| Homebuilt Wind Turbine Explained |
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Wind Speed
Wind speed is usually referred to as the speed of air movement in an outside environment; however speed of air movement inside is also important in many cases, especially in some areas of science such as construction, civil engineering and weather forecasting. High intensity winds can result in very nasty side effects such as typhoons and hurricanes. Wind speed is basically movement velocity of air relative to a fixed point on earth and the simplified definition of wind is air moving from one place to another.
Beaufort scale
This scale, invented in 1805 by the British naval officer Sir Francis Beaufort is an empirical measure for describing wind intensity. The scale is mainly based on observing conditions at sea. A scale was needed at that time because weather observations made by humans could be very subjective, e.g. what one man thought of as very calm conditions another might experience as completely something else. Beaufort scale is actually an abbreviation of the full name Beaufort wind force scale.
The scale was revised and enhanced several times to meet new demands. In the 1850's it was modified to support non-navy use and the scale numbers was made equivalent to cup anemometer rotations. When steam power came along, the sails behavior that was previously used to determine wind intensity; was no longer a factor in the wind speed decision making process and the sea was used instead so the scale descriptions had to be changed. In 1923, the mapping between anemometer rotations and scale numbers were standardized by George Simpson, Director of the UK Meteorological Office. The scale was again changed to suit meteorologists better, a few decades later. In 1946 the Forces 13 to 17 were added to support measurement of extreme conditions, such as typhoons.
The table down below shows the Beaufort wind force scale.
Note: that wave heights in the scale are for conditions in the open ocean, not along shore.
| Beaufort number | Wind speed | Mean wind speed (kt / km/h / mph) | Description | Wave height | Sea conditions | Land conditions | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| kt | km/h | mph | m/s | m | ft | |||||
| 0 | 0 | 0 | 0 | 0-0.2 | 0 / 0 / 0 | Calm | 0 | 0 | Flat. | Calm. Smoke rises vertically. |
| 1 | 1-3 | 1-6 | 1-3 | 0.3-1.5 | 2 / 4 / 2 | Light air | 0.1 | 0.33 | Ripples without crests. | Wind motion visible in smoke. |
| 2 | 4-6 | 7-11 | 4-7 | 1.6-3.3 | 5 / 9 / 6 | Light breeze | 0.2 | 0.66 | Small wavelets. Crests of glassy appearance, not breaking | Wind felt on exposed skin. Leaves rustle. |
| 3 | 7-10 | 12-19 | 8-12 | 3.4-5.4 | 9 / 17 / 11 | Gentle breeze | 0.6 | 2 | Large wavelets. Crests begin to break; scattered whitecaps | Leaves and smaller twigs in constant motion. |
| 4 | 11-16 | 20-29 | 13-18 | 5.5-7.9 | 13 / 24 / 15 | Moderate breeze | 1 | 3.3 | Small waves. | Dust and loose paper raised. Small branches begin to move. |
| 5 | 17-21 | 30-39 | 19-24 | 8.0-10.7 | 19 / 35 / 22 | Fresh breeze | 2 | 6.6 | Moderate (1.2 m) longer waves. Some foam and spray. | Smaller trees sway. |
| 6 | 22-27 | 40-50 | 25-31 | 10.8-13.8 | 24 / 44 / 27 | Strong breeze | 3 | 9.9 | Large waves with foam crests and some spray. | Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. |
| 7 | 28-33 | 51-62 | 32-38 | 13.9-17.1 | 30 / 56 / 35 | Near gale | 4 | 13.1 | Sea heaps up and foam begins to streak. | Whole trees in motion. Effort needed to walk against the wind. |
| 8 | 34-40 | 63-75 | 39-46 | 17.2-20.7 | 37 / 68 / 42 | Gale | 5.5 | 18 | Moderately high waves with breaking crests forming spindrift. Streaks of foam. | Twigs broken from trees. Cars veer on road. |
| 9 | 41-47 | 76-87 | 47-54 | 20.8-24.4 | 44 / 81 / 50 | Strong gale | 7 | 23 | High waves (2.75 m) with dense foam. Wave crests start to roll over. Considerable spray. | Light structure damage. |
| 10 | 48-55 | 88-102 | 55-63 | 24.5-28.4 | 52 / 96 / 60 | Storm | 9 | 29.5 | Very high waves. The sea surface is white and there is considerable tumbling. Visibility is reduced. | Trees uprooted. Considerable structural damage. |
| 11 | 56-63 | 103-117 | 64-72 | 28.5-32.6 | 60 / 111 / 69 | Violent storm | 11.5 | 37.7 | Exceptionally high waves. | Widespread structural damage. |
| 12 | >63 | >117 | >72 | >32.7 | N/A | Hurricane | 14+ | 46+ | Huge waves. Air filled with foam and spray. Sea completely white with driving spray. Visibility very greatly reduced. | Considerable and widespread damage to structures. |
Wind Intensity Measure Instrument
An anemometer is a device that is often used to measure wind speed and pressure; it rotates at the same speed as the wind and indicates speed and/or pressure. They come in a variety of models, from handheld pocket size models to wind mill mounted. When attached to a wind mill it works in conjunction with a wind wane and is the sensor receiving data from the wind vane and calculates the wind intensity. You can read more about anemometers here.