Development of a measurement strategy and supervision of wind measurements

Site: Medium size project in Tunisia, mountainous region

Scope: A local company was in charge of the installation and operation of met masts. The equipment had already been procured. aj was to

• advise on number of masts
• advise on measurement positions
• check and document the masts independently
• check the measured data continuously
• assess the site conditions with respect to turbine specification
• prepare wind resource and energy production assessments

Results:

• Although the site itself was not very complex, the complex surroundings led to varying and hardly predictable wind flow conditions across the site. Namely, flow detachment was detected on one of the mast positions in an important wind direction.
• The placement of the masts was first defined for an initial stage. Care had to be taken to avoid misleading results due to local features.
• As some data of the first and second mast had come in, the remaining open questions regarding the wind flow and the most relevant contributions to the uncertainty could be addressed. One of the masts was relocated to cover these best possible.
• The choice of the mast location not only addressed the needs of the wind resource assessment, but also of turbine specification.
• It was found that some booms had not been mounted as predefined. The wind direction offsets were not correct. The mounting of the anemometers was such that the mast structure influenced the measured data significantly. Together with the installation team, changes of the boom orientations and lengths were agreed. An additional anemometer was mounted to help quantifying all impacts on the measurement and assessing the wind shear with confidence. Finally, sufficient quality and purposefulness of the measured data could be achieved.
• It was found that cable ties had been used that were not UV resistant. They were replaced before any measurement cables could have broken.
• A measurement documentation was prepared by aj that was able to satisfy the requirements of investors and turbine suppliers.
• A wind resource assessment with good confidence and state of the art uncertainty could be prepared by aj based on the data.