Offshore wind turbines, with their fixed-bottom foundations that reach down 60 or so meters, are too deep to be economically feasible in most settings. But the goal to normalize offshore wind isn’t beyond reach. That’s because a whole new generation of floating offshore wind turbines is being harnessed to tackle the mightiest winds that nature produces.
The engineering behind floating offshore wind energy is incredibly sophisticated. Wind turbines are situated on floating platforms made of a concrete, steel, or hybrid substructure on which the wind turbine is installed, providing it with buoyancy and stability. Anchored and moored on the sea bottom, they must battle the unrestrained forces of stormy seas and arbitrary weather.
Offshore wind energy is a source of clean and renewable energy that reaches a high and constant speed due to the lack of barriers. Its high potential and strategic added value, both at a socioeconomic and environmental level, make it one of the renewable sources that will play a crucial role in the decarbonization process.
The global wind industry had its second-best year in 2021, with almost 94 GW of capacity added globally, trailing behind the 2020’s record growth by only 1.8%, according to the Global Wind Energy Council. Europe, Latin America, and Africa and the Middle East had record years for new onshore installations. 21.1 GW of offshore wind capacity was commissioned last year, 3 times more than in 2020, making the best year in offshore wind history accrue a market share in global new installations to 22.5% in 2021.
Yet wind power hasn’t been able to reach its full potential, as 80% of the offshore wind resources in European waters are in places too deep for existing offshore wind turbine technology. Deep water obstacles have also prevented the installation of large offshore wind farms off the US west coast.
As engineers search for ways to capture the most reliably forceful winds, they are moving further out into the ocean to areas of deeper water where especially strong winds are known to blow. Entirely new technologies are in the design stage to rethink deep water barriers.
The Necessity of Stability: Offshore Wind Turbines
Offshore wind turbines have higher load factors than land-based ones and, therefore, suffer from less intermittent energy production. Farther from the coast, they benefit from stronger winds for a greater production capacity.
Floating turbines could open up vast swathes of the ocean to electricity generation. Analysis by the Institut Polytechnique de Paris suggests that floating wind turbines hold promise for energy production worldwide: 330,000 TWh per year, or 79% of the total theoretical potential of offshore wind power. The Global Wind Energy Council forecasts that floating wind will become “one of the key game-changers” in the industry.
Yet the challenges of offshore wind energy projects are substantial and include:
- high costs for support structure, operating and maintenance, electrical infrastructure, and turbines
- strict environmental standards
- lesser established construction techniques
- more difficult access to turbines for maintenance
- cabling that is longer, bigger, and deeper than the cabling for existing offshore wind farms
- drivetrain uncertainties relating to wind speed, turbulence, shear profile, significant wave height, spectral peak period, and wave direction
Billions of dollars are currently being invested in the floating offshore wind industry, as outlined by Wired. To significantly lower the cost of a floating turbine, designers are easing away from the tall tower concept to alternative designs that require less steel to eliminate the mechanism that rotates the nacelle. The result should be a simpler design that is easier to construct so that the entire structure rotates to face the wind.
Norway & Floating Offshore Wind Systems
Various floating turbine designs have emerged that are generating intrigue over cost and efficiency.
The Government of Norway has launched a large-scale investment plan aimed at allocating sea areas to develop 30 GW of offshore wind capacity by 2040. The government said it will facilitate a large-scale offshore wind development that allows for the use of various grid solutions. Cables with two-way power flow, interconnectors to Europe, and interconnectors to Norway will be considered for each call. The Norwegian Water Resources and Energy Directorate (NVE) and the Ministry of Petroleum and Energy (MPE) will study the consequences of the alternatives.
Energy scales exponentially with wind speed. Conventional turbines limit energy output above 11-12 m/s by pitching the blades. Wind Catching Systems (WCS), the developer of floating offshore wind technology, was founded in 2017 with the idea that multi-turbines could maximize power generation from a concentrated area rather than a big turbine. Easy maintenance, durability, and simplicity were the guiding principles when the first Windcatcher was designed as a sail on a trimaran.
WCS’ design for a giant waffle-shaped frame contains at least 126 four-rotor wind turbines. The whole structure, standing as tall as the Eiffel Tower, would perch atop a floating platform, similar to those used by oil rigs. Utilizing the full energy in higher wind speeds and the multirotor effect, the Windcatcher system generates 2.5x more annual energy per swept area than a conventional turbine. Having double the swept area of a conventional 15 MW wind turbine, one Windcatching unit has the potential to generate 5x the annual energy production.
The company is now involved with a Series A investment round of up to $10 million, and GM Ventures has entered into a strategic agreement with or collaboration covering technology development, project execution, offshore wind policy, and the advancement of sustainable technology applications.
What Else is Happening in Offshore Floating Wind R&D?
Other offshore floating wind designs are in the works.
Equinor has designed a new floating wind concept that will enable industrial standardization and maximize opportunities for local supply chains. The Wind Semi, a semi-submersible wind turbine foundation with a type of floating flat triangle with a turbine poised on one corner and is intended to allow for fabrication and assembly based on local supply chain capabilities.
Olympic Wind, Washington-based Trident Winds, issued an unsolicited request for a federal lease in late March. The proposal could include up to 2,000 megawatts of electricity, enough for about 800,000 homes, produced from turbines mounted on platforms and moored to the deep ocean floor about 43 miles off the coast of Grays Harbor County, Washington. This would be the first commercial-scale offshore wind project in Washington at 2,000 MW.
Extensive monitoring of new floating wind farms to collect data on their ecological impacts will be ongoing. One study suggests that erecting floating turbines should be much quieter than installing fixed-bottom offshore machines, and, therefore, less disturbing to marine mammals, since pile-driving for the foundations would no longer be required.
Although offshore wind turbine technology is less mature than its grounded siblings, the current technological advancements for offshore floating multi-turbine platforms are the next tool in the renewable energy toolkit to harness abundant offshore wind.
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