Advantages of VAWT:
w Can capture and utilize wind coming from any direction
w Electric generator is easy to reach as it is beneath the turbine
w Usually those wind turbines have aspect ratios that the ratio between rotor diameter and height is small. So wind energy is utilized in vertical direction. On the contrary, three-bladed HAWT’s should occupy circular swept area which waste large areas in wind farms
w Simple design and manufacturing
w Since the diameter of this kind of turbines is usually small, so low centrifugal forces are there and so low stresses
w Bending on shaft is not too much as it is only resulting from wind drag, but in HAWT it is resulting from weights and centrifugal forces
w Magnetic levitation technology is easy to use to reduce mechanical losses
w In most designs, the turbine may have a base plate and the tip of this plate can run an electric generator of small wheel and then no gear box is required
Disadvantages of VAWT:
w Low values of power coefficient (efficiency) specially in drag types
w In most designs, for a given wind speed the rotational speed of the turbine is not constant because the turbine is not producing power with the same quantity at different positions of the cycle. This problem is avoided in the helical Savonius wind turbine with a twist angle of 180 degrees.
