Europe aims to reduce the operating costs of offshore wind turbines.
Off the coast of Portugal, a team of underwater robots inspects the base of a wind farm’s turbines for signs of damage, while aerial drones check the condition of the blades. This activity is part of a project to reduce inspection costs, keep wind turbines running longer and ultimately lower the price of electricity. Wind energy accounted for more than a third of electricity generated from renewable sources in the EU in 2020 and offshore wind energy is expected to make an increasing contribution in the coming years. Denmark became home to the world’s first offshore wind farm in 1991 and Europe is a world leader in this field.
Yet operating wind farms in seas and oceans is expensive and increases the global cost of this clean energy. In addition, Asian companies are gaining ground in the sector, prompting European industry to maintain a competitive edge.
“Up to 30% of all operating costs are related to inspection and maintenance,” says João Marques, from the research association of INESC TEC in Portugal.
Much of this cost comes from sending maintenance crews on boats to survey and repair offshore wind energy infrastructure. The EU-funded ATLANTIS project is exploring how robots can help with this. The ultimate goal is to reduce the cost of wind energy.
Underwater machines, vehicles that move over the water surface and drones are just some of the robots tested. They use a combination of technologies – such as visual and non-visual imaging – and sonar to inspect the infrastructure. For example, infrared imaging can identify cracks in turbine blades.
Research conducted by the project suggests that robotics-based technologies could extend the time maintenance vessels can operate on wind farms by approximately 35%.
Cost is not the only consideration.
“We also have some security issues,” said Marques, senior researcher on the ATLANTIS project.
Transferring people from boats to turbine platforms, diving under waves to inspect docking points, and climbing turbine towers are dangerous tasks.
It is not safe to move people from boats to turbine platforms until the waves are less than 1.5 meters high. On the contrary, robotic inspection and maintenance systems can be deployed from boats in waves up to 2 meters high.
In addition, simpler and safer maintenance will extend the time that wind farms can be fully operational. In winter it is often impossible to carry out offshore inspections and maintenance and you have to wait for better weather conditions in spring or summer.
“In a month if there is a problem in a wind farm or in a particular turbine where it is not accessible or not accessible, operations should be halted until someone can get to it,” Marques said.
By being able to work in higher waves, the causes of wind farm failures can be tackled more quickly.
The first of its kind
The project’s 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 robotics,” he explains.
In addition to its own robot technologies, ATLANTIS wants to help other research teams and companies to develop their own systems.
European researchers and companies active in this cutting-edge sector should be able to make time to use the facilities from the beginning of this year.
Another way to reduce maintenance costs is to reduce damage and the need for repairs 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 hit by the wind, the turbines extract energy from the airflow. As a result, the airflow at the back of the turbine has less energy, a phenomenon called shading. Due to this uneven distribution of the energy load on the blades and towers, some turbines sustain more damage than others.
The WFC aims for a balanced distribution of wind energy across the park, said Tuhfe Göçmen, project coordinator at the Technical University of Denmark.
There are several ways to reduce the effects of shadowing. One is the misalignment of the turbines. Instead of facing directly into the wind, a turbine can be rotated slightly so that the shadow effect is offset by the turbines behind it.
The pitch and rotational speed of the three turbine blades can also be changed. While reducing the amount of energy the turbine produces, it frees up more energy for processing by the turbines downstream.
In addition to reducing wear and tear and maintenance costs, WFC can make wind farms more productive and help them generate power in a way that is easier to connect to the grid.
Renewable energy, including wind energy, is often produced with a series of highs (peaks) and lows. Sometimes peaks or spikes can overload the power grid.
By making the turbines work together, the power output can be leveled to provide a more consistent and stable input into the power grid, Göçmen said.
“If we jointly control the turbines, everything is more efficient,” he said.
Research has shown that such control of wind farms could increase the energy production of all wind farms in the EU by 1%.
That’s twice as much as a 400-megawatt wind farm, which Gregor Giebel, coordinator of FarmConners at the Technical University of Denmark, said would cost around €1.2 billion to build.
This technology is also easy to implement as most wind turbines can be controlled and adapted to WFC use. Wind farms only need to update their operating software.
There is a lot of commercial interest in the WFC technology, making it a promising way for Europe to expand the use of wind energy, says Göçmen,
It’s a “low cost and high profit potential,” he said. The research in this article was funded by the EU.
This article was originally published in Horizon, the EU Journal of Research and Innovation.