wind turbines - image: courtesy of United States Department of Interior

 

In late October, the Department of the Interior announced that its Bureau of Ocean Energy Management [BOEM] will conduct an offshore wind energy lease sale on Dec. 6th, 2022, that will be the first-ever offshore wind lease sale on America’s West Coast. According to the National Renewable Energy Laboratory’s Offshore Wind Market Report: 2022 Edition, this lease sale will also be the first deployment requiring the use of commercial-scale floating offshore wind technology. The two designated areas off the California coast, Morro Bay and Humboldt Bay, will play an integral role in the Biden-Harris administration’s deployment goals of 30 gigawatts (GW) of offshore wind energy by 2030 and 15 GW of floating offshore wind energy by 2035. 

While offshore wind energy is seen as just one element of the broad renewable energy portfolio required to meet our country’s energy demands, the technical potential of the resource is significant. 

“There’s relatively few surface obstructions that exist in an offshore environment and so the wind speeds tend to be quite good,” said Eric Lantz, group research manager and wind analysis portfolio lead at National Renewable Energy Laboratory. “You can typically place [offshore wind] closer to load centers, much of the cities where electricity is consumed are on coastal regions and you’re not so dependent on transmission to move the electricity from the interior Great Plains to the coastal load centers.” 

Despite the potential of harnessing offshore wind energy, the United States market remains a distant third in size, far behind its counterparts in Europe and Asia. This can be attributed to a myriad of factors that have made developing offshore wind technology challenging in the U.S., and particularly along its West Coast. 

image: courtesy of the U.S. Dept of Interior

One primary challenge lies in the disparity between the two types of offshore wind technologies that exist today: fixed-bottom and floating-based, respectively.

“Most of what’s installed around the world today is fixed-bottom technologies, basically meaning that it’s in shallow to moderate depth waters with some sort of foundation that is embedded or anchored to the seafloor,” said Lantz. “Looking further into the future, we definitely expect floating offshore wind to be a much bigger part of the industry. Right now, [floating offshore wind] really exists at the pilot scale in a few installations around the world, but there’s a lot of optimism for floating offshore wind and how that can contribute to the future utilization of offshore wind resources.”

But in certain coastal regions of the U.S., such as portions of the Northeast, a more shallow topography still provides an opportunity to embrace fixed-bottom installations, much like what exists off the European coasts. 

“On the east coast, you could follow Europe’s lead a little bit more closely,” Lantz said. “The North Sea, where much of the offshore wind in Europe is installed, mostly what’s been installed to date is the fixed-bottom technologies and so they can take those technologies that have been developed and matured in Europe and simply move forward with them on the East Coast.”

The prevalence of fixed-bottom offshore wind technology in the market today demonstrates not only the disparity between the U.S. market versus the European and Asian markets, but also the disparity that exists within the coastal regions of the U.S., as well. 

“The biggest difference between the West Coast and other coastal regions of the U.S. are that the water gets very deep, very quickly,” Lantz said. “There’s very few places that are technically feasible for fixed-bottom offshore wind installations on the West Coast, so you have to wait for the floating technologies to start to mature.”

To understand why fixed-bottom offshore wind technology has developed at a faster rate, it really comes down to the basic physics that make floating offshore wind technology inherently difficult.

“The challenge of floating offshore wind is, you have to be able to balance a system that’s getting a lot of thrust loading against the rotor, without having it be fixed to some firm foundation,” Lantz said. “So you can think about it like a tree in a windstorm. If you’ve got a big, large root bed in a strong tree, that’s going to sustain wind pushing against the tree much better than if you have a very large tree with a very small root bed that could be pushed over.” 

Floating-based technologies are quickly advancing, however, as BOEM, the regulating agency for permitting offshore wind in federal waters, has recently begun considering installation sites for offshore wind turbines up to 1,300 meters below sea level. This includes the offshore wind energy lease sale off the northern and central California coasts scheduled for early December.

“There’s certainly industry members that feel that they will have technology that will allow them to place floating offshore wind turbines in water depths greater than 1,300 meters,” Lantz said. “That hasn’t been demonstrated as of yet, in sort of any real-world pilot conditions, but it’s possible.”

Despite these advancements, additional considerations often need to be taken into account when it comes to installing offshore wind turbines. These concerns further demonstrate why it’s taken so long for offshore wind technology to develop in the U.S. market.

Offshore Wind Turbines – image: Tacowitte, cc 2.0

“People have an interest in the sea and in the marine environment, and they don’t want to see their interest disproportionately or negatively impacted by offshore wind installations,” Lantz said. “They obviously include considerations for things like shipping lanes, dedicated conservation areas, if there’s a particular danger area, maybe from some previously unexploded ordnance, or if something was lost at sea and creates the hazardous area, if there are shipwrecks or sort of historically designated monuments, those are taken off.” 

Another unique, albeit critical consideration that is pertinent to the West Coast, and California in particular, is national security concerns related to the Department of Defense. 

“The Department of Defense has significant interest in protecting the coasts of the United States and they want to ensure that whatever is deployed offshore, whether it’s offshore wind or some other technology or infrastructure, that it’s not going to significantly impact their ability to carry out their mission,” Lantz said. “They flagged a large portion of California that if offshore wind is placed in this part of the state, that it needs additional scrutiny. There have been areas that have been identified as workable through their process, so depending on the specifics of the situation, it could just be a matter of ensuring that there’s no potential risks or factors that need to be considered.”

Yet, while many of these concerns are addressed on a case-by-case basis to identify appropriate locations, floating-based offshore wind technology stands to benefit from fixed-bottom technology’s development toward large-scale commercialization in recent years. Much of floating offshore wind technology uses the same turbines as their fixed-bottom counterparts, with just a few minor structural adaptations. Therefore, with greater advancement and maturation of floating-based technology, the significant advantages of offshore wind in a renewable energy portfolio may soon be realized. 

Wind Dynamo – image: Les Chattfold, cc 2.0

 “There’s a good correlation between when the offshore wind electricity is producing electricity in large quantities and when there’s actually demand and need for that,” Lantz said. “Offshore wind is a good complement to solar [photovoltaic] PV, the bulk of the electricity production is going to be in your afternoon hours, when the sun is sort of at its peak; whereas wind energy is going to continue to generate at nighttime, assuming it’s a reasonably windy time of year.”

Despite its complex challenges, offshore wind technology continues to gain momentum within the renewable energy industry. But even if floating-based technology can mature to the level of its more prevalent, fixed-bottom alternative, offshore wind technology will still need to be produced more cost-effectively in order to compete with traditional energy sources.  

“Floating offshore wind technology matured much more quickly than most people anticipated over the past five to 10 years,” Lantz said.  “There’s a lot of effort put into making electricity and energy as cheap as possible. So while it’s very technically feasible for engineers to come up with solutions, they’ve got to do it at a price point that competes with systems that have been more optimized over decades of use and operation in the past.”


Scott King writes about science and the environment for the Sierra Nevada Ally. He has a Master’s degree in Media Innovation from the University of Nevada, Reno, and a Bachelor’s degree in Professional Writing with a minor in Marketing from Capital University in Columbus, Ohio. Scott served for two years as a literacy instructor with the Peace Corps in the community of Gouyave, Grenada. Support his work.


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