the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Introduction and comparison of novel deep learning and optimization approaches to analytical wake modeling of a tilted wind turbine
Abstract. This paper introduces innovative optimization and deep learning techniques to enhance the prediction of complex wake dynamics in the downstream wind velocity of tilted wind turbines. Traditional methods for calibrating the Bastankhah wake model often lead to increased errors in wind velocity distribution due to overfitting local wake characteristics. To address this, we propose an additional global optimization step to reduce errors in wind velocity predictions with respect to various wake parameters. Despite this improvement, the Bastankhah model's axisymmetric Gaussian wake shape limits its accuracy for complex wake structures. Therefore, we also propose a deep learning approach, which demonstrates promising results by accurately modeling complex wake shapes across a broader range of tilt angles with minimal computational cost. The deep learning approach achieves near-identical predictions to high-fidelity large-eddy simulations, representing a promising advancement in wake modeling.
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RC1: 'Comment on wes-2024-172', Anonymous Referee #1, 06 Feb 2025
The paper presents an analysis and different methods to predict the wake behavior of tilted wind turbines. The model proposed by Bastankhah and Porte-Agel for wind turbines in yaw is extended to tilted wind turbines. A deep learning approach is proposed as an alternative to solving the flow equations to calculate the detailed wake structure. The paper contains relevant information and indicates interesting approaches to study the wakes of tilted wind turbines. Nevertheless, there are significant aspects of the manuscript that require clarification.
- As stated in line 68, the methodology proposed has been obtained for some specific conditions and is not generalizable to other ones. Nevertheless, a justification of why these conditions have chosen is of interest, do they correspond to the more usual or representative working conditions?
- Besides, these working conditions should be more clearly specified; some information is given in line 100, but I miss other relevant parameters dealing with wakes, like the thrust coefficient, ambient turbulence and other inflow conditions. Also, the main machine characteristics and dimensions should be also included without needing to consult bibliography.
- It is not clear what data are you using to train the additional optimization and deep learning approaches, and what data are you using for validation and checking the results. A similar comment can be made about the surrogate model of vertical deflection. A brief comment is made in line 285, but it is not clearly justified if the training and validation data sets, both belonging to the same working conditions, are really independent.
- Besides, the usefulness of the proposed models is not clear, as you have to solve SOWFA first to get the training data for this particular situation. It maybe that if in future work you are contemplating several different working conditions, the utility of the method would be more patent.
Other comments are:
- I think that the Bastankhah and Porte-Agel model was originally proposed for yawed wind turbines and its application to tilted wind turbines is not straightforward, and requires more than an improvement or modification, as seems to be suggested in the abstract and other parts of the paper.
- In line 103, “SOWFA simulations confirm similar trends to previous studies of tilted turbines...” give references of these previous studies.
- Figures 1a and 1b opposite of indicated in text.
- In figure 1 and following ones, it is difficult to see the contrast.
- It is not clear how figure 2a is obtained. Bastankhah and Porte-Agel 2016 is for yawed wind turbines.
- Figure 2b is not referred in the text.
- Regarding line 114, cross stream slices should be symmetrical, but frequently they are not because unavoidable errors. How do you deal with this asymmetry?
- In caption of figure 3, how solid lines are obtained, also from SOLFA?
- In lines 141 to 145, text not very clear.
Citation: https://doi.org/10.5194/wes-2024-172-RC1 -
RC2: 'Comment on wes-2024-172', Anonymous Referee #2, 11 Feb 2025
Review for “Introduction and comparison of novel deep learning and optimization approaches to analytical wake modeling of a tilted wind turbine“
This manuscript investigates the possibility of improving/tuning the Bastankhah 2016 wake model for yawed wind turbines by optimizing key parameters in two different ways. In addition, an alternative employing deep learning to model the wake is investigated. SOFWA simulations of a single inflow condition are used for comparison and as training data.
Overall, the manuscript is written well but there are some aspects that need clarification.
- At present, only one inflow condition is investigated. It therefore seems to be more of a proof of concept or case study since it is not clear to what degree the results are applicable to different ambient conditions, in particular since you argue in ll. 271 that the Bastankhah model could only be improved if more parameters would be included. If this is the intention, clarify.
- More details have to be given on the training data:
- Details of the turbine operational state (thrust coefficient)
- Details of the inflow: TI, shear, veer; is this an atmospheric boundary layer inflow or a uniform inflow? It the latter: why? If the former: What was the atmospheric stability?
- The data seems to be averaged. Is the average converged? Over what time period/how many steps was the average calculated?
- It is not clear how you generate the training data and what data you use to compare your results to. Is it the same data for both?
- There have been other attempts at modeling tilt, more context and motivation of why you chose the Bastankhah model should be added in the introduction.
Specific comments:
- 22: there might be more and older works on wake steering.
- 24 “Bastankhah and Porté-Agel (2016) developed an analytical wake model that is capable of sufficiently modeling the horizontal deflection in the wake” – “sufficienly” is rather unspecific.
- 29 – combinations of tilt and yaw will be even more complex
- In general, you need to specify which version of the Bastankhah model you refer to (2014 or 2016) - maybe call them Bastankhah 2014/Bastankhah 2016 wake model
- It should be specified in which direction the wake is deflected based on which direction the wind turbine is tilted to (e.g. l. 45, 102)
- 56 “holds” (not hold, because it refers to range)
- 72: which tilt angles would be expected for floating offshore wind turbines?
- 81: how is your approach different that you are able taking into account the full wake?
- Figure 1: what causes the span-wise asymmetry of the wake? How was the wake center determined?
- 113 (from “Observing…”): Rephrase the sentence, it is difficult to understand what you mean
- The blue shades are sometimes hard to distinguish
- 121: k is called “wake growth rate” in Bastankhah 2016.
- Section 2.1.1: At present, I do not see a reason for this detailed investigation - what is the aim here? To show that σ can be determined up to 12.5 degrees from mirroring the top half of the skewed Gaussian profile?
- Section 2.1.2: this subsection has 4 lines of text and one figure. Together with 2.1.1, this could be summarized to briefly illustrate the change in wake shape when crossing 15 degrees (I assume that this is the information that you want the reader to have?).
- Section 3.3: With the current progress in AI and computational power, in your opinion, how long will wake models be necessary before deep learning approaches take over?
You clearly show that if you have training data, it is more powerful to use deep learning for generating the wake field than for tuning parameters of a model. - 313 “The optimized Bastankhah wake model can be used in various wind farm optimization tools without significant changes to existing workflows.” since the optimization depends on
- turbine type
- inflow speed / turbine operation
- inflow turbulence/atmospheric stability
- wind shear and veer
this does not seem to be a trivial modification. Please comment.
Citation: https://doi.org/10.5194/wes-2024-172-RC2
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