Offshore Wind Turbines Promise More Power

Wind turbines located in the deep ocean off U.S. shores could one day generate as much as 2.8 terawatts of energy, triple the amount needed to supply all the country’s current electric power needs, according to the National Renewable Energy Laboratory (NREL). But there are many technical, logistical and political challenges that the wind power industry will have to overcome to reach anything near that goal.

In just three decades, the amount of power generated worldwide by offshore wind power has grown from the 5 megawatts (MW) produced by the world’s first offshore wind energy farm in Denmark in 1991 to more than 68,000 MW generated by 13,096 operating offshore wind turbines today. China is the world leader in these efforts, producing 31,000 MW, or 45%, of offshore wind-generated power.

The U.S. got a much slower start. At the end of May 2024, it had just 174 megawatts of offshore wind power in operation, although there is a potential for 80,523 MW over the next several years due to projects now in development, according to the NREL. So, why the delay?

“I think there was initially a concern that offshore wind might not be feasible or that it was too hard to do, but that changed when prices started to come down around 2015,” says Walter Musial, chief engineer for offshore wind at NREL. In addition, the U.S. has other renewable energy options, such as land-based wind and solar power, which are currently the lowest cost electric energy sources. Europe got an early start in the market because national governments there encouraged the development of offshore wind through programs that enable project developers to recover their costs.

States Take the Lead

In the U.S., the offshore wind energy market is driven by state-level offshore wind procurement, planning activities and energy policies, according to NREL’s 2024 Offshore Wind Market Report. Eight states have mandated goals for generating offshore wind energy by a certain date; five others have formal planning targets. Projects are currently underway or proposed for Hawaii; the Pacific Northwest, including Oregon and northern California; the Gulf of Mexico; the North Atlantic Coast from Maine to northern New Jersey; and the mid-Atlantic coast from New Jersey to North Carolina.

But moving offshore wind turbines from the proposal and planning stages to implementation is more difficult than with land-based wind power projects. Because they are in federal waters, offshore wind farms must go through a multi-year process to meet the requirements of the Bureau of Ocean Energy Management and other federal agencies. This long approval period, as well as increased costs due to rising interest rates, inflation and supply chain shortages, may force developers to cancel existing agreements with power companies and states and renegotiate them to ensure that the projects will still be profitable.

Another complication comes from the provisions of the Jones Act, a 1920s-era federal law that dictates that any goods or people being transported from one U.S. port to another must be carried on a U.S.-built ship.

“In the U.S., an offshore wind turbine foundation installed in the ocean is considered a port, so you can’t take a wind turbine installation vessel from Europe, bring it into a harbor in Virginia and then use that vessel to carry goods out to the wind farms,” says Musial. The installation ship must anchor near the wind farm foundation and wait for smaller U.S. flagged ships to bring the equipment and materials they need to the construction site.

The first U.S.-built wind turbine installation vessel, the Charybdis, would help resolve that issue. It is scheduled for launch early in 2025 and will be deployed for two years on Dominion Energy’s wind farm project off Virginia’s coast. But developers may be reluctant to invest in more of these large ships since the continually increasing size of wind turbine blades may mean that the ships couldn’t handle the latest technologies by the time they are ready to launch.

The U.S. infrastructure will also need other improvements before a larger-scale deployment of offshore wind farms can occur. Ports need upgrades to handle larger vessels and large-scale equipment, while transmission lines must be prepared to handle the additional influx of power from offshore wind turbines.

Floating Turbines off the Coast

Composites manufacturers have a big stake in the growth of the offshore wind power industry in the U.S. since they produce, among other wind turbine components, the giant blades and nacelles that house the power generating components.

The University of Maine’s Advanced Structures and Composites Center (ASCC) has been a leader in developing floating offshore wind turbines. Currently, most offshore wind turbines are permanently attached to the seabed in waters up to 150 feet deep. But there is growing interest in floating wind turbines, which can be anchored like ships in deeper waters about 30 to 40 miles offshore.

“Typically, the farther you are from shore the better the winds are. So, you can place floating wind turbines in areas where you have better wind resources, which means better energy production capabilities,” says Habib Dagher, ASCC director. Plus, with the earth’s curvature, these turbines can’t be seen from the shore, eliminating one common objection to offshore wind farms.

ASCC deployed the first grid-connected offshore floating wind turbine, called the VolturnUS, off the coast of Maine in 2013. It included the first turbine tower manufactured with composite materials, a 75-foot, half-scale research model.

“Steel towers are currently used in offshore turbines, and we wanted to prove that composite towers could also work and that they had advantages,” says Dagher. For a 15 MW turbine, a steel tower could include between 1,000 and 1,500 tons of steel; ASCC researchers showed that a similar-sized composite tower would cut that weight in half.

“By going with a composite tower we could make it less top heavy and reduce the size of the hull that supports it. Plus, composites provide corrosion resistance,” says Dagher. Those factors could help offset the higher cost of the composite tower.

ASCC’s structural testing showed that the composites tower had the required strength and stiffness to support the wind blades. The challenge is to convince an industry accustomed to using steel towers that composites are a viable alternative.

Next-Generation Projects

ASCC expects to launch a new version of its floating wind turbine, the VolturnUS+, during the first quarter of 2025. Although it does not include a composite tower, ASCC is testing the use of composite rebar to replace steel rebar in some sections of the reinforced concrete hull that supports the turbine.

“Steel corrodes, and to protect it, you have to bury it in the concrete with a certain amount of cover,” says Anthony Viselli, manager of offshore model testing and structural design at ASCC. “Because the composite rebar is highly corrosion resistant, we believe we can lighten the weight of the foundations by maybe 10% and have a net cost savings. We are also looking at putting in polyethylene and basalt fibers to reduce cracking in the concrete.”

Taking advantage of the power from offshore wind turbines will be a long-term process; currently planned projects may not produce energy until the 2030s or even the 2040s. In the meantime, ASCC is working with the state of Maine and Diamond Offshore Wind (a subsidiary of the Mitsubishi Corporation) to build a floating research wind farm by the end of this decade that will include 10 15MW units.

“What we’re doing right now is collecting information and environmental ecological data, working with the fisheries industry and others to make sure that it’s done right,” says Dagher. “The state of Maine has a plan that we call 1-10-100. We’re going to put one unit in the water first and learn how to do it right, and then put 10 units in the water. Then we’ll be ready to go commercial and put 100 units in the water.”

Political Roadblocks

Plans for more offshore wind farms in the U.S. could be blown off course, however, since the new administration in Washington has made it clear that it prefers to concentrate on traditional fossil fuels for providing power. On his first day in office, President Trump signed an executive order banning new leases, renewal of any leases and permits for any offshore wind projects until the Secretary of the Interior reviews them.But offshore wind advocates believe there are good reasons for continuing to deploy them.

“It’s an industry that is creating a lot of jobs, putting a lot of people to work in different sectors,” says Musial. “Reducing offshore wind projects will hurt all those sectors; it’s not about just one project.”

Long-term environmental impacts also need to be factored in. “What’s important here is that society has to look at new energy resources – renewable resources that reduce our impact on the environment and on the climate. Wind power is one of the technologies that’s been embraced across the world,” says Dagher. “There are over 6,000 offshore wind turbines in Europe right now, and this industry is going to move forward at warp speed. So the question is, will the U.S. continue to lead in the floating wind race, or will we become the followers? That’s really what’s at stake.”