PACIFIC NORTHWEST NATIONAL LABORATORY
West Coast Offshore Wind Industry Brings Energy Benefits, but Not Without Challenges
A new report shows that offshore wind on the West Coast could bring grid resilience benefits to coastal communities.

As electricity use rises to power transportation, buildings, and more, researchers estimate that the western United States will need 400 additional gigawatts (GW) of generation capacity by 2050. 

A new report shows that floating offshore wind could bring 33 GW of energy to the western United States by 2050 and bolster the resilience of coastal communities. And in some scenarios, the additional transmission that would be built to transport the offshore wind could also help to transport lower-cost energy like solar and hydropower, ultimately leading to billions of dollars in savings across the Western Interconnection.

The Department of Energy's (DOE's) Pacific Northwest National Laboratory (PNNL) and National Renewable Energy Laboratory (NREL) spent the last two years studying the costs and benefits of adding floating offshore wind turbines along the United States' Pacific coast. The report, funded by DOE's Grid Deployment Office and co-managed by its Wind Energy Technologies Office, released the report on January 15.

"Offshore wind transmission can deliver a new source of power to support a significant portion of rising energy needs," said Travis Douville, lead author on the report and an advisor at PNNL who leads research on integrating wind energy into the grid. "And even when the wind is not generating electricity locally, networked offshore transmission can still transport low-cost energy from onshore like solar, land-based wind, and hydropower."

Along with system-wide benefits, the report also identified some considerations for future planning. The team found that depending on how offshore wind transmission is built, the benefits may differ by region. The researchers note that more work needs to be done to ensure consumers receive maximum energy benefits at the lowest cost.

"With careful planning and coordination across multiple points in time, we can solve the question of how offshore wind generation and transmission could be developed on the West Coast for maximum benefit," Douville said.

Harnessing winds in the open ocean

The research team scanned the entire West Coast for possible sites to place offshore wind turbines, but one area stood out in terms of wind strength and consistency. Between 10 and 50 miles off the coast of southern Oregon and northern California sits a 9,265-square-mile (24,000 square km) region of ocean where wind speeds average between 9.5 and 10 meters per second (about 22 miles per hour).

"Anytime you're close to 10 meters per second, you're talking about the best of the best" in terms of energetic winds, Douville said. Such energetic locations are unusual, especially on land, he continued. And where they are found on land, they often come with high wind turbulence levels, which requires stronger turbines and careful operational management.

Access to offshore wind energy could improve grid resilience in coastal communities, Douville said. Cities along the coast are far from where energy is generated by other sources, such as hydropower dams, solar panels, land-based wind turbines, nuclear reactors, and natural gas generators. 

"With nearly every point we connect wind energy to the southern Oregon and northern and central California coast, there's immediately an energy resilience benefit from having a generator nearby because there aren't a lot of generators at the coast," Douville said. "Though there are costs to incorporate bulk power flows at these points of interconnection, there are direct improvements in power quality and resilience of the local grid."

Transporting energy from wind to shore

In the study, the researchers first tackled some gaps in research, such as possible locations for floating wind turbines and associated transmission. Besides the lack of existing infrastructure on the coast, the Pacific Ocean floor is sometimes prohibitively deep. For their model wind farms, the researchers used sea floor data to prioritize regions no deeper than 4,265 feet (1,300 meters).

The researchers also made sure to minimize or completely avoid overlap with parts of the ocean that are protected or used by other groups, such as the Coast Guard or Tribal communities.

"We found that approximately 30 GW of offshore wind energy and transmission components could be deployed in economically favorable locations off central and northern California and southern Oregon," said Greg Brinkman, NREL coauthor on the study. "To go beyond 30 GW in this region, waters to the west at greater depths, or north with lesser quality resource could be explored."

Last, the researchers considered how to transport power from the ocean to land. They studied two different transmission structures. The first is a "radial" structure, where each wind farm is connected to one point on the coast. In a "backbone" structure, meanwhile, wind farms are connected to each other in the ocean as well as to points on the coast.

A radial transmission structure, in which individual wind farms (represented by a single wind turbine in the above image) are each connected to shore where power is delivered. HDVC stands for high voltage direct current. (Illustration by Stephanie King | Pacific Northwest National Laboratory)

The radial structure would be simpler to build, Douville said, but it doesn't allow energy to flow easily between operating regions meaning that in some cases, counties that have offshore wind infrastructure might not always see all the benefits that transmission can provide.

A backbone transmission structure, in which the wind farms are connected to each other, then connected to shore at fewer points. (Illustration by Stephanie King | Pacific Northwest National Laboratory)

A backbone structure allows large grid operating regions to connect to each other. Although this scenario would cost more initially (because it would require building more transmission), the benefits outweigh the cost because it would ultimately allow cheaper energy to be transported more efficiently across regions.

With all this in mind, the team modeled the costs and benefits of five different scenarios for connecting floating offshore wind turbines to the coast, two that could be built by 2035 and three by 2050. The researchers prioritized any 2050 buildouts that could logistically evolve from an initial 2035 structure. Overall, the team found that starting with a radial structure in 2035 that would evolve into a backbone structure connecting grid operating regions provides the most benefits at the least cost. They estimated that after construction costs, savings could total $25 billion in today's dollars mostly due to the ability to share lower-cost energy such as solar and hydropower across grid regions.

How wind power affects communities

The new report shows that although it's possible and ultimately beneficial to both energy consumers establishing floating offshore wind on the West Coast faces challenges ahead.

Douville noted that much of the cost savings would come in scenarios where large grid operators such as the Bonneville Power Administration, PacifiCorp, and the California Independent System Operator coordinate any new transmission to connect their grids. These grid operators already share some energy along major transmission lines that run across the Oregon, Nevada, and California boarders. That's how solar power from California can travel to the Pacific Northwest, or hydropower can flow to California. 

But planning and siting new transmission for offshore wind would take effort to make sure costs don't disproportionately affect any region.

In future work, the researchers will study the costs and benefits to specific communities along the coast, and how those costs and benefits differ between regions.

"Building offshore wind comprehensively on the West Coast requires understanding which communities have the potential to benefit and where there are trade-offs between different transmission options," said Katie Arkema, a coauthor on the report who studies the intersection of human and natural systems at PNNL. "Before anything can be built, we need to figure out how to deliver benefits from offshore wind to the communities that need them."