Nobles Wind Farm, Minnesota, United States of America

Nobles wind farm

The 201MW Nobles Wind Farm is located at Nobles County in south-west Minnesota, US. It is the second biggest wind farm in south-west Minnesota, after the 205MW Fenton Wind Farm. Xcel Energy, the owner, invested approximately $500m in the project.

Minnesota Public Utilities Commission approved the wind project in May 2009. The ground-breaking ceremony was conducted in April 2010 and the turbine installation was completed by December 2010. Commercial operations started in December 2010.

The wind farm currently supplies power to approximately 66,500 homes.

Nobles wind project construction and infrastructure

The wind farm is spread over the Olney, Dewald, Larkin and Summit Lake townships in approximately 49m² of agricultural land. It comprises 134 GE wind turbines rated at 1.5MW each. The wind turbine is 389ft tall and consists of a 252.6ft rotor blade with a swept area of 4,654m².

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Major construction activities involved laying 134 turbine foundations, and a 33 mile long and 16ft wide access road. It also included the construction of 86 miles of collection systems and a switchyard for supplying power to the substation.

An underground collector cable system, laid at a depth of four feet, connects the turbine strings to a central substation. The wind speed is measured using five meteorological towers with a hub height of 80m each.

The power station is monitored and controlled from the operations and maintenance building. The generated power is transferred to the Nobles County substation via a 34.5kV transmission line.

Contractors involved with the Nobles wind farm development

The engineering, procurement and construction (EPC) contract was awarded to enXco, a subsidiary of EDF Energies Nouvelles. enXco appointed Mortenson Construction as a subcontractor.

SKF supplied 134 SKF centralised lubrication systems for the wind farm's turbines in 2011.

Turbine technology used at Nobles wind farm

The most prominent features of the GE 1.5MW wind turbine include hydraulic parking brakes, three-phase asynchronous generator and a spur gear system. Lightning receptors and surge protection options are included within the lightning protection system. The lightning receptors are placed at the tip of the turbine blades.

Innovative features such as the programmable logic controllers and a remote control and monitoring system are featured in the turbine control system.

"The wind farm currently supplies power to approximately 66,500 homes."

Turbines function at a wind speed of 12m/s and a wind cut-in speed of 3.5m/s. The cut-out speeds are 28m/s and 25m/s at average time periods of 30s and 600s respectively.

The turbine rotor is equipped with active-pitch controller technology for efficient use of the wind energy captured. The technology also reduces the damage risks occurring in stall-regulated rotors during peak loads.

The pitch angle of the turbine can be adjusted to achieve constant output in accordance with the wind speed.

The turbine gearbox is designed in a three-staged planetary model with a ratio of 1:72. It facilitates transmission of the static/dynamic forces into the tower structure through the yaw system, and features an elastomeric bushing that reduces noise levels during operation.

NRI Energy Technology