Predictive tools for preventive maintenance of wind energy

25 August 2021

As of April 2021, the MAREWIND consortium has started working on WP3 predictive modelling for preventive maintenance of wind energy. This part of the work plan focuses on the development of technologies for monitoring the structural health status of wind offshore facilities. It also develops mathematical models aimed to representing different key aspects related to the durability and maintenance of offshore structures and materials. During the first months, the involved partners led by IDENER have set the bases for the future work.

Monitoring technologies

INEGI will develop a blade monitoring technology that uses cameras mounted onto drones to acquire images (visible and infrared) of the rotating blades. The images will be then digitally analysed for the detection of sub-surface voids, delamination and displacements. INEGI has already designed a lab-scale setup and selected equipment to be used. It also features cameras, synchronization controllers, drone and a representative rotating blade. INEGI will use this lab setup during the upcoming months to test and analyse different configurations of the cameras. That also includes “floating” cameras that will simulate the operation of a camera mounted in a drone.

MAREWIND consortium will be also developing monitoring technologies based on fibre optic sensors. The sensors will be embedded into representative concrete and blade components to build a remote real-time sensing system, able to early detect diseases or damages.

Firstly, CETMA will focus on the installation of sensors into concrete-based components, while INEGI will focus on blade composite elements. CETMA already started the preliminary design of the sensor system, paying special attention to the characteristics and size of the prototypes that will be sensorized in the project.

Likewise, INEGI started the design of the sensor system by defining the sensor placement and equipment for each parameter of assessment. During the following months, CETMA and INEGI will perform the first lab-scale trials of the designed systems.

Water simulations around gravity-based structures

Furthermore, INEGI has started working on the simulations of the water column around the gravity-based structure (GBS) by using computational fluid dynamics. The simulations involved numerical modelling of the flow at the bottom of the sea influenced by waves and currents.

The modelling procedure for such a complex and vast fluid domain was divided in two parts to reduce considerably the computational cost of a complete Computational fluid dynamics 3D model with complex geometries.

  1. The first model was developed in 2D. The main goal was to obtain velocity profiles each time step that captured the effects of surface waves at the bottom of the domain. The effects of currents would be considered directly in the second part of the model.
  2. The 2D model would produce velocity profiles in each time step for the 15-sea state and 3 depths in a total of 15 representative cases. They could be applied to an inlet boundary condition of a 3D model that would include the GBS. This approach reduced the computational cost as the 3D domain could have a limited dimension and could be considered totally submerged, without the need for the high-demanding VOF (Volume of Fluid) multiphase model. In the Figure 1 it is shown the 3D in its final configurations with the main boundary conditions.
Figure 1. Domain and boundary conditions for the second part of the model.

The experts obtained results from the hydrodynamics analysis that was performed using CFD. The collected outputs were pressure maps for each selected case in the transient form. In order to illustrate the results, a static pressure contour for sea state 50 m of depth and current of 1 m/s is displayed is displayed in Figure 2.

Figure 2. Example of results of the computational fluid dynamics model.

Structural Analyses on Composite Blades

RINA will develop a finite element computational model of the reinforced fibre composite developed in the MAREWIND project. The overall model will interconnect three successive sub-models at different scales of the composite and will allow the simulation of the mechanical behaviour of the composite blades.

In the first step of the task, RINA has started the setup of a mathematical model. The model should be of a suitable representative volume element (RVE) of an elementary composite specimen, considering the constituent materials (matrix and fibres) and their combination (Figure 3).

Figure 3. Selection of matrix and fibre materials of the representative volume element

In the upcoming months, RINA will implement this numerical model with the project data. Thus,  allowing the calculation of the properties of an equivalent homogeneous material using the known properties of its base materials.

Modelling of corrosion in atmosphere-exposed metallic structures

During the first months, IDENER started the construction of a corrosion mathematical model by defining a first simple scenario with a single anticorrosion coating layer (sacrificial layer). The approach selected for the model will focus on the description of the dynamics of the interface between the coating and electrolyte, which will be under the effects of corrosion. Once the computational implementation of this first approximation is finished, the complexity of the model will be gradually increased by including the other layers of the anticorrosion protection, such as the self-healing layer.