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wind resource validation
Resource Validation
Following a positive initial assessment of a possible wind project site, a more in-depth resource assessment must be done to validate the energy production potential. The scale of the resource assessment should be proportional to the size of the project. In general, data collection for one year with a 50- or 60-meter tower is sufficient for most community-scale projects, provided that those data can be correlated with another suitable site that has high-quality, long-term data.
Types of Data Required
Hourly data are acceptable for a detailed resource assessment, but data averaged over each 10-minute period are preferred.
Wind Speed: Ideally, 10-minute wind speed data will be taken with calibrated anemometers from two heights for one or more years to get a high-quality estimate of average wind speed, and diurnal and monthly variations. One of these anemometers should be placed at or near the hub height of the proposed wind turbines. If the tower height of the turbines is undecided, data taken at three heights, from 30 m up to 50 or 60 m will be most useful. Collecting data at more than one height provides information about the surface roughness of the site and allows interpolation to wind speeds at greater heights. Hourly averages are acceptable if 10-minute averages are unavailable, but this is the maximum amount of time over which data should be averaged. It is also possible to take data for one year or less if there is a measurement station nearby with which the new data can be correlated. If a strong, long-term correlation between the proposed site and the measurement station is established, it may be possible to use historical data to estimate the wind resource at the proposed site. When using this approach, it is very important to ensure the quality of the data from the measurement station.
Wind Direction: Placing a wind direction sensor at the same height as the primary anemometer and taking data at the same averaging interval as the primary anemometer is necessary to provide information about prevailing wind directions. The wind direction information can be used to create a wind rose and to space the turbines so that they do not experience wake effects from each other or nearby obstacles in the prevailing wind directions.
Temperature: A temperature sensor is important for verifying the quality of the wind speed and direction data. At temperatures near freezing, precipitation can collect and freeze on the sensors, affecting their performance. There may be periods of time when the anemometer is measuring high wind speeds while the wind vane is immobile, or the wind vane may be indicating direction changes while the anemometer is not measuring a wind speed. Correlating temperatures to these data can verify icing conditions. Incorrect data should be removed or corrected before analysis is conducted.
