Design procedures and experimental verification of an electro-thermal deicing system for wind turbines

Getz, David; Palacios, Jose

doi:https://doi.org/10.5194/wes-6-1291-2021

Articles | Volume 6, issue 5

https://doi.org/10.5194/wes-6-1291-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/wes-6-1291-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 6, issue 5

Research article

|

06 Oct 2021

Research article |

| 06 Oct 2021

Design procedures and experimental verification of an electro-thermal deicing system for wind turbines

David Getz and Jose Palacios

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Final revised paper (published on 06 Oct 2021)
Supplement to the final revised paper
Preprint (discussion started on 15 Jun 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of the paper Design Procedures and Experimental Verification of an Electro-Thermal De-Icing System for Wind Turbines', Anonymous Referee #1, 30 Jun 2020
- AC1: 'Reply to comments: Design Procedures and Experimental Verification of an Electro-Thermal De-Icing System for Wind Turbines', Jose Palacios, 14 Jul 2020
RC2: 'review of wes-2020-68', Anonymous Referee #2, 03 Mar 2021

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Jose Palacios on behalf of the Authors (06 Apr 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (20 May 2021) by Alessandro Croce

RR by Alberto Guardone (04 Jun 2021)

RR by Francesco Caccia (16 Jun 2021)

Suggestions for revision or reasons for rejection

The paper describes the design process of an electro-thermal de-icing system for HAWTs. The procedure is based on experiments of ice accretion and ice shedding due to centrifugal force on a rotating blade section. Once data is obtained at different rotational speeds, corresponding to different radial positions, a control sequence is proposed for de-icing a full blade in different icing conditions.

The design procedure proposed is interesting, and the topic is of sure interest to the reader of Wind Energy Science.

The English language is not fully satisfactory. Although its usage is globally correct, some typos and grammatical errors should be corrected (e.g., in ll. 19-20, 39, 45, 55, 57, 68, 122, 153, 159, 185, etc.). Providing some examples from Section I, I advise as well:
1. to check for consistency in the flow of information for easier reading (e.g.: ll. 55-65 regard wind energy in general; ll. 68-73 regard issues related with icing on wind turbines; ll. 56-58 regard wind energy in cold regions, which might be moved right before l. 68);
2. to avoid wordy repetitions (e.g., in ll. 82-87, the subject «de-icing» is repeated in every sentence);
3. to omit unnecessary information, or better contextualize it (e.g., ll. 91-96, which include issues (1) and (2) as well).

The abstract should be rewritten to be more generic and include fewer details: it is difficult to understand all the information provided before reading the whole paper.

An overview of the structure of the paper and its contents is missing. I suggest including it at the end of Section I to facilitate reading.

I have one major concern about the methodology applied.
In particular, it is not clear why the cross-sectional area of accreted ice on the scaled model should match the one of the full wind turbine, as per equations (1) and (2) (ll. 171-172). This assumption, which was not justified and cannot be taken for granted a priori, is critical within the design process since it assigns a centrifugal force that may not be linked to the full-scale model. In fact, the ice accretion rate depends on the shape and the size of the object as well [1, 2, 3].
Moreover, the experiments are carried out on a «1/2 scale model of the 80% span region of a generic 1.5 MW wind turbine blade». It is stated that «representative ice shapes were first accreted as per ice scaling laws provided by Bond et al., 2004» (ll. 156-157); it is not clear if (and which) scaling law is applied, and if this is related to the assumption above. Later, it is stated that the impact velocity only was matched during ice accretion experiments (ll. 232-234). The authors should clarify the approach chosen.
Since the design process is intended for a full-scale model, I invite the authors to discuss the legitimacy or the consequences of their assumptions, either numerically or by providing results from existing literature.

My second concern regards unclear, confusing, or contradictory information provided within the paper. In particular:
1. Linked to what already written above, confusing information is provided regarding the influence of different parameters on ice accretion. In ll. 74-75, authors should mention that the shape and size of the object affect the ice accretion rate on the object itself [1, 2, 3]. In ll. 79-81, it is implicitly stated that impact velocity does not affect the thickness, which is certainly wrong and contradicts the results of the experiments. More attention should be paid while defining the effect of the different parameters on ice accretion.
2. It is not clear if experiments for blade span r/R = 0.8 were run. Line 239 states that «80% span was not tested in the AERTS facility due to the potential rotor imbalance on the test stand at such RPM» (Table 1 still reports «3, 5 and 7» mins of accretion time for that blade span); accordingly, results for that blade span are obtained through extrapolation (please note that the order of results reported in Table 2 may be wrong). In the following Section (V.B), it seems that experiments at r/R = 0.8 will be performed; however, results in Figure 20 do not include r/R = 0.8, so it is not clear how results in Figure 23 are obtained for that blade span. Once more, in Section V.C, r/R = 0.8 is not tested and, accordingly, results are not presented. Was the case of r/R = 0.8 ever tested?

Minor concerns regard occasional scarce attention to details. Some of them are listed below.
- Data described in line 62 does not match what is shown in Figure 2.
- «currently», in line 63, refers to 2011 data. In 2020, it produced 8.42% of electricity in the US [4].
- Units of measure should be written consistently: e.g., 10_GW (line 62), g/m^3 (ll. 226-227).
- Some acronyms have never been introduced (IRT: Icing Research Tunnel; FAR: Federal Aviation Regulations).
- In Figure 11, some lines are overlapping text boxes.
- Resolution of Figure 30 should be improved.
- I suggest changing the title of Section VII to "Conclusions and Future Work".
- The author of NASA/CR—2004-212875 is Anderson only.
- The Bibliography should be ordered alphabetically.

Given the comments above, I suggest that the paper undergoes a major revision, before being reconsidered for publication on Wind Energy Science.

[1] L. Makkonen. «Models for the growth of rime, glaze, icicles and wet snow on structures». In: Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 358.1776 (2000), pp. 2913–2939.

[2] M. C. Homola et al. «The relationship between chord length and rime icing on wind turbines». In: Wind Energy 13.7 (2010), pp. 627–632.

[3] M. Etemaddar, M. O. L. Hansen, and T. Moan. «Wind turbine aerodynamic response under atmospheric icing conditions». In: Wind Energy 17.2 (2014), pp. 241–265.

[4] U.S. Department of Energy, Energy Information Administration. Electric Power Monthly with Data for March 2021. Technical Report. May 25, 2021.

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ED: Reconsider after major revisions (18 Jun 2021) by Alessandro Croce

AR by Jose Palacios on behalf of the Authors (16 Jul 2021) Author's response

ED: Publish as is (29 Jul 2021) by Alessandro Croce

ED: Publish as is (16 Aug 2021) by Jakob Mann (Chief editor)

AR by Jose Palacios on behalf of the Authors (23 Aug 2021)

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Short summary

A methodology to design electrothermal deicing protection for wind turbines is presented. The method relies on modeling and experimental testing to determine the critical ice thickness. The critical ice thickness needed is dependent on the ice tensile strength, which varies with icing conditions. The ice tensile strength must be overcome by the stress that a de-bonded ice structure exerts under centrifugal force at its root region, where it attaches to a non-de-bonded ice region.