Due Diligence
Review of existing site assessment studies

For a wind farm project in its planning phase it is often necessary to review the existing site assessment studies and energy yield calculations. anemos compares the given reports in detail and prepares a review report in consideration of the requirements of the German Technical Guideline 6 (“TR6”) of the Fördergesellschaft Windenergie und Andere Erneuerbare Energien e.V.

The focus of the comparison and plausibility check is on the following aspects:

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  • comparison of all given coordinates, turbine types, power and thrust coefficient curves, for the existing, the planned and the reference turbines
  • input data such as orography, roughness and obstacles
  • wind information (measurements, wind statistics, wind distribution, etc.)
  • methodology, simulation models
  • reference periods
  • long-term correlation
  • plausibility calculations
  • Energy yield calculations, power curves, wind farm efficiency
  • uncertainty analysis
  • information on the wind volatility
  • possible energy loss calculations caused by restrictions due to shade impact or sound emissions, bat flight or sector management

In addition, anemos reviews and evaluates the reports and sites based on its own, long-year experience. Thus, we go beyond the formal requirements of the Technical guideline. Own analyses and calculations are usually not part of the review, but can be agreed upon with the client on an individual basis.

Evaluation of existing wind farms
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The evaluation of existing wind farms is based on its production data. These are long-term correlated in order to estimate the most probably mean long-year energy yield. As such an analysis is directly based on the energy production, most of the uncertainty aspects of a site assessment study can be avoided.

The following steps are part of the analysis:

  • data collection
  • consistency check
  • long-term correlation, usually based on two or three independent long-term data sources, such as e.g. MERRA, anemos indices, IWET Index V11, ERA-Interim, NCEP/NCAR or weather station data
  • weighting of the individual results based on given criteria
  • uncertainty estimation

The reports include all individual results as well as a detailed documentation of the analyses.