As the U.S. considers alternative sources of clean power to wean itself off fossil fuels, offshore wind energy (OWE) has emerged as a promising option with tremendous potential. However, like many other renewable energy sources, it faces its own unique set of challenges, some of which test the premise of “clean.”
OWE may not create greenhouse gases, aside from those generated during initial construction and maintenance, but it does negatively impact the environment in other ways. Environmental groups and scientists have voiced concern about how the development and operation of offshore wind farms can harm marine life in the waters where they are built.
Responding to that concern, multiple studies are examining this negative impact, such as those being conducted in the Mediterranean Sea, to confirm a pattern of disturbance and also to develop protocols for mitigating the impacts. Proponents hope these findings will provide guidance to the industry so that it can avoid the most harmful effects and continue its current trajectory of growth.
The Expanding Role of OWE
While wind power is commonly associated with land-based turbine farms, the offshore version has emerged with great potential. The American Clean Power Association (ACPA) describes OWE as “America’s next major energy source, representing a generational opportunity.”
OWE offers several advantages over other means of clean energy production. It is an abundant, relatively consistent, reliable source of clean and renewable power. In contrast, the variability factors associated with solar and land-based wind energy have always been their biggest drawbacks. OWE could help compensate for this.
The variability factors in solar and land-based wind have always been their biggest drawbacks. Offshore wind energy could help compensate for this.
OWE also offers logistical advantages. The greatest concentrated demand for electricity typically occurs in large urban areas; since many of these megacities are also located in coastal zones, they could be serviced readily by OWE.
Furthermore, OWE offers good economics. Because of its steady and sustainable nature, favorable prices can be locked in for many years.
All these factors have boosted interest in and enthusiasm for the industry. Reuters reports that total U.S. OWE capacity is set to jump from 41 megawatts (MW) in 2023 to almost 1,000 MW in 2024.
Much of this momentum is coming from the federal government. In 2021, U.S. President Biden set the goal of deploying 30 gigawatts of offshore wind electricity generation by 2030—enough to power more than 10 million American homes.
Good But Not So Good
As is the case with so many other promising solutions, not everyone is sanguine about the prospects of OWE. Projects have drawn protesters just about everywhere. Their ranks include environmentalists, fishermen, coastal residents, and no small number of politicians.
They have cited numerous reasons for their opposition, but the negative impacts on sensitive marine animals seem to have attracted the greatest amount of attention.
Offshore wind energy farms can impact marine life in many ways, both from their development and operations.
Concerns are not unfounded. OWE farms can impact marine life in a variety of ways, both from their development and operations. While not necessarily aligning itself with the opposition, the French maritime data analysis company Sinay has identified several issues with OWE.
Ocean-based wind turbines are typically larger than their land-based counterparts. They are often built on huge towers that are anchored into the bedrock on equally substantial foundations. This construction is an efficient conduit of the noise that is generated by the turbine blades, even though they are spinning in the sky, over 100 meters (about 328 feet) above the water.
The sound of the vibrating turbine travels down through the tower into the base and then into the sea floor. These unnatural or anthropogenic (generated by humans) sounds in the aquatic environment create "noise pollution" that interferes with the marine animals living in the area. These animals have developed ways of navigating, communicating, interacting, feeding, and reproducing that often involve the processing of naturally occurring ambient noise in their surroundings. The introduction of noise pollution from wind turbines may alter these sound-reliant behaviors.
Noise from heavy machinery, such as pile drivers that are used to drive the large [wind] towers into the sea floor, generate pronounced noise pollution that can harm wildlife.
Some of the most acute noise pollution comes from the construction of OWE farms. Noise from heavy machinery, such as pile drivers that are used to drive the large towers into the sea floor, generates pronounced noise pollution that can harm wildlife.
Sinay also notes that cables installed to carry the power from turbines to onshore distribution centers emit electromagnetic fields (EMFs) into the surrounding water. The issue of EMFs from land-based high-voltage transmission lines has been controversial, and similar concerns have been raised about the effect of EMFs from offshore turbines on marine life.
EMFs are naturally occurring in the ocean environment, and many aquatic species are naturally adapted to their presence. They are highly sensitive to these energy waves and use them to navigate, forage, hunt for food, and avoid predators. But the man-made EMFs generated by underwater cables can alter the behavior of these animals.
OWE turbines can generate other forms of pollution besides noise. The saltwater in the ocean is highly corrosive and breaks down the metal structures used to support turbines. This metallic breakdown can also become a source of pollution in the ocean environment.
