Locating Wind Energy Generation
Wind Potential
The wind speed varies over both a short time period (a few seconds) and over a larger period of some hours. Consequently there is a continuously varying power output both short and longer term.
Measuring and utilising the output
The scientific way to measure wind speed is to erect an anemometer on a mast with a direction indicator to measure the wind direction. The measurements should be made at the proposed height of the wind turbine rotor hub. To determine annual power output, measurements need to be taken during both the summer and the winter.
Locating Wind Energy Generation -Wind potential at your school or home
The wind turbine needs to be able to capture the wind directly from the prevailing wind direction(s) without the air being impeded by any surrounding buildings or trees. This can generally be ascertained by visually observing the direction and strength of the wind as it blows. The next step is to obtain some direct measurements of the wind speed. The measurement pole needs to be higher than the apex of the house or school building and appropriately stayed using guy ropes. As the wind strength varies considerably, observations should be made at intervals throughout the day over a period of a month or more. This will allow the mean wind speed to be determined. From the turbine manufacturer’s data it will be possible to relate the mean wind speed to power output and to calculate electricity production. This output can then be compared with the electricity consumption indicated on the electricity bill. If the amount generated by the wind turbine exceeds 25% of the electricity consumption, it would be worth considering investing in a small wind turbine.
Siting
Wind turbines need uninterrupted access to the wind if they are to work at their best. As trees, buildings and hills can block the flow of the wind and/or cause ‘turbulence’, locating turbines near them can reduce the amount of electricity that the machine generates. These effects will occur tens of metres above, in front and to the side of trees and buildings and hundreds of metres downwind. Similarly, hillsides may completely block winds from certain directions thereby removing a potential significant wind source. So it is important to think about where you place the turbine and carry out measurements of wind speed to maximise the amount of electricity you get from it. This can take up to a year. Most wind turbines require an open location with average wind speeds of at least 12km per hour.
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