Rapid Estimate of Wind Turbine Energy Loss Due to Blade Leading Edge Delamination Using Artificial Neural Networks

Estimating reliably and rapidly the losses of wind turbine annual energy production due to blade surface damage is essential for optimizing maintenance planning and, in the case of leading edge erosion, assessing the need for protective coatings. These requirements prompted the development of the prototype system presented herein, using machine learning, wind turbine engineering codes, and computational fluid dynamics to estimate annual energy production losses due to blade leading edge delamination. The power curve of a turbine with nominal and damaged blade surfaces is determined, respectively, with the open-source FAST and AeroDyn codes of the National Renewable Energy Laboratory, both using the blade element momentum theory for turbine aerodynamics. The loss prediction system is designed to map a given three-dimensional geometry of a damaged blade onto a damaged airfoil database, which, in this study, features 6000+ airfoil geometries, each analyzed with Navier–Stokes computational fluid dynamics over the working range of angles of attack. To avoid lengthy aerodynamic analyses to assess losses due to damages monitored during turbine operation, the airfoil force data of a damaged turbine required by AeroDyn are rapidly obtained using a machine learning method trained using the pre-existing airfoil database. Presented results demonstrate that realistic estimates of the annual energy production loss of a utility-scale offshore turbine due to leading edge delamination are obtained in just a few seconds using a standard desktop computer. This highlights viability and industrial impact of this new technology for managing wind farm energy losses due to blade erosion.

Late stage of the Gibraltar arc subduction system (western Mediterranean): from slab-tearing to continental-edge delamination

<p>The Gibraltar arc subduction system is the result of the fast westward roll-back of the Alboran slab at the westernmost end of the Mediterranean Sea. This westward motion is controlled, at its northern edge, by slab tearing along a so called STEP (Subduction-Transform-Edge-Propagator) fault under the Betics orogen. The Alboran subduction process is in its last evolutionary stage, where the oceanic lithosphere has been fully consumed and the continental lithosphere attached to it collides with the overriding plate. In this situation the continued slow convergence between Iberia and Africa could lead to a short stage of continental subduction. However, the particular setup after slab tearing, characterized by a sharp lateral contrast between the orogenic Betic lithosphere and the adjacent thinned lithosphere of the overriding Alboran domain, is also prone to trigger continental delamination, i.e. the detachment between the crust and the lithospheric mantle. Several lines of evidence indicate that northwards mantle delamination is likely occurring in the central Betics. The fast average topographic uplift during the last 8 Ma together with the lack of spatial correspondence between the highest topography (Sierra Nevada Mountains) and the thickest crust indicate that the topography could be partly supported by asthenospheric upwelling due to continental delamination. In this study we take advantage of an unprecedented resolution seismic receiver functions lithospheric mapping in the Betic orogen to investigate the conditions for, and consequences of, edge delamination in the Iberian margin after slab tearing. We show that given a weak enough Iberian lower crust the delaminated lithospheric mantle peels off the crust and adopts a geometry consistent with the imaged southward dipping Iberian lithosphere in the central Betics. In contrast, the thinned lower crust beneath the Iberian margin in the eastern Betics prevented mantle delamination via asthenospheric inflow into the lower crust.</p>