Unlike 99 percent of the world’s offshore wind turbines, which are fixed directly to the sea floor in relatively shallow depths, these next-generation machines can be deployed in very deep water, in the outer reaches of ocean space, where they can harvest more powerful, consistent wind.

Far offshore, they might also avoid opposition from shoreside communities, who don’t want green energy to spoil the view.

The question of how to make the whales, fishing fleets and cargo freighters happy is ongoing.

About 90 miles off the coast, in one of the windiest places on Earth, the helicopters took a slow loop past Norway’s newest wind farm, dubbed Hywind Tampen, built by state-owned energy giant Equinor.

The machines, from afar, look like pinwheels. But up close, they’re enormous: each almost as tall as the Eiffel Tower, above and below the waterline, and weighing 12,000 tons, equal to 60 Boeing 747s.

They are held in place by some of the heftiest chains ever crafted, attached to the sea floor by “suction anchors” that burrow into the sand — exhaling and inhaling air — like something out of a sci-fi novel.

“It is a miracle that they float,” said Ole Arild Larsen, manager of operations for Hywind Tampen. He was kidding. He’s spent his career making sure they do.

He compared his company’s “spar buoy” design to a stoppered bottle of water, semi-submerged in the sea. In this case, the “bottle” is a gigantic hollow concrete tube, sealed at both ends and weighted with gravel and water to lower the center of gravity and serve as a counterbalance to keep the rig upright.

The turbines rise, dip and sway in the swell. They are slim, elegant and a little scary.

As we passed, the sweeping blades — each 265 feet long — appeared to be rotating slowly, purposefully, in the light air. But looks can be deceiving: The blades travel at 180 mph. A single turn provides enough electricity to power one Norwegian house for a day. The blades rotate 10 to 15 times a minute; there are 1,440 minutes in a day, 525,600 minutes in a year …

This floating wind farm won’t supply electricity to shore but instead will provide 35 percent of the annual electricity power demand — about 88 megawatts — for five offshore oil platforms, which use large amounts of energy to separate oil, gas and water from the wells.

So, yes, Hywind Tampen is supporting a dirty industry — one that has been lucrative for Norway, helping to grow a sovereign wealth fund worth $1.4 trillion, at a cost to the climate.

The 11 new turbines will reduce the country’s overall emissions this year only slightly, by 0.4 percent. Norway would need several thousand turbines in the North Sea to reach its climate pledge of net zero carbon emissions by mid-century.

But officials say floating wind farms are an essential, revolutionary step in an energy transition.

The helicopters landed on Platform C in the Gullfaks oil and gas field. A few miles away, turbine blades scythed through the haze. Prime Minister Jonas Gahr Store looked out and said he appreciated the symbolism of the juxtaposition.

“The same engineers who built this,” Store told The Washington Post, pointing to the oil platform upon which we stood, “built that.” He pointed toward the wind farm. “We’re proud of that,” he said.

He predicted that the world will continue to need oil and gas in the decades to come. “But the oil platforms will come down,” he said, as the wind industry advances in ways previously thought unimaginable — helped by the transfer of technology and know-how from the exploitation of offshore oil and gas.

Store added that when he has spoken with President Biden, “this is what we talk about … ocean wind.”

When the world’s first offshore wind farm, Vindeby in Denmark, was built in 1991, few believed it was practical — or even possible — to operate wind turbines offshore. The conditions were too harsh.

Vindeby sat just one mile offshore in 12 feet of water. Today, the “techno-economic limit” for wind turbines fixed to the sea floor is about 160 feet.

But energy companies have drawn detailed maps to show where the global winds are best. They found that 80 percent of the world’s offshore wind potential lies in waters deeper than 200 feet, according to the Global Wind Energy Council, an industry group.

Deeper water is where the wind is.

The technology to capture that wind is still young. There are half a dozen different designs in circulation for how best to float wind turbines. The costs are high, economics uncertain, government support tentative.

Before the Hywind Tampen turbines were installed this summer, there were only three floating wind farms on the planet that provided commercial power — one in Portugal and two in Scotland. A handful of prototypes have also been deployed.

But energy companies see the deeper offshore environment as infinitely exploitable.

Mads Nipper, chief executive of Danish wind developer Orsted, says it may be possible to develop floating wind projects in waters 1,000 meters deep — about 3,280 feet, or more than half a mile down.

Kjetil Hove, Equinor’s head of exploration and production in Norway, imagines thousands of floating turbines built around the globe in the coming years.

In a recent multibillion-dollar auction to lease the waters off Scotland to wind farmers, more than half were set to be floating projects. Floating parks may be on their way to South Korea, Chile, Japan, Vietnam and the west coast of the United States.

“This will not be an easy task,” Hove cautioned.

The construction and operation of floating offshore wind projects are complex — and expensive.

Hywind Tampen was initially estimated to cost $500 million. But costs soared to $7oo million. The delays and overruns, the company said, were caused by inflation, plus supply chain hurdles, especially for steel — challenges worsened by the pandemic and fallout from the war in Ukraine. The Norwegian government heavily subsidized the project.

Each of the machines was built dockside, in a deep-water harbor. They were then towed out to sea and tethered to the giant suction anchors. It takes 19 shared anchors to hold down the 11 wind turbines, attached with chains heavy enough to secure a battleship.

With higher winds come more-challenging conditions.

Seas of 20 feet — the height of a two-story building — are not uncommon here. So are winds in excess of 40 mph. These turbines cannot seek shelter in a safe harbor. They cannot run for it.

Sophisticated software helps “pilot” the machines. It can adjust the pitch of the blades and how they face the wind, to keep the turbines upright and balanced — and fight the forces of sea and storm, the yaw, pitch, roll, sway, surge and heave.

When flying past the wind park — or with a good camera lens from the oil platform — one can see the floating turbines not only rise and fall in the waves but also tilt, leaning into the wind. Harder to see with the human eye, the machines can also drift a bit, like an anchored boat.

You cannot land a helicopter on top of a wind turbine. There’s no room. You could dangle a worker, if you really needed to. But you don’t want to. Instead, the maintenance teams come by boat and scramble up ladders.

Larsen said the machines automatically turn themselves off in extreme winds. But they must weather the storms alone.

The fishing and shipping communities are wary of the coming age of offshore wind — the prospect of thousands of machines in deep seas.

So, too, are environmentalists, who support renewable energy but want to be assured that the deep ocean turbines are not harming whales, fish and birds.

Critics of conventional wind farms often complain about noise — the low jet-engine idling sounds they make — and the look of them.

Proponents of floating offshore wind say the turbines will certainly be unheard, and mostly invisible, so far off the coast. But they agree they need to accommodate shipping lanes, fishing grounds and bird migration routes.

On the Gullfaks oil rig, Norway’s Crown Prince Haakon performed the ceremonial stunt, connecting two electric cables to celebrate the opening of the wind farm. Workers on the rig waved Norwegian flags.

Asked about it afterward, the oilmen and women said they welcomed the new technology and the jobs it will bring. It was stunning, they said, that the North Sea might transition from fossil fuels to wind within their lifetimes.