a free evaluation and estimate.

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