sowento pewit – Lidar wind field reconstruction for power performance testing

pewit – a wind field reconstruction software to enable power performance testing with nacelle-based lidar systems.

Why using pewit?

  • Accelerated measurement campaign through the use of more inflow sectors.
  • Easy and clear workflow at the GUI.
  • Evaluation of free stream wind speed.
  • Applicable for flat and complex terrain measurements.
  • Reduced uncertainty on very large rotors.

Key features

  • Graphical Desktop App
  • No additional software required
  • Define measurement scenarios and lidar
    devices in detail
  • Load and save your configurations
  • Plot results for immediate plausibility check

Future challenges in power performance testing

Power performance testing is an important task, not only in the certification phase, but also during the entire lifetime of a wind turbine.

Using a nacelle-based lidar system offers advantages over a conventional meteorological mast:

  • no excluded sectors due to wind directions when the met mast is behind the turbine and thus reduced duration of the measurement campaign.
  • easy installation and thus much more flexibility in the planning of measurement campaigns.
  • lower initial and maintenance costs.

Here, a wind field reconstruction software such as pewit is required to process raw lidar data into useable signals. 

However, with increasing size of wind turbines the distance to reconstruct the free-stream wind speed is very large. In complex terrain the task even gets more challenging. 

This is where pewit provides its unique features!

The lidar is measuring in the induction zone

The influence of the induction zone on the free stream wind speed. The wind speed is reduced by the wind turbine and therefore, the lidar is measuring a reduced wind speed.

The influence of the induction zone on the free-stream wind speed. The wind speed is reduced by the operating wind turbine and therefore, the lidar system is measuring a reduced wind speed.

Previous strategies for power performance testing with nacelle-based lidar aimed to measure outside of the induction zone, typically in a distance of 2.5 rotor diameter. For very large turbines, this is hard to archive due to the limited range of nowadays nacelle-based lidar systems. The wind speed outside the induction zone in complex terrain might be also little related to the wind acting on the rotor due to interactions between the wind and the terrain. 

Thus, we propose to measure closer to the rotor and therefore inside of the induction zone.  Of course, this will reduce the raw wind speed measured by the lidar. However, with the induction zone model feature included in pewit, we reconstruct the free-stream wind speed. Thus, pewit makes power performance testing possible on large wind turbines even with the range limitations of lidar systems. For complex terrain, the free-stream wind speed provided by pewit will be much more related with the wind acting on the rotor than any measurement outside the induction zone.

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