When envisioning an offshore wind farm that includes a 2.3-square-mile artificial island, it doesn’t hurt that the country behind it is exceptionally skilled at two things: reclaiming land from the sea and harnessing the power of the wind.

These uniquely Dutch strengths are driving an ambitious wind power and island-building project in the North Sea. If and when it's completed, this 30-gigawatt wind farm would be by far the largest in the world at 2,300 square miles. The farm's proposed size and capacity, which Quartz notes is roughly eight times the size of New York City and capable of generating double the total amount of all existing European offshore wind power, is a remarkable feat in itself. However, it’s how TenneT, a government-owned entity that oversees the Netherlands’ electric grid, plans to take full advantage of the farm's way offshore location that truly sets the scheme apart.

Although Dutch-helmed, the proposed site of the sprawling farm and its man-made “support” island would be closer to costal England than the Netherlands in an area located roughly 78 miles off of East Yorkshire’s Holderness coast. Known as Dogger Bank, this particularly shallow stretch of the North Sea — technically, a sandbank — serves as an important commercial fishing region (doggers is the old Dutch word for cod fishing vessels) but has never been considered a viable spot for wind turbines due to its remote locale. (Some 20,000 years ago, Dogger Bank — all 6,800 square miles of it — was part of the ancient landmass connecting continental Europe to Great Britain before being flooded by rising sea levels circa 6,500-6,200 BC.)

Today, this optimally windswept spot in the middle of the North Sea has been identified as an ideal place for generating wind energy despite its remote locale. For one, tethering a huge number of wind turbines to the sea floor in such a shallow area is significantly easier from an engineering standpoint — and less costly — than bottom-mounting a fixed turbine foundation in deep water. It's also more economical compared to floating wind turbines, which have their advantages but are expensive to anchor and operate.

Dogger Bank, a large sandbank in the North SeaYet because Dogger Bank is located in such a far-flung part of the North Sea, the cost of installing a multitude of direct current (DC) cables that are needed to transmit wind-harnessed energy to onshore electric grids would be prohibitive — perhaps impossible. That’s the rub with offshore wind power. When you go further out, you have less local opposition and more space — and wind — to work with. Most offshore wind farms — the largest is the 47-square-mile/630-megawatt London Array — remain relatively close to shore. What's more, the further out an offshore wind farm is, the more electricity is lost during transmission.

This is where the TenneT’s artificial North Sea island-based wind power collection and distribution hub comes into play.

Because Dogger Bank is so shallow, constructing a man-made island, like mounting wind turbines, is far easier than in a deeper stretch of sea. And as mentioned, the Dutch are old pros at this.

Rob van der Hage, manager of TenneT’s offshore wind infrastructure program, explains to The Guardian when asked if building a large island in the middle of the North Sea was a daunting task: “Is it difficult? In the Netherlands, when we see a piece of water we want to build islands or land. We’ve been doing that for centuries. That is not the biggest challenge.”

Wind power that's quite literally far out

As envisioned by TenneT, energy generated at the massive offshore wind farm would be sent directly to the island via a series of short cables in lieu of an improbable number of very long ones reaching toward the shore. Once collected at the island's converter stations, alternating current generated by the turbines is transformed into more efficient direct current before being transmitted to electric grids in the Netherlands and U.K. — and potentially Belgium, Denmark and Germany. Far offshore becomes near-shore, essentially. What’s more, the distribution hub would ensure that no energy is wasted, only transmitting electricity to the country or countries that need it most at any even given time.

The Guardian elaborates on the nuts and bolts:

As each further mile out to sea means another mile of expensive cabling to get the power back to land, the firm [TenneT] argues a more innovative approach is needed.

The island idea would theoretically solve that by allowing economies of scale, higher wind speeds and mean relatively short, affordable cables taking power from offshore turbines to the island.

There, converters will change it from alternating current — as used in mains electricity but which incurs losses of power over long distances — to direct current for transmitting back to the UK or Netherlands.
That long distance cable, an interconnector, would give the wind farms flexibility to supply whichever country’s market was paying the most for power at any given time, and mean the power almost always had a use.

As the Guardian goes on to note, numerous not-so-minor elements need to fall into place before this scheme with “sky-high” ambition begins to take fruition. (TenneT aims to have the island up and running by 2027 with the wind farm to follow.)

For starters, while TenneT plans to build the artificial island (and pay for most of the 1.5 billion euro price tag), the company is not allowed to build the wind farm — potentially multiple wind farms — that the island or future islands would support. Offshore wind developers would need to do that. And before that happens, other electric utilities such as the UK’s National Grid need to commit to helping TenneT shoulder the cost of the underwater cables.

Still, van der Hage is optimistic about the viability of developing wind farms located further from shore. "The big challenge we are facing towards 2030 and 2050 is onshore wind is hampered by local opposition and nearshore is nearly full,” he tells the Guardian. “It’s logical we are looking at areas further offshore.”

Inset map of Dogger Bank location: Wikimedia Commons

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.