Power performance measurements

Power performance measurements

DNV GL delivers precision accuracy to inform planning and financial processes.

A wind turbine’s vital statistics are undoubtedly its power curve. Since this determines the turbine’s annual energy production and revenue generated, it plays a vital role in the financial model of a wind farm project and the sales contract for a wind turbine. Moreover, the turbine’s power curve – how net output power varies with the free stream wind speed – is required for certification purposes.

If a turbine is not delivering as much power as predicted, the long-term financial consequences are serious. Such underperformance may be due to an unrealistic sales power curve, manufacturing tolerances of key components or an incorrect set-up of mechanical or software components. To verify the turbine manufacturer’s sales power curve, an appropriate power performance measurement has to be conducted at the wind farm – because without this measurement, an underperformance claim on the contractual power curve warranty is unlikely to succeed.

DNV GL provides a number of power curve services:

  • Performance type test: Measurements of the prototype of a specific wind turbine model deliver the power curve required for the type testing part of the certification process. We have offices with experienced measurement staff in Seattle (US), Shanghai (CN), Madrid (ES) and Kaiser-Wilhelm-Koog (GER), which can be supported by staff from one of our local offices around the world.
  • A meteorological mast installed upstream from the turbine is used to gather hub height measurements of wind speed, wind direction, temperature, pressure and other variables in relation to the power produced by the turbine. The recorded data is then screened, filtered against specific criteria and post-processed by defined procedures to produce the turbine’s power curve.
  • Site calibration: In complex terrain where wind speeds at the meteorological mast are not the same as at the centre of the rotor, site calibration is a necessity. Flow distortion factors derived from data measured at a second meteorological mast installed where the wind turbine will be erected are applied to the wind speed measurements made during the power curve test to calculate the true free stream wind speed.
  • Performance verification: Performance tests are carried out to check if a turbine’s power curve complies with the manufacturer’s guaranteed power curve.
  • Performance testing of small wind turbines: Testing is possible on site or at our own facilities.

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