Powering Europe - European Wind Energy Association
Powering Europe - European Wind Energy Association
Powering Europe - European Wind Energy Association
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temperature gradients, wind speeds and directions at<br />
different heights above ground, and the pressure field.<br />
All models scale down results from the NWP model’s<br />
coarse resolution, which in <strong>Europe</strong> for current models<br />
is between three and 15 km of horizontal resolution.<br />
In some areas with gentle terrain (Denmark, for example),<br />
this resolution is good enough for wind energy.<br />
In complex terrain (for example Spain), such resolution<br />
does not capture all the local effects around the wind<br />
power plant. If this is the case, additional meso-scale<br />
or micro-scale models can be employed, using the<br />
whole meteorological field of the NWP model in a radius<br />
of up to 400 km around the wind power plant. When<br />
using statistical models, the influence of orography on<br />
chApTEr 2 <strong>Wind</strong>generationandwindplants:theessentials<br />
the accuracy of the outcome is less marked, and experience<br />
in Spain shows good results for complex terrains.<br />
The science of short-term forecasting is developing<br />
very rapidly with remarkable results.<br />
In general, advanced statistical models tend to do well<br />
in most circumstances, but they require data accumulated<br />
over half a year before they perform very well.<br />
Physical tools, on the other hand, can create forecasts<br />
even before the wind power plant is erected. Later on,<br />
they can be improved using measured data. Some<br />
physical tools, however, require large computing facilities.<br />
In this case, they have to be run as a service by<br />
the forecaster, while computationally less demanding<br />
models can be installed by the client.<br />
fiGURE 8: oVERViEw of tyPiCal foRECastinG aPPRoaChEs. winD sPEED foRECast Data (1) aRE DEliVERED by a nUMERiCal<br />
wEathER PREDiCtion (nwP) fRoM a wEathER sERViCE anD winD PowER sCaDa Data (3) aRE PRoViDED by thE winD faRMs<br />
the two data sets are combined to provide a forecast for future energy production [tambke 2010]. the variety of<br />
forecast systems can be classified according to the types and combinations of input data and methods of computing<br />
(physical or statistical formulas). for very short term forecasts (1min-2hours) sCaDa data have to be available in<br />
real-time. nwP systems today have different horizons, from short term (1h-12h), intra-day (6h-24h) and day-ahead<br />
(24h-48h) up to medium range (3-10 days) and long range (1-4 weeks) [see www.ecmwf.int].<br />
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