Vertical axis wind turbines
The generator of a vertical axis wind turbine can be placed on the ground which allows an optimization for price and performance. The system developed at Uppsala University uses a direct drive generator and therefore no gearbox, which is beneficial as gearboxes failure is a common cause of downtime for conventional wind turbines. The vertical wind turbine is instead controlled electrically by means of the generator. Elimination of the pitch system further reduces the risk of downtime and the need for maintenance.
The vertical axis turbine have certain environmental advantages over the horizontal axis. The turbine generally have lower rotational speed than the corresponding horizontal axis turbine which results in lower noise level. Ice throw from a vertical-axis turbine is not thrown, as far as there is no vertically component of throw. When the generator is placed on the ground, the design can be made more robust. In some places of the world there is a problem with relatively frequent collisions between rotating blades and birds or bats. A vertical axis turbine is probably safer for birds and bats. This is because a vertical axis turbine is easier to detect for a bird since it does not move in the vertical direction. Furthermore, compared to the horizontal axis turbine, it has lower blade speed which makes it easier to avoid collision.
For more information on vertical axis wind turbines, please contact Hans Bernhoff.