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Posted: Dec 28, 2012

ACTIVEWINDFARMS to optimise atmospheric energy extraction

(Nanowerk News) The EU plans to secure 20% of its energy from alternative sources within the next 8 years. This has led to strong support for and use of wind power in Member States, with wind farms getting larger and larger. But experts say wind farms with a capacity of over one gigawatt of power - to be used over large surface areas - slow down the atmospheric boundary layer (ABL), the lowest portion of the troposphere, reducing their performance. An EU-funded project, ACTIVEWINDFARMS, hopes to address the issue.
The ABL directly feels the effect of the planet's surface, and turbulence is produced in the boundary layer as the wind blows over this surface, as well as by thermals that are triggered by either the Sun or clouds. Turbulence redistributes heat, moisture and the drag on the wind within the boundary layer. When the system is unbalanced, the weather components are affected: wind strength, temperature, air quality and humidity.
ACTIVEWINDFARMS ('Active wind farms: optimization and control of atmospheric energy extraction in gigawatt wind farms') is investigating ways to introduce optimal techniques for improved control of the interaction between large wind farms and the ABL. ACTIVEWINDFARMS is headed by Professor Johan Meyers, of the Katholieke Universiteit Leuven (KU Leuven) in Belgium, who received a European Research Council (ERC) grant worth EUR 1.5 million under the EU's Seventh Framework Programme (FP7).
Developers for past wind farms focused on a bottom-up approach: both climate and meteorology fixed atmospheric wind availability. When the ABL is slowed down, however, the availability of wind at turbine hub height is decreased. For example, in Denmark, the effect has resulted in turbines of large offshore farms performing at only around 45 % of what the same turbine on land-based wind farms does.
Professor Meyers, through ACTIVEWINDFARMS, is working on developing optimal control techniques in combination with time-resolved, three-dimensional (3D) turbulent-flow simulations of wind farm-ABL interaction and multi-scale turbine models. He is carrying out simulations on supercomputing platforms.
Single turbines are used as flow actuators - transducers that convert an electrical signal to a desired physical quality - by dynamically pitching their blades using time scales that range between 10 and 500 seconds. So consumers could benefit in two ways: wind farms would react to the turbulent atmosphere in a positive way, and they could be used to actively control atmospheric conditions. The end result would be more efficient wind farms.
The ERC researcher is also using the simulations to test the wind tunnel validation of optimal turbine placement and turbine-control strategies. The outcome will be better control based on structural mechanics, and enhanced power quality and controller design. ACTIVEWINDFARMS was launched in 2012 and is scheduled to end in 2017.
Providing wind, solar, hydroelectric and tidal power, for example, will allow the EU to decrease greenhouse emissions. The increase of alternative energy sources will also help the EU curb its dependency on imported power.
By increasing our understanding of the ABL, researchers will help improve wind forecasts for the renewable wind energy industry.
Source: Cordis
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