Summary of the monitoring tasks performed after the application of the Rotor Blade Extension

During the prototype stage of the development, installation, and operation of the RBE – Rotor Blade Extension, an extensive monitoring plan was carried out in order to confirm the theoretical values of performance and operational effort obtained while applying the RBE to the turbine.

Two Siemens BONUS 1.3 turbines (from Portugal) are currently being monitored. One of the turbines carried the RBE, whereas the other one is used as a control item in this experiment.

The monitoring of the prototype operational endeavour includes the items mentioned below. All these endeavours and conclusions were obtained after the monitoring task carried out by INEGI, a recognized research institute in wind farm assessment and monitoring activities:

  • Retrieval of the Annual Energy Production (AEP) before and after the application of the RBE, in order to perceive the difference of energy yield achieved by the turbine.

The latest report, dated April 2016, indicates that the turbine with RBE is achieving an increased 7.2% of Annual Energy Production compared to the data obtained before the application of the RBE, with density sea level conditions.

  • Measurement of deformations of the main shaft of the drive train, also before and after the application of the Rotor Blade Extension.

The monitoring system applied to the turbine was achieved in such a way that it may be replicated to any other turbine with the same characteristics. In the words of the report: “The mechanical deformations registered by the monitoring system were always very low and very far for the values permitted by the applied materials”.

  • Monitoring of the blade root forces and bending moments suffered by the rotor blade (according to the IEC 61400-13 standard).

Two identical turbines were monitored, with and without the RBE, which are right besides one another at the wind farm and present the same wind profile during the year. The study concludes that: “The modifications to the edgewise loads induced by the RBE can be considered negligible as, in fact, such loads are virtually weight derived and the increase in weight, due to the RBE, is practically residual in both edgewise and flapwise.”

  • Wear conditions and analysis of the lubricant and grease of the turbine considering the addition of the Rotor Blade Extension.

Both reports (lubricant and grease) share the same conclusion: “… the wear condition of the rolling bearing is not affected by the blade extension…which results from a normal degradation process of the grease and lubricant”.

  • Measurement of the natural frequencies of the turbine and blades to understand the functional security of the turbine.

The test performed led us to conclude that: “…the blade extension produced modifications which did not significantly alter the dynamic behaviour of the wind turbine rotor and tower”.

RBE

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