Project

This project aims to suppress the oscillation motion of floating offshore wind turbines and to improve the structural safety margin of the turbines. The tension leg platform has good vertical stiffness, but insufficient horizontal stiffness and are prone to yawing motion. By establishing a vibration isolation system to resist and dissipate wave impact and wind load impact. The excitation and damage caused by external loads to the wind turbine can be effectively mitigated. The response of the wind turbine is analyzed based on the wave load spectrum and the response curve of the floating platform is calculated using numerical simulation as a basis for designing the hybrid vibration isolation system. A suitable control strategy is selected to first dissipate the waves by controlling the actuators and then dissipate the energy using hybrid vibration isolation. Simulations and experimental studies are used to select the appropriate dynamic parameters for the vibration isolation system to achieve the desired response of the wind turbine. The life state analysis of key components such as tension legs is carried out. The performance degradation characteristics and laws of wind turbines under low-frequency cyclic waves are studied to ensure their safe operation.

Mussels and other marine fouling settle on the part of offshore wind turbines and production platforms that is underwater.
The fouling worsens the load from the waves and reduces the load-bearing capacity of the structure by 25-65 percent. Today, the fouling is removed manually – typically using manually controlled underwater robots – which is a time-consuming and financially burdensome process.

The idea for the solution consists of three elements. 1. cleaning rings around the supporting structures that remove fouling when the water moves. 2. a robot that can move on the supporting structures and send a message about the size of the fouling. 3. A robot that can remove fouling by high-pressure washing underwater. The effect of the solution will be an extension of the service life of the structure, and an expected reduction in costs by 30-40 percent. In the North Sea alone, the industry currently spends a three-digit million amount annually on removing marine fouling.

The purpose of the project is to mature the idea of ​​a novel approach for establishing reliable digital twins of offshore wind turbines, which can be employed for improved operation and maintenance of these systems. Upon successful completion of this, the intention is to apply for an Innovation Fund project or EUDP project. The aim is to develop digital twins based on closed-loop model updating and incorporate them in a systematic procedure for structural health monitoring of wind turbines, and (2) aim To develop data-driven control strategies for vibration damping.

The goal of the project is to significantly strengthen the scientific basis for the wind power industry in general and specifically the Danish wind power industry’s position in offshore applications.

To meet the goal the proposed research must have a significant potential for reduction of cost of energy from large offshore wind farms, and for contributing to reduction of the economic risks arising from inadequately founded design.

The key design driver for most offshore structures is safety. For offshore wind turbines/farms, however, the main design driver is economy and therefore there is a strong requirement for enhancing design tools and avoiding conservatism. Consequently, focus is on the following issues:

1. Mutual shadow effect between large blocks of wind turbines – ignorance of the effect may have disastrous consequences for the economy.
2. Extreme structural loading of offshore wind turbines – detailed understanding and description of extreme winds and gusts and resulting loads is crucial for the safety and economics of the wind turbines.
3. Interaction of large wind farms with waves and current – understanding and modeling may lead to reduced design loads on wind turbine units placed in the downwind end of the wind farms.
4. Grid connection and reliability – An unreliable grid caused by high wind energy penetration is an obvious barrier for the dissemination of the technology.
5. Optimized operation and maintenance for offshore wind farms – presently more than a third of the cost of energy from offshore wind farms relates to O&M and the potential for reductions is therefore large.

The project is sponsored by The strategic Research council and have participant from Risø National Laboratory, Elsam Engineering, Insitut for Mekanik, Energi og Konstruktion DTU, DHI, Svend Ole Hansen and Institute of Energy Technology AAU.

The institute of Energy Technology is especially involved in issue 4 in this project, by Birgitte Bak-Jensen, and also a Ph.D project is set up together with Risø and Elsam Engineering, with the title: Offshore Wind Power – Grid Connection and Reliability, see this project.