Contrary to popular belief, a wind turbine is not pushed round by the wind but pulled round by the aerodynamic lift generated on the blades by the flow of air across them. This transforms the kinetic energy of the wind into rotation of the turbine's shaft. It also slows the airflow, causing the wind to "pile up" in front of the turbine and deflect some of the flow around it. The limit for the energy that can be harvested by a perfect turbine in ideal conditions, published in 1919 by German physicist Albert Betz, is 59.3 per cent of the available wind energy.
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