Europe is the world leader in offshore wind power generation. The first offshore wind farm was installed in Denmark in 1991 and, since then, the share of energy produced offshore has steadily increased. Stronger wind speeds compared to those available on land means that offshore wind power’s contribution in terms of electricity supplied is higher. 

But offshore wind farms are expensive. In current models, the platforms are typically fixed to the seabed and, as a result, cost becomes prohibitive in waters deeper than 50 metres. This limitation is a bottleneck for the further exploitation of wind energy in Europe.

Placing wind turbines farther offshore has several advantages. Stronger and steadier winds, and reduced visual and noise impact, are just a few. Moreover, moving farther offshore will be essential for increasing the share of renewable energy production in the next decade. Yet design and implementation are complicated. Ensuring safety, minimal environmental impact and competitive energy production costs are key challenges.

The answer lies in floating turbines, moored to the seabed on a floating support. Although floating wind turbines are not yet on the market, prototypes are flourishing and this research is essential.

Next generation turbines

The ICFLOAT project set out to fill the knowledge gap surrounding floating turbines by using computational models to reproduce the effect of the ocean on the turbine’s movement, and vice-versa. The project looked at rigid and deformable bodies, submerged in air, water, or both. The result is an open-source framework to compute these mutual interactions – it works by coupling a fluid-dynamics and a structural-dynamics model.

Axelle Viré, recipient of one of the EU’s Marie Curie Intra-European Fellowships (IEF), explains: “Computer models are attractive to design floating wind turbines because they can analyse several different configurations, while limiting expensive laboratory or onsite testing. Reproducing numerically the effect of the ocean on the turbine movement, and vice-versa, is however difficult.”

Viré developed a novel technique to model the fluid-structure interactions. “The fluid-dynamics model calculates the fluid’s motion across the entire domain, while the structural-dynamics model computes the motion of the wind turbine on a separate mesh. I proposed a novel coupling algorithm that satisfies the action-reaction principle between the two models, independently of the mesh resolutions and the order of representation of the forces in each model.”

The project was completed in 2013 but ICFLOAT’s research continues to contribute to the long-term objectives of a sustainable, safe, secure, and affordable energy market for Europe. Although the project’s results have yet to be commercialised, its computational tools are already being used and extended to analyse other types of wind energy devices, such as kite power systems.

The work is likely to have a direct impact on other types of marine renewable energy devices, such as tidal turbines, wave energy converters and airborne wind energy devices, says Viré. It could also be applied to a wide range of engineering disciplines: “Interactions between fluid flows and structures are ubiquitous. The air flowing around an aeroplane, the blood circulating in arteries, or the water currents navigated by a robotic fish are just a few examples.”