OwnEnergy

Prior to constructing a wind farm, onsite wind data must be collected using a meteorological (“met”) tower to assess the local wind energy resource. Such data is essential in order to secure financing for a project.  Typically, met towers are 60 meters tall and configured with anemometers (to measure wind speed) and wind vanes (to measure wind direction), at several different heights above ground level.  Additional data, such as pressure and temperature, may be recorded. The wind data is sampled continuously, recorded over 10-minute intervals by a data logger, and then transmitted remotely using a modem and internet connection.  

The hub height of most utility-scale turbines ranges between 80 and 100 meters. In order to estimate the wind speed at such heights, data collected at various heights on the met tower are used to extrapolate the wind speed from the top of the tower up to 80 or 100 meters. Wind shear is the term used to describe the change in wind speed/direction with height. 

The picture above shows a met tower in Iowa owned by OwnEnergy and a local partner. To minimize the disturbance of airflow from the tower (otherwise referred to as tower shading), instruments are installed on long booms that extend outward. Guy wires are used to support the tower and keep the structure stable.