Windtech: Testing beyond commercial risk

WORLDWIDE: Despite over a decade of research, the achievements of the European Academy of Wind Energy (EAWE) are not well known in the industry.

Perdigao, Portugal - Parallel, partly forested ridges, ideal for flow research
Perdigao, Portugal - Parallel, partly forested ridges, ideal for flow research

Set up to provide high-level education to industry and society, it comprises a number of research institutes and universities in Europe.

"We organise regular PhD student networking events and an annual scientific conference called The Science of Making Torque from Wind," said Jakob Mann, EAWE president and professor at the Technical University of Denmark (DTU). Many of the PhD students are also wind industry employees and, while the EAWE organisations do not discuss or reveal corporate plans regarding detailed design of turbines, components and systems, they encourage pre-competitive research and innovation.

Large scale

One key collaboration has been the Upwind programme, which investigated turbine-scaling challenges, boundaries and directions for large-scale technology development. It found that designing future wind turbines in the 20MW range would be possible and perhaps already operational by 2020. This heralded considerable scepticism from the industry, questioning the programme's realism and understanding of what is really required for advancement of wind power.

Another, less contentious, example is the Lidar-based system research that led to a spin-off company, Windar Photonics, in 2008. It specialises in Lidar-assisted control technology now in use globally.

EAWE has also worked on aerodynamics, atmospheric turbulence, and "crazy concepts" that are not adopted by industry for being either too risky or not showing enough potential in the short term.

The kite wind power systems researched at the Delft University of Technology and a European project on floating structures with a vertical-axis wind turbine were both perhaps too risky for industry.


"Innovative ground-breaking projects always inspire students and provide much fun, like with wind-powered vehicle competitions," said Mann. "Student teams simultaneously learn to put aerodynamic principles into practice, experience designing efficient drive systems, and experiment with structures built from high-strength lightweight materials."

A current project involving several member institutes is exploring the science and technology boundaries of developing smart rotor blades. DTU is building an advanced aero acoustic wind tunnel. Use of advanced materials, including thermoplastic composites for rotor blades and a parallel development of dedicated manufacturing methods including pultrusion, is part of the Materials and Structures domain. This area is among others researched at Delft, Knowledge Centre WMC and the Centre for Renewable Energy Sources (CRES) in Greece.

EAWE also cooperates with industry to solve complex problems. One current project aims to improve fundamental understanding of aerodynamic turbulence, which is today only still partly understood.

Mann's DTU research group studies negative impacts on wake and yield of closely interspaced neighbouring onshore and offshore wind farms. "Over flat and homogeneous terrain much is known about local wind profile and turbulence conditions. But, wind turbines are increasingly installed at sites characterised as inhomogeneous terrain, where the atmospheric boundary layer could change, varying rapidly from place to place depending on specific landscape conditions. In many situations, these circumstances have proven to cause great impact on actual yield versus predicted yields, and at the expected operating lifetime of individual turbines and in wind farm arrangements."

EAWE is also involved in research at offshore projects Kriegers Flak and Horns Rev 3, which is planned in the same area as Horns Rev 1 & 2. Two key research areas are optimising turbine layout in wind farms as well as between the projects.

"If onshore turbines, in another example, are situated close to a steep cliff, this appears to radically alter atmospheric flow," said Mann. "Some turbines will experience stronger winds and higher yield, while others face lower, more unsteady or turbulent winds. This can hamper energy production and increase mechanical loads beyond the IEC class values they were designed for, with potentially negative impact from premature fatigue damage and turbine (structural) failure. Abilities to predict exact wind conditions in such difficult terrain are unfortunately still utterly insufficient."

Dispute resolution

In hilly, forested inland terrain, huge differences between predicted and actual wind resource have led to bitter disputes and court cases between owners/operators and suppliers/advisors. Here again insufficient knowledge of wind flow over complex terrain is the main underlying cause.

EAWE has already demonstrated its valuable role in researching areas that are missed by industry, and there is more that can be achieved.

"Decades of sustained academic research are finally paying off, but there are still many huge challenges ahead. For 2014-2025, EAWE has defined research challenges in ten main areas - from materials and structures to wind and turbulence, aerodynamics, design methods, and offshore environmental aspects. We invite members of industry and society to join the discussion," said Mann.

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