The objective in wind resource assessment is to use the information from the measurements at site to derive an appropriate layout and calculate the expected annual energy production.
The method employed my Modern Energy involves the following steps:
- Long term normalization of field measurements against long term weather model data.
- Running non-linear CFD flow calculations for three different stability classes, and weighting the result against their relative frequency (see Methodology on atmospheric stability).
- Extracting a CFD wind resource map. This means translating the field data, which is typically available at a few locations in the wind farm area, to give an estimate of the wind regime at all locations in the wind farm area using the CFD flow field.
- Use CFD results to extract a “site suitability map” and a “constructability map” to identify areas of high turbine loads and complex terrain.
- The CFD results are also used in an in-house method to calculate and include local turbine performance in the siting process. As a result, areas with severe turbulence and/or strong gradients are avoided (see Site specific turbine performance).
- An ice-loss analysis is performed if the wind farm is located in a cold climate zone. The resulting ice-loss map is utilized in the layout work (see ice-loss analysis).
- A first layout is derived using computer aided optimization based on the information extracted in the previous steps.
- Finally some manual layout optimization performed to incorporate effects such as noise and shadow flicker, or practical constraints such as constructability or consideration for sensitive environment.