The clean wind energy industry must expand significantly in the next two decades to fulfill a strategy of generating 20 percent of the nation’s electricity. To provide the technological foundation for that dramatic growth, the National Renewable Energy Laboratory (NREL) is embarking on significant improvements at its National Wind Technology Center (NWTC) near Boulder, Colorado.

Engineers have installed the two largest turbines ever tested at the laboratory — a 1.5 MW turbine manufactured by General Electric and a 2.3 MW turbine from Siemens Power Generation. The new turbines allow NREL to take a significant step forward in generating its own clean electricity and meeting the Laboratory’s aggressive sustainability goals and reduce greenhouse gas emissions for its expanding research campus and support facilities. The new turbines are expected to generate twice as much energy as the NWTC uses.

The GE turbine is installed atop an 80m (262 feet) steel tower, the diameter of its rotor will reach 77m (253 feet). More than 10,000 GE turbines operate at commercial wind farms around the United States, accounting for about 50 percent of the U.S. wind energy market.

We were tasked with design and installation of the foundation and tower monitoring systems for both the GE turbine and Siemens turbine.

Comprehensive foundation instrumentation includes strain gages attached to the rebar and earth pressure cells underneath the concrete pad of the tower foundation. Load cells installed in the bolts securing the tower to the base provide load monitoring, rosette strain gages installed on the inside of the steel tower provide strain monitoring. Last, accelerometers at the top of the tower provide acceleration monitoring used for triggering.