Europe is trying to reduce the cost of running wind turbines on the water.
Off the coast of Portugal, a team of underwater robots inspects the base of a wind farm’s turbines 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 energy accounted for more than a third of the electricity generated from renewable sources in the EU in 2020, and offshore wind energy is expected to contribute more and more 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.
However, operating wind farms in seas and oceans is expensive and increases the global cost of this clean energy. In addition, Asian companies in the industry are gaining ground, fueling the need for 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 INESC TEC in Portugal.
Many of these costs come from sending maintenance crews on vessels to survey and repair offshore wind infrastructure. The EU-funded ATLANTIS project is exploring how robots can help on this front. The ultimate goal is to reduce the cost of wind energy.
Underwater machines, vehicles that move on the surface of water and drones are just some of the robots being tested. They use a combination of technologies – such as optical and non-optical imaging – and sonar to inspect infrastructure. Infrared imaging, for example, can identify cracks in turbine blades.
Research conducted by the project suggests that robotics-based technologies could increase the time that maintenance vessels can work on wind farms by around 35%.
Expenses are not the only consideration.
“We also have some safety concerns,” said Marques, a senior researcher on the ATLANTIS project.
Carrying people from boats to turbine platforms, diving beneath the waves to inspect mooring points and climbing turbine towers are dangerous jobs.
It is only safe to transfer people from boats to turbine platforms when waves are less than 1.5 meters high. In contrast, robotic inspection and maintenance systems can be deployed from vessels in the presence of waves of up to 2 meters.
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 offshore inspections and maintenance and you have to wait for better weather in spring or summer.
“If there’s a problem at a wind farm or a particular turbine in a month where it’s not possible or not accessible, operations have to stop until someone gets there,” Marques said.
The ability to work at higher waves means that the causes of wind farm outages can be dealt with 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 robotic technologies, ATLANTIS intends to help other research groups and companies develop their own systems.
European researchers and companies active in this cutting-edge field should be able to take 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 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 air flow. As a result, the airflow at the back of the turbine has reduced energy, a phenomenon known as shading. Because of this uneven distribution of energy load on the blades and towers, some turbines are more damaged than others.
The WFC aims to balance the distribution of wind power across the park, according to Tuhfe Göçmen, project coordinator at the Technical University of Denmark.
There are several ways to mitigate the effects of shading. One is misalignment of the turbines. Instead of facing directly into the wind, a turbine can be rotated slightly so that the shadow effect is compensated by the turbines behind it.
The pitch and rotation speed of the three turbine blades can also be changed. While it reduces the amount of energy the turbine produces, it frees up more energy for processing by the turbines further back.
In addition to reducing wear and tear and maintenance costs, WFC can make wind farms more productive and help them generate energy in a way that is easier to tap into the grid.
Renewable energy, including wind power, is often produced with a series of highs (peaks) and lows. Sometimes spikes or surges can overload the power grid.
With the turbines working together, the power output can be leveled to provide a more consistent and stable input to the grid, according to Göçmen.
“If we collectively control the turbines, everything is more efficient,” he said.
Research has shown that this control of wind farms could increase the energy production of all wind farms in the EU by 1%.
That’s twice the output of a 400-megawatt wind farm, which would cost about 1.2 billion euros to build, according to Gregor Giebel, coordinator of FarmConners also at the Technical University of Denmark.
This technology is also simple to implement as most wind turbines can be controlled and adjusted to suit WFC use. Wind farms only need to update their control software.
There is a lot of commercial interest in WFC technology, making it a promising way for Europe to expand the use of wind energy, according to Göçmen,
It’s “low cost and potentially high profit,” 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.