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In the great outdoors, ice can form, break, melt and refreeze many times over a season. Add the realities of a warming climate, and predicting how tons of frozen H₂0 behave is tricky business.

An international team from Aalto University, Delft University of Technology, and Siemens Gamesa Renewable Energy is working to find out just what happens when 200-metre tall wind turbines meet seriously frosty conditions, like those seen in Northern Europe’s Baltic Sea, North America’s Great Lakes or China’s Bohai Bay. At the moment, off-shore wind farms are largely located in waters that don’t enter deep freezes.

‘We don’t actually know what kinds of force and pressure ice creates on off-shore wind turbines,’ says Arttu Polojärvi, assistant professor of ice mechanics at Aalto University. ‘This is the first time anyone has carried out fully controlled model-scale laboratory experiments to find out.’

‘What’s special about our experiments that we’ve tested at -11 degrees Celsius to make sure the ice is strong and breaks realistically,’ explains Hayo Hendrikse, assistant professor in ice-structure interaction at TU Delft.

The physical testing was carried out with a 30:1-scale model pile, with the help of numerical modelling to simulate wind and other conditions a wind turbine would encounter at sea. In real-life terms, the load exerted from the ice during the experiments would be around 8 meganewtons – that’s the combined thrust of 16 of the largest aircraft engines.

‘The preliminary results show something that we haven’t seen before in other structures, like lighthouses, channel markers, or oil and gas platforms. A wind turbine is very tall and slender and can move a lot; what we’ve seen in our experiments seems to be a totally new type of ice-induced vibration,’ says Hendrikse.

The Shiver project team is now working to create robust numerical models based on the data collected in order to test various scenarios that a wind turbine might encounter in chilly conditions over half a century of service. The and is now published in the journal Data-in-Brief.

The research has been funded by Siemens Gamesa Renewable Energy and TKI Wind Op Zee. Polojärvi has recently received funding from The Academy of Finland to lead further development and create a modellingengine for forecasting future marine environmental and ice conditions. The aim is that the modelling engine will also aid in the the design and optimisation of cold-region offshore wind farms.

More information:

Available to comment on how ice breaks, related challenges of climate change and Aalto Ice Tank:

Arttu Polojärvi
Assistant professor, ice mechanics
Department of Mechanical Engineering
Aalto University
Tel: +358504301682
arttu.polojarvi@aalto.fi

Available to comment on ice-induced vibration of offshore wind turbines and the experiments detailed above:

Hayo Hendrikse
Assistant professor, ice-structure interaction
Delft University of Technology
Tel: + 31152788223
H.Hendrikse@tudelft.nl