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From radical idea to reality: Leave it to the Danes

Denmark breaks its own green energy record for the second year in a row and keeps innovating with plans for artificial energy islands and ReliaBlades

By Jenn Schlegel

Last year, Denmark sourced more than half of its electricity from renewable energy. Onshore and offshore wind turbines produced just over 46%, and about 4% of Denmark’s renewable energy was solar. 2020 is the second year in a row that this tiny Nordic country exceeded 50% renewal energy usage.

Now, there are a lot of reasons for this green success. First of all, Denmark is a rather windy place so wind energy is going to work. Secondly, they have 8750 kilometers of coastline and ample place to put wind turbines out on offshore wind farms in the North and Baltic Seas. (This way the tiny nation will not be covered in onshore turbines.) And thirdly, the country has a very sustainable mindset and has been committed to wind energy for decades.

True green energy innovators, the Danes built the world’s first offshore wind farm in 1991. Today, the country is continually improving wind turbine and offshore technology, including the development of two artificial energy islands in the North and Baltic Seas.

An artificial energy island by 2030 With Europe moving towards renewable energy reliance, increasing offshore wind energy capacity and efficiency has become paramount. As wind energy leaders, the Danish are again at the forefront of technology with their planned energy islands. Acting as energy hubs, these energy islands will be able to pool power from multiple offshore farms and feed the energy directly to several neighboring countries. This shifts the concept of offshore wind farms from unilateral supply to multilateral supply, which is a good thing. At maximum capacity, the islands should be able to power over 10 million homes in several countries and create green hydrogen from sea water to power future shipping, aviation, and industry energy requirements.

Measuring 120,000 square meters in size (that is bigger than 18 standard football fields by the way), the main artificial island, located about 80 kilometers off of Denmark’s west coast in the North Sea, will be the largest construction project in Danish history. A second, smaller island has already being planned off Bornholm in the Baltic Sea, to the east of mainland Denmark. This hub will supply energy to Germany, Belgium and the Netherlands. Both islands will give an enormous boost to the European offshore wind capacity and green energy as a whole.

"This is gigantic," states Prof. Jacob Ostergaard of the Technical University of Denmark. "It's the next big step for the Danish wind turbine industry. We were leading on land, then we took the step offshore and now we are taking the step with energy islands, so it'll keep the Danish industry in a pioneering position."

Improving offshore turbine maintenance and longevity Energy islands aside, there is a lot more going on behind the scenes in Denmark to keep the Danish wind energy industry on the cutting edge. Another professor at the Technical University of Denmark, Kim Branner, is busy with something really innovative called ReliaBlade.

Offshore turbines are, well, offshore. The good news is that they are not readily visible, not easily heard and can be optimally positioned for the wind. The bad news is that, when something goes wrong, they are hard to get to. Kim Branner and his team recognized a need for a better way to monitor offshore turbines for maintenance purposes. And this is where the ReliaBlade project, a Danish-German joint research project, steps into the picture.

“The ReliaBlade utilizes a comprehensive digital twin to monitor turbines and make wind turbine blades more reliable. That's why it's called ReliaBlade,” says Kim Branner, a senior researcher and head of section at the DTU Wind Energy department. “The focus is to make wind turbine blades more reliable by using a digital twin. That was one of the ideas behind establishing this project.”

Smart turbine maintenance ReliaBlade wants to ensure that turbine blades last longer without human interaction or other unforeseen problems. By using a digital twin and sensor technologies when building the blades, DTU Wind Energy can develop condition-monitoring systems to observe the blade structure. The system can alert wind turbine owners of potential problems or damage developing in the blade. This allows the wind turbine owner to either change how they operate the turbine or make a repair decision before the issue becomes too critical. For offshore wind farms, this means scheduling the repair when it is easier – say on a summer day – rather than an emergency intervention during a winter storm.

“With the monitoring systems that can come with a digital twin, you have an opportunity to intervene before it becomes a problem and therefore make these structures more reliable,” says Branner.

“We chose Siemens Digital Industries Software as a partner because they have experience working with digital twin technology in other industries and possess a wide branch of software that can support this development,” says Branner. “And it's not used so much in the wind energy industry. Some companies have worked with a digital twin for the bearings and gears in the drive train of the turbine, but not for blades. That's unique and of course, an interesting area for us as we work with blades and test blades.

“But it’s also a very challenging area because those are some of the most highly loaded structures. It’s also a challenge because the goal is it should last 20, 30 years, running on a turbine every day in all kinds of weather. It’s a hostile environment out at sea. So it's really challenging to build the systems that are robust and can work in practice.”

DTU Wind Energy performed physical testing in Simcenter Testlab software, 1D simulation in Simcenter Amesim software and virtual channels in Simcenter Testlab Neo software. Read the full technical case study here

Ready for the next green energy revolution As the Danes start to work on constructing their innovative energy islands out in the North and Baltic Seas, the team behind the ReliaBlade project is taking smart maintenance a step further and showing how advanced digital twin architecture and cutting-edge technology like embedded machine learning methods, automated model updating and vibration-based structural health monitoring can keep the future offshore farms running optimally for decades to come.

Further reading

Some extra reading about wind energy solutions.

Harnessing the power of the wind with Simcenter solutions

Not in my backyard! How annoying is wind turbine noise?

Strategic simulation and testing help Moventas slash wind turbine gearbox weight

Denmark has committed to an ambitious 70% reduction in 1990 greenhouse gas emissions by 2030, and hopes to become CO₂ neutral by 2050