New preprint on large-eddy simulation of airborne wind energy farms

New preprint on Large-eddy simulation of airborne wind energy farms available in open access in Wind Energy Science (WES), the house journal of the European Academy of Wind Energy (EAWE). The interactive peer review is open and we invite interested readers from the scientific community to provide comments. Got to “Discussion” and “Post a Comment” to help the authors improving the quality of the manuscript.

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This article, like the previous one I posted, contains a good number of theoretical predictions supported by a significant number of equations, and also some interesting perspectives, all of this being of an impressive scientific level. And yet, no comments. So let’s try.

  1. Access review
    The associate editor is asked to evaluate whether the manuscript is within the scope of the journal and whether it meets a basic scientific quality. They can suggest technical corrections (typing errors, clarification of figures, etc.) before posting in WESD. Further requests for revision of the scientific contents are not permitted at this stage of the review process but shall be expressed in the interactive discussion.

Peer review is only on the form.

About the paper:

Abstract. The future utility-scale deployment of airborne wind energy technologies requires the development of large-scale multi-megawatt systems.

It is therefore assumed that a solution is proposed. So let’s take a look.

Abstract. In this study, we consider ground-based power generation pumping-mode AWE systems (lift-mode AWES) and on-board power generation AWE systems (drag-mode AWES).

As usual.

Abstract. For the lift-mode AWES, we additionally investigate different reel-out strategies to reduce the interaction between the tethered wing and its own wake. […] Wake-induced performance losses increase gradually through the downstream rows of systems and reach in the last row of the parks up to 17 % for the lift-mode AWE park and up to 25 % and 45 % for the moderate and dense drag-mode AWE parks, respectively. For an operation period of 60 minutes at a below-rated reference wind speed of 10 m s−1, the lift-mode AWE park generates about 84.4 MW of power, corresponding to 82.5 % of the power yield expected when AWE systems operate ideally and interaction with the ABL is negligible. For the drag-mode AWE parks, the moderate and dense layouts generate about 86.0 MW and 72.9 MW of power, respectively, corresponding to 89.2 % and 75.6 % of the ideal power yield.

These very interesting perspectives are well explained within the paper, above all page 17 with figure 3, page 19 mentioning “the targeted wingspan of 60m” , page 20 mentioning “[…] that for lift-mode AWE systems, the wing mass is reduced by 25% in order to account for the absence of on-board turbines”, and page 23 with figure 7 and mentioning that the “drag-mode AWE system operates at a constant tether length l ≈ 650 m and follows an near-circular flight path of diameter D ≈ 200 m at a mean elevation of about 17 degrees”, all that in order to allow understanding the basis; then until the end to understand the different effects according to the two AWES types (lift and drag) and their respective farms.

My feeling is that, a time more, the efficiency by wing area, the wing being taken alone, then reconsidered within a farm, is maximized, but without consider the price to pay: a 6-7 ton wing flying at 60 m/s with a mean elevation of 17 degrees leads to a low altitude of the tether-wing set preventing any secondary use, preventing ships from passing under, so leading to a very low power-to-space-use ratio, increasing the risk of crashes.

Perhaps it would be desirable to have other premises than the usual AWE drag and lift systems, even if one of them might work. Unless of course to consider the AWE research as a field which must remain purely theoretical.