Meteorological towers

Meteorological towers (met towers) are the most common means for measuring the wind speed and direction at a site. A met tower is a tall, tubular steel tower. RERL generally installs 40 m or 50 m towers, with tower diameters of approximately 6-8 inches. These towers are secured via four sets of guy wires, which connect from the tower at several heights to four sets of anchors on the ground. The wind speed and direction are measured using anemometers for the wind speed, and wind vanes for the direction. These sensors are usually positioned at two or three heights on the tower, with two anemometers at each height, and one vane. At each height, approximately six-foot long booms are attached to the tower extending horizontally. The wind monitoring sensors are secured to the end of the booms. Thus, there are usually three booms at each height, and the booms for the anemometers are positioned in opposite directions. By positioning the sensors away from the tower, the effects of the tower wake are reduced. The sensors usually produce data that gives the average wind speed and wind direction over 10-minute intervals. These data are recorded and stored by a logger box at the bottom of the tower, which is connected to the sensors via sensor cable.

The Renewable Energy Research Laboratory has installed numerous met towers in and around Massachusetts. These met towers are sold by NRG systems and by SecondWind. Much of the resource data is public domain and can be downloaded directly from this website.