Preprints
https://doi.org/10.5194/wes-2021-21
https://doi.org/10.5194/wes-2021-21
15 Mar 2021
 | 15 Mar 2021
Status: this preprint has been withdrawn by the authors.

An analytical solution for wind deficit decay behind a wind energy converter using momentum conservation validated by UAS data

Moritz Mauz, Bram van Kesteren, Andreas Platis, Stefan Emeis, and Jens Bange

Abstract. The wind deficit behind a wind energy converter (WEC) results from a complex interaction of forces. Kinetic energy is removed from the atmosphere, but coherent turbulent structures prevent a swift compensation of momentum within the wake behind the WEC. A detailed description of the wake is beneficial in meso-scale weather forecast (e.g. WRF models) and numerical simulations of wind wake deficits. Especially in the near to intermediate wake (0.5−5 rotor diameters D), the dominating processes characterising the wake formation change along the wake. The conservation equation of momentum is used as a starting point to map the most important processes assuming the WEC operates at maximum efficiency in a neutral stratified boundary layer. The wake is divided into three different regions to accommodate the changing impact of atmospheric turbulence and the shear created by the WEC onto the wake. A differential equation that depicts the variable momentum transport into the wind deficit along the wake is derived and solved analytically. Additionally, a numerical solution (Euler method) of the simplified momentum conservation equation is shown to provide a quality control and error estimate to the analytical model. The analytical solution is compared to conventional WEC wake models and in-situ wake measurements behind an Enercon E-112 converter, located in the Jade Wind Park near the North Sea coast in Germany, captured by the MASC-3 UAS (unmanned aircraft system) of the University of Tübingen. The obtained UAS data cover the distance from 0.5−5 D at hub height behind the nacelle. The analytical and numerical model are found to be in good agreement with the data of the three measurement flights behind the WEC.

This preprint has been withdrawn.

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Moritz Mauz, Bram van Kesteren, Andreas Platis, Stefan Emeis, and Jens Bange

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2021-21', Anonymous Referee #1, 13 Apr 2021
    • AC1: 'Reply on RC1', Moritz Mauz, 23 Jun 2021
  • RC2: 'Comment on wes-2021-21', Anonymous Referee #2, 17 May 2021
    • AC2: 'Reply on RC2', Moritz Mauz, 23 Jun 2021

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2021-21', Anonymous Referee #1, 13 Apr 2021
    • AC1: 'Reply on RC1', Moritz Mauz, 23 Jun 2021
  • RC2: 'Comment on wes-2021-21', Anonymous Referee #2, 17 May 2021
    • AC2: 'Reply on RC2', Moritz Mauz, 23 Jun 2021
Moritz Mauz, Bram van Kesteren, Andreas Platis, Stefan Emeis, and Jens Bange
Moritz Mauz, Bram van Kesteren, Andreas Platis, Stefan Emeis, and Jens Bange

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Short summary
The study aims for a computationally inexpensive model describing the wind deficit behind a wind energy converter analytically using some assumptions and basic governing equations of the atmosphere. Thus, the influence of different atmospheric conditions onto the wake development can be studied in the future which is important e.g. in wind park planning. The model is compared to conventional empirical wake models and in-situ UAS measurements captured along the wake at hub height.
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