Dutch not optimistic

More accurate wind forecasting methods will reduce the penalties paid by Dutch wind producers for variable supply to the grid, but other techniques will be required to eliminate the problem, concludes a three year study by the Dutch Energy Research Centre (ECN). According to ECN's Arno Brand, it is "a general rule of thumb that for every 3 kWh of wind energy forecasted in the following 24-48 hours, there is a 1.3 kWh imbalance in actual generation -- or a 43% deviation." A more sophisticated forecasting model can reduce the ratio slightly to a 33% deviation, says Brand.

ECN has developed such a forecasting tool, which uses data from the Dutch meteorological office supplemented by more localised weather data. The program, AVDE, is being tested on a solitary wind turbine in Friesland and a 3.5 MW wind farm south of Dordrecht. This provides a 48-hour forecast that is updated every 15 minutes. Greater accuracy is impossible, says Brand, because general wind speed forecasts -- which are given at ten metres height -- have a standard deviation of 2-3 m/s at the hub height of a wind turbine.

Under the Dutch system, market players pay a penalty for any imbalance introduced into the national grid and a so-called "program responsibility" charge is built into the tariff structure of Dutch wind, which covers the cost of this imbalance and is currently charged at i0.06/MWh. Improved forecasts would reduce this penalty but it will remain significant unless other techniques such as regulated feed-in and power storage are used, concludes the report. The Netherlands' 862 MW installed wind capacity currently covers 1.8% of the country's electricity requirements.