The Esbjerg Declaration demands answers: “We have no idea how to get the energy from energy islands ashore”

30. maj 2022 kl. 11:05
The Esbjerg Declaration demands answers: “We have no idea how to get the energy from energy islands ashore”
Without proper management of the North Sea’s future energy system, outages or imbalances in the electrical grid could lead to large parts of this map going dark. Illustration: North Sea Wind Power Hub.
The Esbjerg Declaration has made the question of how to manage energy systems with offshore wind power, energy islands, and a stable electrical grid relevant again.
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From the middle of this century, we can look forward to having up to 10,000 offshore wind turbines in operation. On Wednesday, European leaders with Prime Minister Mette Frederiksen as host signed a letter of intent to build 150 GW of offshore wind capacity in the North Sea by 2050.

But before the European energy markets can benefit from those enormous amounts of wind energy, new technologies are required.

The Esbjerg Declaration includes a plan for an offshore energy system consisting of many energy islands and wind farms. However, we as a society face several challenges: we do not yet know how such an energy system should work in practice.

We must therefore put efforts into research and development of energy systems that will manage the many gigawatts of energy produced in the North Sea—two of Denmark’s leading energy researchers say regarding the declaration signed on Wednesday.

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“The energy islands present some big, new challenges for our electricity systems, which we don’t know how to solve today. Therefore, it requires a lot of research and development from both universities and manufacturers and developers of technology solutions, as well as those who operate the electrical grid. It takes time,” as Filipe Miguel Faria da Silva, associate professor at AAU Energy, puts it.

“It has taken over 100 years to develop the current electricity system. Now we have to develop a new electrical grid in just a few decades, so this is a big task,” he says.

A system that requires management

The big task is to develop a system that can accommodate the conversion between direct and alternating current, which will be necessary to transport the many GW of wind power from the offshore wind farms via energy islands and finally ashore. Probably to several countries.

As a starting point, the wind turbines will supply power to local AC grids on the energy islands through a power electronic converter. On the energy island, the alternating current is converted to direct current and is brought ashore via high voltage cables (HVDC). If there are several destinations, we get what is called “multiterminal HVDC”.

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Jacob Østergaard, professor and head of center at DTU Electrical Engineering, explains how the whole challenge lies in the fact that it is an energy system based on power electronic converters. It requires a significantly higher degree of management than the synchronous generator based system we are familiar with today, i.e. an energy system with large thermal power stations.

The latter has an inherent inertia in the generators, which can be used to maintain the frequency in case of outages or other imbalances between consumption and production. In a purely converter-based energy system, there is no inertia, so immediate response is required if a wind turbine stops operating.

Otherwise, we risk major power outages across Europe.

That point was clearly outlined in an important white paper co-authored by Jacob Østergaard and Filipe Miguel Faria da Silva. This white paper from September last year is titled ”The Energy Islands: A Mars Mission for the Energy system”, and Ingeniøren has previously discussed it thoroughly. The new declaration makes the arguments in the publication relevant again.

Professor Jacob Østergaard uses a clever analogy to describe the challenges we face with the multiterminal HVDC systems.

“Our current energy system can be compared to an old-fashioned propeller aircraft. If the engine fails, we can still steer and manoeuvre the aircraft and land safely. The energy islands and offshore electrical grids of the future are based on converter technology that must be constantly managed. It’s similar to a modern fighter jet. If the control systems fail, the plane immediately falls to the ground like a rock,” the DTU professor illustrates.

We have to avoid recreating the horse-drawn carriage

Jacob Østergaard explains how many of the essential pieces are in place to create the necessary energy system. But the pieces must be put together in the right way if we are not to trip ourselves up.

“It won’t do to just take all the pieces that we are familiar with from our current electrical system and put them together into something that’s not smart and well thought out from the start. We know that it’s crucial to think in terms of system solutions and holistic perspectives to make sure the energy islands and a new offshore electrical grid are robust and cost-effective,” he says and emphasizes that unknown lock-in effects may occur.

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“It can be seen as analogous to the development of the first cars. Back then, the starting point was the horse-drawn carriage. Therefore, the first cars had large wheels, and the driver sat up front on a box seat before we found out that wasn’t a good idea,” Jacob Østergaard exemplifies and continues:

“By building our knowledge into the energy islands and the upcoming North Sea expansion from the start, we can avoid ‘recreating the horse-drawn carriage’ and build a ‘modern car’ that is optimized for the purpose.”

A question of the right timeframe

As Ingeniøren already outlined before the Esbjerg Declaration was signed, the challenge of establishing the right multiterminal HVDC system is one of the key barriers to overcome on the road to 150 GW of offshore wind in the North Sea.

According to Jacob Østergaard, we still need to, for example, find the methods for managing the converter-based energy system, while we have to widen our knowledge of to a-to-b connections with high voltage cables, as we are familiar with from, for example, the Denmark-Norway submarine cable, to also include points c, d, and e.

Therefore, it seems quite obvious to ask:

Is it realistic to reach the goal of a comprehensive system by 2050?

“It’s something we’re working on already. So even though there are major research challenges ahead of us if we are to do it in a smart and cost-effective way, it is realistic,” says Jacob Østergaard, who is backed by his colleague from AAU.

“It’s precisely the timeframe that is absolutely crucial here. I believe that if we start now, it will be possible to have the right solutions by 2050. But we can’t wait with research and development until 2040,” Filipe Miguel Faria da Silva says.

Looking towards Bornholm

With the planned energy island on Bornholm, we have a completely unique opportunity to test, research, and develop in a manageable setup, Jacob Østergaard says.

“The world’s first energy island on Bornholm can obviously serve as a test site for future energy solutions, as we can learn important lessons there in conditions that are significantly less harsh than far out in the North Sea,” he says and elaborates:

“It’s crucial to be able to test the solutions if the industry is to have the necessary confidence that new solutions that can be simulated on computers at DTU and other universities will also work in reality.”

Looking further outside Denmark

Indonesia is another place where researchers will hopefully be able to draw on concrete experience with energy systems, reminiscent of what we will see in the North Sea.

Or the experience may rather be gained at Aalborg University, where Filipe Miguel Faria da Silva leads a project with the aim of developing a concept for managing multiterminal HVDC between the islands of the Indonesian Archipelago.

“We currently have no results ready for publication from the project in Indonesia, but we expect that there will be useful knowledge to draw on in relation to the forthcoming work with energy islands.”

As Ingeniøren’s sister media site GridTech previously mentioned, several parallels can be drawn between Indonesia and the 2050 North Sea.

Today, Indonesia’s main island of Java is mainly supplied with energy from coal power. If energy consumption is to be converted to renewable energy, power from other islands is needed. Power that is carried ashore on the islands via submarine HVDC cables to the local AC grids and then on to Java. And with a network of islands that produce renewable energy—”energy islands”—we again have multiterminal HVDC.

Thus, relevant knowledge can be acquired in Indonesia.

With the Esbjerg Declaration’s aim of thousands of offshore turbines connected to several energy islands, it will be necessary to draw on all available experience to achieve the goal by 2050. Because as Filipe Miguel Faria da Silva says:

“A single energy island in itself is a challenge. Now we want to multiply that challenge.”

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