Finally, wind turbines and their bases on the sea floor attract marine life looking for cover. This “artificial reef effect” has positive and negative outcomes. It can help compensate for the disruption of habitat caused by the construction of the wind farm, but it can also harbor invasive species and otherwise alter the natural balance in surrounding habitats.
Birds, Whales, and Turtles
In response to concerns voiced by various groups, including fishermen and environmentalists, studies have been conducted to assess the potential damage to marine ecosystems from the development and operation of OWE farms.
A few studies have found that some of the worst fears may be overblown. For example, a study conducted in 2019 on the effects of European and Danish OWE farms on birds found evidence of “widespread avoidance of offshore turbines by large-bodied birds.” In other words, the birds don’t die as feared because they simply fly around the turbines. The National Oceanic and Atmospheric Administration (NOAA) also has found that “there is no scientific evidence that noise resulting from OWE site characterization surveys could potentially cause mortality of whales.”
Recognizing the controversy and the potential problems with offshore wind energy technology, the U.S. federal government approved funding to conduct comprehensive studies of its effects.
However, concerns remain, and much of the research and knowledge about the effects of OWE on marine life is in its infancy. Recognizing the controversy and the potential problems with the technology, the U.S. federal government approved funding to conduct comprehensive studies of its effects on the natural marine environment and wildlife.
In October 2021, the Department of Energy (DOE) announced $13.5 million in funding to provide “critical environmental and wildlife data to support OWE development.” The funding went to four separate projects. Two of these were to support wildlife and fisheries monitoring on the East Coast. The other two focused on West Coast waters.
On the East Coast, Duke University received $7.5 million to examine the effect of OWE development on marine animals, including birds, bats, whales, and turtles. The Coonamessett Farm Foundation received $3.3 million to survey changes in commercial fish populations and aquatic environments at an OWE development site.
On the West Coast, Oregon State University received $2 million to conduct acoustic monitoring of marine mammals and seabirds. The Woods Hole Oceanographic Institution also received $750,000 to develop robotic technology to monitor the effect of wind energy development on marine life.
In 2022, the DOE and the Bureau of Ocean Energy Management (BOEM) announced an additional award. The Electric Power Research Institute (EPRI) received $1.6 million to conduct bat acoustic monitoring at fixed and mobile (floating) sites along the West Coast.
These and other efforts are underway. While strong correlations have yet to be established, the goal is to develop a database of knowledge that can help guide the industry, so that as it grows, it takes the necessary precautions to minimize the effects of OWEs on the environment.
BOEM, the federal agency that grants leases, easements, and rights-of-way for OWE development, has developed measures to mitigate impacts.
Some of these measures are already being implemented. BOEM, the federal agency that grants leases, easements, and rights-of-way for OWE development, has developed measures to mitigate impacts. These include the selection of potential sites that will have the least amount of conflict with marine life and human activities, such as fishing. Seasonal restrictions are also designed to avoid conflict with the migration patterns of certain species.
One of the most consequential activities in wind farm development may be the pile driving of wind turbine towers, mentioned earlier. Construction can last between two and four years, and the noise is intense and may be harmful to resident marine life.
However, a so-called “bubble curtain technique” is being deployed to minimize its impact. This entails using steel-encased, perforated rubber hoses sunk to the seafloor in rings or circles around the base where the tower will be driven into the sea floor. Air is pumped into the hoses, where it escapes through the holes and rises to the surface. As it rises, it creates a “curtain” of bubbles that acts as a buffer that prevents the pile driving noise from escaping into the surrounding ocean environment and can reduce the sound generated by pile driving by as much as 80 to 90 percent.
Sustainable Offshore Wind Energy
The fight against climate change is not just about ending the nation's dependence on carbon-emitting fossil fuels. All forms of energy generation have drawbacks, risks, and harmful impacts. In this sense, the challenge presenting itself to an energy-dependent society is to account for the harmful impacts of all forms of energy production and to sufficiently mitigate them. Just as scientists, innovators, engineers, and governments have demonstrated the ingenuity to develop alternative fuel sources, they have an equal capacity to refine and improve upon even the most seemingly clean and sustainable forms of energy generation.
As the U.S. strives to enlist diverse resources in the fight against carbon emissions, offshore wind has emerged as an energy alternative with potential. To fully meet the challenge of climate change, the OWE industry will have to mitigate the impacts of this very plentiful and otherwise sustainable fuel source.
Industry leaders and many policymakers have shown the will to address these challenges. In time, OWE may prove to be one of the nation's leading sources of clean energy with minimal impact on the aquatic environments whose resources it harnesses.
*Rick Laezman is a freelance writer in Los Angeles, California, US. He has a passion for energy efficiency and innovation. He has covered renewable power and other related subjects for over ten years.