Autonomous drone inspections for detecting structural internal defects in offshore wind turbines

On 22 March, the final of the Offshore Wind Innovators Award 2021 is taking place. Windpowernl spoke to the three nominees prior to the finals. The first one is SpectX, a Delft-based Startup that is developing an autonomous inspection and asset management solution for application in offshore wind farms.

With wind farms being built and planned further offshore, it brings along additional costs. This is also the case for the inspection and maintenance activities taking place once a wind farm becomes operational. Developing solutions that can be performed remotely will help bring down costs. SpectX, founded last year, is working on such a solution.

Akhilesh Goveas, one of the three co-founders of SpectX, explains: “Current initiatives are mainly focused on detecting external damage on wind turbines. However, as is the case with rotor blades, it is often an internal break which occurs.” It is therefore vital to identify this on time, to prevent total shut down of a wind turbine. Beside the loss of power generation and therefore income, it also requires a lot of time to organise a repair campaign. It often requires workers to perform repair activities by rope access, which is not totally without risk, is time-consuming, and restricted by weather windows.

Structural internal defects

SpectX is building an aerial radiography system capable of detecting internal structural defects in real-time through Artificial Intelligence (AI). Goveas: “We have tested several different equipment and, in the end, we found a battery backed X-ray system that can be used non-traditionally. It doesn’t need a bulky system anymore so we tried to base the solution on drones. It now needs to be automated.”

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Inspection is performed by two drones that are stored in a docking station on site. There are several options being investigated for placing the docking station, for example on a wind turbine platform or a future docking station for robots in the wind farm. The drones can be activated and operated remotely, from the control room onshore, therefore no physical presence is required on site.
The two drones with onboard LiDAR system asset mapping work in sync: one functions as a sender and the other as the receiver of the X-ray spectrum. High accuracy is achieved in aerial positioning using the D-GPS position triangulation principle.

Predicting maintenance & repair campaigns in advance

The solution can be used for scanning the entire wind turbine from the splash zone up, with the exception of the nacelle, Goveas says. The data is collected and sent to the control centre after returning to the docking station. The data is stored on the cloud for analyses of the data by deep learning and is made visual for the end user. The data allows for repair campaigns to be predicted and planned in advance, saving expensive OPEX expenditures on unplanned repair campaigns.

SpectX is working on developing drones that have a reach of approximately 10 km radius and have a battery life of around 30 minutes. A full inspection of a wind turbine can take up to 1 or 1.5 hour (based on a 3.5 MW wind turbine). To compare: rope access inspection can easily take several hours (up to 7), requiring several technicians. The drones are expected to be able to operate in weather conditions with wind speeds of up to 10-12 metres per second.

Development and pilot testing

The system is still in the Research & Development stage. While the SpectX-team is working on the software, they have partnered with another company to develop the hardware part of the innovation. Tailor-made drones need to be built to actively suppress vibrations during operations. Existing drones are merely designed for visual inspection. Goveas explains: “This technique had not been tested on composite material wind turbine structure for critical internal defect detection before. Up to now, we have performed feasibility tests on a used wind turbine blade to prove the technology for this specific use case.”

The goal is to perform a test on an onshore wind turbine in summer time next year. The company is currently in talks with a party in Eemshaven. At the moment, the Startup is busy gathering the remaining of the required nearly 1 M Euro to complete the system and start the pilot.

Listen to SpectX and the other three nominees during the final of the Offshore Wind Innovators Award 2021. Register here.

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