By Andrea Hargraves 
Europe is striving to lower the costs of operating wind turbines on water.
Off the coast of Portugal, a team of underwater robots checks the base of turbines on a wind farm for signs of damage while drones check the condition of the blades from the air. This activity is part of a project to reduce inspection costs, keep wind turbines running longer and, ultimately, lower the price of electricity. Wind power accounted for more than a third of electricity generated from renewable sources in the European Union in 2020, and offshore wind power is expected to contribute increasingly in the coming years. Denmark became home to the world’s first offshore wind farm in 1991 and Europe is the world leader in this field.
However, operating wind farms in the seas and oceans is expensive and increases the global cost of this clean energy. Moreover, Asian companies in this sector are gaining ground, stimulating the need for European industry to maintain a competitive advantage.
Lower costs
“Up to 30% of all operating costs are related to inspection and maintenance,” says Joao Marques, of the research association INESC TEC in Portugal.
Many of these costs come from sending maintenance crews on boats to survey and repair offshore wind infrastructure. The European Union-funded Project ATLANTIS is exploring how robots can help in this area. The ultimate goal is to reduce the cost of wind energy.
Underwater machines, surface-to-surface vehicles, and drones are just some of the robots being tested. They use a combination of technologies – such as visual and non-visual imaging – and sonar to scan infrastructure. Infrared imaging, for example, can identify cracks in turbine blades.
Research conducted by the project indicates that robotics-based technologies can increase the working time of maintenance vessels on wind farms by about 35%.
Greater security
Expenses are not the only consideration.
“We also have some security concerns,” said Marquis, the ATLANTIS lead researcher.
Transferring people from boats to turbine platforms, diving under the waves to inspect mooring points and climbing turbine towers are dangerous tasks.
It is safe to transfer people from boats to turbine platforms only when waves are less than 1.5 meters high. Conversely, automated inspection and maintenance systems can be deployed from boats in the presence of waves up to 2 metres.
In addition, easier and safer maintenance will increase the time that wind farms can be fully operational. In winter, it is often impossible to carry out inspections and maintenance outside, and you have to wait for better weather conditions in spring or summer.
“If there’s a problem with a wind farm or a particular turbine in a month where it can’t or isn’t accessible, operations have to stop so someone can go there,” Marques said.
The ability to operate at higher waves means that reasons for wind farm closures can be addressed more quickly.
The first of its kind
The project test site is based on a real offshore wind farm in the Atlantic Ocean, 20 kilometers from the city of Viana do Castelo, in northern Portugal. It is the first of its kind in Europe.
“We need a place to test these things, a place where people can actually develop their own robots,” he explains.
In addition to its own robotic technologies, ATLANTIS intends to help research teams and other companies develop their own systems.
European researchers and companies active in this developing sector should be able to set aside time to use the facilities from the beginning of this year.
Damage prevention
Another way to reduce maintenance costs is to reduce damage and the need for repair in the first place. The recently completed EU-funded FarmConners project sought to do just that through the widespread use of a technology called wind farm control, WFC.
When the wind hits them, the turbines extract energy from the airflow. As a result, the airflow at the back of the turbine lowered the power, a phenomenon known as ghosting. Because of this uneven distribution of the power load to the blades and towers, some turbines are damaged more than others.
The WFC aims to balance the distribution of wind energy across the park, according to Tohve Gutchmen, project coordinator at the Technical University of Denmark.
There are several ways to mitigate the effects of vignetting. The first is the misalignment of the turbines. Instead of facing directly into the wind, the turbine can be turned slightly so that the shadow effect is offset by the turbines behind it.
The inclination and rotational speed of the three turbine blades can also be changed. While it reduces the amount of energy produced by the turbine, it frees up more energy for processing by the turbine again.
Grid-friendly energy
In addition to reducing erosion and maintenance costs, a WFC can make wind farms more productive and help them generate power in an easier way to tap into the power grid.
Renewable energy, including wind energy, is often produced with a series of highs and lows. Sometimes spikes or surges can overload the power grid.
With the turbines working together, power output can be leveled to provide a more uniform and stable input into the grid, according to Göçmen.
“If we collectively control the turbines, everything will be more efficient,” he said.
Research has shown that such control of wind farms could increase the energy production of all wind farms in the European Union by 1%.
That’s twice the output of a 400-megawatt wind farm, which would cost around €1.2 billion to build, according to Gregor Gebel, coordinator of FarmConners also at the Technical University of Denmark.
This technology is also easy to implement, as most wind turbines can be controlled and modified to suit WFC use. Wind farms just need to update their control software.
There is a lot of commercial interest in WFC technology, making it a promising avenue for Europe to expand its use of wind power, according to Gutchmen,
It is a “low cost, potentially high gain,” he said. The research in this article was funded by the European Union.
This article was originally published horizonEuropean Union Journal of Research and Innovation.