Riding a wave of innovation, interest in new floating wind turbine designs is surging to better harness the power of one of the strongest forces in nature.
Wind, one of the strongest forces in nature, is also one of the oldest sources of energy for industry. They were first used across the Middle East in the seventh century, well before the first vertical axis turbine was invented in the 1920s. That bladed “eggbeater windmill” design is still used today. Yet over the past decade or more commercial wind turbine manufacturers have been trying to figure out better ways to move their farms from land to sea.
On the open sea, winds blow harder, faster, and stronger. Whether generated by a torrential coastal storm or the afternoon summer breeze on the beach, the wind blows faster over the oceans than on land because of the lack of friction over the water.
Venturing further out to sea means encountering more energetic winds. However, this deep-sea destination has long been inaccessible, due to the fixed bottom foundations of wind turbines. Generally, they can only extend down 60 meters, far too short to reach the seafloor.
But harnessing the wind in the farthest parts of the open ocean could change the entire landscape of renewable energy, as Wired recently reported.
Nearly 80 percent of the offshore wind resource in European waters is located in places too deep to make today’s fixed-foundation turbines an economically-sensible choice, according to Wind Europe, an industry body based in Brussels.
And in the U.S. , deep water difficulty has also prevented the installation of large offshore wind farms in the states. However, research shows that if successful, wind farms placed in the North Atlantic for example, could generate three times more renewable energy than those on land, allowing power to be extracted and energy replenished at a much higher rate.
On land, in order to harness one gigawatt of energy, a wind farm needs to be 1,000 square kilometers. This one gigawatt can power about 750,000 homes. Out at sea, the amount of power a similarly sized wind farm generates triples to three gigawatts, enough energy for roughly two million homes.
The cost of offshore wind power has been dropping. Billions of dollars have been poured into the ocean of floating turbines. The the war in Ukraine has potentially turned the tides, and prompted a hastened rush away from fossil fuels across the European Union due its dependence on Russian gas. So various floating wind turbine designs are racing to see who can be the most cost-effective and efficient.
Yet, the industry is falling short of what’s needed in order to limit climate change.
Despite 2021 being the second-best year for the wind industry overall, with a record number of offshore wind installations, a new report from the Global Wind Energy Council (GWEC) affirms that this growth needs to quadruple by the end of the decade if the world is to stay on course for a 1.5C progression and net-zero by 2050.
Floating wind is “one of the key game-changers,” the council states, but with the ocean’s swathe of unpredictable weather and stormy seas, designers must overcome these complex engineering challenges. This era brings the industry a flurry of solutions.
Over the last five years, staff workers at the Norway-based Wind Catching Systems (WCS), have crafted their turbine design, which has reinvented the age-old windmill into a giant waffle floating in the middle of the ocean. However, instead of syrup, their Belgian-waffle-shaped frame is adorned with no fewer than 126 four-rotor wind turbines. They resemble battleship boards, suited with an expansive fleet of spinning blades. These structures would stand as tall as the Eiffel Tower atop floating platforms analogous to oil rigs.
“Traditional wind farms are based on the old Dutch windmills,” Ole Heggheim, CEO of Wind Catching Systems, told Fast Company last year. “These wind farms work well on land, but “why is it that when you have something that works on land, you should do the same thing on water?”
By 2040, Norway aims to go from two operational offshore wind turbines to about 1,500, enough to provide 30 gigawatts of offshore wind power, as announced in their 2022 investment plan.
Using solely traditional wind turbines, that would take between 1,500 and 2,000 towers of blades spinning on land. Ole Heggheim, the CEO of WCS, says they can do it with 400. The 126 turbines on the waffle ridges have a capacity of about one megawatt each, however, when placed closely together, they help power each other.
“It’s an added turbulence bonus that you get from putting these turbines together; it’s like a synergy,” Heggheim told Wired. In a compact, multi-rotor system, the gaps between turbines allow air to flow easily past them.
The rotor is the most important component of a wind turbine because it absorbs the kinetic power of the wind and converts energy into rotary motion around a central hub. Much like the aerodynamic force of airplane or helicopter rotor blades, the translation of energy across the rotor is what generates energy. The gaps present in WCS’s design help to pull more air through the rotors themselves.
As an added benefit, this design reduces the amount of cabling. Instead of requiring cabling for each of the rotors, individual floating turbines would each require one cable of their own complete with mooring lines to keep them from floating away.
When the ocean wind is the strongest in ideal conditions, one windcatcher could produce up to 400 gigawatt-hours of energy, WCS says. To put that into perspective, the most powerful wind turbine spinning on the market at present, the V236-15.0, outputs 80 gigawatt-hours.
WCS has a lot of fans. Recently, General Motors Ventures spearheaded a round for up to $10 million in funding for the floating turbine system. Nevertheless, WCS isn’t swimming this race alone.
Located just off the Scottish coast, five towering turbines are poised on buoyant cylinders, called spars, filled with a heavy ballast to ensure a vertical float. Unlike the WCS design, these floating turbines look like the land ones we are accustomed to.
Currently, Hywind powers 36,000 British homes, breaking the UK record for energy output. A year after building the first commercial floating wind farm, the company has set off to build an even bigger one. This concept would achieve the coveted one-gigawatt mark and be positioned on the coast of Norway. This time, instead of employing the cylinder, these turbines will sit atop the corner of a flat, triangular platform called the Wind Semi.
From the Dutch company Seawind’s semi-submersible two-blade design to the triangular pyramid design proposed by Tetrafloat, the race to build the best option continues to expand, and for good reason. As reported in Wired, a spokesperson for Wind Europe explains that the current capacity of Europe’s first few floating wind farms (113 MW) is expected to triple in just two years. By 2030, 10 gigawatts of wind turbines are expected to be installed across the continent, with 100 times the capacity, powering around 10 million homes.
In the US, one company, Olympic Wind, has even proposed building a floating wind farm with up to 2 GW of capacity off the West Coast. And they aren’t the first. In an email to Axios, Chief Financial Officer CFO Ronny Karlsen said, “The areas outside the coast of California would suit our system perfectly, with strong winds in deep waters near the coast.” That venture won't happen before 2025.
“We’re coming to a new age,” Seamus Garvey of the University of Nottingham told Wired. Garvey is the designer behind TetraFloat. However, he says there are too many competitors at the moment. “A plethora of solutions is not necessarily a good route to lowering cost,” he said. He remarks that the concepts that rely on as little steel as possible might have the best chance at success.
Soon, we might see an instruction of “body yawing” floating turbines he says. These floating turbines will be carousels on the sea surface, swiveling in order to orient themselves better and catch the full force of the wind. In order to do this, existing onshore and offshore turbines can rotate the machine housing at the top of their towers.
“It’s not clear to me which is going to be the winner,” Alasdair McDonald at the University of Edinburgh,told Wired broadly referring to the various floating designs now emerging. Building off the necessity of cheaper-to-build designs, McDonald emphasizes durability.
“These are incredibly hostile places,” says McDonald. “You are trying to engineer against the forces of God, almost.