Vertical axis wind turbines (VAWTs) have a main rotor shaft that runs vertically, unlike the more common horizontal axis wind turbines (HAWTs). VAWTs have advantages such as easier maintenance and increased reliability, but are less efficient and not commonly used for commercial purposes. Ongoing research aims to improve VAWT power output and reduce noise. The most common VAWT designs are the Savonious and Darrieus turbines, with other types including the revolution turbulent, aerotecture, giromill, and cicloturbina. Detailed calculations on VAWT rotor aerodynamics are available online.
Typically built with only two or three blades, a vertical axis wind turbine (VAWT) is a type of wind turbine in which the main rotor shaft runs vertically rather than horizontally. While there are several styles of these types of whirlwinds, one version looks a lot like an egg beater. Its motion, on the other hand, is similar to that of a coin spinning on its edge.
When most people hear the phrase “wind turbine,” they visualize a horizontal axis wind turbine (HAWT). A HAWT looks a lot like an aircraft propeller. The reason people closely associate a HAWT with the concept of a wind turbine is simply because the vertical axis wind turbine is not as common as its horizontal counterpart. In fact, VAWTs are generally not used for commercial purposes and are rarely connected to electricity grids.
Of course, despite their differences in appearance and distinct modes of operation, both the VAWT and HAWT generate electricity by converting wind energy into torque using a rotating shaft. That is, the wind spins the wind turbine blades around the turbine rotor. That rotor, in turn, is connected to the main shaft of the turbine, and that main shaft powers a generator, which generates the electricity.
There are some advantages inherent in the vertical axis wind turbine design. The turbine generator and gearbox can be located close to ground level, making maintenance easier and lowering initial construction costs. They also do not need to face the wind like HAWTs, which increases their ability to harness the power of the wind and therefore improves their overall reliability. The manufacturers also claim that the VAWT is quieter than its HAWT counterpart.
The main disadvantage associated with the vertical axis wind turbine, however, is that its efficiency is reduced because wind speeds are lower near the ground. This type of turbine is generally not capable of producing as much electricity as the HAWT design. VAWTs don’t start up on their own either, which is a barrier to grid connectivity. For these reasons, vertical axis wind turbine is often chosen for installation when cost or reliability is the primary concern. When total power and efficiency are the most important considerations, the horizontal axis wind turbine is typically used.
Research into VAWTs is ongoing in an effort to increase their power output and minimize their mechanical and aerodynamic noise. Engineers hope to improve this type of wind turbine so that it can be widely used in urban landscapes where space for wind farm installations is limited.
Of the many types of vertical axis wind turbine designs, the two most commonly built are the Savonious and Darrieus turbines. A Finnish engineer named Sigurd J. Savonius invented the simple drag turbine in 1922 and the French engineer Georges Jean Marie Darrieus invented his more practical lift-off turbine in 1927. Other types of vertical axis wind turbines include the revolution turbulent and silent, aerotecture, giromill and cicloturbina.
Detailed calculations regarding vertical axis wind turbine rotor aerodynamics are available online.
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