Jens Tambke

An offshore transmission grid for wind power integration: The European techno-economic study OffshoreGrid

An offshore power transmission grid in Northern Europe has become a serious and important topic among the power industry, the power transmission sector, national governments and the European Commission. The OffshoreGrid project will provide policy recommendations for the political process towards such a grid in pursuing the efficient integration of renewables, the integration of market regions, security of supply and the competitiveness of the European economy. OffshoreGrid will develop a scientific view on an offshore grid along with a suited regulatory framework considering technical, economic and policy aspects. The project is targeted towards European policy makers, industry, transmission system operators and regulators. In first instance, the geographical scope is Northern Europe. The paper covers the general approach and objectives of the project. Furthermore, the first results of the preparatory work packages are presented and discussed.

Atmospheric Impacts on Power Curves of Multi-Megawatt Offshore Wind Turbines

Power curves for offshore wind turbines within the German offshore wind farm alpha ventus were derived based on the IEC standard. Binning in groups of shear and turbulence intensity as measures of atmospheric stability were performed. The derived power curves show a strong dependency on these two parameters. Differences of up to 15% in power output between unstable and stable stratification in the non-wake case occur. For wind turbines within the wake of others the effects are even more pronounced. Here, the differences in power production between the stability classes approach 20%. This dependency of the power curves on stability can cause significant miscalculations of instantaneous power production, long-term energy yield and loads. Parameters other than the hub height wind speed are often not taken into account in state-of-the-art wind power forecasts. This can lead to substantial over- or underestimation of the resulting power.