WILLIAM BRANGHAM: The Biden administration just approved a wind farm project off the coast of Massachusetts.

It's now the 11th commercial scale wind project of its kind to get such approval.

This comes at a key moment for this sector, because president-elect Trump has been a frequent critic.

As science correspondent Miles O'Brien reports, researchers are racing to answer important questions about the potential unintended consequences of this promising form of renewable energy, even while current windmills are under construction.

MILES O'BRIEN: Three decades after the idea was pioneered in Europe, offshore wind power is just over the horizon in the U.S.

In New Bedford, Massachusetts they are staging and stacking the pieces of the largest one yet, Vineyard Wind 1.

What is the total dollar figure for Vineyard Wind?

KLAUS SKOUST MOELLER, CEO, Vineyard Wind 1: So, we are about $4 billion.

MILES O'BRIEN: Klaus Moeller is the CEO.

KLAUS SKOUST MOELLER: It's in the high end because we have a lot of first-time investments here, but it's not off the charts of what we have done before.

MILES O'BRIEN: Vineyard Wind is one of about a half-dozen utility-scale projects at various stages of completion along the East Coast, from here down to Virginia.

The Biden administration set a national target of 30 gigawatts of offshore wind capacity by 2030.

It would be enough to supply about 11 million homes each year.

What is the huge advantage to putting them offshore?

KLAUS SKOUST MOELLER: Here in Massachusetts, you don't see a lot of space just available to do onshore wind.

Our wind farm is going to produce wind for 400,000 houses in Massachusetts.

That would be very difficult to achieve with an onshore wind farm.

MILES O'BRIEN: These giant offshore wind turbines are twice the height of those built on land.

Their blades are twice as long.

That bigger sweep, combined with stronger wind speeds this far from land, allows them to generate more energy.

Inside the turbine, magnets rotate past coils of wire, generating electricity, which runs down through buried wires back to the grid, electricity out of thin air.

Big as they are, the windmills are 15 miles offshore, too far to see from terra firma.

Cessna 808, cleared for takeoff from runway five.

So, photographer Rob Gourley (ph) and I flew out to take a look.

Providence 55-808, we're going to do some photo work at the wind turbines out there.

Requesting flight (INAUDIBLE) We flew due south of Martha's Vineyard, and there they were.

You can't miss them.

The size of these turbines is pretty stunning.

Each of those blades is more than a football field, so, combined, it's two football fields in diameter.

Plus, it's sitting up pretty high as it is.

It was a very calm day in June, so they were idle.

They remain idle now after a manufacturing flaw caused the structural failure of a blade in July.

Debris fell into the ocean, leading to some beach closures.

The blade was manufactured by GE Vernova, which blames insufficient bonding during production at its facility in Gaspe, Canada.

The company says it is inspecting the approximately 150 offshore wind blades produced at that plant to ensure no similar defects are present.

Construction has resumed, but it gave offshore wind farm opponents more grist for their mill.

Over the years, Donald Trump has led the chorus, trashing turbines since at least 2006, when a proposal to build windmills near his golf course in Scotland first surfaced.

DONALD TRUMP, Former President of the United States (R) and Current U.S. President-Elect: It's like a graveyard for birds.

MILES O'BRIEN: Onshore monopole windmills kill as many as 328,000 birds a year in the U.S. For comparison, buildings kill a billion birds.

There is no data on the threat posed by remote offshore wind.

But many wind opponents are more focused below the surface on whale mortalities.

PROTESTERS: Whale lives matter!

TUCKER CARLSON, Former FOX News Anchor: Wind turbines that appear to be killing large numbers of whales.

SEAN DUFFY, FOX News Anchor: At least they should do studies to see what's killing the darn whales.

MILES O'BRIEN: But these whales died before a single turbine was built in the supposedly culpable wind farm.

JESSICA REDFERN, New England Aquarium: So that link doesn't seem real to me.

It seems like false information.

MILES O'BRIEN: Jessica Redfern is a quantitative ecologist at the New England Aquarium.

She uses mathematics to study ecological questions.

And the arithmetic for North Atlantic right whales is not good.

There are only 370 left.

They're being killed at an alarming rate by vessel strikes and entanglement with fishing gear, not by windmills.

Still, she is concerned that the noise and additional ship traffic during construction might harm the animals.

JESSICA REDFERN: You can think of it as a giant experiment that's occurring in our ocean.

You need to observe.

You need to collect the data.

You need to watch to understand what's happening.

From that, you learn, and that's how we will be able to really responsibly develop wind going forward.

MILES O'BRIEN: The process of putting all that structure in the water is, of course, disruptive.

Thousands of turbines require hundreds of thousands of bone-jarring impacts from pile driving.

Groton, Connecticut-based ThayerMahan is deploying so-called bubble curtains around the pile driving operations.

The concentric walls of bubbles significantly reduce the noise in the water column.

The company is also deploying autonomous acoustic sensors that can detect the sound of vocalizing whales.

Mike Connor is ThayerMahan's founder.

What you have here is, this is -- these are all sensors, these points.

Is that right?

Is that how it is?

MIKE CONNOR, Founder, ThayerMahan: That's right.

MILES O'BRIEN: OK. MIKE CONNOR: Each of those points is a sensor, and then these are the bearings from which we hear whale activity.

MILES O'BRIEN: When a whale is spotted near a wind turbine construction site, the work is supposed to stop immediately.

Based on what you know here, can we say categorically that wind turbines have not killed a whale?

MIKE CONNOR: A wind turbine has not killed a whale.

Pile-driving from wind turbine construction has almost certainly not ever killed a whale.

MILES O'BRIEN: But what happens after the wind farms are completed?

Could they pose a long-term threat to the whales?

Heidi Sosik is conducting research that might provide an answer.

She is a biological oceanographer at the Woods Hole Oceanographic Institution, 25 miles as the crow flies from the Vineyard Wind farm.

HEIDI SOSIK, Woods Hole Oceanographic Institution: Part of what's so fascinating about trying to study the ocean is the challenges that we face in trying to observe it.

I mean, it's just captivating for me.

MILES O'BRIEN: She's in the middle of a multidecade study to better understand what's happening in the microscopic sea.

Four times a year for the past six years, she and her team have steamed from Martha's Vineyard due south across the continental shelf and just over the edge, all the while recording, counting, identifying all manner of phytoplankton with automated high-speed imaging.

The tiny copepods that right whales depend on are themselves dependent on the phytoplankton, a kaleidoscope of microscopic algae that thrive in the ocean.

She suspects all those windmill structures in the water will perturb the ocean circulation and cause turbulence, affecting how and where the plankton grow.

At the bottom of the ledger, it's worth continuing the construction, in your view?

HEIDI SOSIK: The wind farms are going in, and we can't turn back the clock on that, so we need to move forward with the research to make the best decisions we can going forward.

MILES O'BRIEN: Heidi Sosik lives in a solar-powered home and drives an electric car.

She is personally invested in fighting the climate emergency.

She's among many scientists willing to accept the risk of offshore wind, so long as it is well-measured.

For the "PBS News Hour," I'm Miles O'Brien in New Bedford, Massachusetts.

WILLIAM BRANGHAM: In his next report, Miles looks at how offshore wind power may complicate fishing and seafood harvesting for one of the country's most lucrative fishing ports.