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Research project for a traceable efficiency determination of wind turbines on test benches


Wind turbines must be innovative, have reduced cost and, above all, improved performance in order to assert themselves on the market. Standardised tests and validation methods are particularly important for the performance optimisation, but also for quality assurance. The guideline needed to determine the efficiency of wind turbines on test benches is being developed as part of an interdisciplinary EMPIR project called 19ENG08 WindEFCY for the first time.

Wind turbines are an important part of the sustainable energy policy; kinetic wind energy is converted into electricity. In order to maximise the electricity yield, not only the performance of wind turbines needs to be increased, but the efficiency of individual components and the entire system is also to be improved continuously. The tests required for this are carried out – regardless of the prevailing wind conditions – in so-called nacelle test benches (Figure 1 and [1]). 


Figure 1: Schematic diagram of a wind turbine on a nacelle test bench including possible measuring points for mechanical and electrical power measurement to determine the efficiency of the wind turbine. Diagram based on [2].

In such a nacelle test bench, the wind turbine is extensively tested without rotor and tower, instead it is being driven by a motor and it is connected to a grid emulation. The mechanical power measurement consists of rotational speed and torque measurements. On the low-speed shaft of a wind turbine, torque of up to 5 MN m and greater and up to 20 revolutions per minute can occur. In contrast, on the high-speed shaft torque of up to 100 kN m at up to 1600 revolutions per minute are measured.

A procedure including a measurement uncertainty analysis and suitable transfer standards to calibrate mechanical power measurement is currently missing. The signals of the electrical components of wind turbines, which are recorded for the electrical power measurement, show significant harmonics and interharmonics that need to be tolerated and processed correctly by the measurement system. In addition, there are large electromagnetic fields in test benches that can affect the measuring systems. Correct grounding of all systems and electromagnetic shielding of all signal lines is of great importance to avoid this. A metrological framework for electrical power measurement in nacelle test benches and suitable transfer standards are also missing here. Precise synchronisation of the mechanical and electrical power measurements is required to determine the efficiency. In order to make a reliable statement about the efficiency of wind turbines and individual components and to be able to compare the results of different systems with one another, standardised procedures with traceable measuring devices are required.

To this end, the European research project “Traceable mechanical and electrical power measurements for efficiency determination of wind turbines”, short 19ENG08 WindEFCY (Figure 2), which is coordinated by PTB, was started in September 2020. The eleven international project partners work across disciplines on the development of a traceable efficiency determination of wind turbines and their components on nacelle test benches. The project also plans to develop and provide methods for traceable mechanical and electrical power measurements and the transfer standards for torque, rotational speed, current, and voltage. The particular challenge of this project is the collaboration between different departments. The PTB combines all competencies represented by the departments solid mechanics and electrical energy measuring techniques, and the working group explosion-protected electrical drive systems. The duration of this project is three years. Further information and the registration for the newsletter can be found on the project website: Opens external link in new windowhttps://www.ptb.de/empir2020/windefcy/.


Figure 2: Overview of the breakdown of the project.




[1] PTB press release (in German) „Genaue Drehmomentmessung für die Windkraft“, Opens external link in new windowLink

[2] Tobias Duda et al 2018 J. Phys.: Conf. Ser. 1037 052031. DOI: 10.1088/1742-6596/1037/5/052031. Opens external link in new windowLink

[3] EMPIR Projekt MN∙m Torque. Opens external link in new windowLink


Rolf Kumme, FB 1.2, E-Mail: Opens local program for sending emailrolf.kumme(at)ptb.de