ORONO (AP) — As waves grew and gusts increased, a wind turbine bobbed gently, its blades spinning with a gentle woosh. The tempest reached a crescendo with little drama other than splashing water.

The uneventful outcome is exactly what engineers aimed for.

The demonstration featuring a 13-foot-tall floating wind turbine in an indoor pool aimed to ensure it can withstand the strain of powerful water and wind when much larger versions are deployed in the ocean.

It's the University of Maine's contribution to a worldwide race to improve floating machines to tap wind that blows across deeper waters offshore, too deep to attach turbines to the seabed with permanent pilings.

In the next decade, UMaine researchers said, they envision turbine platforms floating in the ocean beyond the horizon, stretching more than 700 feet (210 meters) skyward and anchored with mooring lines.

"These structures are massive," said Anthony Viselli, chief engineer for offshore wind technology at the university's Advanced Composites Center, after the demonstration wrapped up. "These would be some of the largest moving structures that humankind has endeavored to create. And there would be many of them."

As the technology advances, dozens of designs are being promoted by experts who see floating wind turbines as a way to address climate change by shifting away from burning fossil fuels.

Floating turbines are the only way some countries and U.S. states can capture offshore wind energy on a large scale. In the U.S. alone, 2.8 terawatts of wind energy potential blows over ocean waters too deep for traditional turbines that affix to the ocean floor, according to the National Renewable Energy Laboratory. That's enough to power 350 million homes — more than double the number of existing homes in the U.S.

The first floating wind farm started operating off Scotland's coast in 2017. In the United States, the Department of Interior two weeks ago proposed the first floating wind energy auctions for the Gulf of Maine, following lease auctions for the West Coast that began in 2022. The nearly 1 million acres up for auction off the New England coast could generate enough clean wind energy to power more than 5 million local homes, the department said.

UMaine is home to the nation's largest team of engineers dedicated to floating offshore wind. Other big players include Equinor, which has installed a demonstration floating project of the coast of Norway; global company Principle Power, which has installed small-scale projects off Scotland and Portugal; and SBM Offshore, which has a demonstration project off France.

Floating offshore wind is still a nascent industry, however, making it expensive.

The Norwegian company Equinor postponed its Trollvind floating initiative, citing technology availability, rising costs and a strained timetable to deliver on the original concept.

Danish wind energy developer Ørsted decided to focus its efforts on fixed-bottom turbines, foregoing deeper offshore regions including Japan, Norway, Spain, Portugal and the U.S. West Coast. "We care a lot about affordability of renewable power, and floating wind is a lot more expensive than bottom-fixed," said CEO Mads Nipper.

But others are moving forward.

Gazelle Wind Power is developing a modular platform system to make manufacture and assembly cost-effective and efficient.

"This is a global problem and this is an ideal solution in order to deliver power to shore," said Gazelle Wind Power CEO Jon Salazar.

UMaine launched its first floating prototype a decade ago and became a surprise global leader after a study showed that the Gulf of Maine had the wind energy potential of 156 nuclear power plants, due to fast, consistent wind.

The state could meet all its home heating needs and power every car — if they were all electric vehicles — by tapping just 3% of that water. That improves the odds of successfully sharing the resource with fishermen, recreational boaters, the military and, of course, marine life. Indeed, the federal government's lease proposal spares Maine's key lobstering grounds from development, removing a potential obstacle.

Trailblazers in offshore wind are benefiting from work done by the oil industry, which engineered floating oil and gas rigs, said Habib Dagher, director of the Advanced Composites Center.

The university's wind wave basin, which looks something like a swimming pool with wave and wind generators that can mimic ocean conditions up to a 500-year storm, takes that work to the next level.

On a recent day, the semi-submersible floating turbine was tethered to the bottom of the basin. Its 1:70 scale represented a real turbine standing about 800 feet tall atop a platform in the ocean. The goal is to have industrial scale turbines of 15 to 20 megawatts each, Dagher said.

Size and efficiency are keys to profitability. Larger wind turbines mean fewer are needed, reducing construction, installation and maintenance costs, Viselli said. With greater size and efficiency, developers envision only about 50 turbines needed to produce about the same amount of electricity as a nuclear power plant.

Full-size turbines generate peak power starting at about 20 mph. In powerful storms, they shut down automatically to avoid stressing the equipment or breaking. The mooring lines tethered to the ocean floor are made of rope nearly thick as a telephone pole and under heavy tension. That makes them safer for marine mammals.

For all the turbine technology, the platforms developed by UMaine can be built locally with concrete, a simple material that's readily available. The university already has partners around the world interested in licensing its technology. The state of Maine plans to develop a port facility in the Searsport area to build the floating bases and attach turbines before sending them into the Gulf of Maine.

A brand new industry means some experiments in design will succeed and some will fail. And there is work to ensure that wind farms are good neighbors, overcoming objections from others using the ocean.

"We're going to have some problems and we have to figure out how to roll up our sleeves and solve these problems," Dagher said. "And I think we have no choice as a society but to do that."