The spinner anemometer (iSpin) is a proven way to identify yaw-misalignment (DNV-GL) and measure power curves (IEC Standards). While it may be a simple idea, to measure the wind speed and direction from in front of the rotor, many people have submitted questions regarding the technology. Here are the top questions submitted, with responses from Karl Fatrdla of ROMO Wind. If you missed the webinar, you can watch the recording for an in depth discussion of the iSpin technology.
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1. How do you explain that more than 50% of turbines have YaW Mis-alignment?
Answer: Wind measurement technology capable of measuring wind speed and direction on the wind turbine accurately wasn't available until recently. With the nacelle wind vane, such yaw errors remained undetected. Physically, the error is caused by the fact that the nacelle wind vane set characteristic is usually identified during prototype measurements in flat terrain and under free inflow conditions. With changing site conditions compared with the prototype sites and the presence of wake from neighboring turbines, such models don't work properly anymore.
2. How easy is it to retrofit existing wind turbines with the iSpin Anemometer?
Answer: In most types of wind turbines it is very simple and can be completed in 4-5 hours. The system can be mounted from the inside of the spinner. Additional hardware like data collector and communication boxes are installed without drilling via high strength magnets within the hub itself.
3. Can the iSpin anemometer be used to measure power curves in accordance with IEC Standards?
Answer: Yes, the spinner anemometer technology can now be used by IEC accredited wind measurement consultants to measure power curves according to IEC 61400 – 12 – 2 standard. With the publication of the wind tunnel calibration procedure on the IEC homepage the last missing IEC approved process description is now officially available to conduct such a power curve measurement campaign.
4. Is there a different placement of the sensors based on the turbine type?
Answer: Yes, the placement of the iSpin sensors is dependent on the shape and the inner design of the spinner. So far, we are only restricted on Nordex Beta and Gamma type turbines, as their cast-iron hub without spinner doesn’t allow drilling. However, for Beta generation turbines we do have a solution with an additional cone that we mount.
5. Why is a nearby met mast not sufficient for detecting yaw misalignment?
Answer: In general, a met mast is sufficient. However, there are a couple of short comings:
- You do not equip each turbine in a wind park with a met mast.
- Wind met masts are extremely expensive.
- Wind met masts are measuring 2.5 rotor diameters away from the wind turbine, resulting in the met mast possibly not showing the right angle of the wind vector hitting the turbine.
- A wind met mast only measures the wind direction in a very narrow free wind sector. The turbine, however, operates in 360° and in wake as well. Only the iSpin technology is capable to measure 360° yaw misalignment accurately (even in wake).
6. What is the difference compared to Lidar regarding (1) yaw misalignment (2) power performance?
Answer: There are at least three main differentiators:
- iSpin can measure 360° accurately whereas a Lidar can only determine YMA and free wind speeds correctly in a narrow free wind speed sector.
- The iSpin technology due to its simplicity is suited for permanent measurements in the wind turbine over the life time. Lidars will always have a high degree of maintenance effort and situations where they don't work properly (snow, rain, fog, dirt on the lenses, lamps, equipment service every two years, etc.).
- The cost for the iSpin technology is lower as for Lidar campaigns.
7. What about icing? Would the instrument support ice loading in cold climate regions?
Answer: The iSpin technology is perfectly suited to withstand and measure in deep temperatures as we provided heating capabilities in the sensor head (80 W). If you are talking about ice detection, then I would rather say no, as the point on the spinner nose is temperature wise not conclusively relevant for the occurrence of icing. There are other systems on the market that are much better suited for that purpose.
8. Is the iSpin capable of performing dynamic yaw misalignment correction?
Answer: No. We would need to feed the accurate iSpin wind signals into the controller or hi-jack the nacelle wind vane signal, then static yaw misalignment would disappear automatically and the dynamic yaw misalignment may be reduced. It is questionable though, if it is worth the effort of gaining in most of the cases another .5% and in less casees up to 1.5% considering that the OEM's will not allow such a direct exteranl influence during any product warranty or availability guarantee period.
9. What is the cost of the ispin anemometer?
Answer: Lower cost than any other technology on the market. We offer iSpin as a measurement service rather than selling a piece of equipment. This allows our customers to focus on the measurement results and conclusions rather than the installation, validation of data, maintenance, etc.