Are two heads better than one for floating wind?
Swedish floating wind developer Hexicon – famous for housing two turbines instead of one on each of its platforms – has teamed up with local company EAAMA to form a joint venture targeting the development of offshore floating wind projects of the Greek coasts.
The move comes ahead of the Greek government’s upcoming framework for offshore wind development, which will be released later this year, likely with a strong focus on floating wind given the country’s deep waters.
For a typical offshore wind farm, located about 10 kilometers offshore, most waters are in the region of 250 meters deep, making fixed platforms unfeasible in over 90% of its waters. With wind speeds in the region often averaging over 10 meters per second, rivaling even those in the North Sea, Hexicon CEO Marcus Thor said: “Greece has great potential for ‘floating offshore wind energy with some of the best winds in Europe’.
The new joint venture will be called Hexicon Power and will aim to help Greece reach the goal of producing 60% of its electricity from renewable energy, compared to just under 40% today.
The move also echoes Hexicon’s formation of the MunmuBaram joint venture with South Korean firm Coens and Shell Overseas Investment, which will develop and operate a 1.3GW floating offshore wind farm up to 80 kilometers offshore. from South Korea, followed by a 1.7 GW project. at a later date. It is also similar to the 50/50 AvenHexicon JV – with Avapa Energy – which aims to develop floating wind projects off Italy.
Hexicon’s differentiation in the floating wind market is its patented TwinWind design. Each platform in this design accommodates two wind turbines, which rotate around a shared mooring point depending on the prevailing wind direction. This varied from traditional floating designs where individual nacelles had to rotate to align with the wind.
An overhead representation of Hexicon’s TwinWind design
The obvious advantage of TwinWind is that it contains more generating capacity in each floating foundation and more turbines are deployed in a given marine area. Hexicon claims this will increase the energy efficiency of floating wind projects, but the main benefits here are most likely associated with sharing the infrastructure costs normally associated with one turbine, between two instead.
The company says inter-grid cabling at a Hexicon wind farm is reduced by a third, with more turbines located in a smaller area. The amount of steel required for turbine foundations is also significantly reduced per MW of rated capacity, while installation costs are also reduced through fewer wet tows and mooring installations.
Like most floating wind turbine designs, TwinWind can be assembled onshore and at port sites, allowing a fully commissioned system to be ‘wet-towed’ to the offshore site from which it will operate.
However, Hexicon has yet to physically install any of its turbines, so in-situ proof of increased production has yet to be demonstrated. Hosting two wind turbines so close together presents its own risks. Traditionally, wind turbines are spaced laterally by 7 times their measured rotor diameter, and if placed too close together, increased turbulence and air blockage will reduce the amount of wind captured by each wind turbine.
Another potential problem is that of unit failure. If one wind turbine is forced to shut down, the other will have to do the same to prevent asymmetric loading and unwanted rotation of the rig – forcing a fully working wind turbine out of commission. Since the availability of offshore wind turbines can be as low as 90%, this could significantly reduce the gross output of each wind turbine on an annual basis.
Hexicon’s success will depend on these trade-offs between loss of production efficiencies and reduced capital requirements in cabling, steel, facilities and maintenance. It will also depend on its ability to reduce the wake effect of downwind wind turbines, as it claims. The company claims that “The TwinWind can be thought of as a micro wind farm of two turbines that weathervanes so that none of the turbines are affected by wakes from windward platforms”.
Along with partnerships in Italy, Greece and South Korea, Hexicon plans to deploy its first large-scale platform – with multi-megawatt turbines – in 2023, in Norwegian waters over 200 meters deep. It has agreements in place to deploy a 32MW platform in the Celtic Sea in the UK with Bechtel, as well as the potential 100MW Pentland floating wind farm in Scotland with CIP. The company has also set up other JVs in Sweden with Aker Offshore Wind and on the Iberian Peninsula (for Spain and Portugal) with Wundersight, named Freja Offshore and WunderHexicon respectively, and is said to be in discussions with partners on the South African, Irish and American markets. .
Most of these deals have been struck in the past two years, amid a flurry of activity in the floating wind space. Inspired and somewhat facilitated by the success of offshore wind, as well as its reduced cost, floating foundations will allow offshore wind turbines to be positioned farther from shore, reducing visual impact and improving available wind conditions.
In 2021, there are only three floating wind farms in operation: Hywind Scotland (30 MW), WindFloat Atlantic (25 MW) and Kincardine (50 MW). However, the global pipeline of projects recently exceeded 54 GW, much of which will be installed before 2030, and more than half of this amount is planned for European waters.
This presents a huge opportunity for European OEMs to reassert their market lead under continued pressure from their Chinese rivals, quickly taking the lead in the floating market.
The wind sector is still in the brainstorming phase in terms of floating technology, with more than 20 variants currently competing for market attention. The industry will experience radical consolidation. Although oil and gas developers may disrupt this by trying to develop their own designs throughout the fossil fuel transition, we anticipate that once the market matures only 5 or 6 designs will be commercially viable, with Hexicon sitting alongside current favorites Principle Power (WindFloat), Fukushima (Avant) and Ideol (Floatgen).
Semi-submersibles could have a significant advantage here if construction costs and requirements can be reduced, with spar buoys posing difficulties outside their home country of Norway, where near-shore water depths are not sufficient. Innovative approaches to improving electricity generation and sharing infrastructure costs – potentially even with tidal power – are likely to prove vital to winning the race.