The quality of the wind prediction was assessed by comparing 4 months of forecast results with 9 mast measurements from 40 m - 50 m within Dobrogea:

RMSE

The wind speed RMSEs are varying between 1.87 and 2.23 m/s for the first forecast day and between 2.00 and 2.30 m/s for the second forecast day. The RMSE values of present forecasting systems (weather forecasts plus post-processing) are between 1.5 and 2.5 m/s. Considering that the wind forecasts in this study are run without post-processing, the results are very satisfying.

The normalized RMSE varies between 34 and 40% for the first forecast day and between 36 and 42% for the second forecast day. Investigations of typical forecast errors over land show values of 33 - 45% for the normalized RMSE at 10 m height during the first 36 forecast hours. Thus, the forecast of wind speed lies within the range of other models.

Bias

The wind speed bias is very small. Only two locations show slight underestimations. The small bias for the four months of forecasts shows that there is no systematic deviation.

Mean absolute error (MAE)

The error of power production forecasts based on a “virtual wind turbine” is compared with the results of operational wind power forecasting systems. A typical value for normalized MAE of present wind power forecasting systems is about 20%. The normalized MAE of our evaluation does not exceed 15%. These are quite good results, but we need to keep in mind that this is not a comparison with the “real” behaviour of a wind turbine.

Please note that this evaluation is based on a wind speed forecast without post-processing. This usually leads to better results.