Floating Offshore Wind – Statoil’s Hywind project

July 24, 2017

Renewable energy technology in Europe has taken a step forward with the turbines of Statoil’s concept Hywind Pilot Park floating offshore wind farm shortly to be towed into position.

The wind farm, located near Peterhead about 25km off of the north-east coast of Scotland demanded an innovative solution due to waters too deep to deploy conventional bottom-standing turbines. The technology has been extensively tested with a single floating turbine off the coast of Norway since 2009, building on Statoil’s offshore expertise in the oil and gas sector.

The hope is that the technology will see an increase in take-up in the USA and Japan where deep coastal waters prevent the use of conventional turbines directly embedded in the sea floor.

Successful deployment in open-sea conditions could also improve the relationship with bird charities as being able to locate new wind farms well offshore keeps them away from nesting sites, and can help to reduce fatalities.

The floating offshore wind farm is eventually expected to produce 30MW to power approximately 20,000 households, and is expected to start production towards the end of 2017. The pilot park will consist of 5 turbines in an area of about 4 square kilometres, and in a water depth of up to 120 metres.

Hywind – Statoil

At 175 meters high, constructing the turbines has not been easy, requiring the use of the Saipem 7000 heavy lifting vessel, the world’s second largest crane vessel, at the port of Stord in Norway. Statoil has used 6MW Siemens Gamesa turbines, having previously used a 2.3MW turbine from Siemens on their Norway test turbine. One of the main challenges involved developing new software algorithms for the rotor pitch and orientation of the turbines to account for the motion of the water as well as the wind. When eventually in place, the 11,500 tonne turbines will be moored by means of 3 cables, with their floating supports extending 78m below the water.

While the technical challenges of the floating offshore wind farm project have mostly been overcome, as with many new technologies, cost remains a big factor. It is estimated that the wind farm will have cost double that of a conventional windfarm, and the £210 million project was only deemed viable because of a generous subsidy from the Scottish government. Abu Dhabi renewables fund Masdar also holds a 25% stake in the project with an investment of £52.5 million.

A competing technology, the Fukushima Forward project in Japan, uses semi-submersible platforms, moored to the seabed, originally using a 2MW Hitachi turbine, then a much larger 7MW turbine from Mitsubishi Heavy Industries, and finally a 5MW from Hitachi. Japan has also therefore started to build up a large amount of knowledge itself, although it lacks the offshore experience and infrastructure present in Europe. Once again though the Japanese project has been expensive.

Despite the expense of the fledgling technology though, it is foreseen that as costs come down, and the number of windfarm installations increases globally, floating offshore windfarm will increase, and may even eventually outstrip their more conventional counterparts, especially since efficiency gains in being able to construct the turbines close to shore and simply tow them in bulk to their final destinations are a key part of further developments, with the Carbon Trust suggesting that cost parity may be achievable around 2030.

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