Consultancy on wind resource over the time of development of a wind farm project

Site: 300 MW project in Spain

Scope:

• initial estimate of wind resource
• advice on measurement positions
• optimisation of wind farm lay-out
• input to turbine specifications
• regular check on measured data
• independent documentation of wind measurements
• continuous further development of measurement strategy
• preparation of wind resource and energy production assessments
• selection of locations for masts for the power curve verifications

Results:

• Although the wind farm area has a relatively simple structure, the wind resource was found to vary across it in a way that is not predicted by wind flow models and that does not correspond to the impression of the site. The reason is in the large size of the area, in which the regional (mesoscale) variation of the wind field becomes relevant.
• Therefore, the measurement strategy consisted of a tall mast in a central position and a Lidar instrument which was first verified against that mast, then moved consecutively to a number of positions in the area.
• The measurement positions were defined step by step depending on the outcome of the data captured in the meanwhile.
• The wind resource was determined by combining the outcome of mesoscale wind flow calculations with the results of the wind measurements.
• Due to the strong directionality of the wind field, the wind farm was arranged in rows with relatively narrow spacing within the rows but large distances between rows. With this, the wake losses were kept very low for all turbines. At the same time, the cost of infrastructure was minimised.
• Icing was found to be an issue for the site, despite of its Mediterranean character.
• Wind resource and energy production assessments could finally be prepared with good confidence.
• The final results were not far from the initial estimate.
• The largest uncertainties were found with the power performance of the wind turbines and the extrapolation of the measured data to the long term. The best way to reduce the uncertainty of the entire project was to prolong the mast measurement by one year.