The future for floating wind farms

Materials World magazine
,
22 Dec 2016

Khai Trung Le looks at the development of floating wind farm technology across Europe, the USA and Japan.

Offshore wind currently provides around 5% of annual demand in the UK, with this expected to grow to 10% by 2020. But there are a number of restrictions – namely, the current threshold in deployment distance, with most sites remaining close to the coast in shallow waters, and the exponential increase in cost when deploying at greater depths. However, work from Europe, the USA and Japan on floating wind turbines may provide a new path forward.  

The advantages of floating wind farms are seemingly significant. Although there are a number of varieties of floating wind farm technologies, including semi-submersibles, spar-buoys and tension-leg platforms, the underlying concept remains similar. Instead of being affixed to the ocean floor by foundations, requiring time-consuming and expensive installation, they float, held in position by tethers linked to the ocean floor. Not only could this theoretically be quicker and cheaper to construct and deploy, this allows the farms to be positioned further out to sea, where the winds are stronger and more consistent. 

However, floating wind farms remain costly to build and operate. The 2014 paper, Levelised cost of energy for offshore floating wind turbines in a life cycle perspective, published in Renewable Energy, speculates that a hypothetical floating wind farm would cost US$93–$268/MWh – in line with conventional offshore turbines, but far more expensive than hydrocarbon fuels. 

Scotland by way of Norway

Following the success of the Hywind Demo, the world’s first full-scale floating spar-buoy wind turbine with a 2.3MW turbine, Norwegian oil and gas company, Statoil, is working on construction of the Hywind Scotland Pilot Park. This 30MW five-turbine wind farm aims to demonstrate the benefits of commercial scale parks, including cost efficiency and low-risk investment and solutions.

The Hywind Demo, a 2.3MW Siemens turbine installed 10km off the coast of Norway and the world’s first full-scale floating wind turbine, has been operating since 2009. Elin Isaksen, spokesperson for Statoil, said, ‘The experience and measurement data collected from the Hywind Demo has been used to further develop and validate numerical simulation tools, used to optimise and upscale concepts for future projects, as well as optimise the floating motion controller. This will be increasingly important as the turbine size increases.’

Isaksen stated that the company sees ‘industrialisation of floating wind as a key opportunity for companies with skillsets from the oil and gas business,’ noting experience establishing and maintaining marine operations and supply chains. Isaksen continued, ‘As a large operator in offshore installations in the O&G area, Statoil will leverage this knowledge in the wind industry. This approach makes it possible to utilise scale effects in operation and to bring down the cost of operation, thus making offshore wind more competitive than other renewable technologies.’

Although the original Hywind Demo was located 10km off the coast of Skudeneshavn, Norway, the Pilot Park will be erected in Buchan Deep, 25km from Peterhead, Aberdeenshire. Aside from natural wind and ocean conditions, more pragmatic reasons drew Statoil to the UK. ‘The UK has a need for new capacity in the electricity market, as ageing power plants are taken off-stream, and the Scottish Government and Department of Business, Environment and Industrial Strategy have active programmes to encourage low carbon technologies,’ said Isaksen.

The Hywind Pilot Park remains on track, following onshore fabrication, while assembly and installation of the turbines is set to begin from Q2 2017. Statoil believes that the Hywind technology will eventually reach a levelised cost of electricity of £85–95/MWh. 

Portugal by way of the USA

Although ending up in the North Sea, Statoil had previously considered the coast of Maine, USA, and Japan as potential sites for the Hywind Pilot Park, and it is little surprise to see American and Japanese companies also exploring floating wind farms, including USA-based Principle Power. The company’s 2MW WindFloat prototype has been deployed 5km off the coast of Setubul, Portugal, since October 2011, with Shell among the partners, continuing the involvement of oil and gas.

Principle Power has plans for multiple follow-on projects, including a potential turbine off the coast of Scotland. But previous projects have not gone entirely to plan, including a prospective WindFloat project 25km off the coast of Oregon, USA. Principle Power was granted US$47 million from the US Department of Energy, but was unable to find utility customers for the supply. In withdrawing its lease request for the Oregon site, the project was abandoned in September 2016.

Japan, the journey and destination

The Fukushima FORWARD project is considered the first floating wind farm park project. Deploying the semi-submersible Compact Semi-Sub, developed by Mitsui Engineering & Shipping, Japan, off the coast of Fukushima in 2013, the turbine has endured two typhoon events and achieved availability rates of ~88%. However, as the first structure in the Fukushima FORWARD project, Carbon Trust has described the design as ‘highly conservative, with a large mass and high steel content leading to high capital expenditure’.

The project has also been criticised for running almost twice over budget, and as one of the first floating wind farm concepts, there remain significant technological improvements before reaching parity on efficiency and cost with other forms of offshore wind, let alone other forms of energy supply. Nonetheless, Governor of Fukushima, Yuhei Soto, has lobbied persistently in favour of support for Fukushima FORWARD following the 2011 Daiichi nuclear disaster. ‘We are moving ahead one step at a time,’ he said in November 2013. ‘This wind farm is a symbol of our future.’

Could the ocean breeze provide

The June 2015 study, Floating Offshore Wind: Market and Technology Review, published by Carbon Trust, predicts that fixed-bottom offshore wind farms will be the predominant form of offshore wind until as far as 2030, but sees the next 10 years as instrumental in overcoming technical challenges, including repeating claims of similarities made by Statoil with ‘the trend seen in the oil and gas industry when it moved from fixed to floating foundations during the 1970s […] as with wind, one of the main obstacles oil and gas had to overcome was the perceived risk of moving to a new technology.’

Optimism in the sector is enough to propel floating wind farm development across Scotland, Portugal, Germany, France to the USA and Japan, but the next step will be in substantial development to reach parity with other forms of wind energy.