Case study

Complex wind resource assessment of an offshore wind farm

Our analysis gave our client a more accurate characterisation of the wind resource at its site.


Our client was developing an offshore wind farm and as part of its Energy Yield Estimate (EYA), it required an accurate prediction of the wind climate at the site. In the absence of a meteorological mast on site, our client was deriving the wind climate from other sources, including a light detection and ranging method (LIDAR) on a nearby island.

Our work

The LIDAR system had collected a large amount of data but was affected by two elements which had to be compensated for:

  • The wind speeds up over the island, so the wind speed above the LIDAR is not the same as that over the open sea
  • The flow above the LIDAR is non-uniform, which introduces some bias into the measurements.

We were asked to quantify both elements and assess the sensitivity of the conclusions to atmospheric stability. We used computational fluid dynamics (CFD) to simulate the wind over the island, including meshing around the steep cliffs and incorporating atmospheric stability variations into the model. We then assessed the operational performance of the LIDAR unit by calculating the radial velocities that the LIDAR would measure and the way in which it would interpret them, to infer the horizontal wind speed.


This analysis gave our client a more accurate characterisation of the wind resource at the site. From the results, we were able to determine factors to:

  • Relate the LIDAR measured wind speed to the true wind speed above the LIDAR
  • Relate the LIDAR wind speed to the wind over the open sea.

This improved the confidence in the wind resource assessment and reduced uncertainty in the estimate, which will feed into the client’s business case for potential investors in the wind farm.

CFD model of wind over island

Work with Frazer-Nash

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