Community Renewable Energy

Collecting and Correlating Data

Collecting New Data

A guyed tower is the preferred mount for a wind assessment system. The sensors are placed at various heights on booms connected to the tower, and a data logger is placed at the bottom of the tower. An example of a wind assessment system is shown here. Typically, a wind assessment system includes the following components:

Anemometer(s): An anemometer should be calibrated and placed on a boom at the height of the hub or at a height of 50 to 60 meters. Ideally, one or two more should be placed on booms at lower heights. The booms on which the anemometers are mounted should be oriented such that wake effects are minimized in the direction of prevailing winds.

Wind Vane: A wind vane should be calibrated and placed on a boom at the same height as the primary anemometer.

Temperature Sensor: The temperature sensor can be placed at a lower height than the anemometer and wind vane.

Data Logger: The data logger should be placed in a weatherproof container at the base of the tower for easy access. Its batteries, if not charged by a solar panel, will need to be changed regularly.

Wind Assessment System Sources

Companies providing equipment are:

• NRG Systems
  
• Second Wind
  
• Campbell Scientific
  

Programs providing funding and/or equipment:

• USDA Value-Added Producer Grants (VAPGs) are available to fund feasibility studies for renewable energy systems.

• DOE-Native American Anemometer Loan Program
• Energy Trust of Oregon/Oregon State University Anemometer Loan Program (Oregon state only).
  

Using Previously Recorded Data

When using data collected by someone not affiliated with the project, it is essential to verify that the data are accurate, and in a form that allows the appropriate analyses to be completed. Below is a list of of issues to address when using previously recorded data.

Sensor Height: The anemometer must be placed high enough to be free from the effects of any wind obstructions. Most banks require hub height wind measurements to qualify for financing.

Sensor Type: Cup anemometers are the most frequently used and most reliable wind speed sensors. Any other type of sensor should be investigated for its accuracy.

Sensor Calibration: Calibration of the sensors ensures that they are recording accurate information. The most reliable sites will have records that track when the sensors were calibrated.

Averaging Interval: Measurements should be averaged over a period of no more than one hour.  Instantaneous measurements are only useful for detailed site analysis.

Period of Collection: The longer the collection period, the more useful the data. A full year is required to include seasonal variations in the data.

Data Format: Data are most useful in a time series format that lists each sensor’s reading with the correlated time period.

It is possible to correlate data taken at a nearby site with three months or more of current site data to extrapolate the annual wind pattern. If there is a good relationship between the wind speeds at the two sites, and the quality of the previously recorded data can be verified, this is an acceptable way to validate the wind resource for community-scale projects.