It’s not the first project to propose far-offshore wind turbines. Hornsea One, located 89km off the Yorkshire Coast, has 100 of its 174 turbines spinning and will be the largest in the world once it is fully operational in 2022 — supplying electricity to well over a million households in the UK. The Danish developer Ørsted has already constructed five wind farms along the eastern coast of the UK with a total capacity of 1.8 gigawatts (GW), situated between seven to 27km out at sea.
But the North Sea Wind Power Hub, a new proposal published in July by TenneT, the Port of Rotterdam, Energinet and Gasunie, aims to build a series of wind farms with up to 15GW of capacity, enough to supply more than 12 million homes in the UK.
“Current policies, market design and regulatory framework should be urgently reconsidered to enable the successful development of multiple Hub-and-Spoke projects toward 2050,” the consortium’s report stated. The first hubs could be electrically connected to the shore in the 2030s and accelerate the development of wind power in the North Sea to help deliver the goals of the Paris climate agreement.
Aside from the need to hit carbon targets, wind farms way out at sea may solve other problems as well: Wind farms built close to shore can interfere with shipping lanes and fishing grounds, and can be affected by strong tides or unsuitable seabed. The visual impact is also of concern to some people, including Donald Trump who opposed the construction of a wind farm near his golf course in Aberdeen.
But if there is such a huge potential to build a mega power hub in “windier” sites that would benefit five European countries at once, why are we not already building wind farms further offshore? The general rule of thumb is: The further offshore, the steadier and stronger the winds. Moving from the current sites where UK wind farms are to the middle of Dogger Bank could see a ten percent increase in capacity factors, according to Iain Staffell, a lecturer in sustainable energy at Imperial College London. The UK hasn’t really needed to consider this as many reasonably good sites are close to shore, he said.
“We’re only just starting to run out of space closely to shore. It’s particularly Germany and the Netherlands which have quite small coastlines.”
Building far out at sea is a big venture, Staffell said. The running costs of the artificial islands wouldn’t necessarily be more expensive as they would be similar to operating an offshore oil rig with a permanent base. But it only really makes sense for constructions with a capacity of more than 10GW because of the large cost associated with manufacturing the islands and, in particular, the high-voltage direct current cables needed to get the power back to shore.
Undersea cables need to avoid areas where ships may anchor, where trawlers operate or where there are strong currents. The cables then need to come ashore where they aren’t “going to disrupt a port, existing businesses, housing areas or a popular beach and where there is room to install a high-voltage substation and a line of pylons to connect it to the nearest switchyard of the national grid,” said Roger Kemp, a professor of engineering at Lancaster University. That tends to eliminate many cities and areas of outstanding beauty, he adds.
Developers need to weigh up the cost and complexity of building turbines further offshore, against building nearer to shore where sites are more accessible for construction and maintenance, said Ed Reed from Cornwall Insight, an energy consultancy based in Norwich, explaining that “as the offshore wind industry matures, supply chains improve, and technology improvements are made there is a general expectation that offshore wind farms will be deployed further from land, and may even be linked to neighboring markets.”
And it is the connection between neighboring markets that will make the business case for any such mega-project as the North Sea Wind Power Hub, said Staffell.
“One of the biggest benefits of having this offshore hub instead of connecting a couple of wind farms to the UK, a couple to Germany, a couple to Denmark, is connecting them all to those [artificial] islands.” Power can then be transferred between those countries.
On May 26, 2019, UK prices for electricity turned negative for nine consecutive hours due to low demand, forcing on- and offshore wind farms to temporarily shut down. If UK wind farms were connected to other European countries through the proposed island hubs, the country could sell its excess power.
Ørsted says it welcomes the ambitious development proposals for the North Sea but stresses the need to focus on immediate solutions.
“Bold ambitions and new solutions are needed, but we also think it is critical to act in the short-term,” said Ulrik Stridbæk, the company’s head of energy economics.
“The first natural step, in our view, is to develop hybrid solutions, where offshore wind farms are connected to two or more countries.” Those wind farms would be linked through undersea interconnectors — as will soon be the case between the UK and Norway.
Grid operators, developers, policymakers and the offshore wind industry will need to join forces to develop cost-effective transmission solutions to enable decarburization and deliver green electricity to Europe’s power consumers, said Stridbæk.
If given the green light, a project as large as the North Sea Wind Power Hub would involve multiple companies from multiple countries. Staffell reiterates that governments will need to give companies the certainty that there won’t be any roadblocks such as legal challenges around using the seabed, or ramifications if one country decided to pull out.
The North Sea Wind Power Hub consortium can learn from the failings of Desertec, a German-led initiative which hoped to turn the Sahara into a giant solar farm, he said, adding that a giant wind hub in the North Sea would benefit all the countries involved and the UK in particular as it is most strongly affected by the variability of wind output.
“But they all want to pay the least amount possible.”