United States

United States

Technical Digest: Siemens and GE - Side by side testing

America's National Renewable Energy Laboratory (NREL) expects by this month to have completed construction of its two newest and largest wind turbines at its wind energy research facility in Colorado.

The GE 1.5 MW machine and a Siemens 2.3 MW unit are part of ongoing research activities conducted by NREL's National Wind Technology Center (NWTC). Both machines will produce a constant stream of data to improve knowledge on turbine performance, reliability and on how to decrease potentially damaging loads through the drivetrains. Proposed testing for the GE turbine, which on an 80 metre tower and with a 76 metre diameter rotor will weigh in at almost 200 tonnes, includes gearbox comprehensive condition monitoring and measuring micro-climate influence on performance and loads. Proposed testing for the Siemens 101 diameter turbine includes structural and performance testing, modal, acoustics and power quality testing, aerodynamic testing and turbine performance enhancements. The late-stage Siemens prototype features a novel blade design that captures more of the wind's energy - supposedly without forcing any more load onto the turbine's moving parts and control systems. It will produce data on aerodynamics, power characteristics, vibrations, system fatigue, acoustics and other key measurements.

The GE turbine's octagonal concrete foundation pad will measure 15 metres across and weigh about 450 tonnes, and the structural loads on the foundations will be studied through a wider co-operative research and development agreement between NREL and the US division of UK wind developer Renewable Energy Systems (RES). "This will result in some of the first-ever measurements of loads inside and under the foundation of an operating wind turbine," says project leader Jim Green. "We need to understand how these big turbines respond," he adds. In addition NREL and RES will study the thermal performance of underground collection system electrical cables and conduct side-by-side comparisons of alternative wind speed measurement systems. Two meteorological towers being constructed at the site near the turbines will use more than 60 instruments to collect data on wind, temperature, dew point, precipitation and other weather variables.

The agreement is worth almost $500,000 over the next two years. The research aims to increase efficiency, cut maintenance of non-turbine wind farm components and lower the overall cost of wind energy. As the turbines will produce more than twice the power used by NWTC, the excess electricity will be exported to the power grid and sold to utility Xcel Energy.

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