The Atlantic Ocean off the northern coast of Portugal is notorious for its wind and its waves. It draws surfers from all over the world, and the powerful winter storms that frequently sweep through have long made it treacherous for navigation. Yet thanks to a remarkable feat of engineering, it is now home to Europe’s first floating wind farm.

Just 20 kilometres offshore from the town of Viana do Castelo, three towering turbines with 80-metre blades stand 210 metres above the water’s surface — taller than a 60-story skyscraper. These are the largest wind turbines ever installed on floating platforms.

It’s an accomplishment that would have been hard to imagine even a decade ago, but WindFloat Atlantic has been providing electricity to around 60 000 users per year.

Entering its fourth year of operations in 2024, this offshore wind farm produces clean energy to 25 000 Portuguese households annually. The company is also slowly raising GWh production every year, reaching an energy production of 80 GWh in 2023.

Started as a joint venture of EDP Renováveis, Repsol, Engie and Principle Power and with €60 million funding from the European Investment Bank, WindFloat Atlantic is estimated to be saving up to 33 000 tons of CO2 annually.

Why floating wind farm gets more wind

José Pinheiro, the project director for WindFloat Atlantic, says that such floating wind farms have numerous advantages. First and foremost, there’s the wind. In contrast to onshore wind farms, there are no obstacles to impede it, so the wind is reliably steady, and despite the reputation of this area, less turbulent than on land.

“In terms of wind, we normally can say that there's a direct proportionality between the farther you go into the ocean and the wind potential,” he says. And less turbulence means “less harm and less fatigue on the mechanical equipment”.

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How floating wind farm stays upright

But how is it possible to keep such tall structures stable in a place where waves can regularly reach more than 15 metres? “What makes WindFloat Atlantic different from other offshore wind farms is the technology developed and employed: floating platforms,” Pinheiro says.

The semi-submersible platforms are an innovation first created by the fossil fuel industry, and they have been adapted to support these towering turbines amidst the incredible force of the Atlantic.

The platforms are themselves massive, with three columns, 29 meters high and 12 meters in diameter arranged in an equilateral triangle. The main principal keeping the giant turbine towers upright is the same that works for ships: ballast.

But these floating platforms have another advantage. “Their stability is reinforced by a gate system that fills the base of the three pillars with water, combined with a static and active ballast system,” Pinheiro says.

The water can be moved between the pillars to counterbalance the force of the wind. The structures can withstand waves of up to 20 metres, and winds of more than 100 kilometres per hour.

The readiness of these structures was put to the test during storm Cirian at the end of 2023, which brought maximum waves reaching 20 meters high and wind gusts of up to 139 kilometres per hour.

The platforms are anchored to the ocean floor with cables, allowing them to operate much farther away from shore in deeper water. At WindFloat Atlantic’s location, the ocean is about 100 meters deep. Furthermore, the platforms can be towed to shore for maintenance or eventual replacement.

Floating wind farm the future

Piñheiro says the technology, now proven, is the future of offshore wind power. “There’s a greater urgency because of the necessary climate transition”, he says, “and energy companies like EDP and EDP Renewables are a big part of that. With the expertise we’ve developed, we expect to take new steps in this area”.

Through Ocean Winds, a joint venture developed by EDP Renewables and Engie, Pinheiro says, new wind farms are being developed off the coast of Spain, where it has projects in Asturias and the Canary Islands, France, and Scotland, among other places.

Carlos Moedas, the mayor of Lisbon who was the EU Commissioner for Research, Science and Innovation at the time the project was approved, said that the bank’s support of the project “is another example of how EU financing is helping to lower the risk of rolling out innovative energy solutions like WindFloat. We need breakthrough technologies to accelerate the clean energy transition in Europe and lead the global fight against climate change.”

WindFloat Atlantic was recognised in 2023 as one of the most important engineering projects of the 21st century by the Portuguese Engineers Association, which represents around 62 000 engineers in Portugal.