Direct-Drive Wind Turbines

In 2010, NPPD officially returned the Springview Wind Facility to service. Originally a two-turbine, 750-kilowatt demonstration project constructed in 1998 to determine the viability of wind energy and distribution voltages in Nebraska, the site became a new kind of demonstration project 12 years later.

The two direct-drive wind turbines are a new technology in the design of utility-scale wind turbines. They are significantly different than the wind turbines used at NPPD’s Ainsworth Wind Energy Facility and other wind farms in Nebraska. Direct-drive turbines do not use a gear box, which is a major component used to increase the rotation speed of the large rotor to several hundred revolutions per minute for the generator. For this new technology, electric inverters are used to synchronize the generator into the grid versus using gearboxes.

The new turbines are Vensys 77 models with rotors 252 feet in diameter and a hub height of 213 feet. The blades and rotor weigh 38 metric tons, the tower structure 90 metric tons, and the generator 42 metric tons. A total of 300 yards of concrete was used in the pad mounts for each tower. Rotor speed is 17.5 revolutions per minute, and the wind speed rated output for the turbines is 29 miles per hour.

Bluestem, LLC, based in Omaha, owns and operates the turbines, and has a 20-year, power purchase agreement with NPPD who purchases the electric energy and shares the renewable energy credits and knowledge gained with Omaha Public Power District, Lincoln Electric System, Municipal Energy Agency of Nebraska, and the City of Grand Island. Bluestem, LLC, is responsible for maintenance of the turbines. Energy generated from the two turbines is interconnected into the Ainsworth-based KBR Rural Public Power District electric distribution system.