Earlier this year, we announced measurement enhancements and new service capabilities for the WindCube® vertical profiling lidar. We reviewed the details in a webinar the first quarter of this year, and you can watch the on-demand webinar now. Based on industry feedback and questions asked during the webinar, here are the main takeaways of the unparalleled metrology capabilities and service suite that we can offer to our existing and new WindCube users.
Before delivery, each new WindCube unit goes through our rigorous internal validation phase, where output data is compared to a certified or Golden lidar (the Golden lidar is verified against an IEC-compliant met mast).
To ensure transparency and provide customers with the utmost confidence in our validation process, we’ve added a DNV lidar-to-lidar validation step on top of our own internal processes. DNV issues a Golden Validation Report to ensure that the metrological performance of each WindCube is within scope, serving as an additional control layer to our internal quality process.
The Golden Validation does not replace an IEC-compliant verification. However, it ensures the lidar has gone through an extensive quality validation process checked by a trusted third party — and the report is delivered at no additional cost.
Third-party lidar validations against a met mast (i.e., all the tests done to verify lidar accuracy in accordance with IEC 61400-12-1 Ed2 (2017) standard) are conducted outside of Vaisala premises and usually take one to two months to complete.
Understanding campaign timeline constraints for some of our clients, we’ve designed the WindCube lidar in a way that allows for easy integration of Lidar Chains (a Lidar Chain contains all components which influence the measurement quality). Thanks to our partnership with DNV, we hold a stock of DNV-verified Lidar Chains and can directly deliver a full third-party verified WindCube — saving wind developers weeks usually spent on the validation process.
Each customer is provided with a WindCube verification report based on the Lidar Chain verification, including all relevant quality assessment results. The integration of a verified Lidar Chain to produce a verified WindCube has been tested and validated by DNV (e.g., including transport impact on the Lidar Chain). DNV thereby accepts a Lidar Chain verification in the exact same way as a standard IEC verification.
WindCube (i.e., its Lidar Chain) holds its verification status as long as no maintenance impacting the metrology is performed. DNV recommends a verification at least every 30-36 months, but local regulations or use requirements may need a smaller interval.
Taking advantage of the pre-verified Lidar Chain process, Vaisala extends the benefits to our service and support activities across the globe (learn more about this on our blog on global support expansion). When the WindCube’s Lidar Chain needs repair, the system validation is voided.
The validation continuity process ensures access to a stock of DNV pre-verified Lidar Chains ready to be installed for repair by certified Vaisala experts or partner engineers. Once installed, the WindCube directly recovers its verification, which significantly reduces downtime linked to system outage and new lidar availability as well as the IEC re-validation process. This easy access to the Lidar Chain allows for onsite maintenance of the WindCube units (for offshore applications, Lidar Chain swap can be performed in safe and stable conditions at the closest port or other onshore location).
WindCube v2.1 with hybrid wind reconstruction was classified by Deutsche WindGuard® (DWG) in December 2020 according to IEC 61400-12-1, Edition 2, 2017. WindCube v2.1 has shown the strongest performance achieved so far on the market with standard uncertainty of 0.6% at 120m height.
This classification further contributes to the acceptance of lidar technology for Wind Resource Assessment and other types of campaigns. WindCube lidars are trusted and accepted in the industry thanks to the confidence gained over years of operation, validation against met masts, and developing standards. The Golden Validation or full third-party validation against a met mast are also positively contributing to the acceptance of lidar data. Major industry players use lidar standalone when the correct practices are followed, including the use of WindCube-embedded FCR for moderately complex terrain and CFD correction in complex terrain.
The hybrid wind reconstruction algorithm, or hybrid method, is a scientific breakthrough unique to Vaisala, that combines scalar and vector averaging to achieve the lowest measurement uncertainty. Hybrid wind reconstruction is unique to WindCube v2.1 units and is not yet applicable for other types of WindCube lidars.
The 1.1 class number of WindCube v2.1 with embedded hybrid method is derived using the anemometer as a reference, following the IEC 61400-12-1:2017 Annex L. The IEC standard accepts remote sensing devices if classification and calibration cover hub height ±25% and lower blade tip height ± 25%, i.e., with the 135m height covered in the classification, a turbine with hub height of 180m could be tested with measurements over the full rotor area.
Additional uncertainties should be accounted for at heights exceeding the covered classification height as required by the standard. DWG recommends scaling the sensitivities of the highest height covered by the classification (135m) by the ratio of the target measurement height using the following formula: m (H) = m (135m) * H / 135. For example, the final accuracy class is extended from 1.3% at 135m to 1.8% at 180m, which in turn results in a measurement uncertainty below 1.5% for a measurement campaign run up to 180m height.
For upper heights, lidar calibration results at DTU site in Denmark demonstrated high 10-minute mean wind speed and direction accuracy at higher altitudes (244m). The report is available on request.