Vetar turbine works by tricking air into going faster and then using that acceleration to create energy at the most efficient way. 
It is determined by three basic features: 
  • Highly advanced aerodynamics 
  • Pressure game 
  • Highly efficient double rotors 
 In other words, ducted part of the turbine is creating ring like area of high pressure around the turbine, leaving area of lower pressure behind. This works as a funnel sucking air into the turbine. Having in mind that at low speed air is incompressible, it accelerates. 
This accelerated air is then used by two contra-rotating rotors which additionally accelerate each other making turbine even more efficient. 
How much more efficient? Up to 5 times compared to traditional HAWTs.