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INTERVIEW - Floating wind power on the path to maturity, an expert's view

An artists' impression of a floating wind farm that uses TouchWind's Mono turbines. Source: TouchWind BV

January 17 (Renewables Now) - Floating wind power is likely to become competitive with current electricity sources within a decade at the earliest. Countries like France, Japan, the US and even Chile could be among the first beneficiaries and while they should be prepared to pay a premium, getting involved early would put them at a commercial advantage globally, a subject matter expert says.

Mark Spring, who is a Principal Engineer, Renewables O&M, Low Carbon Power Generation at Lloyd’s Register (LR), spoke to Renewables Now about the development of the offshore wind sector, focusing more on the future of floating wind platforms. Spring says that countries with good wind resources, high electricity costs and limited sites for onshore or bottom-fixed offshore wind farms will be the first to develop floating wind at scale.

THE EARLY MOVERS

Not surprisingly Spring first named France and Japan as suitable destinations for floating wind. France’s significant investments in the sector are in part due to difficulties related to complex geology and deep waters that developers experience with bottom-fixed wind projects off its coasts. The subject matter expert noted that areas of the Atlantic and the Mediterranean are likely to be identified as suitable for floating wind.

When it comes to Japan, Spring said that the island nation will have to consider floating wind amongst its first offshore wind projects due to the steeply-shelving sea bed close to the centres of population.

In the US, Spring pointed at California, which will need a combination of renewable energy technologies, including wind power, to achieve its ambitious targets for decarbonisation. “The water depth at Morro Bay plummets to over 200 m (656.2 ft) in just 15 km,” he noted.

Spring is positive that floating wind will play a part in Chile’s energy mix, specifically in regions with lower insolation and high demand. He explained that the country has a very long and fragmented onshore electricity grid with widely separated large cities along the length of the country, isolated to the east by the Andes.

BOLSTERING COMPETITION

It will take between 10 and 15 years for floating wind platforms to mature and be able to compete with currently-available sources of electricity. “Over this period of time it is also likely that electricity demand will increase, pushing prices up at the same time as political commitments to decarbonisation will further favour renewables over conventional fuels,” Spring said.

While bottom-fixed and floating wind foundations will dominate in different markets, Spring believes that in the future floating platforms will be suitable for some sites currently considered only for bottom-fixed wind farms. The suitability of this technology is not limited to deep water sites, he said, adding that the overlay will depend on the available technology and the reduction in costs over the coming years.

COST REDUCTIONS AND CHALLENGES

“Lifecycle costs of floating wind will be slashed when the pipeline for projects is significant enough for manufacturers to develop special wind turbine designs, which are more tolerant of platform movements, tower inclinations, nacelle accelerations and incorporate advanced blade pitch controllers taking into account the hydrodynamics,” Spring said.

At present, bottom-fixed wind farms are cheaper to build because they make use of existing technology for monopiles and jacket structures. However, floating wind may present advantages “where geology is complex, perhaps precluding simple piled foundations but where anchors may be installed relatively cheaply.” The economies of fabrication at volume are also a factor when it comes to comparing costs.

“It may also be that construction costs will be lower for floating platforms because they can be towed to site from specialised fabrication yards or final assembly facilities. However, the need for benign oceanographic conditions during transport to site is likely to preclude very long transport distances, so a sweet spot will be found,” Spring explained.

The safe transfer of technicians to floating platforms is one of the challenges listed by the expert.

“The additional systems and requirements for inspection of the structure of the floating hull adds tasks to be incorporated into maintenance schedules. Because of the increased capital cost, improvements to maintenance scheduling, remote diagnostics and predictive analytics will play an important part in ensuring the cost of energy from floating wind is acceptable to electricity consumers. However, the benefits from these new approaches will be applied equally to bottom-fixed and floating wind projects,” he said.

VARIETY IN DESIGN

The LR expert also talked about the different designs and concepts for floating wind platforms. He said that there is currently a great variety, but the “more exotic” concepts are still in development and “just over the horizon”.

Spring’s list of “exotic” concepts includes the SCD nezzy design by Aerodyn Engineering GmbH, the TetraSpar by Stiesdal Offshore Technologies A/S, and more designs by X1 Wind of Spain, Dutch firm TouchWind BV, and Eolink of France.

“Some of these concepts offer the possibility of adaptable designs, suitable for deep and shallow water, with drag anchors or tension leg systems, single point or multiple point mooring systems, passive weather-vaning platform orientation, downwind tilting aerodynamic rotors, self-erecting drivetrains and many other innovations not yet demonstrated,” he said.

Spring is part of Lloyd’s Register, a provider of classification, compliance and consultancy services to the marine and offshore industries. The company has developed a specialised software for assessing the integrity of floating structures, moorings and anchors. In addition, it has CFD models of the interactions between an access vessel and a floating wind platform, which help operate such facilities.

“It is intended that key lessons from these analyses will be applied in the development of rapid, easy-to-use engineering tools for design and management of floating wind.  Examples include establishing a database of a wind farm operator’s fleet of service vessels and workboats, characterising the capabilities of each and enabling efficient selection of vessels on a monthly, weekly, daily and hour-by-hour basis to improve safety, reduce downtime and operational costs,” Spring explained.

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