Abstract
Actual performances of onshore wind farms are deeply affected both by wake interactions and terrain complexity: therefore monitoring how the efficiency varies with the wind direction is a crucial task. Polar efficiency plot is therefore a useful tool for monitoring wind farm performances. The approach deserves careful discussion for onshore wind farms, where orography and layout commonly affect performance assessment. The present work deals with three modern wind farms, owned by Sorgenia Green, located on hilly terrains with slopes from gentle to rough. Further, onshore wind farm of Nprrekffir Enge has been analysed as a reference case: its layout is similar to offshore wind farms and the efficiency is mainly driven by wakes. It is shown and justified that terrain complexity imposes a novel and more consistent way for defining polar efficiency. Dependency of efficiency on wind direction, farm layout and orography is analysed and discussed. Effects of atmospheric stability have been also investigated through MERRA reanalysis data from NASA satellites. Monin-Obukhov Length has been used to discriminate climate regimes.
Highlights
Performance optimisation of wind farms is a fertile and rapidly growing subject
The present paper aims at giving a contribution on the issue of quantifying and explaining directional dependency of power performance for onshore wind farms: polar efficiency shall be used as the main tool, but its interpretation is even more complex than in the offshore cases
In the present paper an analysis has been performed about polar efficiency for onshore wind farms
Summary
Performance optimisation of wind farms is a fertile and rapidly growing subject. Developments of post-processing techniques of Supervisory Control And Data Acquisition (SCADA) wind turbine databases has proven to be the keystone for quantifying power losses and their causes. Three wind farms owned by Sorgenia Green in southern Italy, sited in terrains from gentle to extremely rough and complex, are investigated in the present paper. The sites under investigations The present work deals with three onshore wind farms, owned by Sorgenia Green and sited in southern Italy They have been chosen because of the different complexity of the terrain and farm layout. The most challenging test case is San Gregorio Magno wind farm: 17 aerogenerators are installed on a very complex terrain, with very high slopes (up to 60%) close to the turbines; the layout is complex and large and there are clusters of considerably near turbines This leads to non trivial combination of complex wind flow and wake interactions. Nørræker Enge is instead on a very plain terrain and the geometry of the wind farm is so regular as to evoke offshore structures
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